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UBC Theses and Dissertations

Daylighting in office buildings Farkas, Tibor 1985

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DAYLIGHTING IN OFFICE BUILDINGS by TIBOR FARKAS B . S c , M c G i l l U n i v e r s i t y , 1970 B.Arch., M c G i l l U n i v e r s i t y , 1975 THESIS SUBMITTED IN PARTIAL FULFILMENT THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARCHITECTURE i n THE FACULTY OF GRADUATE STUDIES Sc h o o l Of A r c h i t e c t u r e We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1985 ' © T i b o r F a r k a s , 1985 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree . t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department of A r c h i t e c t u r e The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date: A p r i l 23, 1985 i i Abst r a c t T h i s t h e s i s p r e s e n t s a c o n c e p t u a l framework f o r the i n t r o d u c t i o n of d a y l i g h t i n g c o n s i d e r a t i o n s i n t o the d e s i g n of o f f i c e b u i l d i n g s . D e s i gn is an i n t u i t i v e p r o c e s s , yet the i n t u i t i o n must be educated by study and a n a l y s i s . The framework d e v e l o p e d in the t h e s i s e n a b l e s the s y s t e m a t i c study of d a y l i g h t i n g p r i n c i p l e s and t e c h n i q u e s and i s a major s t e p towards a g r a s p of d a y l i g h t i n g d e s i g n . The t h e s i s i s d i v i d e d i n t o n i n e c h a p t e r s . The i n t r o d u c t o r y c h a p t e r c o n t a i n s a b r i e f h i s t o r y of d a y l i g h t i n g in o f f i c e b u i l d i n g s , examines reasons f o r d a y l i g h t i n g , and e x p l a i n s the s t r u c t u r e of the t h e s i s . The f o l l o w i n g c h a p t e r a n a l y s e s the performance c r i t e r i a t h a t the luminous environment in o f f i c e i n t e r i o r s must f u l f i l l i n o r d e r t o p r o v i d e a s a t i s f a c t o r y performance of v i s u a l t a s k s and r e s u l t i n user a c c e p t a n c e . Each of the next f i v e c h a p t e r s examine s p e c i f i c t e c h n i q u e s , under f i v e g e n e r a l o b j e c t i v e s : i . p r omoting d a y l i g h t a c c e s s i i . p r omoting d a y l i g h t p e n e t r a t i o n i i i . i n t e r i o r space p l a n n i n g f o r d a y l i g h t i n g advantage i v . c o n t r o l l i n g b r i g h t n e s s extremes v. i n t e g r a t i n g d a y l i g h t w i t h e l e c t r i c a l l i g h t In each c h a p t e r , these t e c h n i q u e s a r e l i s t e d i n o r d e r of d e c r e a s i n g s c a l e : from s i t e p l a n n i n g , through b u i l d i n g c o n f i g u r a t i o n and b u i l d i n g e n v e l o p e , t o b u i l d i n g i n t e r i o r . The t h e s i s shows t h a t d a y l i g h t i n g can be i n c o r p o r a t e d i n t o b u i l d i n g d e s i g n at v a r i o u s l e v e l s of commitment, r a n g i n g from a t o t a l commitment to d a y l i g h t i n g , i n which the b u i l d i n g i s c o n c e i v e d as "a l i g h t f i x t u r e t h a t can be e n g i n e e r e d t o a s t a t e of o p t i m a l performance", t o a minor commitment, i n which, f o r example, p e r i m e t e r l i g h t s i n an o t h e r w i s e s t a n d a r d o f f i c e b u i l d i n g d e s i g n are c o n t r o l l e d i n response t o d a y l i g h t i n g needs. F u r t h e r m o r e , i t i s shown t h a t d a y l i g h t i n g t e c h n i q u e s can be i n t r o d u c e d a t v a r i o u s scales--some t e c h n i q u e s may modulate the ma s s i n g , w h i l e o t h e r s d e a l w i t h s p e c i f i c b u i l d i n g components. F o l l o w i n g the study of t e c h n i q u e s , t h e r e i s a d i s c u s s i o n on d a y l i g h t i n g d e s i g n t o o l s and the i n t e g r a t i o n of d a y l i g h t i n g w i t h o t h e r a s p e c t s of d e s i g n . The t h e s i s c o n c l u d e s t h a t d a y l i g h t i n g o f f e r s a r c h i t e c t s the o p p o r t u n i t y t o d e s i g n o f f i c e b u i l d i n g s so t h a t they use l e s s energy and, a t the same t i m e , p r o v i d e a b e t t e r working environment than i s the case w i t h most b u i l d i n g s today. T a b l e of c o n t e n t s A b s t r a c t i i L i s t of T a b l e s i x L i s t of F i g u r e s x i Acknowledgement x v i Chapter I INTRODUCTION 1 1. NATURAL LIGHT AND ARCHITECTURE 2 2. HISTORY OF DAYLIGHTING IN OFFICE BUILDINGS 3 3. REASONS FOR DAYLIGHTING 7 3.1 C o n s i d e r a t i o n Of User S a t i s f a c t i o n 8 3.2 Economic C o n s i d e r a t i o n s 8 3.3 S o c i o - p o l i t i c a l And E n v i r o n m e n t a l C o n s i d e r a t i o n s ..15 3.4 P h i l o s o p h i c a l C o n s i d e r a t i o n s 16 4. SCOPE OF THESIS 17 4. 1 Goal Of T h e s i s 17 4.2 S t r u c t u r e Of T h e s i s 18 5. NOTES '.• 2 3 Chapter I I DAYLIGHT IN THE INTERIOR VISUAL ENVIRONMENT 2 9 1. INTRODUCTION 3 0 2. TASK LI GHT I NG - - " L I GHT TO SEE BY" 30 2.1 The Task P e r f o r m i n g System 30 2.2 C h a r a c t e r i s t i c s Of Task 32 2.3 Task Per f o r m e r Response C h a r a c t e r i s t i c s 33 2.4 C h a r a c t e r i s t i c s Of L i g h t i n g 34 2.4.1 The E f f e c t Of I l l u m i n a n c e L e v e l On V i s i b i l i t y ...35 2.4.2 The E f f e c t Of Luminance D i s t r i b u t i o n On V i s i b i l i t y 38 2.4.3 The E f f e c t Of L i g h t D i r e c t i o n On Task V i s i b i l i t y 40 2.4.4 The E f f e c t Of S p e c t r a l C h a r a c t e r i s t i c s On V i s i b i l i t y 41 2.4.5 The E f f e c t Of I l l u m i n a n c e V a r i a b i l i t y On V i s i b i l i t y 42 3. LIGHTING FOR USER SATISFACTION--"LIGHT TO SEE" 43 3.1 L i g h t i n g For P h y s i o l o g i c a l W e l l - b e i n g 43 3.2 L i g h t i n g For V i s u a l Comfort 46 3.2.1 B r i g h t n e s s G r a d i e n t s 47 3.2.2 D i s c o m f o r t G l a r e 47 V 3.2.3 V i s u a l Rest C e n t r e s 52 3.3 L i g h t i n g For V i s u a l P e r c e p t i o n 53 3.3.1 View 55 3.3.2 S p a c i o u s n e s s 56 3.3.3 M o d e l l i n g 57 3.3.4 The Drama Of D a y l i g h t 58 3.3.5 Sunshine 60 4. NOTES 61 Chapter I I I PROMOTE DAYLIGHT ACCESS •. 70 1 . INTRODUCTION . 71 1.1 The Three Sources Of D a y l i g h t 71 1.2 The Three D a y l i g h t Design C o n d i t i o n s 74 1.3 Measurement Of Indoor D a y l i g h t 78 2. TECHNIQUES FOR DAYLIGHT ACCESS 79 2.1 B u i l d i n g C l u s t e r i n g 81 2.2 E x t e r i o r S u r f a c e s 86 2.3 B u i l d i n g Massing 89 2.4 B u i l d i n g Layout 90 2.5 A t r i a ". .". . 96 2.6 N o r t h And South O r i e n t a t i o n ....98-2.7 I n t e r i o r S u n l i g h t .......99 2.8 D a y l i g h t i n g Separate From View 104 2.9 D a y l i g h t i n g From The Top 105 2.10 O b s t r u c t i o n s 110 3 . NOTES 1 1 8 Chapter IV PROMOTE DAYLIGHT PENETRATION 124 1 . INTRODUCTION 125 2. TRADITIONAL DAYLIGHTING TECHNIQUES 125 2.1 C o n f i g u r a t i o n And L o c a t i o n Of D a y l i g h t i n g A p e r t u r e 127 2.2 G l a z i n g M a t e r i a l S e l e c t i o n 134 2.3 Maintenance F a c t o r 140 2.4 Net G l a z i n g Area 142 2.5 Depth And D e t a i l i n g Of W a l l Around D a y l i g h t i n g A p e r t u r e 143 2.6 Room Geometry 146 2.6.1 I n t e r i o r R e f l e c t a n c e s 148 3. INNOVATIVE DAYLIGHTING TECHNIQUES 152 3.1 Deep D a y l i g h t i n g Through View Windows 154 3.2 Deep D a y l i g h t i n g — T h r o u g h W a l l A p e r t u r e s Above Eye L e v e l 160 v i 3.2.1 C l a s s i f i c a t i o n 160 3.2.2 L i g h t s h e l v e s 163 3.2.3 P r i s m a t i c Systems 167 3.2.4 Louvre Systems ..173 3.3 Deep D a y l i g h t i n g - - t h r o u g h Roof A p e r t u r e s 176 4. NOTES 179 Chapter V INTERIOR SPACE PLANNING IN DAYLIT BUILDINGS 187 1 . INTRODUCTION 188 2. TECHNIQUES FOR SPACE PLANNING 188 2.1 L o c a t i o n Of A c t i v i t i e s 190 2.2 Open P l a n I n t e r i o r 194 2.3 L o c a t i o n Of C e l l u l a r O f f i c e s 195 2.4 D e t a i l i n g Of C e l l u l a r O f f i c e s 197 2.5 D a y l i g h t i n g And A c o u s t i c s 200 3. NOTES 203 Chapter VI CONTROL OF BRIGHTNESS EXTREMES 206 1 . INTRODUCTI ON' ' ' 207 2. TECHNIQUES FOR BRIGHTNESS CONTROL 210 2.1 L a n d s c a p i n g For G l a r e C o n t r o l 210 2.2 D a y l i g h t From More Than One D i r e c t i o n 215 2.3 G l a r e And S o l a r Heat C o n t r o l — East And West ....216 2.4 G l a r e And S o l a r Heat C o n t r o l — South 224 2.5 G l a r e C o n t r o l — N o r t h 227 2.6 G l a z i n g T i l t 227 2.7 I n t e r i o r L i g h t s h e l v e s 232 2.8 C o n t r a s t G r a d i n g 235 2.9 L i g h t - c o l o u r e d S u r f a c e s 237 3. NOTES 242 Chapter V I I INTEGRATION OF DAYLIGHTING WITH ELECTRICAL LIGHTING 248 1. INTRODUCTION 249 2. TECHNIQUES OF INTEGRATING DAYLIGHT AND ELECTRICAL LIGHT 250 2.1 L i g h t i n g Design P h i l o s o p h y 250 2.2 F i x t u r e C i r c u i t i n g 257 2.3 Au t o m a t i c C o n t r o l s 258 v i i 3. NOTES 265 Chapter V I I I DAYLIGHTING AND THE DESIGN PROCESS 269 1. INTRODUCTION 270 2. DAYLIGHTING DESIGN TOOLS 271 2.1 C o m p u t a t i o n a l Methods ...272 2.2 G r a p h i c Techniques ....275 2.3 P h y s i c a l M o d e l l i n g 276 3. DAYLIGHTING IN THE WIDER DESIGN CONTEXT ..279 3.1 D a y l i g h t i n g In The Context Of E n e r g y - r e s p o n s i v e O f f i c e B u i l d i n g Design 279 3.2 D a y l i g h t i n g In The Wider Design Context 283 4. NOTES 285 Chapter IX CONCLUSIONS 291 B i b l i o g r a p h y 296 L i s t of t a b l e s I . M a t r i x of d a y l i g h t i n g t e c h n i q u e s 20 I I . Task c h a r a c t e r i s t i c s a f f e c t i n g v i s i b i l i t y 33 I I I . Task p e r f o r m e r response a f f e c t i n g v i s i b i l i t y 34 IV. C h a r a c t e r i s t i c s of t a s k l i g h t i n g a f f e c t i n g v i s i b i l i t y 35 V. Recommended luminance r a t i o s w i t h i n the v i s u a l f i e l d 48 V I . R e i n f o r c e m e n t of s u b j e c t i v e i m p r e s s i o n s by l i g h t i n g cues 57 V I I . D e s i g n responses r e q u i r e d under d i f f e r e n t d a y l i g h t i n g c o n d i t i o n s 77 V I I I . R e f l e c t a n c e s of v a r i o u s outdoor s u r f a c e s 88 IX. T a b l e of performance d a t a f o r g l a z i n g a s s e m b l i e s ..135 X. C h o i c e of g l a z i n g f o r d a y l i t o f f i c e b u i l d i n g s 139 X I . . M aintenance f a c t o r s f o r windows and roof l i g h t s i n o f f i c e s 141 X I I . I l l u m i n a t i o n r e q u i r e m e n t s and p r e f e r r e d zone l o c a t i o n of v a r i o u s o f f i c e a c t i v i t i e s 192 X I I I . L i g h t i n t e n s i t i e s (% of t h a t o u t s i d e ) under mature s t a n d s of v a r i o u s t r e e s 213 XIV. R e f l e c t a n c e s of common b u i l d i n g m a t e r i a l s 239 XV. R e f l e c t a n c e v a l u e s f o r t y p i c a l c o l o u r s 240 XVI. Summary of c h a r a c t e r i s t i c s of the t h r e e o f f i c e l i g h t i n g parameters 253 X V I I . Summary of e l e c t r i c l i g h t i n g c o n t r o l s 263 X V I I I . U s e f u l n e s s of v a r i o u s d a y l i g h t i n g t o o l s at each d e s i g n phase 272 i x L i s t of f i g u r e s 1. O f f i c e b u i l d i n g form and d a y l i g h t i n g i n h i s t o r y ..4 2. M a t r i x a r r a n g e d a c c o r d i n g t o (a.) stu d y or (b.) d e s i g n format 22 3. Components of the t a s k p e r f o r m i n g system 31 4. R e l a t i o n s h i p between luminance l e v e l and performance .37 5. Components of the v i s u a l f i e l d 39 6. G l a r e as a f u n c t i o n of area and l o c a t i o n of source ...49 7. Range of sky luminance a c c e p t a b l e w i t h a f i x e d l e v e l of supplementary l i g h t i n g 50 8. The t h r e e s o u r c e s of d a y l i g h t 72 9. D a y l i g h t i n g t e c h n i q u e s u s i n g the t h r e e s o u r c e s of d a y l i g h t 74 10. The luminance d i s t r i b u t i o n of the o v e r c a s t and the c l e a r sky 76 11. Summary of t e c h n i q u e s of d a y l i g h t a c c e s s 80 12. D a y l i g h t p e n e t r a t i o n and Waldram diagrams f o r p a r a l l e l and c r u c i f o r m l a y o u t s 82 13. Comparison among d i f f e r e n t b u i l d i n g l a y o u t s of e q u a l h e i g h t and d e n s i t y " 83 14. T a l l b l o c k s wide a p a r t ensure b e t t e r p e n e t r a t i o n of d a y l i g h t 84 15. D a y l i g h t a v a i l a b i l i t y f o r two b u i l d i n g l a y o u t s 85 16. The ERC i s co m p r i s e d of s u r f a c e s b oth above and below the working p l a n e 86 17. E x t e r i o r s u r f a c e s as secondary l i g h t s o u r c e s 89 18. B u i l d i n g form responses t o l i g h t 90 19. T y p i c a l b u i l d i n g s whose massing responds t o d a y l i g h t .91 20. An example of d a y l i g h t - r e s p o n s i v e massing and i t s r e s o l u t i o n i n d e t a i l 92 X 21. The e f f e c t of b u i l d i n g p l a n on d a y l i g h t a c c e s s 92 22. Examples of e x i s t i n g b u i l d i n g s whose l a y o u t responds t o d a y l i g h t i n g needs 93 23. A e r i a l view of A a l t o ' s F i n n i s h N a t i o n a l P e n s i o n s I n s t i t u t e 94 24. Examples of e x i s t i n g d a y l i t b u i l d i n g s w i t h a t r i u m p l a n s 96 25. Response t o d a y l i g h t i n g i n b u i l d i n g s t h a t must have a dominant n o r t h - s o u t h a x i s 100 26. Techniques f o r a d m i t t i n g s u n l i g h t i n t o i n t e r i o r s ....101 27. B u i l d i n g s u t i l i z i n g d a y l i g h t i n g a p e r t u r e s s e p a r a t e from view 105 28. A s k y l i g h t w i t h a l i g h t w e l l can d e l i v e r l i g h t deep i n t o i n t e r i o r s 107 29. D a y l i g h t i n g and s u n l i g h t i n g w i t h s t a n d a r d s k y l i g h t s .108 30. I n t e g r a t e d t o p l i g h t i n g examples 108 31. T y p i c a l t o p l i g h t i n g l a y o u t s 109 32. O b s t r u c t i o n s a t the bottom or the top of a d a y l i g h t i n g a p e r t u r e 111 33. O b s t r u c t i o n s at the massing s c a l e (a.) and the component s c a l e (b. ) 112 34. O b s t r u c t i o n s above d a y l i g h t i n g a p e r t u r e s due t o facade geometry 114 35. R e l a t i o n s h i p between o b s t r u c t i o n depth and d a y l i g h t p e n e t r a t i o n 115 36. O b s t r u c t i o n s a t d i f f e r e n t h e i g h t s above a d a y l i g h t i n g a p e r t u r e h a v i n g i d e n t i c a l e f f e c t on d a y l i g h t p e n e t r a t i o n 115 37. The e f f e c t of ground r e f l e c t a n c e on d a y l i g h t a c c e s s , w i t h an o b s t r u c t i o n above the d a y l i g h t i n g a p e r t u r e ..117 38. Summary of t r a d i t i o n a l t e c h n i q u e s p r o m o t i n g d a y l i g h t p e n e t r a t i o n 126 39. The i n f l u e n c e of s i z e and l o c a t i o n of the d a y l i g h t i n g a p e r t u r e on d a y l i g h t p e n e t r a t i o n 128 40. D a y l i g h t p e n e t r a t i o n w i t h h o r i z o n t a l o b s t r u c t i o n ....131 x i 41. D a y l i g h t p e n e t r a t i o n w i t h v e r t i c a l o b s t r u c t i o n 133 42. Terms used i n window t r a d e l i t e r a t u r e 143 43. E f f e c t of w a l l t h i c k n e s s on d a y l i g h t p e n e t r a t i o n and examples of t h i c k w a l l s 144 44. P l a n views of s p l a y e d jamb c o n f i g u r a t i o n s 145 45. E f f e c t of room geometry on d a y l i g h t p e n e t r a t i o n 147 46. The c o n t r i b u t i o n of the IRC t o the i l l u m i n a n c e w i t h i n a room 149 47. The i n f l u e n c e of room s u r f a c e r e f l e c t a n c e s on d a y l i g h t l e v e l s 150 48. Comparison of d a y l i g h t p e n e t r a t i o n a c h i e v e d by t r a d i t i o n a l and i n n o v a t i v e t e c h n i q u e s 153 49. Summary of i n n o v a t i v e t e c h n i q u e s promoting d a y l i g h t p e n e t r a t i o n 1 55 50. D a y l i g h t beaming mechanisms i n t e g r a t e d i n t o the b u i l d i n g e nvelope 1 56 . 5 1 . D a y l i g h t beaming mechanism as an e x t e r i o r a c c e s s o r y .158 52. D a y l i g h t beaming mechanism as an i n t e r i o r a c c e s s o r y .159 53. Beamed d a y l i g h t i n g d e s i g n s a t d i f f e r e n t l o c a t i o n s i n e x t e r i o r w a l l s 161 54. The components of a l i g h t s h e l f system 164 55. T y p i c a l l i g h t s h e l f c o n f i g u r a t i o n s 166 56. E l e v a t i o n a l t r e a t m e n t s of l i g h t s h e l v e s 168 57. The components of a p r i s m a t i c beamed d a y l i g h t i n g system 1 69 58. Use of p r i s m a t i c d a y l i g h t i n g system i n an o b s t r u c t e d s i t u a t i o n 1 70 59. E l e v a t i o n a l t r e a t m e n t s of p r i s m a t i c systems 172 60. Examples of e l e v a t i o n a l t r e a t m e n t s w i t h e x t e r i o r l o u v r e s 175 61. L a r g e - s c a l e beamed d a y l i g h t i n g from the top 177 62. Example of beaming mechanism added t o s t a n d a r d s k y l i g h t 1 78 x i i 63. H i g h l y o p t i m i z e d s k y l i g h t d e s i g n s 179 64. Summary of t e c h n i q u e s f o r i n t e r i o r space p l a n n i n g ...189 65. The t h r e e zones of d a y l i g h t p e n e t r a t i o n 190 66. A r e c e n t example of o f f i c e f l o o r p l a n h a v i n g c e l l u l a r o f f i c e s on the i n t e r i o r 195 67. Layout of c e l l u l a r o f f i c e s a t b u i l d i n g p e r i m e t e r t o en a b l e some d a y l i g h t p e n e t r a t i o n 197 68. D e t a i l i n g of g l a z e d p a r t i t i o n s f o r c e l l u l a r o f f i c e s a t b u i l d i n g p e r i m e t e r 198 69. A t e c h n i q u e f o r i n d i r e c t l y d a y l i g h t i n g i n t e r i o r a r e a s o b s t r u c t e d from d a y l i g h t i n g a p e r t u r e s by s o l i d p a r t i t i o n s 200 70. D e t a i l s t h a t i n t e g r a t e a c o u s t i c a l and d a y l i g h t i n g r e q u i r e m e n t s 201 71. Reducing b r i g h t n e s s extremes u s i n g t r a d i t i o n a l and i n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s 208 72. Summary of t e c h n i q u e s f o r c o n t r o l l i n g b r i g h t n e s s extremes 209 73. G l a r e r e d u c t i o n by f i l t e r i n g d u r i n g summer and w i n t e r 211 74. G l a r e c o n t r o l a t west or e a s t w a l l s w i t h t r e l l i s e s ..213 75. Optimum p o s i t i o n i n g of p l a n t i n g and of the e x t e r i o r r e f l e c t i n g s u r f a c e 214 76. D a y l i g h t i n g a p e r t u r e s on more than one s i d e reduces b r i g h t n e s s g r a d i e n t s 215 77. Heat a b s o r b i n g g l a s s as a sunshade 218 78. Luminous performance of v a r i o u s v e r t i c a l s h a d i n g d e v i c e s h a v i n g e q u i v a l e n t t h e r m a l performance 220 79. R e t u r n w a l l s on e a s t or west f a c a d e s can p r o v i d e s u n s c r e e n i n g w h i l e a l l o w i n g d a y l i g h t i n 221 80. Example of v e r t i c a l a d j u s t a b l e l o u v r e s on west facade 221 81. E g g c r a t e l o u v r e s b e i n g used on s o u t h e a s t f a c i n g windows 223 82. Luminous performance of v a r i o u s h o r i z o n t a l shading x i i i d e v i c e s h a v i n g e q u i v a l e n t t h e r m a l performance 225 83. R e f l e c t a n c e v a l u e s t h r o u g h g l a s s a t v a r i o u s a n g l e s of i n c i d e n c e 228 84. T i l t e d g l a z i n g as means of g l a r e and s o l a r heat g a i n c o n t r o l 229 85. A b u i l d i n g facade w i t h s l o p e d g l a s s and overhang ....230 86. I n c o r p o r a t i n g window t i l t a t massing or component s c a l e 231 87. The mechanism of g l a r e r e d u c t i o n by an i n t e r i o r l i g h t s h e l f 233 88. I n t e r i o r l i g h t s h e l v e s i n the Lockheed M i s s i l e s no. 157 b u i l d i n g •* 234 89. Examples of c o n t r a s t g r a d i n g 236 90. Summary of t e c h n i q u e s f o r i n t e g r a t i n g d a y l i g h t i n g w i t h e l e c t r i c a l l i g h t i n g 251 91. D e c i s i o n t r e e f o r o f f i c e l i g h t i n g 252 92. R e l a t i v e c o s t of t a s k / a m b i e n t and ambient systems ...253 93. Zones of v a r y i n g d a y l i g h t p e n e t r a t i o n i n a b u i l d i n g .258 94. Advantage of s o u r c e - s w i t c h i n g d e v i c e ..260 95. S c h e m a t i c s f o r v a r i o u s c o n t r o l d e v i c e s 261 96. A p p r o p r i a t e c o n t r o l s f o r v a r i o u s d a y l i g h t l e v e l s ....262 97. Range of p o s s i b l e s o l u t i o n s f o r e n e r g y - r e s p o n s i v e o f f i c e b u i l d i n g s 280 x i v Acknowledgement I w i s h t o extend my a p p r e c i a t i o n t o P r o f e s s o r Raymond J . C o l e f o r h i s p a t i e n t guidance and s t r i v i n g f o r e x c e l l e n c e . Much of the m e r i t t h i s paper has i s due t o him, a l t h o u g h i t s sh o r t c o m i n g s a r e o b v i o u s l y due t o my own l i m i t e d v i s i o n . I a l s o w i s h t o thank P r o f e s s o r C h a r l e s A. T i e r s , f o r the a d v i c e he gave i n the i n i t i a l s t a g e s of the work and f o r t a k i n g time to. review and comment on the m a n u s c r i p t . F i n a l l y , my thanks go t o my w i f e , C a t h a r i n e , and d a u g h t e r , Megan, f o r t h e i r c o n t i n u e d and c h e e r f u l s u p p o r t . 1 I . INTRODUCTION ono We were born of l i g h t . The seasons a r e f e l t t h r o u gh l i g h t . We o n l y know the w o r l d as i t i s evoked by l i g h t , and from t h i s comes the thought t h a t m a t e r i a l i s spent l i g h t . To me n a t u r a l l i g h t i s the o n l y l i g h t , because i t has mood--it p r o v i d e s a ground of common agreement f o r man--it p u t s us i n touch w i t h the e t e r n a l . N a t u r a l l i g h t i s the o n l y l i g h t t h a t makes a r c h i t e c t u r e a r c h i t e c t u r e . L o u i s Kahn 1 When i t comes t o d e s i g n — the d e s i g n of our environment, c i t i e s , b u i l d i n g s , houses, u t e n s i l s , c l o t h e s , f u r n i t u r e , c a r s and p l a n e s — t h e r e i s one o v e r r i d i n g t e s t : i s i t done w i t h a deep sense of commitment t o p e o p l e , a commitment i n the b r o a d e s t sense t o man i n a l l h i s c o m p l e x i t i e s - - h i s d e s i r e s , hopes, f e a r s , a n d , above a l l , h i s w e l l - b e i n g ? I t i s a s u r p r i s i n g l y s i m p l e t e s t . " Moshe S a f d i e 2 2 1 . NATURAL LIGHT AND ARCHITECTURE L i g h t g i v e s l i f e t o form, t o p a t t e r n , t o v o i d and s o l i d . A r c h i t e c t u r e i s the s h a p i n g , i n l i g h t , of v e s s e l s f o r human a c t i v i t i e s — m a d e of v o i d and s o l i d , p a t t e r n , form. The l i g h t of the s u n - - d i f f u s e d through sky and c l o u d s and r e f l e c t e d from the g r o u n d — h a s i n e v i t a b l y been the means of c e l e b r a t i n g the power and m a j e s t y , the drama and p l a y of a r c h i t e c t u r e , both on the e x t e r i o r and the i n t e r i o r of b u i l d i n g s . The use of n a t u r a l l i g h t f o r the l i g h t i n g of i n t e r i o r s p aces, w i t h the predominant g o a l of f a c i l i t a t i n g the performance of v i s u a l a c t i v i t i e s , we c a l l d a y l i g h t i n g . D a y l i g h t i n g i s c o e v a l w i t h a r c h i t e c t u r e . U n t i l as r e c e n t l y as s i x t y y e a r s ago, d a y l i g h t was the pre-eminent means of l i g h t i n g the i n t e r i o r of b u i l d i n g s . The need t o a l l o w d a y l i g h t i n t o b u i l d i n g i n t e r i o r s has n a t u r a l l y had an impact on m a s s i n g , l a y o u t and d e t a i l i n g of b u i l d i n g s . The e x t e n t of t h i s impact has been g r e a t e r i n b u i l d i n g t y p e s d e d i c a t e d t o v i s u a l l y demanding a c t i v i t i e s , such as i n d u s t r i a l b u i l d i n g s , h o s p i t a l s and o f f i c e b u i l d i n g s . T h i s t h e s i s e x p l o r e s the impact of d a y l i g h t i n g r e q u i r e m e n t s on the form and d e t a i l i n g of the modern o f f i c e b u i l d i n g . T h i s b u i l d i n g type was chosen, because i t i s the predominant type i n 3 the c o m m e r c i a l / i n s t i t u t i o n a l b u i l d i n g s e c t o r . F u r t h e r m o r e , energy use f o r o f f i c e b u i l d i n g s i s a s u b s t a n t i a l p e rcentage of the t o t a l b u i l d i n g s e c t o r use, and d a y l i g h t i n g can h e l p i n r e d u c i n g these c o s t s . L a s t l y , the n a t u r e of v i s u a l t a s k s i n o f f i c e s i s demanding enough t o o f f e r scope f o r t e s t i n g d a y l i g h t i n g p r i n c i p l e s and t e c h n i q u e s . 2. HISTORY OF DAYLIGHTING IN OFFICE BUILDINGS The h i s t o r y of d a y l i g h t i n g i n o f f i c e b u i l d i n g s may be d i v i d e d i n t o f o u r e r a s , as shown i n f i g u r e 1 . E x c l u s i v e use of d a y l i g h t i n g O f f i c e b u i l d i n g s became a s e p a r a t e b u i l d i n g t y p e , p h y s i c a l l y removed'from i n d u s t r i a l f a c i l i t i e s , soon a f t e r the onset of the I n d u s t r i a l R e v o l u t i o n i n the e a r l y 1800's 3. T h e i r number m u l t i p l i e d as the i n c r e a s i n g c o m p l e x i t y of o r g a n i z a t i o n s l e d t o a s t e a d i l y r i s i n g demand f o r management and c l e r i c a l p e r s o n n e l . By 1890, the t e l e p h o n e , the e l e c t r i c lamp and the e l e c t r i c e l e v a t o r had a l l been i n v e n t e d , and the f i r s t s t e e l frame h i g h -r i s e b u i l d i n g had been c o n s t r u c t e d i n New York C i t y " . These developments l a i d the groundwork f o r a r e v o l u t i o n i n the d e s i g n of l a r g e b u i l d i n g s and i n the appearance of c i t i e s . In t h i s p e r i o d , the depth ( i . e . the w i d t h i n p l a n ) of o f f i c e b u i l d i n g s was l i m i t e d by the d a y l i g h t p e n e t r a t i o n . W i t h the p r e v a l e n t c e i l i n g h e i g h t s , s a t i s f a c t o r y d a y l i g h t i n g c o u l d be o b t a i n e d t o a depth of about 6m. Thus, w i t h d o u b l e - l o a d e d 4 RETIRED IU.UNIIW LEVEL If ^ J SECTION SH0WIN6 INTERIOR LIGHT LEVELS. n < F • D A Y L I 6 H T C O N T R I B U T I O N , TOTAL HORIZONTAL UMIIMNC& EL£CTRlCAL LIGHTING ~ -~><L"" CONTRIBUTION "—" —4'* . .r* . . . . . . . . . i 9 . 5 m SECTION SHOWING INTERIOR LIGHT LEVELS TYPICAL PLAN a. TOTALLY DAYLIT BUILDING A L T E R N A T E P L A N S H A P E S £ •* 1 1 ! i TYPICAL PLAN b. R5.A.LI. 6UILDIN6 • | ^ ^ • - - L W T u i a n i i ^ n i i i i i w i w SECTION 6H0WINfi INTERIOR Ll&HT LD/ELS TOTAL HORIZONTAL ILLUMINANCE ELECTRICAL LIGHTING CONTRIBUTION -V~5 —^-- — •*• — PAVLlGHT COMTEK*. ZONE 9 - /2m iTYFl&Uj SECTION SHOWING INTERIOR LIGHT LEVELS I—DAYLIGHT CONTROL r - r — T i ZONE TYPICAL PLAN TYPICAL PLAN c. P. A.L.(TOTALLY AKTiFiciAiLY LIT) BUILDING d. MODERN DAYLIT BUILDING F i g u r e 1 - O f f i c e b u i l d i n g form and d a y l i g h t i n g i n h i s t o r y 5 c o r r i d o r s , the t y p i c a l b u i l d i n g depth g e n e r a t e d was thus 12 t o 1 5m5 . E a r l y o f f i c e b u i l d i n g s were r e s t r i c t e d i n h e i g h t t o 3-5 f l o o r s by the l i m i t a t i o n s of c o n s t r u c t i o n m a t e r i a l s and the l a c k of e l e v a t o r s . By the t u r n of the c e n t u r y , the s t e e l frame and e l e v a t o r s made p o s s i b l e t a l l e r o f f i c e b u i l d i n g s . However, t h e i r depth remained l i m i t e d , as b e f o r e , by d a y l i g h t p e n e t r a t i o n . The r e s u l t i n g b u i l d i n g s were thus t a l l and t h i n , s l a b l i k e ; w i t h r e c t a n g u l a r , 'U', 'X' shaped, or s i m i l a r f l o o r p l a n s ( f i g u r e 1 a ) . T r a n s i t i o n from d a y l i g h t i n g t o e x c l u s i v e e l e c t r i c l i g h t i n g In the two decades between the World Wars, t e c h n o l o g i c a l improvements i n e l e c t r i c a l l i g h t i n g l e d t o i t s p r o l i f e r a t i o n . A f t e r the Second World War, a system of l i g h t i n g known as Permanent Supplementary A r t i f i c i a l l y L i t I n t e r i o r s (PSALI) was proposed i n Europe f o r i n s t i t u t i o n a l and commercial b u i l d i n g s . I t endeavoured t o i n c r e a s e the depth of o f f i c e space by h a v i n g the a r e a s a t a d i s t a n c e from windows permanently l i t by e l e c t r i c l i g h t 6 . The added b e n e f i t s were the f e a s i b i l i t y of lower c e i l i n g h e i g h t s and a r e d u c t i o n i n the luminous g r a d i e n t from windows t o the b a c k 7 . The depth of u s e f u l space was extended t o about 9.5m, r e s u l t i n g i n an o v e r a l l b u i l d i n g w i d t h of 20 t o 24m 8 ( f i g u r e 1 b . ) . The concept of PSALI was exp e r i m e n t e d w i t h i n Europe f o r about a decade, but because of r a p i d l y c h a n g i n g t e c h n o l o g y , c o m p l e x i t y of the d e s i g n p r o c e s s , or perhaps p h i l o s o p h i c a l r e s i s t a n c e , i t was e v e n t u a l l y dropped i n 6 f a v o u r of the "North-American" system of a l l - e l e c t r i c l i g h t i n g 9 . E x c l u s i v e use of e l e c t r i c l i g h t A f t e r t h e Second World War, r a p i d p r o g r e s s i n m e c h a n i c a l and e l e c t r i c a l systems made p o s s i b l e the c r e a t i o n of a r t i f i c i a l l y c o n t r o l l e d e n v i r o n m e n t s . I n e x p e n s i v e e l e c t r i c i t y , u t i l i t y company a d v e r t i s i n g , and e n g i n e e r i n g z e a l , a l l c o n t r i b u t e d t o the d e s i g n of Permanently A r t i f i c i a l l y L i t (PAL) b u i l d i n g s 1 0 . C o n s i d e r a t i o n of n a t u r a l l i g h t i n g was not c o n s i d e r e d a c r i t e r i o n f o r c h o o s i n g the massing, f l o o r p l a n and depth of t h e s e b u i l d i n g s . As a r e s u l t , o f f i c e spaces 40m or g r e a t e r i n d e p t h became common 1 1 ( f i g u r e 1 c ) . L i g h t came t o be u n d e r s t o o d o n l y i n terms of l i g h t f i x t u r e s ; windows were reduced t o v i e w i n g a p e r t u r e s and a b s t r a c t d e s i g n elements on f a c a d e s ; the u s e r s had t o adapt t o the i n c o n v e n i e n c e s of any h e a t i n g or c o o l i n g problem these d e s i g n d e c i s i o n s c r e a t e d , and/or more equipment was i n t r o d u c e d t o c o u n t e r the n e g a t i v e e f f e c t s 1 2 . E l e c t r i c l i g h t s were used day and n i g h t , and e v e n t u a l l y e l e c t r i c l i g h t i n g , and the energy used t o remove the heat g e n e r a t e d by l i g h t i n g , became the l a r g e s t p o r t i o n s of t h e energy used i n o f f i c e b u i l d i n g s 1 3 , 1 " . I n t e g r a t i o n of d a y l i g h t w i t h e l e c t r i c l i g h t i n g The energy c r i s i s of 1973-74 has brought about changes i n a l l i n d u s t r i a l i z e d economies. In the o f f i c e b u i l d i n g s e c t o r , l i g h t i n g has been c l e a r l y i d e n t i f i e d as the most i m p o r t a n t energy c o n s e r v a t i o n item. Optimum b u i l d i n g depths f o r 7 d a y l i g h t i n g have been r e d i s c o v e r e d ( f i g u r e 1 d . ) , but advanced HVAC and l i g h t i n g t e c h n o l o g y now a l l o w s f l e x i b i l i t y i n t h i s r e g a r d . Energy r e s p o n s i v e , d a y l i t o f f i c e b u i l d i n g s d e s i g n e d s h o r t l y a f t e r the energy c r i s i s 1 5 were t y p i c a l l y p r e m i s e d on the id e a t h a t "the b u i l d i n g i s a l i g h t f i x t u r e t h a t can be e n g i n e e r e d t o a s t a t e of o p t i m a l p e r f o r m a n c e " 1 6 . More r e c e n t l y , i s s u e s of both l i g h t q u a l i t y and q u a n t i t y a re b e i n g a d d r e s s e d by many d e s i g n e r s . Many re c e n t p r o j e c t s have demonstrated t h a t n a t u r a l l i g h t can be a b e a u t i f u l , as w e l l as e f f i c i e n t , s o u r c e of l i g h t 1 7 . 3. REASONS FOR DAYLIGHTING There a r e many advantages t o d a y l i g h t i n g t h a t more than compensate f o r the e x t r a t i m e , p a t i e n c e and i n g e n u i t y needed t o i n t e g r a t e d a y l i g h t i n g c o n c e p t s w i t h o t h e r r e q u i r e m e n t s . These may be a d d r e s s e d under the f o l l o w i n g h e a d i n g s : i . C o n s i d e r a t i o n s of user s a t i s f a c t i o n i i . Economic c o n s i d e r a t i o n s i i i . S o c i o - p o l i t i c a l and e n v i r o n m e n t a l c o n s i d e r a t i o n s i v . P h i l o s o p h i c a l c o n s i d e r a t i o n s 8 3.1 C o n s i d e r a t i o n Of User S a t i s f a c t i o n D a y l i g h t i n f l u e n c e s v a r i o u s a s p e c t s of our b e i n g : our b o d i e s r e a c t t o the e n e r g i e s i n l i g h t , our eyes p e r c e i v e i t , our minds i n t e r p r e t the i n f o r m a t i o n and our emotions r e a c t t o t h e s e . W h i l e these i n f l u e n c e s a re h i g h l y i n t e r a c t i v e , t hey can n e v e r t h e l e s s be c o n s i d e r e d as a f f e c t i n g e s s e n t i a l l y e i t h e r the p r o d u c t i v i t y , c o m f o r t , or h e a l t h of b u i l d i n g u s e r s . The c o n s i d e r a t i o n of improved human s a t i s f a c t i o n i s c e n t r a l i n the d e s i g n of d a y l i t o f f i c e b u i l d i n g s . These i s s u e s w i l l be d i s c u s s e d a t some l e n g t h i n c h a p t e r 2. 3.2 Economic C o n s i d e r a t i o n s Whatever the m e r i t of d a y l i g h t i n g may be i n terms of e n v i r o n m e n t a l b e n e f i t s - - b o t h a t the human and at the s o c i e t a l s c a l e - - e c o n o m i c b e n e f i t s on a p r o j e c t by p r o j e c t b a s i s must be demonstrated, i n or d e r f o r i t t o g a i n a c c e p t a n c e . Economic b e n e f i t s f a l l under one of the f o l l o w i n g : i . s a v i n g s i n e l e c t r i c a l energy i i . s a v i n g s i n peak demand charge i i i . f a i l u r e t o l e r a n c e i v . i n c r e a s e d b u i l d i n g v a l u e v. l e g a l and t a x a t i o n i n c e n t i v e s S a v i n g s i n e l e c t r i c a l energy W i d e l y p u b l i s h e d l i t e r a t u r e by r e s e a r c h e r s , a r c h i t e c t s , 9 i l l u m i n a t i n g e n g i n e e r s and m e c h a n i c a l e n g i n e e r s i n d i c a t e s t h a t d a y l i g h t i n g can p r o v i d e s u b s t a n t i a l s a v i n g s i n the e l e c t r i c a l energy used i n o f f i c e b u i l d i n g s 1 8 , 1 9 , 2 0 , 2 1 , 2 2 , 2 3 . L i g h t i n g i s a dominant l o a d i n o f f i c e b u i l d i n g s . Average f i g u r e s f o r N o r t h America i n d i c a t e t h a t e l e c t r i c a l energy used i n these b u i l d i n g s a t t r i b u t a b l e t o l i g h t i n g i s between 40750% of annual energy c o n s u m p t i o n 2 " . For m i l d c l i m a t e s l i k e C a l i f o r n i a , t h i s f i g u r e can be up t o 60% of t o t a l o n - s i t e energy c o n s u m p t i o n 2 5 . For c o l d c l i m a t e s , because of the e x t r a h e a t i n g l o a d , the per c e n t a g e f i g u r e s a t t r i b u t a b l e t o l i g h t i n g may be l e s s per u n i t f l o o r a r e a , but the a b s o l u t e f i g u r e s a re s i m i l a r 2 6 . When we l o o k a t energy c o s t s , r a t h e r than energy u n i t s , the importance of l i g h t i n g becomes even more e v i d e n t . H e a t i n g , the o t h e r main component of the energy l o a d i n o f f i c e b u i l d i n g s , i s g e n e r a l l y p r o v i d e d by f o s s i l f u e l s on s i t e , whereas l i g h t i n g and a i r c o n d i t i o n i n g use e l e c t r i c i t y , which i s more e x p e n s i v e per u n i t of energy and i n c u r s peak demand charges t h a t f u r t h e r add to i t s c o s t . Thus, l i g h t i n g c l e a r l y becomes the major t a r g e t f o r energy c o n s e r v a t i o n i n o f f i c e b u i l d i n g s . S a v i n g s due t o a r e d u c t i o n i n peak demand Owners of o f f i c e b u i l d i n g s pay f o r t h e i r e l e c t r i c i t y not o n l y i n energy consumed but a l s o f o r t h e i r .peak power demand, c a l l e d a demand c h a r g e . T h i s demand charge r e f l e c t s the c o s t i n c u r r e d by the u t i l i t y i n h a v i n g t o p r o v i d e e l e c t r i c a l g e n e r a t i n g c a p a c i t y s u f f i c i e n t t o meet the peak demand; t h i s g e n e r a t i n g equipment i s i n e v i t a b l y i d l e a t o t h e r than peak 1 0 demand t i m e s 2 7 . Demand c h a r g e s 2 8 a r e a s i g n i f i c a n t f r a c t i o n of t h e t o t a l e l e c t r i c a l b i l l 2 9 , 3 0 . Most of t h i s demand c h a r g e i s money t h a t can be s a v e d by t h e b u i l d i n g owner w i t h a p p r o p r i a t e m i c r o p r o c e s s o r c o n t r o l s , o f f - p e a k t h e r m a l s t o r a g e , o n - s i t e power g e n e r a t i o n a n d / o r w i t h d a y l i g h t i n g 3 1 . E l e c t r i c a l c o n s u m p t i o n i n o f f i c e b u i l d i n g s t y p i c a l l y peaks d u r i n g summer m o n t h s 3 2 , when c o o l i n g l o a d s a r e a t a maximum. T h i s c o i n c i d e s w i t h t h e t i m e o f most abundant d a y l i g h t : t h e sun i s up f o r more h o u r s , o u t d o o r i l l u m i n a t i o n l e v e l s a r e h i g h e r and c l e a r s k i e s a r e more p r e v a l e n t . By s u b s t i t u t i n g p a r t o f t h e e l e c t r i c a l l i g h t i n g component w i t h d a y l i g h t , peak power demand can be c o n s i d e r a b l y r e d u c e d 3 3 . A s e c o n d a r y e f f e c t of a r e d u c t i o n e l e c t r i c a l l i g h t i n g i s a p r o p o r t i o n a t e r e d u c t i o n i n t h e h e a t - o f - l i g h t component o f t h e c o o l i n g l o a d : e v e r y watt r e d u c t i o n i n e l e c t r i c a l l i g h t i n g r e s u l t s i n 1/2 w a t t r e d u c t i o n i n t h e c o o l i n g l o a d 3 " . However, t h i s r e d u c t i o n can o n l y be r e a l i z e d i f a p p r o p r i a t e s t e p s a r e t a k e n , a t t h e same t i m e , t o m i n i m i z e s o l a r h e a t g a i n . B r y a n 3 5 has i n d i c a t e d t h a t i n many i n s t a n c e s , t h e s a v i n g s i n peak demand c h a r g e t h r o u g h d a y l i g h t i n g can be s i g n i f i c a n t l y g r e a t e r t h a n s a v i n g s i n e n e r g y c o s t s . S e l k o w i t z 3 6 and Bobenhausen and L e w i s 3 7 have c a l c u l a t e d t h a t between t y p i c a l l y 10-20% o f peak power s a v i n g s c a n be a c h i e v e d by d a y l i g h t i n g c o n v e n t i o n a l l y d e s i g n e d b u i l d i n g s . F a i l u r e t o l e r a n c e o f d a y l i t b u i l d i n g s Our b u i l d i n g s , e s p e c i a l l y the l a r g e r ones, are dependent on 11 complex, c e n t r a l i z e d energy systems t o meet user needs. The e l e c t r i c a l g r i d i s one of these systems. D i s r u p t i o n s , a l t h o u g h not common, have g e n e r a t e d l a r g e s c a l e d i s a s t e r s when they have happened i n r e c e n t y e a r s . S e l k o w i t z 3 8 w r i t e s c o n c e r n i n g f a i l u r e t o l e r a n c e of d a y l i t b u i l d i n g s : D a y l i g h t i n g , as w e l l as p a s s i v e s o l a r h e a t i n g and c o o l i n g , i s a d e s i g n o p t i o n w hich, a t the s c a l e of a s i n g l e b u i l d i n g , r e v e r s e s the t r e n d toward g r e a t e r r e l i a n c e on remote c e n t r a l i z e d systems. As such, i t has a f l e x i b i l i t y and a degree of f a i l u r e t o l e r a n c e t h a t appears t o be i m p o r t a n t , but which i s d i f f i c u l t to q u a n t i f y . A c t i v i t i e s i n a b u i l d i n g w i t h d a y l i g h t i n g w i l l be l e s s s u b j e c t t o d i s r u p t i o n from a power f a i l u r e or brownout than th o s e r e l y i n g e n t i r e l y on e l e c t r i c i t y f o r i l l u m i n a t i o n . S e l k o w i t z has made p r e l i m i n a r y c a l c u l a t i o n s on the c o s t of d i s r u p t i o n due t o a power l o s s on worker p r o d u c t i v i t y 3 9 . With p r e s e n t worker's s a l a r i e s and energy c o s t s f o r a t y p i c a l o f f i c e s i t u a t i o n , the s a v i n g s r e s u l t i n g from even a s i n g l e hour's p r o d u c t i v e work d u r i n g a power l o s s a r e s i g n i f i c a n t . In f a c t , though energy s a v i n g s a r e not i n s i g n i f i a n t , the s a v i n g s due t o even t h a t one hour i s e q u i v a l e n t i n d o l l a r v a l u e t o energy s a v i n g s f o r a whole y e a r . S a v i n g s i n l i f e c y l c l e c o s t s D a y l i g h t i n g schemes are p o t e n t i a l l y e c o n o m i c a l a t p r e s e n t energy c o s t s f o r a l a r g e number of o f f i c e b u i l d i n g s , i f the l i f e c y c l e c o s t of the b u i l d i n g i s used as a c r i t e r i o n . These schemes a r e p e n a l i z e d by s h o r t term investment g o a l s " 0 . For some of the more e l a b o r a t e d a y l i g h t i n g s t r a t e g i e s (eg. beamed d a y l i g h t i n g ) economic v i a b i l i t y may have t o tak e i n t o account 1 2 the i n c r e a s e d v a l u e of the b u i l d i n g due t o an improved v i s u a l environment and consequent i n c r e a s e i n worker p r o d u c t i v i t y . Lam, whose c o n s u l t i n g f i r m has e x t e n s i v e d a y l i g h t i n g e x p e r i e n c e , has s t a t e d t h a t w i t h a p p r o p r i a t e i n t e g r a t i o n of a r c h i t e c t u r e , s t r u c t u r e and s e r v i c e s , i t i s p o s s i b l e to r e a l i z e even f i r s t c o s t s a v i n g s f o r e l a b o r a t e l y d a y l i t p r o j e c t s " 1 . T h i s i s c o n f i r m e d by Bryan and B a z j a n a c " 2 . Such s u c c e s s undoubtedly depends l a r g e l y on the s k i l l s of the c o n s u l t a n t s and t h e i r c o - o p e r a t i o n . N o t w i t h s t a n d i n g Lam's comments, many a u t h o r i t i e s i n the f i e l d concede t h a t e l a b o r a t e d a y l i g h t i n g schemes w i l l u s u a l l y c a r r y a f i r s t c o s t p e n a l t y " 3 . With l e s s e l a b o r a t e schemes, even w i t h o u t optimum i n t e g r a t i o n between a r c h i t e c t u r e , s t r u c t u r e and s e r v i c e s , net s a v i n g s i n i n i t i a l c a p i t a l c o s t may be r e a l i z e d i n a d d i t i o n t o energy s a v i n g s ' throughout the l i f e of the b u i l d i n g . T h i s i s because the e x t r a c o s t of dimmers and c i r c u i t i n g i s more than o f f s e t by reduced c h i l l e r s i z e s and s m a l l e r HVAC d i s t r i b u t i o n components"". As d a y l i g h t i n g d e s i g n e x p e r t i s e w i t h i n the p r o f e s s i o n s i n c r e a s e s , as the t e c h n o l o g y matures, as the c o n s t r u c t i o n i n d u s t r y becomes more f a m i l i a r w i t h d a y l i g h t i n g c o n c e p t s , and as the c o s t of c o n v e n t i o n a l energy s o u r c e s c o n t i n u e s t o e s c a l a t e , the l i f e c y c l e c o s t of d a y l i g h t i n g schemes w i l l become more and more f a v o u r a b l e . I n c r e a s e d b u i l d i n g v a l u e An i n c r e a s e i n b u i l d i n g v a l u e due t o improved e n v i r o n m e n t a l c o n d i t i o n s - - a s would be i n the case of a w e l l d e s i g n e d d a y l i t . 13 b u i l d i n g - - c a n be t a n g i b l e , but not r e a d i l y q u a n t i f i a b l e . An i n c r e a s e d b u i l d i n g v a l u e can be dem o n s t r a t e d i f the improved e n v i r o n m e n t a l c o n d i t i o n s can t r a n s l a t e , on the s p e c u l a t i v e market, i n t o h i g h e r r e n t a l v a l u e ; or i n p e r c e p t i b l e g a i n i n p r o d u c t i v i t y , f o r the owner-tenant, due t o i n c r e a s e d worker w e l l - b e i n g . Workers' enthusiasm f o r the luminous environment i n some d a y l i t b u i l d i n g s has been noted i n the l i t e r a t u r e " 5 . I f t h i s e nthusiasm can be demonstrated t o r e s u l t i n i n c r e a s e d w e l l - b e i n g and h i g h e r p r o d u c t i v i t y , then t h i s b e n e f i t w i l l c e r t a i n l y i n c r e a s e the v a l u e of the b u i l d i n g . Because more than 90% of o v e r a l l c o s t s of o p e r a t i n g a commercial e n t e r p r i s e goes t o s a l a r i e s , w i t h o n l y about 8% a c c o u n t i n g f o r the c o n s t r u c t i o n and o p e r a t i o n of the b u i l d i n g , an improvement of worker p r o d u c t i v i t y of o n l y 6 1/2% would be c o s t e f f e c t i v e even i f i t q u a d r u p l e d the c o s t of the b u i l d i n g 4 6 . D a y l i t commercial b u i l d i n g s can a l s o be shown t o have an i n c r e a s e d v a l u e because, u s i n g l e s s e l e c t r i c a l energy, they a f f o r d a degree of p r o t e c t i o n from i n f l a t i o n and e s c a l a t i n g f u e l p r i c e s * 7 . S o c i a l a t t i t u d e s change, sometimes r a p i d l y . The i n c r e a s e d f r u s t r a t i o n e x p e r i e n c e d by workers from many e n v i r o n m e n t a l f a c t o r s i n p r e s e n t - d a y o f f i c e s 4 8 , 4 9 , 5 0 , may, i n a few y e a r s , r a d i c a l l y a l t e r the v a l u e we g i v e t o p a s s i v e e n v i r o n m e n t a l t e c h n o l o g i e s . P r e f e r e n c e may s h i f t s t r o n g l y towards t h e s e p a s s i v e e n v i r o n m e n t a l s o l u t i o n s , i n c l u d i n g d a y l i g h t i n g . 1 4 L e g a l and t a x a t i o n i n c e n t i v e s Two major l e g a l d e v i c e s may g r e a t l y i n c r e a s e the use of d a y l i g h t i n g : i . i n c e n t i v e s i n the form of s u b s i d i e s or tax breaks i i . mandatory d a y l i g h t i n g r e q u i r e m e n t s i n the form of z o n i n g by-laws and b u i l d i n g codes I n c e n t i v e s may c o n s i s t of l o a n s , g r a n t s , income tax r e b a t e s , e t c . f o r d a y l i g h t i n g components. Government a s s i s t a n c e and r e g u l a t i o n can do a g r e a t d e a l i n overcoming the s h o r t term d i s a d v a n t a g e s of c o n c e p t s - - s u c h as d a y l i g h t i n g - - t h a t c l e a r l y p r o v i d e l o n g term b e n e f i t s . These would be s i m i l a r t o tax c r e d i t s , e t c . a v a i l a b l e f o r p a s s i v e s o l a r h e a t i n g i n many s t a t e s of U.S.A. I t has been s u g g e s t e d 5 1 t h a t some u t i l i t i e s c o u l d p r o f i t a b l y s u b s i d i z e the c o s t of dimmers, b a l l a s t s and c i r c u i t r y a s s o c i a t e d w i t h d a y l i g h t i n g schemes, as they would thus not need t o add t o t h e i r peak demand c a p a c i t y ; the payback f o r the u t i l i t i e s f o r t h i s investment would be e x c e l l e n t — a b o u t 2-4 y e a r s 5 2 . C o d i f i c a t i o n i s a n o t h e r d e v i c e t h a t w i l l i n e v i t a b l y i n c r e a s e the use of d a y l i g h t i n g . Minimum d a y l i g h t i n g s t a n d a r d s f o r a l l b u i l d i n g t y p e s , as w e l l as f o r urban p l a n n i n g , were c o d i f i e d i n G r e a t B r i t a i n i n t h e 1940s t h r o u g h 6 0 s 5 3 , 5 " , 5 5 and r e s u l t e d i n w i d e s p r e a d use of d a y l i g h t i n b u i l d i n g s . No such s t a n d a r d s have been adopted i n C a n a d a 5 6 . The C a l i f o r n i a Energy Commission has r e c e n t l y d e v e l o p e d 15 Energy E f f i c i e n c y S tandards for. n o n - r e s i d e n t i a l b u i l d i n g s . One major method p r e s c r i b e d f o r r e d u c i n g energy usage i s by d a y l i g h t i n g 5 7 . T h i s w i l l have the e f f e c t of c r e a t i n g a g r e a t e r awareness by both the d e s i g n p r o f e s s i o n a l s and d e v e l o p e r s about the p o t e n t i a l s of d a y l i g h t i n g . I f energy budgets f o r new commercial b u i l d i n g s become mandatory i n more j u r i s d i c t i o n s , and e s p e c i a l l y i f minimum d a y l i g h t i n g s t a n d a r d s w i l l be c o d i f i e d , d a y l i g h t i n g w i l l e n t e r i n t o the mainstream of d e s i g n p r a c t i c e . In 1982, d a y l i g h t i n g c o n s i d e r a t i o n s became mandated as p a r t of z o n i n g r e g u l a t i o n s of Midtown New York C i t y . The c i t y p l a n n i n g department used d a y l i g h t a v a i l a b i l i t y i n s i d e b u i l d i n g s and on the s t r e e t , as a major c r i t e r i o n f o r c o n t r o l l i n g b u i l d i n g b u l k 5 8 , 5 9 . The k i n d of r e g u l a t i o n s used f o r New York, o n l y c r e a t e s the p o t e n t i a l f o r , but does not g u a r a n t e e , a s e n s i t i v e urban i n f r a s t r u c t u r e . N e v e r t h e l e s s , i t can be expected t h a t t h r o u g h the p r o c e s s of mandating d a y l i g h t i n g c o n s i d e r a t i o n s , the m u l t i f a c e t e d b e n e f i t s of d a y l i g h t i n g w i l l become more w i d e l y apprec i a t e d . 3.3 S o c i o - p o l i t i c a l And E n v i r o n m e n t a l C o n s i d e r a t i o n s P a s s i v e e n v i r o n m e n t a l t e c h n o l o g i e s — a l s o termed " s o f t energy p a t h s " 6 0 - - o f which d a y l i g h t i n g i s a p a r t i c u l a r form, do not have the l a r g e s c a l e n e g a t i v e e n v i r o n m e n t a l , economic and s o c i o - p o l i t i c a l consequences t h a t c e n t r a l i z e d c o a l , o i l , or n u c l e a r based energy s y s t e m s — " h a r d energy p a t h s " - - h a v e 6 1 . D a y l i g h t i n g i s t h e r e f o r e a r e a l , i f humble, c o n t r i b u t i o n t o the r e s o l u t i o n of these l a r g e r problems. D a y l i g h t i n g of commercial 1 6 b u i l d i n g s e n a b l e s : i . r e d u c t i o n i n a d d i t i o n a l e l e c t r i c a l u t i l i t y g e n e r a t i o n c a p a c i t y i i . r e d u c t i o n of dependence on imported f o s s i l f u e l i i i . r e d u c t i o n of dependence on c e n t r a l i z e d energy d i s t r i b u t i o n networks S c h u m a c h e r 6 2 , B o c k r i s 6 3 , L o v i n s 6 " and most r e c e n t l y , L o v i n s and L o v i n s 6 5 , have d i s c u s s e d a t l e n g t h the l a r g e s c a l e i m p l i c a t i o n s of energy use s t r a t e g i e s . 3.4 P h i l o s o p h i c a l C o n s i d e r a t i o n s You get an o r d e r from the s c h o o l b o a r d t h a t s a y s , 'We have a g r e a t idea.' We s h o u l d not put windows i n the s c h o o l , because the c h i l d r e n need w a l l space f o r t h e i r p a i n t i n g s , and a l s o windows can d i s t r a c t from the t e a c h e r . ' Now, what t e a c h e r d e s e r v e s t h a t much a t t e n t i o n ? I'd l i k e t o know. Because a f t e r a l l , the b i r d o u t s i d e , the person s c u r r y i n g f o r s h e l t e r i n the r a i n , the l e a v e s f a l l i n g from the t r e e , the c l o u d s p a s s i n g by, the sun p e n e t r a t i n g : these a r e a l l g r e a t t h i n g s . They are l e s s o n s i n t h e m s e l v e s . Windows are e s s e n t i a l t o the s c h o o l . You a r e made from l i g h t , and t h e r e f o r e you must l i v e w i t h the sense t h a t l i g h t i s i m p o r t a n t . . . Without l i g h t t h e r e i s no a r c h i t e c t u r e . 6 6 In the above passage, L o u i s Kahn t a l k s about s c h o o l s , but what he says i s a r c h e t y p a l and h o l d s t r u e , i n e s s e n c e , about any b u i l d i n g w i t h i n which p e o p l e spend t h e i r l i v e s . Good a r c h i t e c t u r e e x h i b i t s a commitment t o the w e l l - b e i n g — i n the b r o a d e s t sense of the word--of the p e o p l e whose l i v e s i t a f f e c t s . 1 7 D a y l i g h t and s u n l i g h t t o u c h deep chords w i t h i n us. The rhythm of day and n i g h t i s a c o n s t a n t reminder of an o r d e r i n the cosmos t h a t t r a n s c e n d s the more immediate chaos on e a r t h . The m i r a c l e of a n n u a l r e b i r t h of p l a n t l i f e i s t r i g g e r e d by the sun's r a y s and s u s t a i n e d by i t s e n e r g i e s . No two days a r e a l i k e i n c h a r a c t e r - - a reminder of i n e v i t a b l e changes i n our l i v e s , w i t h i n a framework of o r d e r l y rhythm. D a y l i g h t i s a v a i l a b l e t o a l l p e o p l e - - i t can be shared and i s n o t , as a r e s u l t , e x h a u s t e d — r e m i n d i n g us t h a t c o - o p e r a t i o n can t r a n s c e n d c o m p e t i t i o n . F i n a l l y , b r i n g i n g d a y l i g h t i n d o o r s can h e l p c e l e b r a t e the beauty of the w o r l d we l i v e i n - - a c e l e b r a t i o n t h a t can be a p o w e r f u l a n t i d o t e t o the g l o b a l t u r m o i l , which b e s e t s our t i m e s . 4. SCOPE OF THESIS 4.1 G o a l Of T h e s i s W i t h the re-emergence of d a y l i g h t i n g as a v i a b l e method of i n t e r i o r i l l u m i n a t i o n and energy c o n s e r v a t i o n s t r a t e g y i n o f f i c e b u i l d i n g s , t h e r e has been a tremendous body of i n f o r m a t i o n emerging on a l l f a c e t s of the problem. Y e t , t h e r e has been t o d a t e no p u b l i s h e d work on e s t a b l i s h i n g a comprehensive c o n c e p t u a l framework f o r d a y l i g h t i n g t e c h n i q u e s 6 7 . At the p r e s e n t s t a g e of the c o l l e c t i v e p r o f e s s i o n a l e x p e r i e n c e , e d u c a t i n g the i n t u i t i o n i s an i m p o r t a n t p a r t of the p r o c e s s of d a y l i g h t i n g d e s i g n 6 8 . T h i s t h e s i s p r o v i d e s a 18 framework f o r d a y l i g h t i n g p r i n c i p l e s and t e c h n i q u e s a s s i s t i n e d u c a t i n g the d e s i g n e r ' s i n t u i t i o n , as stone to d e s i g n i n g w i t h d a y l i g h t . 4.2 S t r u c t u r e Of T h e s i s The t h e s i s examines the f o l l o w i n g : i . p r i n c i p l e s of d e s i g n f o r the v i s u a l environment i i . c o n c e p t u a l framework f o r d a y l i g h t i n g t e c h n i q u e s i i i . i n t e g r a t i o n of d a y l i g h t i n g i n d e s i g n which w i l l a s t e p p i n g -The i n t e r i o r v i s u a l environment Design w i t h d a y l i g h t i n g can o n l y be a c c o m p l i s h e d i f the g o a l s of d a y l i g h t i n g are e x p l i c i t . These g o a l s can be e x p r e s s e d i n terms v i s u a l q u a l i t y p a r a m e t e r s . Chapter 2 t h e r e f o r e p r o v i d e s an o v e r v i e w of the p arameters which a r e of p r i m a r y importance i n d a y l i g h t i n g . A c o n c e p t u a l framework f o r d a y l i g h t i n g t e c h n i q u e s The e s s e n t i a l problem of d e s i g n i n g a d a y l i t space a r i s e s from two f a c t s : i . D a y l i g h t o r i g i n a t e s o u t s i d e the space b e i n g l i t i i . D a y l i g h t i s v a r i a b l e The s c i e n c e and a r t of d a y l i g h t i n g c o n s i s t s l a r g e l y of r esponses t o t h e s e two i s s u e s i n terms of d e s i g n and c o n s t r u c t i o n t e c h n i q u e s whose aim i s b r i n g i n g d a y l i g h t i n t o i n t e r i o r s under c o n t r o l l e d c o n d i t i o n s and compensating f o r i t s 1 9 v a r i a b i l i t y . These t e c h n i q u e s can be c l a s s i f i e d as f o l l o w s : 1. Techniques aimed at m a x i m i z i n g d a y l i g h t p o t e n t i a l : i . p r o v i d i n g a c c e s s t o a v a i l a b l e d a y l i g h t through massing, l a y o u t , e t c . i i . p r o v i d i n g a p e r t u r e s through which d a y l i g h t can e n t e r i n t o the b u i l d i n g i n t e r i o r i i i . p l a n n i n g the i n t e r i o r space t o t a k e advantage of i n t e r i o r d a y l i g h t . 2. Techniques aimed at c o n t r o l of d a y l i g h t and i t s i n t e g r a t i o n w i t h e l e c t r i c a l l i g h t i n g : i . c o n t r o l l i n g b r i g h t n e s s extremes i i . i n t e g r a t i n g w i t h e l e c t r i c a l l i g h t i n g - The main body of the t h e s i s c o n s i s t s of a range of these t e c h n i q u e s , o r g a n i z e d i n a m a t r i x . One d i m e n s i o n of t h i s m a t r i x l i s t s the o b j e c t i v e s b e i n g aimed a t , as o u t l i n e d above. The o t h e r d i m e n s i o n of the m a t r i x i s t h a t of the s c a l e b e i n g c o n s i d e r e d . S c a l e thus encompasses p r o g r e s s i v e l y more s p e c i f i c c o n c e r n s : s i t e p l a n n i n g ( i n c l u d i n g l a n d s c a p i n g and b u i l d i n g c l u s t e r i n g ) ; b u i l d i n g c o n f i g u r a t i o n ( i n c l u d i n g massing and p l a n ) ; b u i l d i n g component; and b u i l d i n g i n t e r i o r . The " s c a l e " d imension of the m a t r i x e n a b l e s any t e c h n i q u e under a p a r t i c u l a r o b j e c t i v e t o be s o r t e d a c c o r d i n g t o i t s l e v e l of g e n e r a l i t y , and hence, the s t a g e at which i t w i l l be c o n s i d e r e d i n d e s i g n 6 9 . T a b l e I shows the complete m a t r i x . In the c h a p t e r s t h a t d e s c r i b e the t e c h n i q u e s , the format used i s t h a t of g r o u p i n g them by o b j e c t i v e , and under each S C A L E 0 6 J E C T I V E S SITE PLANNING BUILDING CONFIGURATION BUILDING COMPONENT BUILDING INTERIOR DAYLIGHT ACCESS ' BUILDING CLUSTERING • EXTERIOR SURFACES • BUILDING MASSING • BUILDING LAYOUT • ATRIA • WORTH AND SOUTH ORIENTATION • INTERIOR SUNLIGHT • DAYLI6HTIN6 SEPARATE FROMVEV • DAYLIGHTING FROM THE TOP •06S1RUCTI0NS DAYLIGHT PENE-TRATION • CONFIGURATION AND LOCATION OF DAYL. APERTURE • GLA2IN6 MATERIAL SELECTION •MAINTENANCE FACTOR •NET GLAZING AREA • DEPTH & DETAIL'S OF WALL AROUND DAYL. APERT. • OOM GEOMETRY •INTERIOR REFLECTANCES •DEEP DAYLIGHT'6 THROUGH VIEW WINDOWS • DEEP DAYLIGHT& THR.WALL APERT. ABOVE EYE LEVEL • DEEP DAYLIGHT'6 THROUGH ROOF APERTURES SPACE PLANNING • LOCATION OF ACTIVITIES • OPEN PLAN INTERIOR • LOCATION OF CELLULAR OFFICES • DETAILING OF CELLULAR OFFICES • DAYLIGHTING. AND ACOUSTICS CONTROL OF BRIGHT-NESS • LANDSCAPES FOR GLARE CONTRA • DAYLIGHTING FROM MORE THAN ONE DIRECTION • CLARE/SOLAR HEAT CONTROL - EAST & VEST • GLARE/SOLAR HEAT CONTROL - SOUTH •GLARE CONTROL - NORTH •GLAZING TILT •INTERIOR LIGHTSHELVES •CONTRAST GRADING • LI&HT-COLOURED SURFACES INTEGRA-TION WITH ELECTRIC, LIGHT • LIGHTING PHILOSOPHY • FIXTURE CIRCUITING • AUTOMATIC CONTROLS T a b l e I - M a t r i x of d a y l i g h t i n g t e c h n i q u e s 2 1 o b j e c t i v e , examining t e c h n i q u e s i n t u r n , i n o r d e r of d e c r e a s i n g s c a l e . T h i s o r g a n i z a t i o n i s shown s c h e m a t i c a l l y i n f i g u r e 2 a. A c c o r d i n g t o Ubbelohde et a l . 7 0 , t h i s type of format i s a p p r o p r i a t e f o r l e c t u r e s and st u d y : i t f a c i l i t a t e s the u n d e r s t a n d i n g o f , and d e v e l o p i n g r e l a t i o n s h i p s f o r , s e v e r a l p r i n c i p l e s i n t u r n . C h a p t e r s 3, 4 and 5 examine a range of t e c h n i q u e s t h a t aim at m a x i m i z i n g d a y l i g h t p o t e n t i a l . Techniques f o r p r o m o t i n g d a y l i g h t a c c e s s , f o r promoting d a y l i g h t p e n e t r a t i o n , and f o r im p r o v i n g i n t e r i o r space o r g a n i z a t i o n a re t r e a t e d i n t u r n , i n an o r d e r of d e c r e a s i n g s c a l e . C h a p t e r s 6 c o n s i s t s of t e c h n i q u e s f o r c o n t r o l l i n g d a y l i g h t : methods of a v o i d i n g b r i g h t n e s s extremes i n g e n e r a l , and g l a r e i n p a r t i c u l a r , a r e examined. Chapter 7 examines the c o - o r d i n a t i o n and i n t e g r a t i o n of d a y l i g h t w i t h e l e c t r i c l i g h t i n g : the s a l i e n t f e a t u r e s of s u c c e s s f u l l y i n t e g r a t e d d a y l i g h t i n g / e l e c t r i c a l l i g h t i n g d e s i g n s a r e ov e r v i e w e d . D a y l i g h t i n g and the p r o c e s s of d e s i g n By c o n t r a d i s t i n c t i o n t o the study s i t u a t i o n , the d e s i g n p r o c e s s u n f o l d s from the g e n e r a l t o the s p e c i f i c , and from l a r g e r t o s m a l l e r s c a l e , w i t h a l l o b j e c t i v e s b e i n g g i v e n some c o n s i d e r a t i o n a t each s t e p 7 1 , 7 2 . F u r t h e r m o r e , the d e s i g n p r o c e s s i s i t e r a t i v e , and a t h i r d d i m e n s i o n emerges i n the m a t r i x : i t c o n s i s t s of the v a r i o u s s t a g e s of d e s i g n — c o n c e p t u a l , s c h e m a t i c , d e s i g n d e v e l o p m e n t 7 3 . For d e s i g n p u r p o s e s , t h e r e f o r e , the m a t r i x would be a r r a n g e d as shown i n f i g u r e 2 b. 22 S C A L E > o u> —1 o A | & C | D 1 t> Ktr SEQUENCE OF'TECHNIQUES DUR1N6 LEAF>N)N)<3 STAGE ( SEQUENCE FOLLOWED IN THE THESIS) S C A L E > 2. o -> O 3. A II b f c t > • I \ 7 7 7 SEQUENCE OF TECHNIQUES DURING DE.SIGN STA&E DE5I6N FIN AL12ATI0N S T A G E DESIGN DEVELOPMENT S T A G E SCHEMATIC D E S I G N STAGE F i g u r e 2 - M a t r i x a r r a n g e d a c c o r d i n g t o (a.) study or (b.) d e s i g n format 23 Chapter 8 o u t l i n e s how d a y l i g h t i n g c o n c e p t s may be a s s i m i l a t e d i n t o the d e s i g n p r o c e s s . An assessment of d a y l i g h t i n g d e s i g n t o o l s i s f i r s t g i y e n . T h i s i s f o l l o w e d by o b s e r v a t i o n s on the i n t e g r a t i o n of d a y l i g h t i n g i n t o the o v e r a l l d e s i g n p r o c e s s . Chapter 9 summarizes the f i n d i n g s and p l a c e s them i n t o the l a r g e r p e r s p e c t i v e of f u t u r e o f f i c e b u i l d i n g d e s i g n . 5. NOTES 1. L o u i s Kahn, as quoted i n M a r s h a l l Meyers, "Masters of L i g h t : L o u i s Kahn," A l A J o u r n a l , September 1979, p. 60. 2. Moshe S a f d i e , Form and Purpose ( B o s t o n : Houghton M i f f l i n , 1982), p. x v i . 3. Max H. Leu, "Energy C o n s e r v a t i o n i n O f f i c e B u i l d i n g s , " M a s t e r ' s T h e s i s a t U n i v e r s i t y of B r i t i s h Columbia, 1980, p. 21 . 4. R. S. Armstrong, The O f f i c e I n d u s t r y : P a t t e r n s of Growth  and L o c a t i o n (Cambridge, Mass.: MIT-Press, 1972), p.9, as quoted i n Leu, p. 23. \ 5. Leu, p.56. 6. R. G. Hopkinson, A r c h i t e c t u r a l P h y s i c s : L i g h t i n g (London: Her M a j e s t y ' s S t a t i o n e r y O f f i c e , 1963), pp. 298-300. 7. Leu, p. 60. 8. I b i d . 24 9. I b i d . 10. I b i d . 11. I b i d . 12. J o e l E. L a k i n and M. S. M i l l e t , "Road Map t o the S t a r s : T e a c h i n g an I n t e g r a t e d Approach t o Energy C o n s e r v i n g D e s i g n , " P r o c e e d i n g s of the 6th N a t i o n a l P a s s i v e S o l a r  C o n f e r e n c e , September 8-12, 1981 i n P o r t l a n d , Oregon, Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1972, p. 498. 13. F r e d S. Dubin and Chalmers G. Long, Energy C o n s e r v a t i o n  S t a n d a r d s (New York: M c G r a w - H i l l , 1978), p. 8. 14. Leu, p. 61. 15. For example, the TVA b u i l d i n g , i n Chattanouga, Tenn. 16. L a k i n and M i l l e t , p. 498. 17. I b i d . 18. S e l k o w i t z mentions s a v i n g s of 10-75% of t o t a l l i g h t i n g energy, -depending on the l e v e l of commitment t o d a y l i g h t i n g , and on the b u i l d i n g program. Stephen S e l k o w i t z , " D a y l i g h t i n g and P a s s i v e S o l a r B u i l d i n g s , " P r o c e e d i n g s of the 3rd N a t i o n a l P a s s i v e S o l a r C o n f e r e n c e ,  January 11-13, 1979 i n San J o s e , C a l i f . , Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1979, pp. 277-78. 19. F r a n c e s c o N. Arumi, "Computer A i d e d Energy Design f o r B u i l d i n g s , " i n Energy C o n s e r v a t i o n Through B u i l d i n g Design , e d i t e d by Donald Watson, (New-York: M c G r a w - H i l l , 1979), p. 160. 20. Matthews and C a l t h o r p e mention 20-60% r e d u c t i o n i n t o t a l energy consumption, w i t h the proper a d m i s s i o n and c o n t r o l of d a y l i g h t , when compared w i t h a c o n v e n t i o n a l energy-c o n s e r v i n g , c l i m a t e r e j e c t i n g b u i l d i n g . S c o t t Matthews and P e t e r C a l t h o r p e , " D a y l i g h t as a C e n t r a l Determinant of D e s i g n , " A l A J o u r n a l , September 1979, p. 86. 21. L i g h t i n g Design and A p p l i c a t i o n s , "TVA O f f i c e Complex - A Teamwork Approach t o Energy E f f i c i e n c y , " L i g h t i n g Design  and A p p l i c a t i o n s , November 1980, p. 33. 22. Sanchez and Rudoy mention r e d u c t i o n s i n e l e c t r i c a l l i g h t i n g consumtion of up t o 90%, w i t h p r o p e r d a y l i g h t i n g d e s i g n . N e s t o r E. Sanchez and W i l l i a m Rudoy, "Energy Impact of the Use of D a y l i g h t i n g i n O f f i c e s , " ASHRAE 25 T r a n s a c t i o n s , 1981, p t . 2 , pp. 145-60. 23. S. A. J u r o v i c s , " D a y l i g h t G l a z i n g and B u i l d i n g Energy M i n i m i z a t i o n , " ASHRAE T r a n s a c t i o n s , 1982, p. 375. 24. Tyrone F. P i k e and Joseph R i z z u t o , "Commercial O f f i c e D a y l i g h t i n g D e m o n s t r a t i o n , " P r o c e e d i n g s of the 6 t h  N a t i o n a l P a s s i v e S o l a r C o n f e r e n c e , September 8-12, 1981 i n  P o r t l a n d , Oregon, Newark, Delaware: American S e c t i o n o f the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1972, p. 870. 25. Lee Stephen Windheim and K y l e v. Davy, "The S u b s t i t u t i o n of D a y l i g h t i n g f o r E l e c t r i c L i g h t i n g i n a Large O f f i c e B u i l d i n g , " P r o c e e d i n g s of the 6th N a t i o n a l P a s s i v e S o l a r  C o n f e r e n c e , September 8-12, 1981 i n P o r t l a n d , Oregon, Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1972, p. 875. 26. Dubin and Long, p. 5. 27. In f a c t , the a b s o l u t e u t i l i t y peak time i s the most im p o r t a n t f o r the u t i l i t i e s . T h i s may o c c u r i n summer or w i n t e r , depending on the c l i m a t e and mix of b u i l d i n g t y p e s i n the r e g i o n . R e l a t i v e d a i l y or monthly peaks a r e i m p o r t a n t t o c u s t o m e r s , as t h e s e determine the demand p o r t i o n of the e l e c t r i c b i l l . 28. Many u t i l i t i e s have a l s o implemented " t i m e - o f - d a y " p r i c i n g as an e x t e n s i o n of peak demand c h a r g e s . 29. S e l k o w i t z , p. 277. 30. A p p r o x i m a t e l y 35% of u t i l i t y b i l l . V a r i e s w i t h l o c a t i o n and user r a t e s c h e d u l e . G e n e r a l S e r v i c e s A d m i n i s t a a t i o n , Energy C o n s e r v a t i o n G u i d e l i n e s f o r B u i l d i n g O p e r a t i o n s (Washington, D. C : GSA, [ 1 975 ] ) , p. 22 . 31. Harvey Bryan, "Power P l a y , " P r o g r e s s i v e A r c h i t e c t u r e , A p r i l 1983, pp. 104-05. 32. Assuming a gas, or o i l f i r e d b o i l e r f o r h e a t i n g . 33. Stephen U. C h o i , R i c h a r d Johnson, and Stephen S e l k o w i t z , "The Impact of D a y l i g h t i n g on Peak E l e c t r i c a l Loads," P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l D a y l i g h t i n g  C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, p. 383. 34. R i c h a r d G. S t e i n , A r c h i t e c t u r e and Energy (New York: Anchor/Doubleday, 1977), p. 124. 35. B r y a n , p. 105. 26 36. S e l k o w i t z , p. 277. 37. W. Bobenhausen and S. L e w i s , "Impacts of D a y l i g h t i n g on E l e c t r i c a l and C o o l i n g Peak Demands i n Commercial B u i l d i n g s , " P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l  D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, p. 393. 38. Stephen S e l k o w i t z , " E f f e c t i v e D a y l i g h t i n g i n B u i l d i n g s - -P a r t 2," L i g h t i n g Design and A p p l i c a t i o n s , March 1979, p. 46. 39. I b i d . 40. S c o t t Matthews, " P r o v i n g the B e n e f i t s of D a y l i g h t i n g , " A r c h i t e c t u r a l Record, Mid-August, 1981, p. 51. 41. W. M. C. Lam, S l i d e p r e s e n t a t i o n a t the 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , F e b r u a r y 17, P h o e n i x , A r i z o n a . 42. Harvey Bryan and V l a d i m i r B a z j a n a c , " D a y l i g h t i n g Design f o r New C a l i f o r n i a S t a t e O f f i c e B u i l d i n g - - S i t e 1-C," P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l D a y l i g h t i n g  C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983., p. 1*95. 43. Mathews and C a l t h o r p e , p. 92. 44. Bobenhausen and L e w i s , p. 395. 45. B e l i n d a Lowenhaupt C o l l i n s , Windows and P e o p l e : A  L i t e r a t u r e Survey (NBS B u i l d i n g S c i e n c e S e r i e s 70, Washington, D. C : Department of Commerce, 1975), p. 55. 46. Sim Van Der Ryn, " B u i l d i n g V a l u e : Energy Design G u i d e l i n e s f o r B u i l d i n g s , " i n A r c h i t e c t u r a l Handbook, e d i t e d by A l f r e d M.Kemper (New York: W i l e y , 1979), p. 553. 47. S o l a r V i s i o n , N a t u r a l L i g h t i n g : How t o Use D a y l i g h t ( H a r r i s v i l l e , N e w Hampshire: S o l a r V i s i o n , 1982), p. 10. 48. George Rand, " C a u t i o n : The O f f i c e Environment May be Hazardous t o Your H e a l t h , " AIA J o u r n a l , October 1979, pp. 38-41, 78. 49. Donna Anderson, " R i g h t L i g h t : Your H e a l t h may Depend on L e v e l of U l t r a v i o l e t , " The Vancouver Sun, March 24, 1983, p. c6. 50. E l i a S t e r l i n g , Theodore S t e r l i n g , and D a v i d M c l n t y r e , "New H e a l t h Hazards i n S e a l e d B u i l d i n g s , " AIA J o u r n a l , A p r i l 1983, pp. 64-67. 27 51. James J e w e l l , T a l k g i v e n a t the P l e n n a r y S e s s i o n , 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , F e b r u a r y 17, 1983, P h o e n i x , A r i z o n a . 52. I b i d . 53. R. G. Hopkinson, P. P e t h e r b r i d g e , and T. Longmore, D a y l i g h t i n g (London: Heinemann, 1966), p. 10. 54. J . A. Lynes, P r i n c i p l e s of N a t u r a l L i g h t i n g (London: E l s e v i e r , 1968), p. 156. 55. G. P. Woodford, "Open Spaces, B l i n d A l l e y s , " i n Developments i n L i g h t i n g — P a r t j _ , e d i t e d by J . A. Lynes (London: A p p l i e d S c i e n c e , 1978) , p. 204 . 56. - The c o d i f i c a t i o n of " r i g h t - t o - l i g h t " i n most m u n i c i p a l b y laws, i n the R e s i d e n t i a l S t a n d a r d s , and the N a t i o n a l B u i l d i n g Code of Canada, a p p l i e s o n l y t o r e s i d e n t i a l development. A s s o c i a t e Committee on the N a t i o n a l B u i l d i n g Code, N a t i o n a l B u i l d i n g Code of Canada, 1980 E d i t i o n , (Ottawa: N a t i o n a l R esearch C o u n c i l , 1980), S e c t i o n 9.7, p. 223. S e t b a c k s , f l o o r - a r e a - r a t i o s , and b u i l d i n g h e i g h t r e s t r i c t i o n s i n z o n i n g by-laws a t t e m p t , i n an i n d i r e c t way, t o c r e a t e the p o t e n t i a l f o r d a y l i g h t i n g . W h i l e these p r o v i s i o n s p r o v i d e improved d a y l i g h t p e n e t r a t i o n i n t o the s t r e e t , they cannot' c o n t r o l the amount of d a y l i g h t r e a c h i n g i n t o b u i l d i n g i n t e r i o r s . 57. John Schade and Gregg Ander, " C a l i f o r n i a Energy Commission B u i l d i n g Standards Development P r o j e c t : D a y l i g h t i n g f o r the Mass B u i l d i n g Market," P r o c e e d i n g s of the 1983  I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983  i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, pp. 385-92. 58. M i c h a e l K w a r t l e r and Raymon M a s t e r s , "Zoning f o r D a y l i g h t i n g i n Midtown Manhattan," P r o c e e d i n g s of the 1983  I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983  i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, pp. 397-99. 59. James A. Moore, " D a y l i g h t i n Manhattan," S o l a r Age, December 1981, pp. 32-36. 60. Amory B. L o v i n s , S o f t Energy P a t h s : Toward a D u r a b l e Peace (New York: Harper, 1977), p. 11. 61 . I b i d . , pp. 38-46. 62. Schumacher, E r n s t F, S m a l l i s B e a u t i f u l (New York: Harper and Row, 1973). 28 63. B o c k r i s , J . O'M, Energy Options.: R e a l Economics and the  S o l a r - H y d r o g e n System (London: T a y l o r and F r a n c i s , 1980). 64. L o v i n s , s u p r a . 65. Amory B. L o v i n s and L. Hunter L o v i n s , " B r i t t l e Power," S o l a r Age, F e b r u a r y 1983, i n s e r t pp. 1-8. 66. John L o b e l l , Between S i l e n c e and L i g h t : S p i r i t i n the  A r c h i t e c t u r e of L o u i s I . Kahn ( B o u l d e r , C o l o r a d o : Shambhala, 1979), p. 47. 67. IES D a y l i g h t i n g Committee, "Recommended P r a c t i c e of D a y l i g h t i n g , " L i g h t i n g D e s i gn and A p p l i c a t i o n s , F e b r u a r y 1979, pp. 25-60., mentions many t e c h n i q u e s f o r d a y l i g h t i n g , but t h e r e i s no d e t a i l e d s tudy of any of t h e s e and no c l e a r o r g a n i z a t i o n ; Benjamin H. Evans, D a y l i g h t i n A r c h i t e c t u r e (New York: M c G r a w - H i l l , 1981)., examines d a y l i g h t i n g t e c h n i q u e s i n some d e p t h , but no s y s t e m a t i c o r g a n i z a t i o n of t h e s e i s a t t e m p t e d ; W i l l i a m T. Meyer, Energy Economics and B u i l d i n g D e s i gn (New York: McGraw H i l l , 1983)., p r o v i d e s a s y s t e m a t i c l i s t of energy-s a v i n g and d a y l i g h t i n g t e c h n i q u e s , but does not d i s c u s s t h e s e i n depth or a r r a n g e them a c c o r d i n g t o s c a l e . 68. S. Ternoey e t a l , Design of E n e r g y - r e s p o n s i v e Commercial  B u i l d i n g s (Golden.,Co.: S o l a r Energy Research I n s t i t u t e , 1-984), p. 10. 69. L a k i n and M i l l e t , p. 499. 70. M. Suzan Ubbelohde, G. Z. Brown, and John S. R e y n o l d s , "An Approach t o T e a c h i n g C a l c u l a t i o n P r o c e d u r e s f o r P a s s i v e D e s i g n , " P r o c e e d i n g s of the 6th N a t i o n a l P a s s i v e S o l a r  C o n f e r e n c e , September 8-12, 1981 i n P o r t l a n d , Oregon, Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1972, p. 495. 71. Donald Watson, C l i m a t i c D e s i gn (New York: M c G r a w - H i l l Book Company, 1983. 72. L a k i n and M i l l e t , p. 499. 73. Ubbelohde et a l . , p. 495. 29 11 . DAYLIGHT IN THE INTERIOR VISUAL ENVIRONMENT ono o 30 1 . INTRODUCTION L i g h t i n b u i l d i n g s s e r v e s two b a s i c f u n c t i o n s : 1. I t e n a b l e s the occupant t o a c c o m p l i s h v i s u a l t a s k s such a s : r e a d i n g , w r i t i n g , h o l d i n g m e e t i n g s , examining goods, e t c . T h i s " t a s k l i g h t i n g " can be c o n s i d e r e d b r o a d l y as " l i g h t t o see by". i i . I t p r o v i d e s v i s u a l d e f i n i t i o n of spaces: a sense of o r i e n t a t i o n , drama, v i s u a l f o c u s ; and s a t i s f i e s p h y s i o l o g i c a l and p s y c h o l o g i c a l needs. T h i s "ambient l i g h t i n g " can be b r o a d l y c o n s i d e r e d as " l i g h t t o see". In t h i s c h a p t e r , the r e q u i r e m e n t s of l i g h t i n g f o r t a s k performance and l i g h t i n g f o r . p e r c e p t i o n of space are examined, drawing p a r t i c u l a r emphasis t o the s u i t a b i l i t y of d a y l i g h t i n f u l f i l l i n g t hese two purposes. 2. TASK LIGHTING""LIGHT TO SEE BY" 2.1 The Task P e r f o r m i n g System L i g h t i n g i s o n l y one of many components, a l b e i t an i m p o r t a n t one, i n the t a s k p e r f o r m i n g system. An e x a m i n a t i o n of the s e components i s t h e r e f o r e u s e f u l as a means of p l a c i n g the i n f l u e n c e of l i g h t i n g i n c o n t e x t . F i g u r e 3 1 i l l u s t r a t e s t h a t 31 F i g u r e 3 - Components of the t a s k p e r f o r m i n g system components i n t h i s system may a f f e c t t a s k performance e i t h e r i n d i r e c t l y or d i r e c t l y . Components t h a t i n f l u e n c e task performance i n d i r e c t l y a r e : i . e n v i r o n m e n t a l v a r i a b l e s such a s : h e a t , h u m i d i t y , n o i s e , e t c . - - b y a f f e c t i n g p h y s i o l o g i c a l mechanisms of the t a s k p e r f o r m e r i i . the ambient l i g h t i n g — b y a f f e c t i n g the c o m f o r t and sense of s a t i s f a c t i o n of the the t a s k p e r f o r m e r w i t h the v i s u a l environment i i i . the t a s k p e r f o r m e r ' s s o c i a l e n vironment, m o t i v a t i o n , a t t i t u d e , e x p e c t a t i o n , s k i l l , e t c . The l a s t .of t h e s e components are n o n - p h y s i c a l v a r i a b l e s t h a t ' can o n l y m a r g i n a l l y be c o n t r o l l e d by m a n i p u l a t i o n of the 32 p h y s i c a l environment, yet they can s u b s t a n t i a l l y i n f l u e n c e t a s k p e r f o r m a n c e 2 . Components t h a t d i r e c t l y i n f l u e n c e t a s k performance do so by a f f e c t i n g the a b i l i t y of the t a s k p e r f o r m e r t o e x t r a c t i n f o r m a t i o n from the v i s u a l environment. Such r e q u i r e m e n t s f o r v i s i b i l i t y may i n v o l v e d e t e c t i o n , r e c o g n i t i o n or i d e n t i f i c a t i o n 3 , becoming p r o g r e s s i v e l y more s t r i n g e n t as one proceeds from d e t e c t i o n t h rough r e c o g n i t i o n t o i d e n t i f i c a t i o n . There are t h r e e components whose c h a r a c t e r i s t i c s a f f e c t s t a s k performance d i r e c t l y . These a r e : i . the t a s k i i . response of the t a s k p e r f o r m e r i i i . the l i g h t i n g 2.2 C h a r a c t e r i s t i c s Of Task T a b l e I I , adapted from H a r k e r " , summarizes the e f f e c t s of the p h y s i c a l c h a r a c t e r i s t i c s of the task which a f f e c t t a s k v i s i b i l i t y . In g e n e r a l o f f i c e s i t u a t i o n s , the s i z e and c o n t r a s t of the t a s k are the most im p o r t a n t t a s k c h a r a c t e r i s t i c s a f f e c t i n g v i s i b i l i t y 5 , 6 . An i n c r e a s e i n c o n t r a s t and the r e s u l t i n g i n c r e a s e i n v i s i b i l i t y has a much g r e a t e r i n f l u e n c e on v i s u a l performance than c o r r e s p o n d i n g changes i n i l l u m i n a n c e 7 , 8 . L e v y 9 has even shown t h a t i n c r e a s i n g the i l l u m i n a n c e on a t a s k of low c o n t r a s t may never be a b l e t o b r i n g about the performance l e v e l of a t a s k of h i g h e r c o n t r a s t . Berman and C l e a r 1 0 have c a l c u l a t e d t h a t , f o r l i g h t l e v e l s above as l i t t l e as 100 l u x i n a t y p i c a l o f f i c e s i t u a t i o n , an improvement i n c o n t r a s t or 33 T A S K ATTRIBUTE DEFINING CHARACTERISTICS C O M M E N T * SIZE ANGULAR SEPARATION,CYCLE FREQUENCY OF DETAIL CONTRAST ACHROMATIC, RELATIVE REFLECTANCES OF DETAIL AKIb BACKGROUND CHROMATIC, BIAS IN RELATIVE REFLECTANCE AT DIFFERENT WAVELENGTHS DEPTH TWO DIMENSIONAL VERSUS THREE DIMENS-IONAL TEXTURE SPECULAR IT Y SELECTIVE REFLECTIONS AT DIFFERENT VIEWING Alk5I.ES TO THE SURFACE, WCH ARE SPECIFIC TO THE VIEWING POSITION DENsrry OF DETAIL DETAIL EMBEDDED IN A COMPLEX ARRAY PATTERN TIKE AVAILABLE FOR VIEWING REGULARITY DEFINITIONS OF RIGID, SEHI-RkSlD PACING VERSOS THE UN PACED CONDITION CONSISTENCY Of SfNSORY INrUT COINCIDENCE OF VISUAL AND OTHER S1GMALS PREDICTABLE CONSEQUENCES FOR EASE OF SEEING PREDICTABLE COKlSEiJUENCES WHICH INTERACT WITH "SIZE KNOWN EFFECTS BUT DIFFICULT TD QUANTIFY VARIANCE IN OFFICE TASKS IS NOT AS 6REAT AS IN INDUSTRIAL TASKS SOURCE OF CONSIDERABLE VARIANCE PROBLEM FOR DETECTION OF IttFREqUENTLY OCCURRIN6 ITEMS MAY AID IN LOCATION OF DETAIL VERY RI6ID PACING \S UNDESIRABLE FoR THE HUMAN OPERATOR NEED TO IDENTIFY THE CRITICAL CUES T a b l e I I - Task c h a r a c t e r i s t i c s a f f e c t i n g v i s i b i l i t y c o n t r a s t s e n s i t i v i t y i s 3 t o 10 times' more c o s t e f f e c t i v e than an i n c r e a s e i n i l l u m i n a n c e on t a s k . T h i s improvement may be a c c o m p l i s h e d , f o r example, by u s i n g forms w i t h l a r g e r p r i n t , x e r o g r a p h i c c o p i e s i n s t e a d of carbon or mimeograph, e t c . 2.3 Task P e r f o r m e r Response C h a r a c t e r i s t i c s The response c h a r a c t e r i s t i c s of the t a s k p e r f o r m e r d i r e c t l y a f f e c t i n g t a s k v i s i b i l i t y a r e summarized i n t a b l e I I I 1 1 . These i n c l u d e v i s u a l c a p a c i t y , p o s i t i o n w i t h r e s p e c t t o the t a s k , v i s u a l a d a p t a t i o n , e t c . The a b i l i t y of the human eye t o adapt t o a v e r y wide range of l u m i n a n c e s , i s an i m p o r t a n t phenomenon i n the d e s i g n of i n t e r i o r l i g h t i n g . The eye a d a p t s t o a g e n e r a l l e v e l of luminance and can p e r c e i v e a range of b r i g h t n e s s e s above and 34 PERFORMER RESPONSE DEFINING CHARACTERISTIC* C O M M E N T S VI6UAL CAPACITY • A&ILITY TO FOCUS THE EYE • VARIES WITH INDIVIDUAL • CONTRAST SENSITIVITY • DECREASES WITH AGE VI6UAL ADAPTATION • ABILITY OF EYE TO ADAPT TO • BRIGHTNESS RATIOS ARE PREVAILING LUMINANCE LEVELS IMPORTANT. ABSOLUTE LUM-INANCE NOT IMPORTANT • INSTANTANEOUS PERCEPTION OF LIMITED LUMINANCE RANGE AS COMPARED WITH TOTAL RANGE OF EYE SENSITIVITY. POSITION WITH RESPECT DEFINED BY POSTURE OF TASK • MAY GREATLY AFFECT VISIBILITY TO TASK PERFORMER, POSITION OF TASK, BUT OPTION TO CHANGE ANGLE OF VIEW THI5 PAFsAMETEFs IS NOT ALWAYS AVAILABLE CONFLICT BETWEEN REQUIREMENT FOR CONCURRENT • MOSTLY IN INTERFACING WITH VISUAL AND ACTIVITY MOTOR CONTROL AND VISUAL MACHINES - A PROBLEM IN REQUIREMENTS INSPECTION OF WORK, ERGONOMICS T a b l e I I I - Task pe r f o r m e r response a f f e c t i n g v i s i b i l i t y below t h i s l e v e l 1 2 . Because of the phenomenon of a d a p t a t i o n , a b s o l u t e luminance l e v e l s a r e not as imporant i n t a s k performance as the luminance r a t i o s of the s u r f a c e s w i t h i n the f i e l d of view. 2.4 C h a r a c t e r i s t i c s Of L i g h t i n g Task l i g h t i n g has been d e f i n e d a s 1 3 : a l i g h t i n g i n s t a l l a t i o n which p r o v i d e s the c o r r e c t q u a n t i t y of l i g h t on the v i s u a l t a s k , f l o w i n g from the c o r r e c t d i r e c t i o n , w i t h r e s p e c t t o the worker and the wo r k i n g p l a n e or p l a n e s i n v o l v e d , b e i n g of the a p p r o p r i a t e s p e c t r a l q u a l i t y , and d e s i g n e d t o p r o v i d e good v i s i b i l i t y . T a b l e IV , adapted from H a r k e r 1 * , l i s t s the v a r i o u s 35 LIGHTING ATTRIBUTE M E A S U R E C O M M t A J T * ILLUMINANCE PLANAR ON WORK SURFACE MOST FREQUENTLY USED STANDARD EFFECTIVE IN INCREASING VISIBILITY WHEN LEVELS ARE LOW BUT FOUOWS. LA\V OF DIMINISHING RETURNS DIRECTIONAL LIGHTING CONTRAST RENDERING FACTOR (CRF) RELATES IMPORTANT FOR MATERIALS WITH DEPTH TO SPHERE ILLUMINANCE. SPECIFIC TO AND SPECULAR COMPONENTS VIEUWG ANGLE AND MATERIAL CHARAC-TERISTICS BALANCE OF GENERAL ILLUMINATION TO DIRECTIONAL COMPONENTS (VECTOR-SCALAR RATIO IS ONE MEASURE) DIFFICULT TO MEASURE FOR MATERIAL POSITION BUT MAY BE IMPORTANT "WHERE BOTH TRANSMITTED AND REFLECTED LIGHT ARE IMPORTANT SPECTRAL QUALITY FREQUENCY SPECTRUM OF LIGHT SOURCES CHOICE OF SOURCE LIMITED TO A PREDETER-MINED RANGE OF ALTERNATIVES. T a b l e IV - C h a r a c t e r i s t i c s of t a s k l i g h t i n g a f f e c t i n g v i s i b i l i t y p arameters of l i g h t i n g a f f e c t i n g v i s i b i l i t y . These parameters a r e : i . i 1 l u m i nance i i . l uminance d i s t r i b u t i o n i i i . d i r e c t i o n of l i g h t i v . s p e c t r a l q u a l i t y v. v a r i a b i l i t y i n time 2.4.1 The E f f e c t Of I l l u m i n a n c e L e v e l On V i s i b i l i t y The importance of i l l u m i n a n c e as a parameter i n f l u e n c i n g t a s k v i s i b i l i t y has been o v e r - r a t e d f o r many r e a s o n s 1 5 , 1 6 , m o s t l y due t o the p r o m o t i o n of e x a g e r a t e d l i g h t l e v e l s d u r i n g the e r a of cheap f u e l s 1 7 , the easy use of i l l u m i n a n c e as a 3 6 y a r d s t i c k 1 8 , and an e r roneous i d e n t i f i c a t i o n of h i g h e r l i g h t l e v e l s w i t h more p r o d u c t i v i t y . I t i s w i d e l y u n d e r s t o o d now t h a t above l i g h t l e v e l s of 200 l u x , v i s i b i l i t y , and hence p e r f o r m a n c e , becomes p r o g r e s s i v e l y i n s e n s i t i v e t o an i n c r e a s e i n l u m i n a n c e 1 9 . In f a c t , a t l i g h t l e v e l s c u r r e n t l y p r e s c r i b e d f o r b u i l d i n g s , performance does not a p p r e c i a b l y change w i t h l u m i n a n c e 2 0 . T h i s i s shown i n f i g u r e 4 . I n c r e a s e s i n 100 3 60 I 40 o * 20 0 F i g u r e 4 - R e l a t i o n s h i p between luminance l e v e l and per formance i l l u m i n a n c e are v e r y e x p e n s i v e 2 1 , and c u r r e n t t h i n k i n g i s t h a t i t must r e s u l t i n improved v i s i b i l i t y and, hence, improved p e r f o r m a n c e t o be j u s t i f i e d . L i g h t i n g i n s t a l l a t i o n s d e l i v e r i n g the same "raw" i l l u m i n a n c e 2 2 can r e s u l t i n w i d e l y d i f f e r i n g v i s i b i l i t y on the t a s k . T h i s i s because v i s i b i l i t y i s not o n l y a f u n c t i o n of i l l u m i n a n c e , but a l s o of l i g h t s o u r c e d e s i g n and l o c a t i o n ; of task' and room r e f l e c t a n c e s ; and of l i g h t 37 s o u r c e / t a s k / t a s k p e r f o r m e r geometry. The E q u i v a l e n t Sphere I l l u m i n a t i o n (ESI) i s a r e f e r e n c e l i g h t i n g c o n d i t i o n used t o measure v i s i b i l i t y 2 3 . I t i s d e s i g n e d t o make the i m p o r t a n t d i s t i n c t i o n between "raw" i l l u m i n a n c e l e v e l s and the r e s u l t i n g v i s i b i l i t y 2 " by q u a n t i f y i n g the e f f e c t s of the v a r i o u s f a c t o r s a f f e c t i n g v i s i b i l i t y 2 5 . I t i s used t o compare the v i s i b i l i t y produced by d i f f e r e n t l i g h t i n g schemes. Some p r a c t i t i o n e r s have e x p r e s s e d r e s e r v a t i o n s about the use of (ESI) i n f i e l d s i t u a t i o n s 2 6 , 2 7 but o t h e r s have found i t h e l p f u l i n d e s i g n i n g e f f e c t i v e l i g h t i n g w h i l e r e d u c i n g l i g h t i n g energy c o n s u m p t i o n 2 8 , 2 9 . The concept of v i s i b i l i t y as a c r i t e r i o n of l i g h t i n g performance i s very i m p o r t a n t i n i n t e r i o r s u s i n g d a y l i g h t f o r t a s k performance. The IES D a y l i g h t i n g Committee, i n t h e i r 1979 e d i t i o n of the "Recommended P r a c t i c e of D a y l i g h t i n g " , have w r i t t e n 3 0 : The d i s t i n c t i o n between the i l l u m i n a t i o n l e v e l and any r e s u l t i n g v i s i b i l i t y i s e s p e c i a l l y i m p o r t a n t f o r d a y l i g h t i n g a n a l y s i s . In many a p p l i c a t i o n s , d a y l i g h t i s i n c i d e n t a t the t a s k from d i r e c t i o n s ( s i d e and back) which produce h i g h c o n t r a s t [and h i g h v i s i b i l i t y ] and c o n s e q u e n t l y , h i g h E S I . Thus, i t can happen t h a t a s m a l l amount of d a y l i g h t can produce the same t a s k v i s i b i l i t y as a l a r g e r amount of [ overhead] e l e c t r i c l i g h t i n g . . . The f u l l p o s s i b i l i t y of d a y l i g h t b e n e f i t s can be d i f f i c u l t t o demonstrate w i t h o u t the use of the ESI c o n c e p t . G r i f f i t h 3 1 has w r i t t e n : . . . d a y l i g h t i l l u m i n a t i o n t h r ough windows has been shown t o be 3 t o 4 t i m e s as e f f e c t i v e i n i n c r e a s i n g v i s u a l performance as e q u a l i l l u m i n a t i o n from c o n v e n t i o n a l e l e c t r i c l i g h t i n g i f p r o p e r l y u t i l i z e d . . . W i t h p r o p e r l a y o u t of w o r k p l a c e s [ d a y l i g h t from the 38 s i d e ] 20 to 30 f o o t c a n d l e s of d a y l i g h t can p e r m i t b e t t e r v i s u a l performance than 70 t o 100 f o o t c a n d l e s of c l a s s i c a l overhead l i g h t i n g . An e x t e n s i v e computer s i m u l a t i o n study by T h r u n 3 2 f o r P u b l i c Works Canada, on d a y l i g h t i l l u m i n a n c e l e v e l s a v a i l a b l e i n t y p i c a l o f f i c e i n t e r i o r s , has shown t h a t when a l l p e r t i n e n t f a c t o r s r e l a t i n g t o t a s k v i s i b i l i t y a re taken i n t o c o n s i d e r a t i o n a l o n g w i t h i l l u m i n a n c e , and e x p r e s s e d as E q u i v a l e n t Sphere I l l u m i n a t i o n , the ESI v a l u e s f o r d a y l i g h t from windows averaged between 2 t o 4 times the v a l u e of the " t r a d i t i o n a l i n c i d e n t i l l u m i n a t i o n " 3 3 ( i . e . "raw" i l l u m i n a n c e ) throughout the room. The a c t u a l v a l u e s a r e a f u n c t i o n of the o r i e n t a t i o n , time of day, e t c 3". 2.4.2 The E f f e c t Of Luminance D i s t r i b u t i o n On V i s i b i l i t y V i s i b i l i t y i s i n g e n e r a l governed by the t o t a l amount of l i g h t which may be seen w i t h i n the v i s u a l f i e l d . T h i s f i e l d i s composed - of the t a s k , the immediate su r r o u n d and the g e n e r a l s u r r o u n d 3 5 , as shown i n f i g u r e 5 . The t o t a l amount of l i g h t i s a f u n c t i o n of both the luminance of the v i s u a l f i e l d (which i s p r o p o r t i o n a l t o the i l l u m i n a n c e and the r e f l e c t i v i t y of the s u r f a c e ) , as w e l l as i t s a r e a . A change i n luminance a l o n e w i l l have l e s s i n f l u e n c e on v i s i b i l i t y than on v i s u a l c o m f o r t . C o n t r a s t between t a s k and immediate s u r r o u n d a l s o a f f e c t s v i s i b i l i t y 3 6 . An extreme i n s t a n c e of t h i s i s d i s a b i l i t y g l a r e , which s u b s t a n t i a l l y a f f e c t s v i s i b i l i t y , but t h i s phenomenon i s not v e r y common i n i n t e r i o r l i g h t i n g s i t u a t i o n s 3 7 . Hopkinson 39 !!!!!!!I|HI Si iillll IHliiillilifii1' /rn-uttntnj •Iillll- -.'Hi! i lit ill !••• 1% Si ^Wiiil Upfli! /0I iillll i liiiHiiiiib 1HW* II • / — T H E IMMEDIATE : SDRROUAJD JCpT- -W i l l 11 iiililllv mm - \ V F i g u r e 5 - Components of the v i s u a l f i e l d and C o l l i n s 3 8 , r e p o r t t h a t optimum luminance of the s u r r o u n d f o r t a s k v i s i b i l i t y i s e q u a l or somewhat l e s s than t h a t of the t a s k i t s e l f . V i s i b i l i t y d e c r e a s e s v e r y g r a d u a l l y as the luminance of .the immediate s u r r o u n d i s reduced, but d e c r e a s e s . s h a r p l y as i t s l uminance i s i n c r e a s e d above t h a t of the t a s k 3 9 . V i s i b i l i t y a l s o improves by about 25% w i t h an i n c r e a s e of s u r r o u n d a r e a up t o a s u b t e n d i n g a n g l e of about 6°. Examples of t h i s a r e road s i g n s , where a q u i t e s m a l l immediate s u r r o u n d i s s u f f i c i e n t t o p r o v i d e good v i s i b i l i t y of the s i g n . Beyond the s i z e of immediate s u r r o u n d i n d i c a t e d , improvement i n v i s u a l p erformance i s m i n i m a l * 0 . In d a y l i t i n t e r i o r s , l o c a t i o n s remote from d a y l i g h t i n g a p e r t u r e s may r e q u i r e e l e c t r i c t a s k l i g h t i n g s u p p l e m e n t a t i o n . In o t h e r r e s p e c t s , d a y l i g h t can p r o v i d e luminance r a t i o s w i t h i n the v i s u a l f i e l d t h a t e n a b l e good t a s k v i s i b i l i t y . 40 2.4.3 The E f f e c t Of L i g h t D i r e c t i o n On Task V i s i b i l i t y The d i r e c t i o n of l i g h t w i l l a f f e c t t a s k v i s i b i l i t y " 1 , q u i t e a p a r t from i t s e f f e c t on v i s u a l q u a l i t y of the space. Improvement i n v i s i b i l i t y i s most marked f o r t h r e e d i m e n s i o n a l t a s k s where a change i n the d i r e c t i o n of l i g h t w i l l g r e a t l y i n f l u e n c e the p e r c e p t i o n of form, depth and t e x t u r e , but i t w i l l a l s o a f f e c t two d i m e n s i o n a l t a s k s h a v i n g a degree of s p e c u l a r i t y . The r a t i o between the l e v e l of the d i r e c t i o n a l l i g h t i n g and the l e v e l of the g e n e r a l l i g h t i n g i s c a l l e d the V e c t o r / S c a l a r r a t i o . In some s i t u a t i o n s , such as those i n v o l v i n g model-making or the e x a m i n a t i o n of o b j e c t s h a v i n g s p e c u l a r c h a r a c t e r i s t i c s , an i n c r e a s e i n t h i s r a t i o - - b r o u g h t about, f o r example, by an i n c r e a s e i n i l l u m i n a n c e on the v e r t i c a l p l a n e - -w i l l improve t a s k v i s i b i l i t y " 2 . In o f f i c e s , the predominant mode of d a y l i g h t i n g i s through s i d e l i g h t i n g . T h i s d i r e c t i o n of l i g h t r e s u l t s i n l i t t l e or no v e i l i n g r e f l e c t i o n s f o r h o r i z o n t a l t a s k s and optimum m o d e l l i n g f o r t h r e e d i m e n s i o n a l t a s k s . G r i f f i t h has demonstrated the advantage of s i d e l i g h t i n g i n r e d u c i n g v e i l i n g r e f l e c t i o n s and r e s u l t a n t c o n t r a s t d e g r a d a t i o n , as compared w i t h c o n v e n t i o n a l t o p l i g h t i n g " 3 . , 4 1 2.4.4 The E f f e c t Of S p e c t r a l C h a r a c t e r i s t i c s On V i s i b i l i t y The s p e c t r a l c h a r a c t e r i s t i c s of the l i g h t s ource w i l l n a t u r a l l y i n f l u e n c e the c o l o u r r e n d e r i n g " " of o b j e c t s seen i n i t s l i g h t . Thus, the a b i l i t y t o d i s c r i m i n a t e c o l o u r d i f f e r e n c e s i n some t a s k s w i l l v a r y g r e a t l y under d i f f e r e n t l i g h t s o u r c e s . Beyond t h i s e f f e c t , however, t h e r e i s e v i d e n c e t h a t l i g h t s o u r c e s w i t h b e t t e r c o l o u r - r e n d e r i n g c h a r a c t e r i s t i c s ( i . e . ap p r o a c h i n g the c o l o u r - r e n d e r i n g of n a t u r a l l i g h t ) p r o v i d e g r e a t e r ' v i s u a l c l a r i t y ' " 5 than s o u r c e s of p o o r e r c o l o u r -r e n d e r i n g c h a r a c t e r i s t i c s . T h i s means t h a t a l i g h t source w i t h a h i g h c o l o u r - r e n d e r i n g i n d e x " 6 can have lower i l l u m i n a n c e - ~ b y as much as 40%" 7--and s t i l l p r o v i d e e q u i v a l e n t v i s i b i l i t y " 8 . T h i s phenomenon i s known t o the s c i e n t i f i c community but has not ' been acknowledged i n l i g h t i n g s t a n d a r d s " 9 . E l e c t r o m a g n e t i c r a d i a t i o n t h a t makes up d a y l i g h t i s e v e n l y d i s t r i b u t e d w i t h i n the range v i s i b l e t o the human eye, whereas the v i s i b l e r a d i a t i o n from common l i g h t s o u r c e s f a v o u r s some c o l o u r s over o t h e r s . T h e r e f o r e , t h e r e i s a b e t t e r c o l o u r p e r c e p t i o n under d a y l i g h t , as compared w i t h most of the commonly used e l e c t r i c a l l i g h t i n g 5 0 , and a c o r r e s p o n d i n g i n c r e a s e i n v i s i b i l i t y . The l i g h t i s a l s o p e r c e i v e d as p l e a s a n t 5 1 , w i t h a v i b r a n c y and c o l o u r b a l a n c e t h a t can be s i m u l a t e d o n l y w i t h i n s t a l l a t i o n s of r a t h e r e x p e n s i v e , " f u l l - s p e c t r u m " , f l u o r e s c e n t lamps 5 2 . 42 2.4.5 The E f f e c t Of I l l u m i n a n c e V a r i a b i l i t y On V i s i b i l i t y A f l u c t u a t i o n i n i l l u m i n a n c e has an impact on v i s i b i l i t y and t a s k performance. The degreee of impact i s a f u n c t i o n of the r a t e and a m p l i t u d e of f l u c t u a t i o n , as w e l l as of the meaning a t t a c h e d t o t h i s f l u c t u a t i o n . The f l i c k e r produced by f l u o r e s c e n t lamps, f o r example, can i m p a i r the v i s i b i l i t y of t a s k s t h a t i n v o l v e r a p i d m otion, as w e l l as reduce performance because of the d i s t r a c t i o n i t causes. Other phenomena, such as s t a g e d s w i t c h i n g of l i g h t s i n response t o f l u c t u a t i n g d a y l i g h t l e v e l s , w i l l not cause a r e d u c t i o n i n v i s i b i l i t y , but may n e v e r t h e l e s s i m p a i r t a s k performance because of t h e i r d i s t r a c t i n g e f f e c t . D a y l i g h t i s n a t u r a l l y v a r i a b l e , but i t s r a t e of v a r i a b i l i t y and the a m p l i t u d e of v a r i a b i l i t y w i t h i n s h o r t i n t e r v a l s a r e such t h a t they do not i m p a i r v i s i b i l i t y . S h o r t term f l u c t u a t i o n i n d a y l i g h t l e v e l s — such as d u r i n g p a r t l y c l o u d y days — a r e g e n e r a l l y c o n s i d e r e d p l e a s a n t because of the p o s i t i v e a s s o c i a t i o n s they evoke, and do not i m p a i r t a s k performance. In d a y l i t b u i l d i n g s i n t e g r a t e d w i t h e l e c t r i c l i g h t i n g , the c o n t i n u o u s dimming- of e l e c t r i c l i g h t , w i t h time d e l a y and dead-band c h a r a c t e r i s t i c s 5 3 , a v o i d s d i s t r a c t i n g v a r i a t i o n s i n i n t e r i o r l i g h t l e v e l s . 43 3. LIGHTING FOR USER SATISFACTION--"LIGHT TO SEE" G e n e r a l l i g h t i n g of i n t e r i o r space, or ambient l i g h t i n g , f u l f i l l s the f o l l o w i n g r o l e s : i . responds t o the p h y s i o l o g i c a l needs of the occ u p a n t s i i . i n f l u e n c e s ( a l o n g w i t h t a s k l i g h t i n g ) the v i s u a l c o m f o r t , i n p s y c h o - p h y s i c a l terms, of the occupants i i i . promotes v i s u a l d e f i n i t i o n of s p a c e s : a sense of o r i e n t a t i o n , g u i d a n c e , v i s u a l f o c u s , e t c . i v . i n f l u e n c e s the o v e r a l l i m p r e s s i o n c r e a t e d by the space: s p a c i o u s n e s s , p r i v a c y , e t c . To the e x t e n t t h a t ambient l i g h t i n g f u l f i l l s the above r o l e s , i t w i l l i n d i r e c t l y , through the the s a t i s f a c t i o n of the occupants w i t h the v i s u a l environment, a l s o a f f e c t t a s k performance. 3 . 1 L i g h t i n g For P h y s i o l o g i c a l W e l l - b e i n g L i g h t has e x t r a s e n s o r y e f f e c t s on a l l l i v i n g o r g a n i s m s . In human b e i n g s , these e f f e c t s occur m o s t l y t h r o u g h the eye and the s k i n . S i g n a l s from l i g h t on the eye a r e i n t e r p r e t e d by p a r t s of the b r a i n not a s s o c i a t e d w i t h v i s i o n and these r e g u l a t e normal b i o l o g i c a l r h y t h m s 5 " , 5 5 . The t r i g g e r i n g wavelengths f o r some of the s e a r e i n the v i s i b l e p o r t i o n of the spectrum, f o r o t h e r s , i n the near or m i d - u l t r a v i o l e t p o r t i o n 5 6 . L i g h t s t r i k i n g the s k i n i s w e l l known t o a i d i n s y n t h e s i z i n g v i t a m i n D 5 7 . For t h i s , the most a c t i v e wavelengths a re the mid-44 u l t r a v i o l e t r a n g e 5 8 . Both mid and n e a r - u l t r a v i o l e t r a y s a r e known t o have b a c t e r i o c i d a l e f f e c t on the s k i n ' s s u r f a c e 5 9 . A l t h o u g h i n c o n c l u s i v e , r e s e a r c h r e s u l t s a r e making i n c r e a s i n g l y c l e a r t h a t " l i g h t i n g e x e r t s i m p o r t a n t e f f e c t s upon human h e a l t h and p r o d u c t i v i t y , f a r beyond i t s r e q u i r e m e n t s f o r v i s i o n " 6 0 . A c c o r d i n g t o p h o t o b i o l o g i c a l r e s e a r c h , " i t seems r e a s o n a b l e t h a t the l i g h t s o u r c e s t o which we expose p e o p l e s h o u l d not d e v i a t e markedly from the l i g h t i n g environment under which p e o p l e e v o l v e d i n n a t u r e . The f r a g m e n t a r y d a t a now a v a i l a b l e s u g g e s t s t h a t w o r k i n g under such ' n a t u r a l ' c o n d i t i o n s s i g n i f i c a n t l y d e c r e a s e s v i s u a l f a t i g u e and may a l s o i n c r e a s e p r o d u c t i v i t y " 6 1 . There i s , however, no consensus on t h i s s u b j e c t . P a r t l y because of i n c o n c l u s i v e e v i d e n c e , but m o s t l y because of v e s t e d commercial i n t e r e s t s by the l a r g e l i g h t i n g m a n u f a c t u r e r s , the importance of p r o v i d i n g d a y l i g h t , or d a y l i g h t - s i m u l a t i n g e l e c t r i c a l l i g h t i n g , i n b u i l d i n g i n t e r i o r s i s much d e b a t e d 6 2 , 6 3 , 6 \ 6 5 . L i g h t i n the i n t e r i o r of b u i l d i n g s comes e i t h e r from e l e c t r i c l i g h t s o u r c e s or from d a y l i g h t t r a n s m i t t e d t h r o u g h d a y l i g h t i n g a p e r t u r e s . These two l i g h t s o u r c e s may be examined t o d e t e r m i n e t o what e x t e n t these d i f f e r from outdoor s u n l i g h t and d a y l i g h t , under which man has e v o l v e d . P h o t o b i o l o g i c a l e f f e c t of e l e c t r i c l i g h t S c i e n t i f i c o p i n i o n d i f f e r s on the i s s u e of h e a l t h e f f e c t s of a r t i f i c i a l l i g h t i n g s o u r c e s : whether they a r e n o n - i n j u r i o u s , 45 d e f f i c i e n t i n some a s p e c t s or p o s i t i v e l y h a r m f u l 6 6 , 6 7 . The answer p a r t l y depends on the d e f i n i t i o n of these terms. Moderate amounts of u l t r a v i o l e t r a y s and of the s h o r t e r w avelength v i s i b l e r a y s appear to be b e n e f i c i a l t o human h e a l t h . The common f l u o r e s c e n t l i g h t i n g e x h i b i t s a narrow-band l i g h t d i s t r i b u t i o n and a g e n e r a l d e f f i c i e n c y i n the UV w a v e l e n g t h s 6 8 . One c o n c e r n i s t h a t p e o p l e , w o r k i n g under th e s e l i g h t s and exposed t o v e r y l i t t l e d a y l i g h t ( e s p e c i a l l y d u r i n g w i n t e r s ) , become d e p r i v e d of the c a t a l y t i c e n e r g i e s p r e s e n t i n the s h o r t e r v i s i b l e , and UV w a v e l e n g t h s . F u l l spectrum f l u o r e s c e n t lamps, d u p l i c a t i n g the s p e c t r a l c o m p o s i t i o n of d a y l i g h t , are a v a i l a b l e 6 9 , but these are 5 t o 10 times more e x p e n s i v e than s t a n d a r d f l u o r e s c e n t lamps and t h e r e i s c o n s i d e r a b l e c o n t r o v e r s y i n the i n d u s t r y c o n c e r n i n g the u s e f u l n e s s of t h e s e l a m p s 7 0 . Some r e s e a r c h even suggests t h a t f u l l - s p e c t r u m lamps have h a r m f u l s i d e - e f f e c t s 7 1 . P h o t o b i o l o g i c a l e f f e c t of d a y l i g h t The o t h e r way of r e c e i v i n g b i o l o g i c a l l y d e s i r a b l e s p e c t r a l b a l a n c e i n l i g h t i s from d a y l i g h t , coming t h r o u g h windows, s k y l i g h t s , e t c . A l t h o u g h d i r e c t s u n l i g h t i s the most p o t e n t p h o t o b i o l o g i c a l l y , o v e r c a s t s k i e s f i l t e r out o n l y about 20% of the u l t r a v i o l e t l i g h t 7 2 , 7 3 and hence, c l o u d y days a r e almost as benef i c i a l . The main i s s u e , t h e r e f o r e , i s whether or not window g l a s s w i l l t r a n s m i t the wavelengths n e c e s s a r y f o r h e a l t h . C l e a r g l a s s t r a n s m i t s a l a r g e p a r t of the near u l t r a v i o l e t r a y s (320-46 380nm) but t h a t t r a n s m i s s i v i t y f a l l s o f f s h a r p l y a t the mid-u l t r a v i o l e t wavelengths (290-320nm) 7 *. S i n c e the p h o t o b i o l o g i c a l l y a c t i v e wavelengths a r e i n the v i s i b l e , near-u l t r a v i o l e t and m i d - u l t r a v i o l e t ranges ( v a r y i n g f o r d i f f e r e n t p h y s i o l o g i c a l p r o c e s s e s ) , t h i s means t h a t o r d i n a r y c l e a r g l a s s i s t r a n s p a r e n t t o much, though perhaps not a l l , of these w a v e l e n g t h s . Low i r o n g l a s s , h a v i n g h i g h t r a n s m i t t a n c e t o the mid and near u l t r a v i o l e t r a y s , and h i g h e r t r a n s m i t t a n c e i n the v i s i b l e - p o r t i o n of the spectrum than s t a n d a r d c l e a r g l a s s , i s now b e i n g manufactured, so t h a t the f u l l b e n e f i t of these e l e c t r o m a g n e t i c f r e q u e n c i e s may be r e a l i z e d i n s i d e b u i l d i n g s 7 5 . Heat a b s o r b i n g and e s p e c i a l l y heat r e f l e c t i n g g l a s s e s r e f l e c t most of u l t r a v i o l e t r a y s ; these a l s o of c o u r s e reduce the q u a n t i t y of v i s i b l e l i g h t t r a n s m i t t e d 7 6 . The t e n t a t i v e c o n c l u s i o n one may draw from these f a c t s i s t h a t n a t u r a l l y l i t b u i l d i n g s , w i t h c l e a r window g l a s s , a re more a b l e t o p r o v i d e t h e i r occupants w i t h the k i n d of l i g h t t h a t i s n e c e s s a r y f o r b i o l o g i c a l h e a l t h of the human organism, than t o t a l l y e l e c t r i c a l l y l i t b u i l d i n g s t h a t i g n o r e the p o t e n t i a l f o r d a y l i g h t i n g . 3.2 L i g h t i n g For V i s u a l Comfort L i g h t i n g f o r ease of s e e i n g , or v i s u a l comfort i n s t r i c t l y p s y c h o p h y s i c a l terms, can be d i v i d e d i n t o the f o l l o w i n g g o a l s : i . c o n t r o l of b r i g h t n e s s g r a d i e n t s 47 i i . a v o i d a n c e of d i s c o m f o r t g l a r e i i i . p r o v i s i o n of v i s u a l r e s t c e n t r e s 3.2.1 B r i g h t n e s s G r a d i e n t s The p e r c e p t i o n of b r i g h t n e s s i s governed by the phenomenon of l i g h t n e s s c o n s t a n c y 7 7 . Because of l i g h t n e s s c o n s t a n c y , an o b j e c t w i l l appear t o be e q u a l l y b r i g h t under a wide range of i l l u m i n a n c e l e v e l s , and i t s p e r c e i v e d l u m i n o s i t y - - o r b r i g h t n e s s 7 8 - - w i l l depend on the r e l a t i o n s h i p t o i t s s u r r o u n d i n g s . The p r a c t i c a l r e s u l t of t h i s i s t h a t the a b s o l u t e luminance of s u r f a c e s w i t h i n the f i e l d of view (and hence, the i l l u m i n a n c e on them), i s of l i t t l e consequence i n j u d g i n g b r i g h t n e s s l e v e l s . I t i s the luminance r a t i o s among these s u r f a c e s t h a t i s i m p o r t a n t . Table V ,7 9 l i s t s recommended maximum luminance r a t i o s between t a s k and s u r r o u n d i n g s t h a t w i l l p r o v i d e v i s u a l comfort c o n d i t i o n s w i t h i n o f f i c e i n t e r i o r s . A c c e p t a b l e luminance ranges may be o b t a i n e d i n d a y l i t i n t e r i o r s w i t h c a r e f u l d e t a i l i n g : r e l a t i v e l y h i g h room s u r f a c e r e f l e c t a n c e s , c o n t r a s t g r a d i n g around d a y l i g h t i n g a p e r t u r e s , g l a r e c o n t r o l d e v i c e s a t d a y l i g h t i n g a p e r t u r e s , e t c . These t e c h n i q u e s a r e examined i n l a t e r c h a p t e r s . 3.2.2 D i s c o m f o r t G l a r e D i s c o m f o r t g l a r e i s an extreme s i t u a t i o n of b r i g h t n e s s c o n t r a s t o c c u r i n g when an o b j e c t w i t h i n the f i e l d of v i s i o n has a luminance e x c e e d i n g the range t o which the eye i s adapted at 48 S U R F A C E * BEING COMPARED MAX. BRIGHTNESS RATIOS T A 6 K AND ADJACENT SURROUNDINGS t TO 1 / 3 TASK AND MORE REMOTE DARKEFS SURFACES I TO «/io TAiK AND MORE REMOTE LIGHTER SURFACES 1 TO 10 FENESTRATION AND ADJACENT SURFACES 20 TO 1 • ANY TWO SURFACES WITHIN THE NORMAL FIELD OF VIEW 40 TO 1 T a b l e V - Recommended luminance r a t i o s w i t h i n the v i s u a l f i e l d the t i m e . D i s c o m f o r t g l a r e i s a f u n c t i o n of the luminance of the o f f e n d i n g s o u r c e , the s o l i d a n g l e subtended by i t a t the p o i n t of o b s e r v a t i o n , i t s l o c a t i o n w i t h i n the v i s u a l f i e l d , t he r e f l e c t a n c e s of the room s u r f a c e s and the g e n e r a l i l l u m i n a n c e i n the s p a c e 8 0 . As a r e s u l t , g l a r e c o n t r o l can be a c h i e v e d by r e d u c i n g the luminance of the g l a r e source and/or r e d u c i n g i t s p e r c e i v e d s i z e ; moving i t s l o c a t i o n t o the p e r i p h e r y of v i s i o n ; i n c r e a s i n g the g e n e r a l background luminance by i n c r e a s i n g the ambient i l l u m i n a n c e and the r e f l e c t a n c e s of major s u r f a c e s i n the f i e l d of view; and i n g e n e r a l , by d e c r e a s i n g the c o n t r a s t between the l i g h t source and i t s s u r r o u n d i n g s 8 1 . F i g u r e 6 8 2 shows t h e s e r e l a t i o n s h i p s . S u b s t a n t i a l l y g r e a t e r luminance v a l u e s a r e t o l e r a t e d a t the p e r i p h e r y of v i s i o n than a t the c e n t r e of v i s i o n (by a f a c t o r of 4 ) 8 3 , and t h e r e f o r e h i g h e r b r i g h t n e s s l e v e l s can be t o l e r a t e d f o r luminous c e i l i n g s , f o r example, than f o r w a l l a r e a s , which a r e more prominent i n the f i e l d of v i s i o n . 49 IriCRCASC IN OF SOUECC > F i g u r e 6 - G l a r e as a f u n c t i o n of ar e a and l o c a t i o n of source The p e r c e p t i o n of g l a r e i s not a c o n s t a n t f a c t o r , but i s an i n v e r s e f u n c t i o n of the a d a p t a t i o n r e f e r e n c e l e v e l of the eye, which c o r r e s p o n d s t o the average i l l u m i n a t i o n l e v e l a t the t a s k and the immediate t a s k s u r r o u n d . T h e r e f o r e , the h i g h e r the i l l u m i n a n c e w i t h i n a space and/or the h i g h e r the r e f l e c t a n c e s of the i n t e r i o r s u r f a c e s , the g r e a t e r luminance a s o u r c e of i l l u m i n a t i o n - - a window, f o r example—may have b e f o r e i t becomes a sou r c e of g l a r e . For the range of l i g h t i n g l e v e l s of 300 t o 1 000 l u x found i n p r e s e n t day o f f i c e s , c r i t i c a l sky luminance i s 6 000 and 20 OOOasb r e s p e c t i v e l y 8 4 . T h i s c o i n c i d e s w i t h v a l u e s o b t a i n e d by Hopkinson and o t h e r s , shown g r a p h i c a l l y i n f i g u r e 7 8 5 , 8 6 . " In Vancouver, the luminance of a c l e a r sky ( e x c l u d i n g the 50 i ceo 100 2D0 "WO too loco 20O0 4000 OOOO \OOoo 20BOO Luminance of horizon sky in &pos"h'lhs F i g u r e 7 - Range of sky luminance a c c e p t a b l e w i t h a f i x e d l e v e l of supplementary l i g h t i n g r e g i o n near the sun, which i s assumed t o be s h i e l d e d from the i n t e r i o r ) i s between 13 000 and 20 OOOasb, depending l a r g e l y on a n g u l a r a l t i t u d e ; the luminance of a c l o u d y sky i s between 7 000 and 14 OOOasb 8 7. T h e r e f o r e , w i t h h i g h i n d o o r , i l l u m i n a n c e l e v e l s and/or a p a r t i a l l y o b s t r u c t e d s k y v a u l t , g l a r e may not be a problem. T h i s i s a l s o the c o n c l u s i o n of G a l b r e a t h 8 8 who has s t a t e d t h a t when d i r e c t s u n l i g h t i s e x c l u d e d , a c l e a r sky i s seldom so b r i g h t as t o cause d i s c o m f o r t . M a t t h e w s 8 9 c o n c u r s , s a y i n g t h a t the problem of g l a r e has been overe m p h a s i z e d i n p r e s e n t - d a y d e s i g n t e c h n i q u e s . In the worst case s i t u a t i o n s , such as tho s e i n v o l v i n g h i g h e x t e r i o r luminances and low i n t e r i o r l u m i n a n c e s , t h e problem i n v o l v e s r e d u c i n g the luminance through the window by a f a c t o r 51 of about 3. T h i s o b s e r v a t i o n i s c o n f i r m e d by S e l k o w i t z 9 0 , who has o b s e r v e d t h a t " g l a r e i s a problem of k n o c k i n g down the b r i g h t n e s s by a f a c t o r of 2 or 3". S i n c e h i g h e r b r i g h t n e s s i s t o l e r a t e d a t the p e r i p h e r y of v i s i o n , g l a r e may be reduced by a r r a n g i n g w o r k i n g p o s i t i o n s so t h a t unscreened windows are n o t . i n the l i n e of s i g h t of w o r k e r s 9 1 . T h i s s o l u t i o n i s not always as f e a s i b l e i n p r e s e n t day o f f i c e s i t u a t i o n s as i t was i n the p a s t due t o i n c r e a s e d c o m p l e x i t y of o f f i c e a c t i v i t i e s and i n c r e a s e d d e n s i t i e s . On the o t h e r hand, i t may be p o s s i b l e , e s p e c i a l l y w i t h work s t a t i o n s u t i l i z i n g the newer o f f i c e f u r n i t u r e systems, t o a r r a n g e components t o s h i e l d d i r e c t v iews of unscreened windows; movable b u l l e t i n b o a r d s , a c o u s t i c s c r e e n s , s h e l v e s , hanging p l a n t s , can a l l be used f o r t h i s purpose. L y n e s 9 2 has c a u t i o n e d t h a t g l a r e l i m i t s a p p r o p r i a t e f o r e l e c t r i c l i g h t s o u r c e s — s m a l l or l a r g e — w i l l be too c o n s e r v a t i v e i f a p p l i e d t o d a y l i g h t i n g a p e r t u r e s , because of two phenomena: i . Because of the_,.."proximity e f f e c t " , the sky, b e i n g p e r c e i v e d as f u r t h e r away, w i l l f e e l l e s s o p p r e s s i v e than a luminous s o u r c e w i t h i n the i n t e r i o r space, even when the luminance and s o l i d a n g l e subtended by b o t h are the same. i i . Because of the " h a b i t u a t i o n e f f e c t " , most p e o p l e f i n d the s k y , which they have known s i n c e b i r t h , l e s s o b j e c t i o n a b l e as a g l a r e s o u r c e than e l e c t r i c l i g h t i n g of s i m i l a r luminous c h a r a c t e r i s t i c s . In a s i m i l a r v e i n , Lam 9 3 has s t a t e d t h a t when the s t i m u l u s i s m e a n i n g f u l , r e l e v a n t , and e x p e c t e d , much h i g h e r luminances 52 a r e a c c e p t a b l e . Thus a p a t t e r n of l i g h t f i x t u r e s or a luminous c e i l i n g may be judged as g l a r i n g or a n n o y i n g , w h i l e under i d e n t i c a l i n t e r i o r - l i g h t l e v e l s , a window view of g r e a t e r luminance may be p e r c e i v e d as s p a r k l i n g and e n j o y a b l e . A c c o r d i n g to Lam, "people p e r c e i v e i n f o r m a t i o n and r e l a t i o n s h i p s , not a b s o l u t e i n t e n s i t y l e v e l s of l i g h t " 9 " . S i n c e the phenomenon of g l a r e i s an extreme s i t u a t i o n of b r i g h t n e s s d i f f e r e n c e s , a l l methods t h a t h e l p i n b a l a n c i n g the p e r c e i v e d b r i g h t n e s s i n a space, do a l s o , t o some e x t e n t , reduce the g l a r e problem. 3.2.3 V i s u a l Rest C e n t r e s The p r o v i s i o n of v i s u a l r e s t c e n t r e s w i t h i n a work space i s a n o t h e r r e q u i r e m e n t f o r v i s u a l c o m f o r t . The eye muscles need p e r i o d i c r e l a x a t i o n from the e f f o r t of c l o s e - u p work; they can r e l a x when the eye i s f o c u s e d on d i s t a n t o b j e c t s , termed " v i s u a l r e s t c e n t r e s " . In p r a c t i c e , o b j e c t s or s u r f a c e s 6m or f a r t h e r from one's l o c a t i o n can s e r v e the purpose. The v i s u a l r e s t c e n t r e s h o u l d p r e f e r a b l y be an a r e a of low p h o t o t r o p i c a t t r a c t i o n - i . e . of e q u a l or lower b r i g h t n e s s than the v i s u a l t a s k , and h a v i n g no c o n s p i c u o u s v i s u a l p a t t e r n t h a t may s e r i o u s l y i n t e r f e r e w i t h the eye's r e l a x a t i o n 9 5 . Examples ar e views out of windows (some a r e b e t t e r f o r t h i s purpose than o t h e r s ) , l o n g views a c r o s s rooms, a r e a s of c l e a r c o l o u r , e t c . 9 6 Windows can s e r v e w e l l as v i s u a l r e s t c e n t r e s , even though t h e i r b r i g h t n e s s l e v e l i s g e n e r a l l y g r e a t e r than t h a t of the t a s k , s i n c e they o f f e r d i s t a n t o b j e c t s f o r the eye t o f o c u s on, 53 and r e l i e f from the v i s u a l work b e i n g done. Windows t h a t p r o v i d e a view of s o f t l a n d s c a p i n g , of sky and of s i m p l e v i s u a l p a t t e r n s , s e r v e best as v i s u a l r e s t c e n t r e s , but windows o v e r l o o k i n g a c t i v e scenes can a l s o be s a t i s f a c t o r y f o r r e l a t i v e l y s t a t i c v i s u a l t a s k s , such as r e a d i n g or w r i t i n g , s i n c e a degree of p s y c h o l o g i c a l s t i m u l a t i o n i s a c c e p t a b l e f o r t h e s e a c t i v i t i e s . 3.3 L i g h t i n g For V i s u a l P e r c e p t i o n There i s g e n e r a l agreement among l i g h t i n g d e s i g n e r s t h a t c o n s i d e r a t i o n of p e r c e p t u a l f a c t o r s i s n e c e s s a r y f o r good l i g h t i n g d e s i g n 3 7 . T h i s i s f o r the f o l l o w i n g r e a s o n s : i . The o v e r a l l v i s u a l i m p r e s s i o n t h a t occupants have of t h e i r work environment w i l l i n f l u e n c e t h e i r s a t i s f a c t i o n w i t h , and a c c e p t a n c e o f , the space, and t h i s i n t u r n , w i l l a f f e c t work p e r f o r m a n c e 9 8 . i i . C o n s c i o u s use of p e r c e p t u a l f a c t o r s i n the d e s i g n of l i g h t i n g can h e i g h t e n the p e r c e p t i o n of form and space f o r p r a g m a t i c as w e l l as a e s t h e t i c ends. L i g h t may be used t o c r e a t e p e r c e p t u a l i m p r e s s i o n s t h a t have immediate and p r a c t i c a l p urposes: t o emphasize a r c h i t e c t u r a l f o c a l p o i n t s , c l a r i f y s t r u c t u r e , draw a t t e n t i o n t o dangerous edges, e t c . L i g h t i s thus c o n s c i o u s l y u t i l i z e d t o r e i n f o r c e p e r c e p t u a l c l u e s w i t h a r e s u l t a n t i n c r e a s e i n s p a t i a l c l a r i t y and e a s i e r use of the b u i l d i n g . However, the use of l i g h t i n t h i s way can go beyond the p r a g m a t i c , and may be p a r t 54 of a l a r g e r purpose: t o mould and i n t e r p r e t space and h i g h l i g h t i t s beauty. L a m " , J a y 1 0 0 and B o y c e 1 0 ' have a l l d i s c u s s e d the r o l e and importance of p e r c e p t u a l i m p r e s s i o n s i n l i g h t i n g d e s i g n . F l y n n 1 0 2 has d e v i s e d r e s e a r c h m e t h o d o l o g i e s - - f a c t o r a n a l y s i s , m u l t i d i m e n s i o n a l s c a l i n g and semantic d i f f e r e n t i a l t e c h n i q u e s - -t h a t can s y s t e m a t i c a l l y i d e n t i f y and s c a l e t h e s e i m p r e s s i o n s . The p r i n c i p l e s f o r m a n i p u l a t i n g l i g h t i n g t o g i v e d e s i r e d i m p r e s s i o n s i n spaces have been w e l l f o r m u l a t e d , and a r e of g r e a t v a l u e . U l t i m a t e l y , however, t h e i r a p p l i c a t i o n i n v o l v e s s y n t h e s i s and i n t u i t i o n . The d e t a i l e d d i s c u s s i o n of l i g h t i n g i n g e n e r a l , t o a c h i e v e d e s i r e d i m p r e s s i o n s i n i n t e r i o r s , i s beyond the scope of t h i s t h e s i s . D a y l i g h t i n g and s u n l i g h t i n g i n b u i l d i n g i n t e r i o r s r e s u l t i n p e r c e p t u a l advantages which a r e due e i t h e r t o the mode of e n t r y of d a y l i g h t / s u n l i g h t i n t o i n t e r i o r s or the i n h e r e n t n a t u r e of these l i g h t s o u r c e s . These a r e d i s c u s s e d under the f o l l o w i n g h e a d i n g s : i . view i i . s p a c i o u s n e s s i i i . m o d e l l i n g i v . drama of d a y l i g h t v. sunshine 55 3.3.1 View View--or some c o n t a c t w i t h the o u t s i d e w o r l d - - i s c o n s i d e r e d by occupants one of the most h i g h l y v a l u e d b e n e f i t s p r o v i d e d by w i n d o w s 1 0 3 . The a b i l i t y t o r e s t one's eyes on some d i s t a n t o b j e c t , t o be aware of the time of day, of changes i n weather and of u n f o l d i n g e v e n t s o u t d o o r s , a l l c o n t r i b u t e t o the v a l u e of view. Whereas a l l windowed b u i l d i n g s p r o v i d e view t o a g r e a t e r or l e s s e r e x t e n t , d a y l i t b u i l d i n g s can enhance t h a t p o t e n t i a l . In d a y l i t b u i l d i n g s , windows a r e c o n s i d e r e d a s s e t s i n the t o t a l energy p i c t u r e ; i n c o n v e n t i o n a l d e s i g n , they a re c o n s i d e r e d t h e r m a l l i a b i l i t i e s r e q u i r i n g t r a d e - o f f s between human s a t i s f a c t i o n and energy use. The l o c a t i o n of windows f o r d a y l i g h t i n g may not c o i n c i d e w i t h the p r e f e r e d l o c a t i o n f o r vie w , but the v e r y f a c t t h a t i n d a y l i g h t i n g d e s i g n windows are c o n s i d e r e d i n t h e i r v a r i o u s f u n c t i o n a l a s p e c t s ( r a t h e r than p r e d o m i n a n t l y as elements i n a v i s u a l c o m p o s i t i o n ) and window s i z e i s not m i n i m i z e d , w i l l i n c r e a s e the l i k e l i h o o d of view b e i n g g i v e n due c o n s i d e r a t i o n . View and c o n n e c t i o n w i t h the o u t d o o r s i s enhanced f u r t h e r i n d a y l i t b u i l d i n g s by the i n c r e a s e d p e r c e p t i o n of the s u b t l e changes i n the i n t e n s i t y of d a y l i g h t and, i n some d e s i g n s , by the p l a y of s u n l i g h t on some i n t e r i o r s u r f a c e s . In many new o f f i c e b u i l d i n g s , a l a r g e p e r c e n t a g e of e x t e r i o r w a l l a r e a may be c o v e r e d w i t h r e f l e c t i v e g l a s s of v e r y low ( 7 - 2 0 % ) t r a n s m i t t a n c e . Some s u r v e y s have found t h a t t h e 56 reduced luminance of the o u t d o o r s c r e a t e d a sense of v i s u a l gloom t h a t the occupants found t o be d e p r e s s i n g . A l s o , the g l a s s , because of i t s low t r a n s m i t t a n c e , t u r n e d i n t o a m i r r o r whenever i l l u m i n a t i o n l e v e l s o u t d o o r s were r e l a t i v e l y low i n the daytime. T h i s was found to be d i s t r a c t i n g 1 0 " . At c e r t a i n sun a n g l e s , r e f l e c t i v e g l a s s can a l s o c o n t r i b u t e t o annoying g l a r e (and s u b s t a n t i a l l o a d on the AC system) i n a d j a c e n t b u i l d i n g s . Thus, v e r y low t r a n s m i t t a n c e g l a s s , a l t h o u g h p r o v i d i n g a s o l u t i o n t o the problems of i n t e r i o r g l a r e and s o l a r heat g a i n , has a d v e r s e e f f e c t on the p e r c e p t i o n of the o u t d o o r s . I t a l s o e l i m i n a t e s the p o t e n t i a l of d a y l i g h t i n g i n b u i l d i n g s where i t i s used. 3.3.2 S p a c i o u s n e s s The p r e s e n c e of windows i n a room make i t seem more s p a c i o u s 1 0 5 , reduces f e e l i n g s of e n c l o s u r e and r e s t r i c t i o n and i n c r e a s e s i t s apparent s i z e 1 0 6 . I t adds an i m p o r t a n t p s y c h o l o g i c a l d i m e n s i o n to a room, almost u n r e l a t e d t o such f a c t o r s as view or s u n s h i n e . Windows need not be too l a r g e f o r t h i s purpose but cannot be too s m a l l 1 0 7 . T h i s may perhaps be because the m o d e l l i n g e f f e c t of d a y l i g h t , which i s a f a c t o r i n the p e r c e i v e d s p a c i o u s n e s s of a space, d i s a p p e a r s when the window i s t o o s m a l l . S p a c i o u s n e s s of i n t e r i o r s due t o the presence of windows i s not l i m i t e d t o b u i l d i n g s p u r p o s e l y d e s i g n e d t o t a k e advantage of d a y l i g h t i n g , but d a y l i g h t i n g w i l l enhance t h i s q u a l i t y . F l y n n ' s s t u d y 1 0 8 , summarized i n t a b l e VI , t e s t i f i e s t o the 57 p o s i t i v e e f f e c t of p e r i p h e r a l l i g h t i n g i n g e n e r a l . The s p a c i o u s n e s s c r e a t e d by windows, may be seen as an example of t h i s more g e n e r a l phenomenon. SUBJECTIVE. IMPRESSION L IGHTING CUES IMPRESSION OF PERCEPTUAL CLARITY IMPRESSION" OF SPACIOUSNESS IMPRESSION OF RELAXATION IMPRESSION OF PRIVACY" IMPRESSION OF PLEASANTNESS • BRIGHT, UNIFORM LI6HTIN6. • PERIPHERAL EMPHASIS, SUCH AS WITH HIGH REFLECTANCE WALLS, OR WALL U6HTIW6. • UNIFORM, PER1PHERAL(\VAU)LI6HTIN6. • BRIGHTNESS IS A REINFORCING. FACTOR, BUT NOT A DECISIVE ONE. •NON-UNIFORM LIGHTING.. > PERIPHERAL (ll/ALL)EMPHASIS, RATHER THAW OVERHEAD LIGHTING. •NON-UWTFORM LIGHTING. •TENDENCY TOWARD LOW LIGHT INTENSITIES IN THE IMMEDIATE LOCALE OF THE USER, WITH HIGHER BRIGHTNESSES REMOTE FROM THE USER. PERIPHERAL (WALL)EMPHASIS 15 A REINFORCING FACTOR, BUT NOT A DECISIVE ONE. • NON-UNIFORM LIGHTING. •PERIPHERAL (WALL)EMPHASIS. T a b l e VI - R e i n f o r c e m e n t of s u b j e c t i v e i m p r e s s i o n s by l i g h t i n g cues 3.3.3 M o d e l l i n g In o f f i c e s , the predominant m o d e l l i n g r e q u i r e m e n t i s t h a t of s e e i n g p e o p l e s ' f a c e s d u r i n g c o n v e r s a t i o n s . L y n e s 1 0 9 has found t h a t f o r t h i s r e q u i r e m e n t , t h e r e was a d i s t i n c t p r e f e r e n c e f o r l i g h t i n g w i t h some d i r e c t i o n a l c h a r a c t e r and c l o s e t o the h o r i z o n t a l — 1 5 - 4 5 ° above the h o r i z o n t a l b e i n g the range of the most- p r e f e r r e d d i r e c t i o n s . The l e a s t a c c e p t a b l e d i r e c t i o n was 58 found t o be l i g h t i n g d i r e c t l y t h a t d a y l i g h t i n g a p e r t u r e s above the work p l a n e , c h a r a c t e r i s t i c s . 3.3.4 The Drama Of D a y l i g h t C u r r e n t e n v i r o n m e n t a l d e s i g n p r a c t i c e s aim at u n i f o r m t e m p e r a t u r e s and u n v a r y i n g l i g h t l e v e l s i n our b u i l d i n g s , and as such, the v a r i a b i l i t y of d a y l i g h t may a t f i r s t thought appear t o be u n d e s i r a b l e . However, e x p e r i e n c e and r e s e a r c h suggest t h a t the changes and v a r i a b i l i t y i n t r o d u c e d i n t o a space by d a y l i g h t a r e v a l u e d by the occupants and even p r e f e r r e d over u n i f o r m l i g h t i n g c o n d i t i o n s 1 1 0 , 1 1 1 , 1 1 2 . L a r s o n 1 1 3 has w r i t t e n : Good l i g h t i n g , i n terms of e f f i c i e n c y of work and p s y c h o l o g i c a l i n t e r e s t must be s u i t a b l y v a r i a b l e but c o n s t a n t l y adequate... For r e l a t i v e l y s t a t i c v i s u a l t a s k s , c o n s t a n c y on the work s u r f a c e and v a r i a t i o n w i t h i n t h e space are c o n d u c i v e t o a h e a l t h y v i s u a l s i t u a t i o n . The worker and not the work i s the f i n a l reason f o r l i g h t i n g a p a r t i c u l a r way: l i g h t i n g s h o u l d be d e s i g n e d w i t h the best p h y s i o l o g i c a l , p s y c h o l o g i c a l and e s t h e t i c i n t e r e s t s of the worker i n mind. The s h o r t term v a r i a t i o n s have been found t o add a dynamic q u a l i t y t o d a y l i t i n t e r i o r s , c o n t r i b u t i n g t o an a v o i d a n c e of the monotony t h a t e l e c t r i c a l l i g h t i n g i n s t a l l a t i o n s sometimes e v o k e 1 1 " . T h i s c h a r a c t e r i s t i c v a r i a b i l i t y i s sometimes c a l l e d the " l i v i n g q u a l i t y " of d a y l i g h t 1 1 5 . There i s a marked d i f f e r e n c e i n the " f e e l " of d a y l i t o verhead. I t i s c l e a r from t h i s l o c a t e d i n e x t e r i o r w a l l s , at or p r o v i d e p r e f e r r e d m o d e l l i n g 59 spaces, as compared t o those l i t by e l e c t r i c l i g h t i n g 1 1 6 . They have a "more p l e a s i n g and n a t u r a l c h a r a c t e r " 1 1 7 . Surveys made on l i g h t i n g p r e f e r e n c e s have r e v e a l e d a w i d e s p r e a d b e l i e f t h a t d a y l i g h t i n g i s a b e t t e r l i g h t source than e l e c t r i c l i g h t i n g 1 1 8 . In some i n n o v a t i v e d a y l i t b u i l d i n g s t h e r e has been "overwhelming worker e n t h u s i a s m f o r d a y l i g h t and the concept of n a t u r a l l i g h t as the p r e f e r a b l e source of o f f i c e l i g h t i n g " 1 1 9 . In G reat B r i t a i n , when the system known as the Permanent Supplementary A r t i f i c i a l L i g h t i n g I n s t a l l a t i o n (PSALI) was c o n c e i v e d i n the 1950's f o r commercial and i n s t i t u t i o n a l b u i l d i n g s , i t was deemed impo r t a n t t h a t most of the i l l u m i n a t i o n be p r o v i d e d by d a y l i g h t , w i t h e l e c t r i c l i g h t i n g s u p p l e m e n t i n g i t . I t was f e l t t h a t " d a y l i g h t i n a l l i t s v a r i e t y and s t i m u l a t i o n must be p r o v i d e d , and must be the dominant • f e a t u r e of the room l i g h t i n g , r a t h e r than i t s h o u l d be shut out by b l i n d s or m e r e l y a l l o w e d t o peep t h r o u g h s m a l l view w i n d o w s " 1 2 0 . E v a n s 1 2 1 i d e n t i f i e s t h a t moderate changes i n i l l u m i n a n c e promote "comfort and a g r e e a b l e n e s s " and t h a t the i n t r o d u c t i o n of d a y l i g h t i n t o i n t e r i o r s i s "the s i m p l e s t and most e f f e c t i v e way t o p r o v i d e t h e s e v a l u a b l e [ c h a n g e s ] . . . o f r e a s o n a b l y subdued s u r f a c e - b r i g h t n e s s v a r i a t i o n s , w i t h some v i s u a l f l e x i b i l i t y and s t i m u l i " . V a r i a t i o n s i n i l l u m i n a n c e l e v e l a re known t o have a r e l a x i n g e f f e c t on the eyes and t o promote p o s i t i v e p s y c h o l o g i c a l r e a c t i o n s 1 2 2 . I t has a l s o been found t o a s s i s t c o n c e n t r a t i o n , as measured by the span of a t t e n t i o n 1 2 3 . 60 3.3.5 Sunshine D a y l i t b u i l d i n g s a re not the o n l y ones t h a t can admit s u n s h i n e i n t o t h e i r i n t e r i o r s ; a l l b u i l d i n g s w i t h windows or s k y l i g h t s can p o t e n t i a l l y do so. However, i n the d e s i g n of most commercial b u i l d i n g s , s u n s h i n e i s t r e a t e d as a problem: the a d d i t i o n a l heat i n t r o d u c e d p l a c e s a burden on the HVAC system; g l a r e i s a n u i s a n c e ; f u r n i t u r e and f a b r i c s fade. T h e r e f o r e , e f f o r t i s made t o s c r e e n out the sun. In s p i t e of t h i s , e x p e r i e n c e shows t h a t s u n l i g h t i n t r o d u c e d j u d i c i o u s l y and s p a r i n g l y - - a s a " w a l l wash" or o t h e r s i m i l a r means of h i g h l i g h t i n g s u r f a c e s of i n t e r e s t - - c a n make a w o r t h w h i l e a d d i t i o n t o the i n t e r i o r space. Sunshine, as d i f f e r e n t i a t e d from d a y l i g h t from the s ky-v a u l t , has been found t o c r e a t e a s e t of d i s t i n c t p s y c h o l o g i c a l r e a c t i o n s 1 2 " . The d e s i r a b i l i t y of sunshine i n i n t e r i o r spaces has been found by r e s e a r c h e r s t o v a r y w i t h the type of a c t i v i t y : h o s p i t a l p a t i e n t s and housewives found sunshine e x t r e m e l y i m p o r t a n t ( 8 5 - 9 1 % wanted i t ) ; s c h o o l t e a c h e r s and h o s p i t a l w orkers l e s s so (52-60%); o f f i c e workers were i n between (73% wanted s u n s h i n e ) 1 2 5 . The n a t u r e of the v i s u a l t a s k b e i n g p e r f ormed and the degree of freedom i n d i v i d u a l s have i n the space, undoubtedly a f f e c t s t h e i r p r e f e r e n c e f o r s u n s h i n e : the more i n d i v i d u a l s a r e a b l e t o c o n t r o l g l a r e and o v e r h e a t i n g by the use of s h a d i n g , or t o move around i n t h e i r t a s k , the more l i k e l y they w i l l a p p r e c i a t e s u n s h i n e 1 2 6 . The d e s i r e f o r s u n s h i n e i n the i n t e r i o r of b u i l d i n g s has 61 a l s o been found t o be s t r o n g e s t i n m a r i t i m e r e g i o n s and n o r t h e r n l a t i t u d e s , where the d u r a t i o n of s unshine i s most l i m i t e d ' 2 7 . The B.C. Lower M a i n l a n d f o r example, w i t h i t s " d r e a r y " w i n t e r s , i s an a p p r o p r i a t e g e o g r a p h i c a l a rea f o r the i n t r o d u c t i o n of s u n l i g h t s p a r k l e i n s i d e b u i l d i n g s . Lam has argued t h a t "most people view s u n l i t s u r f a c e s as d e s i r a b l e p o i n t s of i n t e r e s t , because of the importance of s u n l i g h t i n man's b i o l o g i c a l h i s t o r y " 1 2 8 . A l t h o u g h l e s s e x p e r i e n c e d d e s i g n e r s have been c a u t i o n e d a g a i n s t use of s u n l i g h t i n t a s k o r i e n t e d i n t e r i o r s , because of grave p e n a l t i e s a s s o c i a t e d w i t h d e s i g n e r r o r s 1 2 9 , examples of s u c c e s s f u l s o l u t i o n s are v e r y d r a m a t i c and a p p e a l i n g 1 3 0 . In c o n c l u s i o n , a c c o r d i n g t o a v a i l a b l e r e s e a r c h on the s u b j e c t , the q u a l i t y of i l l u m i n a t i o n p r o v i d e d by both d a y l i g h t and s u n l i g h t has a "tremendous p s y c h o l o g i c a l impact upon p e o p l e i n b u i l d i n g s " 1 3 1 . 4. NOTES 1. Adapted from f i g u r e s 1 and 2 of S. D. P. H a r k e r , "An A n a l y t i c a l Framework f o r D e s c r i b i n g the L i g h t i n g Requirements of I n d u s t r i a l Tasks," i n Developments i n  L i g h t i n g - - 2 : I n d u s t r i a l , e d i t e d by D. C. P r i t c h a r d (London: A p p l i e d S c i e n c e , 1982), pp. 22-23. 62 2. H a r k e r , pp. 22-23; 40-44. 3. Gary T. Yonemura, " C r i t e r i a f o r Recommending L i g h t i n g L e v e l s , " P r o c e e d i n g s of the Symposium._on "The I n t e g r a t i o n  of V i s u a l Performance C r i t e r i a i n t o the "~I l l u m i n a t i o n  Design P r o c e s s " , January 25-27, 1982. Ottawa: P u b l i c Works Canada, 1982, p. 387. 4. H a r k e r , p. 31. 5. A. W. Levy, " I n t e r i o r L i g h t i n g Design and Energy C o n s e r v a t i o n , " D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l Research C o u n c i l of Canada, Canadian B u i l d i n g D i g e s t 192, 1 977, p. 1 . 6. Yonemura, p. 387. 7. Levy, p. 3. 8. R. G. Hopkinson, A r c h i t e c t u r a l P h y s i c s : L i g h t i n g (London: Her M a j e s t y ' s S t a t i o n e r y O f f i c e , 1963), p^ 161. 9. Levy, p. 3. 10. Samuel Berman and Robert C l e a r , " R e l a t i n g P r o d u c t i v i t y t o V i s i b i l i t y and L i g h t i n g , " P r o c e e d i n g s of the Symposium on  "The I n t e g r a t i o n of V i s u a l Performance C r i t e r i a i n t o the  I l l u m i n a t i o n Design P r o c e s s " , January 25-27, 1982. Ottawa: P u b l i c Works Canada, 1982, p. 185. 11. Summarized p a r t l y from H a r k e r , pp. 37-42. 12. Derek P h i l l i p s , L i g h t i n g i n A r c h i t e c t u r a l Design ( T o r o n t o : M c G r a w - H i l l ) , 1964. 13. J . W. C a r l t o n , " E f f e c t i v e Use of L i g h t i n g , " i n Developments i n L i g h t i n g - - 2 : I n d u s t r i a l , e d i t e d by D. C. P r i t c h a r d (London: A p p l i e d S c i e n c e , 1982), p. 70. 14. H a r k e r , p. 15. 15. R. J . C o l e and R. W. Seaton, C l a s s handout, A r c h i t e c t u r e 431, " L i g h t , C o l o u r and Space", U n i v e r s i t y of B r i t i s h C olumbia, F e b r u a r y 27, 1978. 16. R i c h a r d G. S t e i n , A r c h i t e c t u r e and Energy (New York: Anchor/Doubleday, 1977), pp. 124-54. 17. L e s l i e L a r s o n , L i g h t i n g and I t s Design (New York: Whitney, 1964), p. 19. 18. J . A. Lynes, P r i n c i p l e s of N a t u r a l L i g h t i n g (London: E l s e v i e r , 1968), p. 138. 63 19. Berman and C l e a r , p.185. 20. J . J . Vos, "Can the CIE of V i s u a l Performances be A p p l i e d t o P r e s c r i b e L e v e l s of I n t e r i o r L i g h t i n g ? , " P r o c e e d i n g s of  the Symposium on "The I n t e g r a t i o n of V i s u a l Performance  C r i t e r i a i n t o the I l l u m i n a t i o n Design P r o c e s s " , January 25-27, 1982. Ottawa: P u b l i c Works Canada, 1982, p p . 5 5 , 5 6 . 21. Berman and C l e a r , p. 185. 22. That i s , i l l u m i n a n c e measured by a l i g h t meter, w i t h o u t c o n s i d e r i n g the q u a l i t y of l i g h t on the t a s k . A l s o termed " c l a s s i c a l i l l u m i n a n c e " or " t r a d i t i o n a l i n c i d e n t l u m i nance". 23. IES D a y l i g h t i n g Committee, "Recommended P r a c t i c e of D a y l i g h t i n g , " L i g h t i n g D e s i gn and A p p l i c a t i o n s , F e b r u a r y 1979, p. 30. 24. I b i d . 25. Levy, p. 2. 26. Vos, pp. 53-63. 27. Howard B r a n d s t o n , " L i g h t i n g D e s i g n : A P r a c t i t i o n e r ' s Problem," P r o c e e d i n g s of the Symposium' on "The I n t e g r a t i o n  of V i s u a l Performance C r i t e r i a i n t o the I l l u m i n a t i o n  D e s i g n P r o c e s s " , J a n u a r y 25-27, 1982. Ottawa: P u b l i c Works Canada, 1982, p. 42. 28. Levy, p. 2. 29. I s a a c Goodbar, "The A p p l i c a t i o n of the ESI System t o O f f i c e L i g h t i n g , " P r o c e e d i n g s of the Symposium on "The  I n t e g r a t i o n of V i s u a l Performance C r i t e r i a i n t o the  I l l u m i n a t i o n D e s i g n P r o c e s s " , January 25-27, 1982. Ottawa: P u b l i c Works Canada, 1982, pp. 123-183. 30. IES D a y l i g h t i n g Committee (1979), p. 31. 31. James W. G r i f f i t h , " B e n e f i t s of D a y l i g h t i n g : Energy and Cost S a v i n g s , " ASHRAE J o u r n a l 20, January 1978, p. 55. 32. P u b l i c Works Canada, L e v e l s of Performance R e l a t e d  I l l u m i n a t i o n A v a i l a b l e from D a y l i g h t i n T y p i c a l O f f i c e and  S c h o o l I n t e r i o r s (Ottawa: P u b l i c Works Canada, [ 1 980 3 ) . 33. I b i d . 34. E r i c Thrun and Robert J e n n i n g s , " L e v e l s of Performance R e l a t e d I l l u m i n a t i o n A v a i l a b l e from D a y l i g h t i n T y p i c a l O f f i c e S c h o o l I n t e r i o r s , " J o u r n a l of IES, October 1981, 64 pp. 7-10. 35. Hopkinson, p. 257. 36. As measured by the ease of r e a d i n g or by v i s u a l a c u i t y ( i . e . the a b i l i t y t o d e t e c t d e t a i l s i n the t a s k ) . R e s u l t s by both c r i t e r i a are s i m i l a r . 37. W. R. S t e v e n s , B u i l d i n g P h y s i c s : L i g h t i n g ( O x f o r d : Pergamon,1969), p. 24. 38. R. G. Hopkinson and J . B. C o l l i n s , The Ergonomics of  L i g h t i n g (London: MacDonald, 1970), p. 59. 39. I b i d . , p. 60. 40. I b i d . , p. 61. 41. H a r k e r , p. 33. 42. I b i d . 43. G r i f f i t h , p. 55. 44. "The term ' c o l o u r r e n d e r i n g ' w i t h r e f e r e n c e t o l i g h t s ources i s a measure of the degree t o which the p e r c e i v e d c o l o u r s of o b j e c t s i l l u m i n a t e d by v a r i o u s l i g h t s o u r c e s w i l l match the p e r c e i v e d c o l o u r s of the same o b j e c t when i l l u m i n a t e d by s t a n d a r d [ r e f e r e n c e ] l i g h t s o u r c e s , f o r s p e c i f i c v i e w i n g c o n d i t i o n s " . The r e f e r e n c e l i g h t s o u r c e most commonly used i s d a y l i g h t . G e n e r a l E l e c t r i c , L i g h t  and C o l o r ( P u b l i c a t i o n no. TP'19, 1967), p. 23. 45. S. M. A s t o n and H. E. B e l l c h a m b e r s , " I l l u m i n a t i o n , C o l o u r r e n d e r i n g and V i s u a l C l a r i t y , " L i g h t i n g R e s e a r c h and  Technology,1(1969)259-261. 46. The c o l o u r r e n d e r i n g index compares the averaged c o l o u r r e n d e r i n g of a l i g h t source a t d i f f e r e n t wavelengths w i t h t h a t of a b l a c kbody r a d i a t o r o r , i f the c o l o u r t e m p e r a t u r e i s above 5000K 0 ( f l u o r e s c e n t l i g h t s o u r c e s a r e ) , then w i t h the n e a r e s t r e c o n s t i t u t e d d a y l i g h t s o u r c e . R e c o n s t i t u t e d d a y l i g h t i s a p h y s i c a l s t a n d a r d , d e r i v e d by m a t h e m a t i c a l l y a v e r a g i n g the range of c h a r a c t e r i s t i c s of d a y l i g h t a t d i f f e r e n t l o c a t i o n s , e l e v a t i o n s , t i m e s - a t a g i v e n c o l o u r t e m p e r a t u r e . G. E., L i g h t and C o l o u r , p. 26. 47. Luke T h o r i n g t o n , " L i g h t , B i o l o g y and P e o p l e , P a r t 2," L i g h t i n g D e s i gn and A p p l i c a t i o n s , December 1973, p. 33. 48. Levy, p. 3. 49. T h o r i n g t o n , p. 33. 65 50. S c o t t Matthews and P e t e r C a l t h o r p e , " D a y l i g h t as a C e n t r a l Determinant of D e s i g n , " AIA J o u r n a l , September 1979, p. 88. 51. A r t h u r H. R o s e n f e l d and Stephen E. S e l k o w i t z , "Beam D a y l i g h t i n g : An A l t e r n a t i v e I l l u m i n a t i o n t e c h n i q u e , " Energy and B u i l d i n g s , 1 ( 1 9 7 7 ) : 4 3 . 52. H e r b e r t A. Anderson, " O f f i c e D e s i g n Case Study: H i g h Colour R e n d e r i n g L i g h t Sources Improves M a n u f a c t u r i n g F a c i l i t y , " B u i l d i n g O p e r a t i n g Management, June 1973, pp. 26-28. 53. F r a n c i s R u b i n s t e i n , t a l k g i v e n a t the P l e n n a r y S e s s i o n of P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983. 54. T h o r i n g t o n , p. 32. 55. R. J . Wurtman, " B i o l o g i c a l I m p l i c a t i o n s of A r t i f i c i a l I l l u m i n a t i o n , " I l l u m i n a t i n g E n g i n e e r i n g , 63(1968):523-29. 56. The v i s i b l e spectrum ranges between 760nm at the r e d end and 380nm at the v i o l e t end; near u l t r a v i o l e t r a y s a r e 380-320nm; m i d - u l t r a v i o l e t r a y s a r e 320-290nm. F a r u l t r a v i o l e t r a y s (below 290nm), which a r e h a r m f u l t o man and most o t h e r l i v i n g o r g a n i s m s , a r e f i l t e r e d out by the atmosphere. 57. T h o r i n g t o n , p. 34. 58. S y l v e s t e r K. Guth, "Some O b s e r v a t i o n s on the B i o l o g i c a l E f f e c t s of L i g h t , " L i g h t i n g D e s i g n and A p p l i c a t i o n s , November 1973, p. 26. 59. Zane R. Kime, S u n l i g h t C o u l d Save Your L i f e ( P e n r y n , C a l i f o r n i a : World H e a l t h , 1980), p. 171. 60. R. J . Wurtman, " B i o l o g i c a l C o n s i d e r a t i o n s i n L i g h t i n g Environment," P r o g r e s s i v e A r c h i t e c t u r e , September 1973, p. 79. 61. I b i d . , p. 81. 62. F. D. H o l l i s t e r , G r e a t e r London C o u n c i l : A Report on the  Problems of Windowless Environments (London: Hobbs the P r i n t e r s , 1968), pp. 64-66. 63. B e l i n d a Lowenhaupt C o l l i n s , Windows & Human S a t i s f a c t i o n  i n S o l a r R a d i a t i o n C o n s i d e r a t i o n s i n B u i l d i n g P l a n n i n g and  Design (Washington, D. C : N a t i o n a l Academy o f S c i e n c e s , 1976), pp. 69-70. 66 64. T h o r i n g t o n , supra and T h o r i n g t o n , " L i g h t , B i o l o g y and P e o p l e , P a r t 1," L i g h t i n g Design and A p p l i c a t i o n s , November 1973, pp. 19-23. 65. Guth, s u p r a . 66. R i c h a r d C o r t h and Roger A. Hoffman, "Does A r t i f i c i a l L i g h t i n g A f f e c t Man's H e a l t h ? P r o b a b l y Not," L i g h t i n g  Design and A p p l i c a t i o n s , November 1973, pp. 30-36. 67. J . N. O t t , H e a l t h and L i g h t (Old Grenwich:Devon-Adair, 1973) . 68. Duro-Test, " V i t a - L i t e " t r a d e l i t e r a t u r e . 69. I b i d . 70. T h i s i s p a r t l y because one r e l a t i v e l y s m a l l l i g h t b u l b company has e x c l u s i v e m a n u f a c t u r i n g r i g h t s on the f u l l s pectrum f l u o r e s c e n t lamps. 71. C o r t h , s u p r a . 72. Kime, p. 249. 73. B: J . B r i n k w o r t h , S o l a r Energy f o r Man ( S a l i s b u r y , Great B r i t a i n : The Compton P r e s s , 1972), pp. 232-34. 74. P i l k i n g t o n G l a s s Company, Trade l i t e r a t u r e : " P i l k i n g t o n ' G l a s s Facts'--13A" 75. Kime, p. 249. 76. S a i n t Gobain G l a s s , Trade l i t e r a t u r e ; a l s o P. P. G. Trade l i t e r a t u r e , s u p r a . 77. Lynes, pp. 1-3. 78. ' B r i g h t n e s s ' i s a s u b j e c t i v e , p s y c h o p h y s i c a l term, d e s c r i b i n g the p e r c e i v e d l u m i n o s i t y of an o b j e c t ; 'luminance' i s a p h o t o m e t r i c term, d e s c r i b i n g the amount of l i g h t f l u x e m i t t e d , r e f l e c t e d or t r a n s m i t t e d i n a g i v e n d i r e c t i o n (Lynes, pp. 2, 2 3 ) . . 79. Murdoch G a l b r e a t h , " D a y l i g h t D e s i g n , " D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l Research C o u n c i l of Canada, Canadian B u i l d i n g D i g e s t 17, May 1961, p. 4. 80. Hopkinson and C o l l i n s , p. 101. 81. P h i l l i p s , p.43. 82. F i g u r e a f t e r John E. F l y n n and Samuel M. M i l l s , 67 A r c h i t e c t u r a l L i g h t i n g G r a p h i c s (New York: Van N o s t r a n d R e i n h o l d , 1962), p~] 58. Lumi nance v a l u e s t w i c e as h i g h may be a c c e p t a b l e i f r e l a t i v e l y h i g h s u r f a c e r e f l e c t a n c e s a re used throughout the room, thus r e d u c i n g d i s t r a c t i n g c o n t r a s t s and r a i s i n g a d a p t a t i o n l e v e l s ( F l y n n and M i l l s , p. 58). 83. I b i d . 84. G a l b r e a t h , p. 4. T h i s i s assuming average s u r f a c e r e f l e c t a n c e s of 50% and u s i n g the r u l e of thumb of 1 t o 40 between any two s u r f a c e s w i t h i n the normal f i e l d of view. 85. Hopkinson, A r c h i t e c t u r a l P h y s i c s , p. 120 86. D. P. T u r n e r , ed, Windows and Environment (Newton-le-W i l l o w s : P i l k i n g t o n E n v i r o n m e n t a l A d v i s o r y S e r v i c e , 1969), pp. 2.38-2.39. 87. Measurements made by a u t h o r , a t noon, i n s p r i n g , summer and w i n t e r , 1983. The lower v a l u e s were measured a t the w i n t e r s o l s t i c e ; s p r i n g and summer v a l u e s a re near the h i g h end. 88. G a l b r e a t h , p. 4. 89. S c o t t Matthews, " L i g h t i n g from the Top",' T a l k g i v e n a t P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983 90. R i c h a r d Rush, " G l a s s o l i n e , " P r o g r e s s i v e A r c h i t e c t u r e , September, 1981,-p. 238. 91. D. C. P r i t c h a r d , L i g h t i n g (London:Longman, 1969), p. 87. 92. Lynes, pp. 153-54. 93. W i l l i a m M. Lam, P e r c e p t i o n and L i g h t i n g as F o r m g i v e r s f o r  A r c h i t e c t u r e (New York: M c G r a w - H i l l , 1977), p. 70. 94. I b i d . 95. P h i l l i p s , p. 36 and Hopkins o n , A r c h i t e c t u r a l P h y s i c s , p. 21 . 96. Leonard Menasseh and P e t e r C u n l i f f e , O f f i c e B u i l d i n g s (New York: R e i n h o l d , 1962), p. 33. 97. Yonemura, p. 384. 98. I b i d , p. 385. 68 99. Lam, s u p r a . 100. P. A. J a y , " L i g h t i n g and the Search f o r Meaning," i n Developments i n L i g h t i n g - - P a r t J_, e d i t e d by J . A. Lynes (London: A p p l i e d S c i e n c e , 1978), pp. 7 7-111. 101. P. R. Boyce, "Under the I n f l u e n c e of L i g h t i n g , " i n Developments i n L i g h t i n g - - P a r t J_, e d i t e d by J . A. Lynes (London: A p p l i e d S c i e n c e , 1978), pp. 47-76. 102. John E. F l y n n , "A Study of S u b j e c t i v e Responses t o Low Energy and Nonuniform L i g h t i n g Systems," L i g h t i n g Design  and A p p l i c a t i o n s , F e b r u a r y 1977, pp. 6-15. 1 03 . C o l l i n s , p. 76. 104. I b i d . , p. 66. 105. I b i d . , p. 77. 106. I b i d . , p. 75. 107. I b i d . , p. 76. 108. F l y n n , p. 8 and Boyce, p. 67. 109. Lynes, pp. 48-50. 110. Stephen E. S e l k o w i t z , " D a y l i g h t i n g and P a s s i v e S o l a r B u i l d i n g s , " P r o c e e d i n g s of the 3rd N a t i o n a l P a s s i v e S o l a r  C o n f e r e n c e , J a n u a r y 11-13, 1979 i n San J o s e , C a l i f . , Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1979, p. 279. 111. IES D a y l i g h t i n g Committee (1979), p.26. 112. M a r g u e r i t t e V i l l e c c o , S. S e l k o w i t z , and J . W. G r i f f i t h , " S t r a t e g i e s of D a y l i g h t D e s i g n , " A l A J o u r n a l , September 1979, p. 68. 113. L a r s o n , pp. 7-8. 114. G. K. J a c k s o n and J . G. Holmes, " L e t ' s Keep I t Simple ( I l ) - - W h a t we want from d a y l i g h t , " L i g h t and  L i g h t i n g , March 1973, p. 80. 115. Lynes, p. 51. 116. J a c k s o n , p. 80. 117. C o l l i n s , p. 55. 118. I b i d . , p.33. 69 119. Matthews and C a l t h o r p e , p.88. 120. Hopkinson, A r c h i t e c t u r a l P h y s i c s , p. 318. T'21 . Benjamin H. Evans, D a y l i g h t i n A r c h i t e c t u r e (New York: M c G r a w - H i l l , 1981), p. 21. 122. IES D a y l i g h t i n g Committee (1979), p. 34. 123. Lynes, p. 51. 124. C o l l i n s , p. 58. 125. I b i d . , pp. 59,60. 126. I b i d . , p. 60. 1 27. I b i d . , p. 61. 128. W i l l i a m M. C. Lam, " S u n l i g h t i n g as F o r m g i v e r f o r A r c h i t e c t u r e , " P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l  D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, p. 78. 129. Harvey Bryan, p r e s e n t a t i o n a t the D a y l i g h t i n g D e s i gn T o o l s Workshop, The 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . 130. Lam, W. M. C. S l i d e p r e s e n t a t i o n at the 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , F e b r u a r y 17, P h o e n i x , A r i z o n a . 131. C o l l i n s , p. 54. 70 III-. PROMOTE DAYLIGHT ACCESS 71 1. INTRODUCTION D a y l i g h t , u n l i k e e l e c t r i c l i g h t , o r i g i n a t e s o u t s i d e the b u i l d i n g , and as such, i t must p e n e t r a t e i n t o the b u i l d i n g t h r o u g h a p e r t u r e s i n the envelope. By i n c r e a s i n g the exposure of the d a y l i g h t i n g a p e r t u r e s i n t h i s envelope t o d a y l i g h t - - i , e . i m p r o v i n g the b u i l d i n g ' s d a y l i g h t a c c e s s - - p o t e n t i a l l y g r e a t e r amount of d a y l i g h t can r e a c h task a r e a s w i t h i n the i n t e r i o r . 1.1 The Three Sources Of D a y l i g h t There a r e t h r e e l i g h t s o u r c e s through which d a y l i g h t impinges on the b u i l d i n g e n v e l o p e , as shown i n f i g u r e 8 These a r e : i . the sky i i . the sun i i i . the ground The sky as a l i g h t s ource D a y l i g h t from the s k y v a u l t , or a t m o s p h e r i c a l l y d i f f u s e d s u n l i g h t , i s u s u a l l y termed the Sky Component(SC). I t i s the p r i n c i p a l c h a n n e l f o r i n d o o r d a y l i g h t i n most d e s i g n s . When compared w i t h the sun, the sky has a l a r g e v i s u a l area and r e l a t i v e l y low luminance. The luminance d i s t r i b u t i o n v a r i e s 72 V I / / REFLtCTEJ \ LIGHT \ 1 \ DIRECT 3MU6HT \ \ / / 4 . T n n n T . DIFFUSE U&HTy |r»* clonal*^ F i g u r e 8 - The t h r e e s o u r c e s of d a y l i g h t w i t h l a t i t u d e , time of day, c l o u d i n e s s , and t u r b i d i t y 1 of the atmosphere. O v e r c a s t and c l e a r s k i e s have d i f f e r e n t , but p r e d i c t a b l e , l u m i n o s i t y d i s t r i b u t i o n a c r o s s the s k y v a u l t . Thus, l u m i n o s i t y v a l u e s . f o r any g i v e n time can be p r e d i c t e d w i t h r e a s o n a b l e a c c u r a c y and the SC of d a y l i g h t c a l c u l a t e d f o r v a r i o u s o r i e n t a t i o n s and outdoor i l l u m i n a n c e l e v e l s . Most t e c h n i q u e s t h a t aim at m a x i m i z i n g the p o t e n t i a l f o r d a y l i g h t i n g i n a b u i l d i n g , do so by i n c r e a s i n g a c c e s s of the b u i l d i n g envelope t o the s k y v a u l t : m a n i p u l a t i n g massing and l a y o u t and s t r a t e g i c a l l y l o c a t i n g d a y l i g h t i n g a p e r t u r e s f o r maximum i n t e r i o r d a y l i g h t i n g . 73 The sun as a l i g h t s ource In terms of i t s luminous p r o p e r t i e s and g e o m e t r i c a l r e l a t i o n s h i p t o b u i l d i n g s , the sun may be d e s c r i b e d as a p o i n t s o u r c e of l i g h t 2 , of extreme luminous i n t e n s i t y , moving a c r o s s the s k y v a u l t i n a v a r y i n g , but p r e d i c t a b l e , p a t h . The i l l u m i n a n c e produced by the sun on an e x t e r i o r s u r f a c e i s a f u n c t i o n of the a l t i t u d e a n g l e of the sun; the a n g l e between the i n c i d e n t s u n l i g h t and the s u r f a c e r e c e i v i n g the l i g h t ; and the t u r b i d i t y of the atmosphere. S i n c e the luminous e f f i c a c y of s u n l i g h t i s v e r y h i g h 3 , the sun would be a v e r y d e s i r a b l e s o u r c e of l i g h t , were i t not f o r i t s movement i n the s k y v a u l t . The movement makes d i s t r i b u t i o n of s u n l i g h t w i t h i n the i n t e r i o r of b u i l d i n g s d i f f i c u l t t o achieve;, and w i t h o u t the a b i l i t y t o d i s t r i b u t e t h i s c o n c e n t r a t e d l i g h t , i t becomes a g l a r e and/or heat g a i n problem. For t h i s r e a s o n , s u n l i g h t i s s c r e e n e d out most of the time i n l a r g e r b u i l d i n g s , e i t h e r by opaque c o n t r o l d e v i c e s or by t i n t e d g l a z i n g l However, i t i s p o s s i b l e t o i n t r o d u c e s u n l i g h t i n t o o f f i c e b u i l d i n g i n t e r i o r s , u s i n g t e c h n i q u e s t h a t can c o n t r o l and d i s t r i b u t e i t a p p r o p r i a t e l y . The ground as a l i g h t s ource D a y l i g h t from the ground--here meaning a d j a c e n t b u i l d i n g s , b o d i e s of water and l a n d s c a p i n g - - i s u s u a l l y termed the E x t e r n a l l y R e f l e c t e d Component (ERC). I t i s a secondary s o u r c e of i n d o o r d a y l i g h t . U n l i k e d i f f u s e d a y l i g h t and s u n l i g h t , t h i s component i s r e a d i l y i n f l u e n c e d by the a c t i v i t i e s of man, and t h u s may be s u b j e c t t o s h o r t - t e r m , as w e l l as l o n g - t e r m changes 7 4 a t a g i v e n s i t e . I t may a l s o be s e a s o n a l l y v a r i a b l e ( e . g . snow c o v e r ) . A l t h o u g h the i n c l u s i o n i n d e s i g n of the ERC can t h u s be p r o b l e m a t i c , i t can n e v e r t h e l e s have an i n f l u e n c e on the q u a n t i t y of l i g h t i n some i n t e r i o r s , and an even g r e a t e r impact on the q u a l i t y of l i g h t . F i g u r e 9 - D a y l i g h t i n g t e c h n i q u e s u s i n g the t h r e e s o u r c e s of d a y l i g h t F i g u r e 9 shows t y p i c a l t e c h n i q u e s t h a t can a c c e s s one or more of these t h r e e s o u r c e s of d a y l i g h t . 1.2 The Three D a y l i g h t Design C o n d i t i o n s A b u i l d i n g must respond t o one or more of t h r e e predominant d a y l i g h t c o n d i t i o n s : i . o v e r c a s t sky i i . c l e a r sky, w i t h d i r e c t s u n l i g h t e x c l u d e d from t h e i n t e r i o r 75 i i i . c l e a r sky, w i t h d i r e c t s u n l i g h t a d m i t t e d i n t o the i n t e r i o r O v e r c a s t sky T h i s sky c o n d i t i o n i s common i n much of Europe and i n m a r i t i m e c l i m a t e s g e n e r a l l y , and thus d e s i g n methods f o r t h i s c o n d i t i o n have been w e l l d e v e l o p e d . F i g u r e 10 a. shows t h a t a u n i f o r m l y o v e r c a s t sky i s a p p r o x i m a t e l y 3 times as b r i g h t a t the z e n i t h as a t the h o r i z o n " . A l t h o u g h c l o u d i n e s s i s a v a r i a b l e f a c t o r , the luminance d i s t r i b u t i o n of a f u l l y and u n i f o r m l y o v e r c a s t sky i s independent of s o l a r p o s i t i o n and l a t i t u d e 5 . Only a b s o l u t e luminance l e v e l s are thus v a r i a b l e f o r a g i v e n o r i e n t a t i o n and t h e r e f o r e the o v e r c a s t sky c o n d i t i o n i s r e l a t i v e l y s i m p l e t o model. The c l e a r sky, w i t h d i r e c t s u n l i g h t e x c l u d e d F i g u r e 10 b. shows the approximate luminance d i s t r i b u t i o n of a c l e a r s k y 6 . The luminance d i s t r i b u t i o n i s the r e v e r s e of the o v e r c a s t sky s i t u a t i o n , w i t h the luminance near the h o r i z o n a p p r o x i m a t e l y t h r e e times as h i g h as t h a t a t the z e n i t h . In a d d i t i o n , the sky i s v e r y b r i g h t i n the p r o x i m i t y of the sun and a minimum luminance o c c u r s i n the quadrant of the sky o p p o s i t e the sun. A l t h o u g h the luminance of the c l e a r sky a t any time of day can be p r e d i c t e d , the d i s t r i b u t i o n p a t t e r n i s more complex and v a r i e s w i t h s o l a r a l t i t u d e and a z i m u t h . Under c l e a r sky c o n d i t i o n s , even w i t h d i r e c t s u n l i g h t 76 A. TYPICAL LUM1NAMCE WLUES FORtNCRCASI 5KY sun &. TYPICAL LUMINANCE VALUES FDR CLEAR SKY F i g u r e 10 - The luminance d i s t r i b u t i o n of the o v e r c a s t and the c l e a r sky e x c l u d e d , b u i l d i n g o r i e n t a t i o n s f a c i n g e a s t , west and s o u t h , w i l l , on the a v e r a g e , e x p e r i e n c e h i g h e r d a y l i g h t l e v e l s than those o r i e n t e d towards the n o r t h . S u r f a c e s f a c i n g the sun thus r e c e i v e 3-5 t i m e s the i l l u m i n a n c e r e c e i v e d by s u r f a c e s f a c i n g away from the s u n 7 , v a r y i n g somewhat w i t h t h e time of day and the season. The v a r i a t i o n i s m a i n l y due t o the d i f f e r e n c e i n sky b r i g h t n e s s , but a l s o t o t h e h i g h e r r e f l e c t e d component a t sunward o r i e n t a t i o n s . 77 •The c l e a r sky, w i t h d i r e c t s u n l i g h t a d m i t t e d D i r e c t s u n l i g h t may be a d m i t t e d s u c c e s s f u l l y i n t o b u i l d i n g i n t e r i o r s , w i t h o u t t h e r m a l and g l a r e p e n a l t i e s , but as t h i s i n v o l v e s a c c u r a t e s i m u l a t i o n t e c h n i q u e s and more or l e s s e l a b o r a t e d i s t r i b u t i o n mechanisms, the luminous d e s i g n of o f f i c e i n t e r i o r s u s i n g d i r e c t s u n l i g h t r e q u i r e s d e s i g n s k i l l and e x p e r i e n c e t o implement. N e v e r t h e l e s s , some e x i s t i n g s o l u t i o n s c r e a t e i n t e r i o r luminous environments of g r e a t human a p p e a l 8 . T a b l e V I I summarizes the d e s i g n responses r e q u i r e d under each of the t h r e e d e s i g n c o n d i t i o n s d i s c u s s e d above. I t may be DAYLI6HT CONDITION LUMMANCE DISTRIB. RESPONSE BY ORIENTATION 60LAR CONTROL GLARE CONTROL OVERCAST SKY PREDICTABLE AND ALL ORIENTATIONS NOT REQUIRED MAY OR MAY NOT BE CONSTANT SIMILAR REQUIRED CLEAR WITHOUT PREDICTABLE AND ORIENTATIONS TO SUN SON BLOCKED CAN USUALLY BE AC-SUN VARIES WITH BRIGHTER CONTROL VARIES COMPLISHED BY SOLAR ALTITUDE EAST AND NEST DIF- WITH ORIENTA- SOLAR CONTROL AND AZIMUTH FICULT TO CONTROL TION NORTH EXPOSURE REQUIRES SEPARATE ATTENTION CLEAR. wrrH — II — SPECIAL DISTRIBUTE REQUIRES SUN- STRICT ATTENTION SUN TECHNIQUES ON LIGHT DISTRI- REQUIRED SOUTH SIDE BUTION TECH- MAY BE. RESOLYED DIFFICULT ON EAST NIQUES IN AS PART OF SUN -AND WEST INTERIOR LIGHT DISTR. TECHNIQUES T a b l e V I I - Desi g n responses r e q u i r e d d a y l i g h t i n g c o n d i t i o n s under d i f f e r e n t 78 seen t h a t the number of v a r i a b l e s c h a r a c t e r i z i n g each c o n d i t i o n i n c r e a s e p r o g r e s s i v e l y , and t h e r e f o r e the d e s i g n response becomes p r o g r e s s i v e l y more complex, and r e q u i r e s more e l a b o r a t e a n a l y s i s and p r e d i c t i o n t e c h n i q u e s f o r s u c c e s s f u l luminous and th e r m a l performance. 1 . 3 Measurement Of Indoor D a y l i g h t C l e a r or o v e r c a s t s k y - - d i r e c t sun e x c l u d e d I t has been found t h a t the r a t i o between the d a y l i g h t l e v e l at a g i v e n p o i n t i n a b u i l d i n g and the d a y l i g h t l e v e l of the u n o b s t r u c t e d sky i s c o n s t a n t over a v e r y wide range of e x t e r i o r d a y l i g h t l e v e l s . T h i s c o n s t a n t has been termed the D a y l i g h t F a c t o r ( D F ) 9 . The most common r e f e r e n c e i s t o the h o r i z o n t a l working p l a n e between 0.7-1.0m from the f l o o r , but v e r t i c a l r e f e r e n c e p l a n e s may a l s o be u s e d 1 0 , i f the f u n c t i o n of the space r e q u i r e s the i n v e s t i g a t i o n of i l l u m i n a n c e l e v e l s on the s e p l a n e s . As has been seen i n the p r e v i o u s c h a p t e r , above i l l u m i n a n c e l e v e l s of 100 l u x , v i s u a l comfort c o n d i t i o n s , as w e l l as v i s u a l performance, depend more on the luminance r a t i o w i t h i n the v i s u a l f i e l d than on a b s o l u t e i l l u m i n a n c e l e v e l s . Because the eyes w i l l adapt t o the p r e v a i l i n g luminance, the p e r c e i v e d b r i g h t n e s s r a t i o s w i t h i n a room w i l l remain c o n s t a n t , r e g a r d l e s s of the f l u c t u a t i n g i l l u m i n a n c e l e v e l s . The concept of the DF can be used t o e x p l o r e these r a t i o s . D a y l i g h t f a c t o r s have been h i s t o r i c a l l y g i v e n f o r o v e r c a s t 79 sky c o n d i t i o n s (e.g. the s t a n d a r d CIE o v e r c a s t s k y ) . R e c e n t l y , the concept of the DF has been extended by Bryan et a l . 1 1 t o i n c l u d e c l e a r sky c o n d i t i o n s . Because the i l l u m i n a n c e i m p i n g i n g on an e x t e r i o r s u r f a c e under c l e a r sky c o n d i t i o n s v a r i e s w i t h s o l a r a l t i t u d e and a z i m u t h , c o m p a r a t i v e e v a l u a t i o n of v a r i o u s d e s i g n o p t i o n s can o n l y be done f o r i d e n t i c a l o r i e n t a t i o n s and s p e c i f i c time of day. C l e a r s k y - - d i r e c t s u n l i g h t a d m i t t e d In i n n o v a t i v e , deep d a y l i g h t i n g t e c h n i q u e s , a d m i t t i n g d i r e c t s u n l i g h t t o the i n t e r i o r , the concept of DF as an index of luminous performance i s no l o n g e r a c c u r a t e or u s e f u l , s i n c e i l l u m i n a n c e l e v e l s w i l l change not o n l y w i t h s o l a r a l t i t u d e and a z i m u t h , but w i l l ' a l s o v a r y w i t h i n s h o r t i n t e r v a l s w i t h the s p e c i f i c t e c h n i q u e used t o p r o j e c t s u n l i g h t / d a y l i g h t i n t o the i n t e r i o r . The luminous environment i s i n t h i s case best p r e d i c t e d by measuring i l l u m i n a n c e l e v e l s i n p h y s i c a l models, o b t a i n i n g d i s t r i b u t i o n a t v a r i o u s s o l a r a l t i t u d e s and a z i m u t h s , at more or l e s s f r e q u e n t i n t e r v a l s , and comparing them f o r d i f f e r e n t d e s i g n c o n f i g u r a t i o n s . 2. TECHNIQUES FOR DAYLIGHT ACCESS The t e c h n i q u e s p r e s e n t e d i n t h i s c h a p t e r a r e summarized i n f i g u r e 1T . 80 S C A L E S I T E P L A N N I N G ) BUILDING CONFIGURATION BUILDING COMPONENT 6UILDIN6 MASSING BUILDING CLUSTERING OBSTRUCTIONS BUILDING LAYOUT EXTERIOR SURFACES ATRIA X NORTH & SOUTH ORIENTATION INTERIOR SUNLIGHT DAYLIGHT SEPARATE FROM VIEW r A Q ^ ^ 3 DAYLI6HTING FROM THE TOP F i g u r e 11 - Summary of t e c h n i q u e s of d a y l i g h t a c c e s s 81 2.1 B u i l d i n g C l u s t e r i n g In medium t o h i g h d e n s i t y urban a r e a s , a d j a c e n t b u i l d i n g s w i l l , t o a g r e a t e r or l e s s e r e x t e n t , o b s t r u c t each o t h e r ' s a c c e s s t o the sky component of d a y l i g h t . For a g i v e n d e n s i t y of development ( t o t a l f l o o r a r e a f o r the s i t e ) , some p l a n n i n g s t r a t e g i e s w i l l r e s u l t i n b e t t e r d a y l i g h t a c c e s s f o r b u i l d i n g s than o t h e r s 1 2 . In the 1940s, the B u i l d i n g R e s e a r c h E s t a b l i s h m e n t of Great B r i t a i n c a r r i e d out a number of i n v e s t i g a t i o n s 1 3 on the way c l u s t e r i n g of d i s c r e t e , r e p e t i t i v e b u i l d i n g s a f f e c t e d d a y l i g h t a c c e s s t o i n t e r i o r s . D e n s i t y was kept c o n s t a n t throughout t h e s e e x p e r i m e n t s ; s i t e l a y o u t , b u i l d i n g p l a n and b u i l d i n g h e i g h t were v a r i e d . i . In one s t u d y , p l a n and h e i g h t of b u i l d i n g s were kept c o n s t a n t and o n l y the arrangement of b u i l d i n g s on the s i t e was v a r i e d . I t was found t h a t c e r t a i n arrangements were s u p e r i o r t o o t h e r s i n terms of d a y l i g h t i n g . The Waldram diagrams i n f i g u r e 12 1 *, 1 5 , 1 6 show t h a t the b e t t e r d a y l i g h t p e n e t r a t i o n i n the case of l a y o u t no. 2, i s due t o the i n c r e a s e d sky component (SC) v i s i b l e and a l s o because the sky i s v i s i b l e a t a much lower a n g l e . Thus, the SC c o n t r i b u t e s t o the d a y l i g h t a v a i l a b l e deeper i n s i d e the room and a l s o t o a b a l a n c e of b r i g h t n e s s i n the r o o m 1 7 . i i . In a n o t h e r s t u d y , the h e i g h t of the b u i l d i n g s were kept c o n s t a n t , and the p l a n s were v a r i e d 1 8 . The h o l l o w square l a y o u t , which was a common p l a n t ype i n urban a r e a s d u r i n g 82 BO io w 20 o 20 40 to eo PARALLEL BUILDINGS 8 0 « » W 0 M « M B 0 CRUCIFORM BUILDINGS Waldram diagrams to show the view cf sky obtained with comparative arrangements of buildings. O 2 </) —I LAYOUT 2 LAYOUT 1 PENETRATION CURVES 0-2' P E R C E N T " -•'--•'J f 1 • * • rt :\\ ' ': O . z 1 0 PER CENT"* S K Y F A C T O R C O N T O U R S LAYOUT 1 LAYOUT 2 120 25 120 25 L A Y O U T I mm LAYOUT 2' mm Daylight penetration with parallel and with cruciform layout of buildings. The latter gives better penetration of light from the low-angle sky F i g u r e 12 - D a y l i g h t p e n e t r a t i o n and Waldram diagrams f o r p a r a l l e l and c r u c i f o r m l a y o u t s 83 the 1 9 4 0 s 1 9 , was c o n t r a s t e d w i t h t h e a l t e r n a t i n g s l a b arrangement of the p r e v i o u s example and a c r u c i f o r m a r r a n g e m e n t 2 0 . As f i g u r e 13 shows, p l a n s no.2 and no.3 p r o v i d e d b e t t e r d a y l i g h t a c c e s s f o r t y p i c a l r o o m s 2 1 , 2 2 . PLAN I . PLAN 2. P L A N J . S E C T I O N THROUGH R O O M . P E N E T R A T I O N CURVES F i g u r e 13 - Comparison among d i f f e r e n t b u i l d i n g l a y o u t s of eq u a l h e i g h t and d e n s i t y i i i . In a t h i r d s t u d y , the p l a n shape was kept c o n s t a n t , w h i l e the h e i g h t and s p a c i n g of the b u i l d i n g s was v a r i e d . I t was found t h a t f o r an e q u i v a l e n t d e n s i t y , t a l l b l o c k s , wide a p a r t , r e s u l t e d i n more f a v o u r a b l e d a y l i g h t a c c e s s than l o w - r i s e b l o c k s . The e f f e c t i s shown i n f i g u r e 14 , where the a n g l e of o b s t r u c t i o n d e c r e a s e s as s p a c i n g i n c r e a s e s 2 3 . 84 5PACIN6V SPACING V SPACING ' c ' F i g u r e 14 - T a l l b l o c k s wide a p a r t ensure b e t t e r p e n e t r a t i o n of d a y l i g h t T h e r e f o r e , i n medium t o h i g h d e n s i t y s i t u a t i o n s , medium or h i g h - r i s e b l o c k s are s u p e r i o r t o l o w - r i s e b u i l d i n g s i n terms of d a y l i g h t i n g . I t i s t o be noted from the diagram t h a t when the s p a c i n g between b u i l d i n g s i s i n c r e a s e d , the f i r s t few i n c r e m e n t s of change a r e more p r o d u c t i v e tharj subsequent s t e p s 2 " . Thus, when s o c i a l and t e c h n i c a l consequences of h i g h - r i s e b u i l d i n g s are c o n s i d e r e d a l o n g w i t h d a y l i g h t i n g , medium-rise b u i l d i n g s a r e , i n many i n s t a n c e s , an optimum c h o i c e , i v . In a f o u r t h s t u d y , b oth b u i l d i n g p l a n and h e i g h t were v a r i e d . F i g u r e 15 shows two l a y o u t s on i d e n t i c a l s i z e l o t s ; t h e h e i g h t of the c r u c i f o r m p l a n i s g r e a t e r than t h a t of t h e h o l l o w square p l a n t o a l l o w the F l o o r Area R a t i o s (FAR's) t o be the same f o r b o t h . Even though the c r u c i f o r m b u i l d i n g i s t a l l e r , the d a y l i g h t a c c e s s f o r most of the rooms i n t h i s l a y o u t i s s u p e r i o r t o the d a y l i g h t • a v a i l a b l e i n the h o l l o w square p l a n ; a l s o , n e i g h b o u r i n g 85 F i g u r e 15 - D a y l i g h t a v a i l a b i l i t y f o r two b u i l d i n g l a y o u t s b u i l d i n g s enjoy a l e s s o b s t r u c t e d s k y v a u l t w i t h the c r u c i f o r m arrangement than w i t h the h o l l o w s q u a r e . T h e r e f o r e , f o r a g i v e n d e n s i t y of development, and even a l l o w i n g f o r d i f f e r e n t h e i g h t s of b u i l d i n g s , the p l a n form  i s the main f a c t o r i n d e t e r m i n i n g d a y l i g h t a v a i l a b i l i t y i n d o o r s 2 5. I t may be noted t h a t the above mentioned s t u d i e s of b u i l d i n g c l u s t e r i n g , u s i n g d i s c r e t e , r e p e t i t i v e forms, a r e an o v e r s i m p l i f i c a t i o n of most d e s i g n s i t u a t i o n s . More complex b u i l d i n g massing, i n t e r c o n n e c t e d b u i l d i n g s , b u i l d i n g s w i t h s u i t a b l y p r o p o r t i o n e d a t r i a , e t c . were not s t u d i e d . However, the e x p e r i m e n t s do i n d i c a t e g e n e r a l l y how the v a r i a b l e s a t t h i s broad s c a l e a f f e c t d a y l i g h t a c c e s s . I t may a l s o be o b s e r v e d t h a t the importance of the f o r e g o i n g "open p l a n n i n g " p r i n c i p l e s i n c r e a s e s w i t h g r e a t e r d e n s i t i e s . At d e n s i t i e s of l e s s than 1.0 F l o o r Area R a t i o , the a n g l e of l i g h t e n t e r i n g t h r o u g h windows w i l l be low enough so 86 that acceptable l i g h t penetration can be obtained with any layout and height of building. At densities above 1.25 FAR, the open plan forms can su b s t a n t i a l l y improve the general daylight a v a i l a b i l i t y in the development 2 6. 2. 2 Exterior Surfaces Where possible, the location and d e t a i l i n g of neighbouring land forms, structures and vegetation should minimize obstructions and promote the best use of externally r e f l e c t e d daylight. The Externally Reflected Component (ERC) within a Figure 16 - The ERC i s comprised of surfaces both above and below the working plane d a y l i t i n t e r i o r — i.e. r e f l e c t e d from the ground and other exterior surfaces—represents about 15% of the to t a l daylight reaching the windows on sunny exposures (may be higher with l i g h t vegetation, snow cover, etc.) and on northern elevations, i > i 87 may a c c o u n t f o r o v e r 5 0 % of t h e t o t a l d a y l i g h t r e a c h i n g windows i n l o w - r i s e b u i l d i n g s 2 7 . In the l o w e r f l o o r s of b u i l d i n g s s u r r o u n d e d by h i g h - r i s e d e v e l o p m e n t , t h e ERC w i l l c o m p r i s e an e ven l a r g e r p r o p o r t i o n o f t h e t o t a l a c c e s s i b l e d a y l i g h t . A h i g h v a l u e f o r t h e ERC c o r r e s p o n d i n g l y i n c r e a s e s t h e i n t e r n a l l y r e f l e c t e d component (IRC) of d a y l i g h t , w h i c h i n t h e p r e v i o u s c h a p t e r has been seen t o be t h e d o m i n a n t component a t t h e back of d a y l i t s p a c e s 2 8 , 2 9 , 3 0 . As shown i n f i g u r e 16 , t h e ERC may be c o n s i d e r e d as b e i n g c o m p r i s e d of s u r f a c e s b o t h above and below t h e w o r k i n g p l a n e . The p o r t i o n o f ERC above w i l l c o n t r i b u t e t o t h e d i r e c t component on t h e w o r k i n g p l a n e , whereas the p o r t i o n below w i l l enhance the d a y l i g h t on t h e w o r k i n g p l a n e a f t e r b e i n g r e f l e c t e d f r o m room s u r f a c e s . S u r f a c e s i n t h e p o r t i o n o f ERC above t h e w o r k i n g p l a n e , o b s t r u c t p a r t o f t h e sky ( w h i c h has a much g r e a t e r l u m i n o s i t y ) and t h e r e f o r e r e d u c e d a y l i g h t a c c e s s t o t h e i n t e r i o r o f a d j a c e n t b u i l d i n g s . I f the l o c a t i o n of t h e s e o b s t r u c t i o n s i s w i t h i n t h e c o n t r o l o f t h e d e s i g n e r , he s h o u l d a t t e m p t t o r e l o c a t e them i n o r d e r t o improve d a y l i g h t a c c e s s . V e r y o f t e n t h o u g h , r e l o c a t i o n o f t h e s e o b s t r u c t i o n s i s not p o s s i b l e f o r v a r i o u s . r e a s o n s , and t h e o n l y o t h e r o p t i o n t h a t can be c o n s i d e r e d i s t o m a x i m i z e , i f p o s s i b l e , t h e r e f l e c t a n c e o f t h e s e s u r f a c e s . The p o r t i o n o f t h e ERC below t h e w o r k i n g p l a n e c a n n o t , by d e f i n i t i o n , be e l i m i n a t e d , but i n c r e a s i n g t h e r e f l e c t a n c e o f s u r f a c e s v i s i b l e from d a y l i g h t i n g a p e r t u r e s w i l l a l w a y s i n c r e a s e t h e a c c e s s of b u i l d i n g i n t e r i o r s t o d a y l i g h t . Whenever r e f l e c t a n c e s f o r t h e ERC a r e w i t h i n t h e c o n t r o l o f t h e 88 desi g n e r , a high, but d i f f u s e r e f l e c t a n c e can be s e l e c t e d — a n d maintained by c l e a n i n g and p a i n t i n g . These measures w i l l a l s o reduce the harsh c o n t r a s t between sky and e x t e r i o r s u r f a c e s 3 . 1 . SURFACE R E F L E C T A N C E . (%1 25 ALFALFA DARK 6REEN ALUMINUM FOIL ASPHALT BAF.E GROUND, DRV — BARE GROUND, WET — BLACK 60D"Y CONCRETE DARK. FOREST DESERT DRV 6RASS GREEN FIELDS GRASS ,HI6H FRESH OAK WOODLAND — FINE FOREVT FLASTER .WHITE 5AND,DRV 5AND.NET — SNOW, FRESH WATER f NORMAL INCIDENCE • AT •bO"INCIDENCE -AT 60° INCIDENCE AT SO' INCIDENCE WHITE 60DY 50 15 ISO Table VIII - R e f l e c t a n c e s of v a r i o u s outdoor s u r f a c e s Table VIII 3 2 shows r e f l e c t a n c e s f o r common ground s u r f a c e s : F i g u r e 17 shows p o s s i b i l i t i e s f o r using the ground and e x t e r n a l s u r f a c e s as secondary l i g h t sources. I t i s shown how non-specular r e f l e c t i o n of southern s u n l i g h t by lan d s c a p i n g f e a t u r e s can in t r o d u c e more inte n s e and warmer l i g h t from the south i n t o n o r t h - f a c i n g windows. 89 F i g u r e 17 - E x t e r i o r s u r f a c e s as secondary l i g h t s o u r c e s 2.3 B u i l d i n g M a s s i n g C e r t a i n b u i l d i n g forms w i l l p r o v i d e a c c e s s t o more d a y l i g h t than o t h e r forms, the key d e t e r m i n a n t s b e i n g the s k i n t o f l o o r a r e a r a t i o and the a r e a of sky t h a t may be "seen" by the e x t e r n a l s u r f a c e s . F i g u r e 1 8 3 3 and f i g u r e 19 3 *, i l l u s t r a t e t h a t b u i l d i n g s whose massing p r o v i d e s good d a y l i g h t a c c e s s t o t h e i r own i n t e r i o r spaces a l s o t e n d t o o b s t r u c t l e s s the d a y l i g h t a c c e s s of t h e i r n e i g h b o u r s . C o n v e r s e l y , b u i l d i n g s whose massing reduces d a y l i g h t a c c e s s t o t h e i r own i n t e r i o r s p a c e s , w i l l a l s o t e n d t o reduce the d a y l i g h t a c c e s s t o t h e i r n e i g h b o u r s . B u i l d i n g s massing may be r e s o l v e d at the d e t a i l s c a l e i n 90 MINIMUM MAXIMUM * 7 -> I 1 - » > ^ I M * U S S l£^>t> NL SL > l ' M O B e MOM M O R E L I G H T R E C E P T I O N T H R O U G H W A L L S C O U R T Y A R D R E C E P T I O N F i g u r e 18 - B u i l d i n g form r e s p o n s e s t o l i g h t v a r i o u s ways t h a t r e c o n c i l e d a y l i g h t i n g needs w i t h o t h e r r e q u i r e m e n t s . For example, f i g u r e 20 shows t h a t a p y r a m i d a l mass . may be r e s o l v e d i n t o a stepped pyramid i n t e g r a t i n g s t r u c t u r a l , HVAC and o t h e r f u n c t i o n a l r e q u i r e m e n t s . 2.4 B u i l d i n g Layout For o f f i c e b u i l d i n g s of more than one s t o r e y , window ope n i n g s i n w a l l s a r e the predominant mode of d a y l i g h t i n g . Some b u i l d i n g l a y o u t s , such as those w i t h a h i g h r a t i o of e x t e r i o r e n v e l o p e a r e a t o f l o o r a r e a , p r o v i d e a c c e s s t o d a y l i g h t t o a g r e a t e r p e r c e n t a g e of a g i v e n f l o o r a r e a than o t h e r b u i l d i n g l a y o u t s . T h i s means t h a t l o n g and r e l a t i v e l y narrow l a y o u t s , f o r example, have g r e a t e r p o t e n t i a l f o r d a y l i g h t i n g 91 F i g u r e 19 - T y p i c a l b u i l d i n g s whose massing responds t o d a y l i g h t than square shaped p l a n s ( l a y o u t c. v s . l a y o u t a., i n f i g u r e 21 ). F i g u r e 22 i l l u s t r a t e s s c h e m a t i c a l l y l a y o u t s of e x i s t i n g b u i l d i n g s t h a t respond t o d a y l i g h t i n g n e e d s 3 5 . An e x c e l l e n t example of the impact of d a y l i g h t i n g c o n s i d e r a t i o n on b u i l d i n g form (both massing and f l o o r l a y o u t ) i s found i n A l v a r A a l t o ' s F i n n i s h N a t i o n a l P e n s i o n s I n s t i t u t e , H e l s i n k i , b u i l t between 1952 and 1956, an a e r i a l view of which i s shown i n f i g u r e 23 3 S . Here, A a l t o b u i l t a l a r g e o f f i c e complex w i t h i n a h i g h d e n s i t y b u s i n e s s d i s t r i c t of the c i t y . 92 F i g u r e 21 - The e f f e c t of b u i l d i n g p l a n on d a y l i g h t a c c e s s 93 F i g u r e 22 - Examples of e x i s t i n g b u i l d i n g s whose l a y o u t responds t o d a y l i g h t i n g needs B u i l d i n g massing and l a y o u t respond t o program r e q u i r e m e n t s , w h i l e at. the same time p r o v i d i n g narrow p l a n depths and i n c r e a s e d . p e r i m e t e r s t h a t enable good d a y l i g h t i n g . The t o p f l o o r s of the low r i s e ma'sses are d a y l i t t h r ough s k y l i g h t s ; f o u r v e r y l a r g e s k y l i g h t s t r u c t u r e s l i g h t up an a t r i u m on the main f l o o r 3 7 . An i n c r e a s e i n p e r i m e t e r t o accommodate d a y l i g h t i n g i s not w i t h o u t consequences: i . The i n c r e a s e i n p e r i m e t e r may cause h i g h e r b u i l d i n g c o s t s i n c e c o r n e r s and e x t e r i o r w a l l s a r e g e n e r a l l y e x p e n s i v e . However, w h i l e the c o s t of the b u i l d i n g envelope may i n c r e a s e , the t o t a l b u i l d i n g c o s t i n a w e l l i n t e g r a t e d 9 4 F i g u r e 23 - A e r i a l view of A a l t o ' s F i n n i s h N a t i o n a l P e n s i o n s I n s t i t u t e d e s i g n may be unchanged or even r e d u c e d 3 8 , i i . An i n c r e a s e i n p e r i m e t e r w i l l l e a d t o i n c r e a s e d heat l o s s i n w i n t e r and p o s s i b l y , t o i n c r e a s e d s o l a r g a i n i n summer 3 9, u n l e s s t h e i r major o r i e n t a t i o n i s n o r t h and s o u t h . However, w i t h p r o p e r o r i e n t a t i o n , a l a r g e r e n v e l o p e a r e a c r e a t e d by narrower b u i l d i n g shape or o t h e r m a n i p u l a t i o n s of the p l a n t o accommodate d a y l i g h t i n g , c a r r i e s a t the v e r y l e a s t no p e n a l t i e s and, i n a m i l d c l i m a t e , o f f e r s s u b s t a n t i a l net s a v i n g s i n energy c o s t . 95 A c c o r d i n g t o Matthews and C a l t h o r p e " 0 , o f f i c e b u i l d i n g s , b e i n g g e n e r a l l y i n t e r n a l l o a d dominated, a r e not i n f a c t , v e r y s e n s i t i v e t o an i n c r e a s e i n the r a t i o of envelope t o f l o o r a r e a . T h i s means t h a t p e n a l t i e s of i n c r e a s e d heat l o s s i n w i n t e r and i n c r e a s e d s o l a r g a i n i n summer can be more than o f f s e t by energy s a v i n g s t h r o u g h d a y l i g h t i n g . B a z j a n a c " 1 , u s i n g e x t e n s i v e computer s t u d i e s on b u i l d i n g energy use, i n d i c a t e s t h a t o f f i c e b u i l d i n g s a c t u a l l y b e n e f i t from a l a r g e r s k i n a r e a i n warm and temperate c l i m a t e s . In c o l d c l i m a t e s , t h e r e i s o n l y m i n i m a l advantage i n c h o o s i n g a r e c t a n g u l a r p l a n over a square p l a n i n s o f a r as the t o t a l energy use of the b u i l d i n g i s c o n c e r n e d " 2 , but the advantage of a r e c t a n g u l a r p l a n i n terms of d a y l i g h t i n g r emains, i i i . T e c h n i c a l c o n s i d e r a t i o n s may i n many i n s t a n c e s not be the predominant f a c t o r s d e t e r m i n i n g f l o o r l a y o u t . The s o c i a l o r g a n i z a t i o n of the ow n e r s / t e n a n t s and the s i t e c o n f i g u r a t i o n may make a p r e f e r r e d l a y o u t from a d a y l i g h t i n g p o i n t of view an i n a p p r o p r i a t e response. In t h i s c o n n e c t i o n , Lynes, w r i t i n g i n the 1960s" 3, has p o i n t e d out t h a t "the f u t u r e shape of o f f i c e b u i l d i n g s may w e l l depend more on ... s o c i a l consequences than on the d a y l i g h t f a c t o r " . N e v e r t h e l e s s , the impact of b u i l d i n g form on d a y l i g h t i n g c o n s i d e r a t i o n s have t o be u n d e r s t o o d , even i f t h e s e c o n s i d e r a t i o n s may i n many i n s t a n c e s be o v e r r i d d e n by o t h e r r e q u i r e m e n t s . 96 2.5 A t r i a I f p r o p e r l y dimensioned and d e t a i l e d f o r d a y l i g h t i n g , a t r i u m d e s i g n s can i n c r e a s e the b u i l d i n g p e r i m e t e r h a v i n g a c c e s s t o d a y l i g h t . At the same time they a v o i d the h e a t i n g and c o o l i n g p e n a l t i e s a t t e n d a n t w i t h l a r g e e x t e r i o r s u r f a c e a r e a ( h i g h p e r i m e t e r ) s o l u t i o n s . A. D. i l l ISI III 3 ~ i l tsr E. F i g u r e 24 - Examples of e x i s t i n g d a y l i t b u i l d i n g s w i t h a t r i u m p l a n s 97 A study of the d e s i g n c o n c e p t s of the b u i l d i n g s p l a n s shown i n f i g u r e 24 "", (as w e l l as of o t h e r a t r i u m b u i l d i n g s ) r e v e a l s t h a t the a t r i a p l a y a key r o l e i n r e s o l v i n g c o n s t r a i n t s of s i t e , s t r u c t u r a l r e q u i r e m e n t s , c i r c u l a t i o n , g e n e r a l program needs, as w e l l as r e q u i r e m e n t s f o r d a y l i g h t i n g and energy s a v i n g . D a y l i g h t i n g r e q u i r e m e n t s a r e , t h e r e f o r e , an i m p o r t a n t , but not s u f f i c i e n t reason f o r c h o o s i n g an a t r i u m c o n c e p t . In the l a t e 1970's a t r i u m p l a n s became p o p u l a r as i n n o v a t i v e s o l u t i o n s t o energy r e l a t e d i s s u e s i n o f f i c e b u i l d i n g d e s i g n — i n p a r t i c u l a r , the i s s u e of d a y l i g h t i n g . Matthews and S e l k o w i t z " 5 have r e p o r t e d t h a t g e n e r a l l y they have not performed as a n t i c i p a t e d : the energy dynamics i n a t r i a a r e complex and t h e r e i s sometimes a poor match between p r e d i c t e d and a c t u a l energy b e h a v i o u r . The c o n t r i b u t i o n of a t r i a t o energy s a v i n g i s now found t o be q u e s t i o n a b l e " 6 . In some c a s e s , a t r i a do not s i g n i f i c a n t l y c o n t r i b u t e t o energy s a v i n g s even i n o f f i c e l i g h t i n g " 7 . T h i s however does not mean t h a t the d a y l i g h t r e a c h i n g o f f i c e s t h r o u g h such a t r i a does not c o n t r i b u t e t o an improvement i n the q u a l i t y of l i g h t ; o n l y t h a t i t c o n t r i b u t e s l i t t l e t o the h o r i z o n t a l i l l u m i n a t i o n . A t r i a , whatever t h e i r energy s a v i n g p o t e n t i a l may be, can be i n t e r e s t i n g and d e l i g h t f u l spaces t o be i n and l o o k i n t o ; and many d e s i g n e r s now agree t h a t t h i s s h o u l d be the major c r i t e r i o n f o r t h e i r d e s i g n " 8 , " 9 . 98 2.6 N o r t h And South O r i e n t a t i o n • O p t i m i z e d p l a n shapes from the p o i n t of view of d a y l i g h t i n g w i l l have a r e l a t i v e l y h i g h p e r i m e t e r t o f l o o r a r e a r a t i o . The h i g h p e r i m e t e r may r e s u l t from c r i n k l i n g of the envelope of a b a s i c a l l y compact l a y o u t or i t may r e s u l t from an e l o n g a t e d l a y o u t . For o f f i c e b u i l d i n g l a y o u t s t h a t have the l e n g t h of the b u i l d i n g s u b s t a n t i a l l y g r e a t e r than the w i d t h , as w e l l as f o r a t r i u m type d e s i g n s , an o r i e n t a t i o n i n which the major facades f a c e n o r t h and south i s p r e f e r a b l e . As C a l t h o r p e 5 0 a r g u e s : When you b e g i n to g r a p p l e w i t h problems of d a y l i g h t i n g a b u i l d i n g and s h a d i n g i t a g a i n s t heat g a i n a t the same t i m e , o r i e n t a t i o n becomes v e r y i m p o r t a n t . E a s t and west facades are e x t r e m e l y d i f f i c u l t t o d e a l w i t h as l i g h t s o u r c e s because' they a r e , of c o u r s e , so c r i t i c a l from the p o i n t of view of heat g a i n . S a n c h e z 5 1 c o n c u r s , s t a t i n g t h a t f o r c o o l i n g l o a d dominated b u i l d i n g s , such as o f f i c e s , a n o r t h / s o u t h o r i e n t a t i o n r e s u l t s i n the l e a s t t o t a l energy used by the b u i l d i n g . Two b u i l d i n g s t h a t demonstrate the advantage of o r i e n t i n g the b u i l d i n g f a c a d e s to the n o r t h and the s o u t h a r e the Lougheed M i s s i l e s no. 157 b u i l d i n g and the TVA b u i l d i n g i n Chattanooga, Tennesee. In b o t h , the major a x i s i s o r i e n t e d e a s t - w e s t and e s s e n t i a l l y , t hey are both d a y l i t from the n o r t h and s o u t h . Both have a t r i a a l o n g t h e i r l e n g t h , w i t h d a y l i g h t b l o c k e d a t the e a s t and west ends, thus a v o i d i n g the problems i n h e r e n t w i t h d a y l i t e a s t and west e l e v a t i o n s 5 2 , 5 3 . 9 9 S i t u a t i o n s may a r i s e i n which a predominant e a s t - w e s t a x i s i s not f e a s i b l e . The c o n f l i c t between d a y l i g h t i n g and o t h e r r e q u i r e m e n t s may be r e s o l v e d , as shown i n f i g u r e 25 , a t v a r i o u s s c a l e s . At the b u i l d i n g c o n f i g u r a t i o n s c a l e , t h i s may be r e s o l v e d by r e c o n s i d e r i n g the massing concept or by r e o r g a n i z i n g the p l a n ; a t the envelope s c a l e , by l e t t i n g i n d a y l i g h t s e p a r a t e from view and t h e r e b y p r o v i d i n g g r e a t e r p o t e n t i a l t o c o n t r o l the u n d e s i r a b l e s i d e e f f e c t s of e a s t and west f a c i n g a p e r t u r e s ; o r , a t the element s c a l e , by the r e s o l u t i o n of the c o n f l i c t between s h a d i n g and d a y l i g h t i n g r e q u i r e m e n t s u s i n g a c c e s s o r i e s such as a u t o m a t i c V e n e t i a n b l i n d s , a r c h i t e c t u r a l p r o j e c t i o n s , e t c . 2.7 I n t e r i o r S u n l i g h t As shown i n f i g u r e 26 , s u n l i g h t i n o f f i c e b u i l d i n g s may be a d m i t t e d i n t o one of the f o l l o w i n g a r e a s : i . the work area i i . the p e r i p h e r y of the work a r e a i i i . n on-task a r e a s The f u n c t i o n of s u n l i g h t i s d i f f e r e n t i n each c a s e . S u n l i q h t i n g the work a r e a W h i l e s u n l i g h t i n d o o r s i s i n g e n e r a l found t o be a d e s i r a b l e amenity, t h e r e appear t o be d i f f e r i n g o p i n i o n s whether d i r e c t s u n s h i n e s h o u l d be a l l o w e d w i t h i n t h e o f f i c e workspace. T h i s i s because s u n l i g h t , i f u n c o n t r o l l e d , can l e a d t o s u b s t a n t i a l o v e r h e a t i n g and/or g l a r e p r o b l e m s 5 " ; the former 100 •ATRiUM BASE BUILDING A. INCREASE N+5 FACING WALL* B. CREATE ATRIUM C tfcYUaHTS CLE RESTORE V Oft CEiLiwa PUNUUM OflsN/MSS WORTH OR SOOTH-FACING WIDOWS ON EAST + WEST VERTICAL PHAGES <?R TRELUSC5 PROVIDE DAVLI6HT APEKTPRES SEPARATE. PRoM VIEW APERTURES P . MANIPULATE EHld WALLS TO REDUCE DIRECT 5UWLI6HT USE SHADING DEVICES F. F i g u r e 25 - Response t o d a y l i g h t i n g i n b u i l d i n g s t h a t must have a dominant n o r t h - s o u t h a x i s 101 F i g u r e 26 - Techniques f o r a d m i t t i n g s u n l i g h t i n t o i n t e r i o r s r e s u l t i n g i n c o s t l y a i r c o n d i t i o n i n g , and the l a t t e r i n worker d i s c o m f o r t and an a t t e n d a n t reduced performance. However, s u n l i g h t i s an i l l u m i n a n t of h i g h luminous e f f i c a c y : 100-120 l u m e n s / w a t t 5 5 as compared w i t h 11-22 lumens/watt f o r i n c a n d e s c e n t lamps, and -40-80 lumens/watt f o r f l u o r e s c e n t l a m p s 5 6 . I f d i s t r i b u t e d u n i f o r m l y , the lumens c o n t a i n e d i n 1m2 of s u n l i g h t c o u l d p r o v i d e 500 l u x of i l l u m i n a t i o n over an a r e a of 195m2 5 7 . The problem i s , t h e r e f o r e , one of d i s t r i b u t i o n and c o n t r o l . S u n l i g h t i s a d m i t t e d i n t o t a s k a r e a s p r i m a r i l y t o r a i s e the h o r i z o n t a l t a s k i l l u m i n a n c e w i t h i n the space. T r a d i t i o n a l d a y l i g h t i n g t e c h n i q u e s are g e n e r a l l y u n a b l e t o d i s t r i b u t e and c o n t r o l the g r e a t i n t e n s i t y of s u n l i g h t near the f e n e s t r a t i o n 1 02 and t h e r e f o r e d i r e c t s u n l i g h t i s g e n e r a l l y s c r e e n e d out i n o r d e r t o p r o v i d e an a c c e p t a b l e luminous environment i n the i n t e r i o r . There a r e e x c e p t i o n s t o t h i s . At c e r t a i n times of the d a y - e a r l y w i n t e r mornings f o r e x a m p l e — s u n s h i n e may be a l l o w e d i n s i d e an o f f i c e b u i l d i n g t o a s s i s t i n h e a t i n g up the b u i l d i n g 5 8 and p r o v i d i n g a l i v e l y p l a y of l i g h t f o r an hour or so as the workday b e g i n s . An example of t h i s i s the CIGNA b u i l d i n g i n B l o o m f i e l d , C o n n e c t i c u t 5 9 . O r d i n a r i l y , however, o n l y i n n o v a t i v e s u n l i g h t "beaming" systems can e f f e c t i v e l y p r o j e c t and d i s t r i b u t e s u n l i g h t deep i n t o s p a c e s , and can a l s o d e a l w i t h the problem of heat g a i n and g l a r e i n h e r e n t i n the m a n i p u l a t i o n of d i r e c t s u n l i g h t . S u n l i g h t i n q the p e r i p h e r y of the work area S u n l i g h t i s i n t r o d u c e d i n t o the p e r i p h e r y of the w o r k i ng area t o p r o v i d e ambient l i g h t f o r c i r c u l a t i o n , c r e a t e p o i n t s of i n t e r e s t and b a l a n c e the l e v e l of b r i g h t n e s s at l o c a t i o n s away from d a y l i g h t i n g a p e r t u r e s . S u n l i g h t f o r these purposes need not have as s t r i n g e n t d i s t r i b u t i o n and c o n t r o l s i n c e the i l l u m i n a n c e l e v e l s are not c r i t i c a l . The use of d a y l i g h t i n t h i s way t a k e s advantage of the f a c t t h a t "most peop l e view s u n l i t s u r f a c e s as d e s i r a b l e p o i n t s of i n t e r e s t because of the importance of sun l i g h t i n man's b i o l o g i c a l h i s t o r y " 6 0 . The s t r o n g p o s i t i v e a s s o c i a t i o n s t h a t p e o p l e i n c o l d c l i m a t e s have f o r s u n l i g h t , as w e l l as the v a r i a b i l i t y and dynamic q u a l i t y of s u n s h i n e , can t h u s be an a s s e t . The Johnson C o n t r o l o f f i c e s i n Utah (by Donald Watson A r c h i t e c t s ) 6 1 i s an example of s u n l i g h t 1 03 used as w a l l washer, c r e a t i n g a luminous p l a n e p r o v i d i n g supplementary i l l u m i n a t i o n and a v i s u a l f o c u s , as w e l l as a i d i n g o r i e n t a t i o n w i t h i n the b u i l d i n g . S u n l i g h t i n g i n non-task a r e a s S u n l i g h t i s a d m i t t e d i n non-task a r e a s - - s u c h as l o u n g e s , c a f e t e r i a s , s t a i r w e l l s , e n t r a n c e f o y e r s , e t c . - - t o c e l e b r a t e the drama of s u n s h i n e , to c r e a t e a s t r o n g b i o l o g i c a l c o n n e c t i o n w i t h the o u t d o o r s and t o c o n t r a s t the exhuberance of these a r e a s w i t h the c o n t r o l l e d v i s u a l environment i n t a s k a r e a s . S u n l i g h t i n t r o d u c e d i n t h e s e a r e a s needs l i t t l e or no c o n t r o l and may be d i s t r i b u t e d by s i m p l e t e c h n i q u e s , such as the use of h i g h r e f l e c t a n c e s u r f a c e s t o bounce l i g h t around. Because v i s u a l performance i s not c r i t i c a l i n these a r e a s , the amount of s u n l i g h t and the means of b r i n g i n g i t i n t o such spaces i s d e t e r m i n e d by the l i m i t s f o r o v e r h e a t i n g and envelope heat l o s s t h a t a r e c o n s i d e r e d a c c e p t a b l e . I t i s i n t h e s e secondary and t r a n s i t i o n a l a r e a s t h a t the l i g h t i n g can be c o n t r a s t e d _ _ w i t h t h e d a y l i g h t i n g schemes w i t h i n work a r e a s r e q u i r i n g a more d i s c i p l i n e d d e s i g n approach. F i n e examples of these k i n d of spaces a r e the AAL b u i l d i n g c a f e t e r i a i n A p p l e t o n , W i s c o n s i n 6 2 , 6 3 and the e n t r a n c e l o b b y of the V e n t u r a C o a s t a l C o r p o r a t i o n b u i l d i n g i n V e n t u r a , C a l i f o r n i a 6 " . 1 04 2.8 D a y l i g h t i n g S e p a r a t e From View View windows ar e the most common method of d a y l i g h t i n g o f f i c e s , because the c o m b i n a t i o n of d a y l i g h t i n g and view t o o u t d o o r s i s o b v i o u s and low i n c o s t , and because o f f i c e s , b e i n g g e n e r a l l y m u l t i - s t o r e y and m o n o l i t h i c , p r o v i d e o p p o r t u n i t i e s f o r d a y l i g h t i n g m o s t l y through the w a l l s . However, d a y l i g h t i n g t h r o ugh view a p e r t u r e s can encounter some of the f o l l o w i n g d i f f i c u l t i e s : i . I f windows ar e of optimum s i z e f o r d a y l i g h t i n g (and even i f below the optimum), t h e r e may be a problem of g l a r e t h a t r e q u i r e s s p e c i a l a c c e s s o r i e s and/or d e t a i l i n g t o c o n t r o l . i i . Windows s i z e d o p t i m a l l y as d a y l i g h t i n g a p e r t u r e s can be a s o l a r heat g a i n and/or an envelope heat l o s s l i a b i l i t y . i i i . The l o c a t i o n and shape of windows f o r view i s g e n e r a l l y not the optimum l o c a t i o n and shape f o r d a y l i g h t i n g a p e r t u r e s : a p e r t u r e s h i g h e r , c l o s e r t o the c e i l i n g , and r e s p o n s i v e t o o b s t r u c t i o n s due t o the b u i l d i n g shape and o t h e r s u r r o u n d i n g b u i l d i n g s , w i l l o p t i m i z e d a y l i g h t i n g , t h u s o f t e n c o n f l i c t i n g w i t h r e q u i r e m e n t s f o r view. i v . R e s t r i c t i n g d a y l i g h t i n g a p e r t u r e s t o view windows means t h a t a l a r g e p e r c e n t a g e of the b u i l d i n g envelope h a v i n g a c c e s s t o d a y l i g h t i s not b e i n g used f o r t h i s purpose; t h i s r e p r e s e n t s a l o s t o p p o r t u n i t y . F i g u r e 27 shows b u i l d i n g s u t i l i z i n g d a y l i g h t i n g a p e r t u r e s s e p a r a t e from view windows. 1 05 A T R I A SKYLIGHTS LI6HT WELLS 5 r PLENUM LIGHTING AND CIERESTOREY LIGHTING SUN CATCHER BAFFLES AND S>UNSC00Pf> WITH CLEKE6T0REYS F i g u r e 27 - B u i l d i n g s u t i l i z i n g d a y l i g h t i n g a p e r t u r e s s e p a r a t e from view 2.9 D a y l i g h t i n g From The Top S m a l l o f f i c e b u i l d i n g s of two s t o r e y s a r e the median s i z e f o r N o r t h A m e r i c a 6 5 , and s i n g l e s t o r e y c ommercial b u i l d i n g s make up 58% of USA n o n - r e s i d e n t i a l b u i l d i n g s t o c k 6 6 . A l t h o u g h s i d e l i g h t i n g i s of n e c e s s i t y predominant i n most o f f i c e b u i l d i n g s 6 7 , t o p l i g h t i n g can e a s i l y p r o v i d e a s u b s t a n t i a l p o r t i o n of the l i g h t i n g f o r the t o p f l o o r s of o f f i c e b u i l d i n g s d u r i n g w o r k i n g h o u r s and can save energy as w e l l 6 8 , 6 9 . The o p p o r t u n i t i e s f o r 1 06 top l i g h t i n g a r e thus s u b s t a n t i a l , and m o s t l y u n r e a l i z e d , a t p r e s e n t . Top l i g h t i n g can d e l i v e r l a r g e q u a n t i t i e s of d a y l i g h t w i t h minimum s i z e d o p enings, because the i l l u m i n a t i o n f a l l i n g on the h o r i z o n t a l p l a n e of the roof i s g e n e r a l l y many times t h a t which f a l l s on the v e r t i c a l p l a n e of t y p i c a l w i n d o w s 7 0 . Whil e more a p p r o p r i a t e i n l i g h t i n g t o p f l o o r s of b u i l d i n g s , t o p l i g h t i n g t hrough l i g h t w e l l s can b r i n g l i g h t t o lower f l o o r s as w e l l , as shown s c h e m a t i c a l l y i n f i g u r e 28 7 1 , 7 2 . Top l i g h t i n g may be r o u g h l y d i v i d e d i n t o two c a t e g o r i e s : s k y l i g h t s and roof m o n i t o r s . S k y l i g h t may be d e f i n e d as d a y l i g h t i n g a p e r t u r e s p a r a l l e l t o the roof p l a n e , whereas roo f m o n i t o r s a r e d a y l i g h t i n g a p e r t u r e s i n the v e r t i c a l p l a n e . T y p i c a l s k y l i g h t s o l u t i o n s a r e shown i n . f i g u r e 29 7 3 . In a., the s k y l i g h t w e l l i s s p l a y e d t o i n c r e a s e spread of d a y l i g h t f o r a g i v e n s k y l i g h t a r e a . In b., a t y p i c a l s k y l i g h t i s shown f i t t e d w i t h an a d j u s t a b l e r e f l e c t o r / s h a d e t o i n c r e a s e the d a y l i g h t / s u n l i g h t p e n e t r a t i o n . In c. , the d e v i c e i s a d j u s t e d t o p r o v i d e s h a d i n g , and reduce s o l a r heat g a i n . In the above examples, a d i s t i n c t l y s e p a r a t e mechanism f o r c o n t r o l l i n g g l a r e and i n c r e a s i n g d a y l i g h t p e n e t r a t i o n i s i n s t a l l e d on a s t a n d a r d s k y l i g h t . The examples shown i n f i g u r e 30 7 * are roo f m o n i t o r s t h a t have the g l a r e , s o l a r heat g a i n and heat l o s s c o n t r o l s i n t e g r a t e d w i t h the d a y l i g h t i n g a p e r t u r e . The c o n t r o l d e v i c e s a r e an e x t e n s i o n of the b u i l d i n g envelope and s u r f a c e s : an overhang c o n t r o l s unwanted s o l a r heat g a i n and h i g h r e f l e c t a n c e s u r f a c e s d i s t r i b u t e the l i g h t . 107 F i g u r e 28 - A s k y l i g h t w i t h a l i g h t w e l l can d e l i v e r l i g h t deep i n t o i n t e r i o r s The c h o i c e between roof m o n i t o r s and s k y l i g h t s i s u s u a l l y made not o n l y on the b a s i s of the q u a n t i t y of l i g h t and t h e r m a l t r a d e o f f s i n v o l v e d w i t h each t y p e , but a l s o on the impact of each type on the b u i l d i n g form and the m o d u l a t i o n of the r e s u l t i n g i n t e r i o r l i g h t . Thus, s k y l i g h t s p r o v i d e more l i g h t per g l a z e d a r e a than r o o f m o n i t o r s and r e s u l t i n l e s s e x p e n s i v e r o o f c o n s t r u c t i o n and s i m p l e r r o o f shapes. However, s k y l i g h t s on f l a t r o o f s , because they are o r i e n t e d t o the z e n i t h , r e q u i r e s p e c i a l a t t e n t i o n t o g l a r e and s o l a r heat c o n t r o l . Because s k y l i g h t s a r e i n c o r p o r a t e d i n the r o o f p l a n e and do not g e n e r a l l y i n v o l v e a d d i t i o n a l p r o j e c t i n g p l a n e s , they can be e c o n o m i c a l l y be l a i d out i n p a t t e r n s t h a t r e s u l t i n an even 108 F i g u r e 30 - I n t e g r a t e d t o p l i g h t i n g examples 109 d a y l i g h t d i s t r i b u t i o n on the h o r i z o n t a l work p l a n e . Roof m o n i t o r s can be used as l a r g e , d r a m a t i c , s e m i - i n d i r e c t d a y l i g h t i n g a p e r t u r e s (two examples are shown i n f i g u r e 30 ). They can be o r i e n t e d t o any d i r e c t i o n , and can t h e r e b y a v o i d s o l a r heat g a i n , i f t h i s i s u n d e s i r a b l e . Lam 7 5 has used "sun c a t c h e r b a f f l e s " t o r e f l e c t s u n l i g h t i n t o r o o f m o n i t o r s f a c i n g n o r t h , t h e r e b y t a k i n g advantage of the sun's l i g h t w i t h o u t the a t t e n d a n t heat g a i n . S o u t h - f a c i n g m o n i t o r s can s i m i l a r l y i n c o r p o r a t e s o l a r c o n t r o l s , e i t h e r as b a f f l e s or as overhangs. For reasons of economy, r o o f m o n i t o r s w i l l g e n e r a l l y be l a r g e a r c h i t e c t u r a l e l e m e n t s . As such, they w i l l d e l i v e r l a r g e p o o l s of l i g h t i n t o the i n t e r i o r , but t h i s l i g h t w i l l not be as e v e n l y d i s t r i b u t e d as i s p o s s i b l e w i t h s k y l i g h t s . Depending on the end use i n t e n d e d , t h i s may, or may not be a problem. o o o o o o o o o o o o o o o o o o o o o o o o o o o Finni'sk National Pensions InsTtfulV, U t U m l a F i g u r e 31 - T y p i c a l t o p l i g h t i n g l a y o u t s D a y l i g h t i n g a s u b s t a n t i a l p o r t i o n of a f l o o r w i t h s k y l i g h t s AAL Otitis i AppUfon, Wisconsin 1 1 0 may i n v o l v e the use of e i t h e r l i n e a r s k y l i g h t s or compact c i r c u l a r , square or r e c t a n g u l a r ones on a g r i d p a t t e r n as shown i n f i g u r e 31 7 6 . The c h o i c e i s g e n e r a l l y d e t e r m i n e d by c o n c e r n s of a e s t h e t i c s , s t r u c t u r e , and i n t e g r a t i o n w i t h o t h e r e n v i r o n m e n t a l c o n c e r n s . Both l a y o u t s shown can p o t e n t i a l l y p r o v i d e good d a y l i g h t p e n e t r a t i o n . 2.10 O b s t r u c t i o n s O b s t r u c t i o n s t o d a y l i g h t a c c e s s may o c c u r e i t h e r a t the bottom of the d a y l i g h t i n g a p e r t u r e ( g e n e r a l l y due t o the presence of nearby b u i l d i n g s or l a n d s c a p e elements) or a t the to p ( g e n e r a l l y due t o elements of the b u i l d i n g i t s e l f ) . T h i s i s shown i n f i g u r e 32 . F u r t h e r , o b s t r u c t i o n s t o d a y l i g h t a c c e s s above d a y l i g h t i n g a p e r t u r e s may occur e i t h e r a t the massing or component s c a l e , as shown i n f i g u r e 33 O b s t r u c t i o n a t the massing s c a l e has been d i s c u s s e d i n a p r e v i o u s s e c t i o n ; the fo c u s i n t h i s s e c t i o n i s on o b s t r u c t i o n t o d a y l i g h t J a c c e s s a t the component s c a l e . C o n s i d e r a t i o n of overhead o b s t r u c t i o n s i s e s p e c i a l l y i m p o r t a n t when window openings are a l r e a d y o b s t r u c t e d by o t h e r b u i l d i n g s or l a n d s c a p e f e a t u r e s 7 7 . Types of o b s t r u c t i o n O b s t r u c t i o n s above a d a y l i g h t i n g a p e r t u r e are of t h r e e t y p e s : 111 F i g u r e 32 - O b s t r u c t i o n s a t the bottom or the top of a d a y l i g h t i n g a p e r t u r e i . The f i r s t type of o b s t r u c t i o n s a r e those c r e a t e d by e x t e r n a l s h a d i n g d e v i c e s . P a r t i a l o b s t r u c t i o n of the s k y v a u l t by e x t e r i o r h o r i z o n t a l sun c o n t r o l d e v i c e s i s , i n p r a c t i c e , u n a v o i d a b l e , s i n c e i n s c r e e n i n g out the sun, they i n v a r i a b l y mask a p o r t i o n of the sky. However, sun c o n t r o l d e v i c e s which are e q u a l l y e f f e c t i v e i n s c r e e n i n g out the sun, can v a r y w i d e l y i n luminous performance. T h e r e f o r e , i t i s p o s s i b l e t o s e l e c t sun c o n t r o l d e v i c e s t h a t p e r f o r m t h e i r p r i m a r y f u n c t i o n w i t h a minimum o b s t r u c t i o n of d a y l i g h t . i i . The second type of o b s t r u c t i o n s a r e due t o geometry of the f a c a d e . Once t h i s geometry i s chosen, o b s t r u c t i o n of the 1 12 F i g u r e 3 3 - O b s t r u c t i o n s a t the massing s c a l e (a.) and the component s c a l e (b.) s k y v a u l t above d a y l i g h t i n g a p e r t u r e s due t o t h i s c h o i c e i s u n a v o i d a b l e . F i g u r e 34 shows t h r e e t y p i c a l c a s e s . In a. a bay window i s shown. T h i s type of d a y l i g h t i n g a p e r t u r e provides- a p o o l of l i g h t near the a p e r t u r e , w i t h l i t t l e d a y l i g h t p e n e t r a t i o n 7 8 . I t s luminous performance i s e q u i v a l e n t t o t h a t of a d a y l i g h t i n g a p e r t u r e i n the p l a n e of the facade w i t h a t r a p e z o i d a l s h a d i n g d e v i c e o v e r h e a d 7 9 , 8 0 . T h e r e f o r e , bay windows a r e not e f f e c t i v e d a y l i g h t i n g elements and s h o u l d be chosen o n l y i f they a r e found t o be d e s i r a b l e i n m o d u l a t i n g e l e v a t i o n s and f l o o r a r e a s . F i g u r e 3 4 b. shows a c o r n e r window. The luminous performance of t h i s d e s i g n i s e q u i v a l e n t t o t h a t o f o a 113 d a y l i g h t i n g a p e r t u r e a c r o s s the opening, w i t h a p o i n t e d hood ( s h a d i n g d e v i c e ) o v e r h e a d 8 1 . F i g u r e 34 c. shows a d a y l i g h t i n g a p e r t u r e w i t h s l o p e d g l a s s . In t h i s c a s e , as shown i n the d r a w i n g , the luminous performance of t h i s d a y l i g h t i n g a p e r t u r e i s e q u i v a l e n t to t h a t of an a p e r t u r e w i t h v e r t i c a l g l a z i n g at the same l o c a t i o n as the base of the o r i g i n a l d a y l i g h t i n g a p e r t u r e and a s h a d i n g d e v i c e overhead. The s l o p e of the g l a s s w i l l reduce g l a r e from the s k y v a u l t , but by i t s e l f has a s m a l l e f f e c t on d a y l i g h t p e n e t r a t i o n 8 2 . However, the e f f e c t of the "overhang" i s t o reduce d a y l i g h t a c c e s s , i i i . The t h i r d type of o b s t r u c t i o n s above d a y l i g h t i n g a p e r t u r e s a r e those c r e a t e d by f l o o r a r e a s p r o j e c t i n g beyond the l i n e of the d a y l i g h t i n g a p e r t u r e (eg. c a n t i l e v e r e d f l o o r s , b a l c o n i e s , e t c . ) . E f f e c t of o b s t r u c t i o n parameters Four o b s t r u c t i o n parameters may be i d e n t i f i e d as a f f e c t i n g d a y l i g h t a c c e s s : i . O b s t r u c t i o n depth has a major e f f e c t on d a y l i g h t a c c e s s from the i n t e r i o r . I t may be seen i n f i g u r e 35 8 3 , t h a t a s h a l l o w o b s t r u c t i o n a f f e c t s p o i n t s near the d a y l i g h t i n g a p e r t u r e but not f u r t h e r away, whereas deeper o b s t r u c t i o n s reduce d a y l i g h t l e v e l s p r o g r e s s i v e l y f u r t h e r i n the i n t e r i o r . T h i s i s because the deeper o b s t r u c t i o n s reduce the sky v i s i b l e and hence a l s o the i n t e r i o r r e f l e c t e d component 8 *, 8 5 . 1 1 4 LUMINOUS PtMMANCf OF 1. 16 EtJttVALENT TO 2. F i g u r e 34 - O b s t r u c t i o n s above d a y l i g h t i n g a p e r t u r e s due t o facade geometry F i g u r e 35 - R e l a t i o n s h i p between o b s t r u c t i o n d e pth and d a y l i g h t p e n e t r a t i o n F i g u r e 36 - O b s t r u c t i o n s a t d i f f e r e n t h e i g h t s above a d a y l i g h t i n g a p e r t u r e h a v i n g i d e n t i c a l e f f e c t on d a y l i g h t p e n e t r a t i o n i i . H e i g h t of o b s t r u c t i o n above the d a y l i g h t i n g a p e r t u r e i s a second parameter a f f e c t i n g d a y l i g h t a c c e s s . F i g u r e 36 shows two o b s t r u c t i o n s , of d i f f e r e n t d e p t h s and d i f f e r e n t " h e i g h t s above the d a y l i g h t i n g a p e r t u r e . They b l o c k a c c e s s 1 1 6 t o d a y l i g h t from the s k y v a u l t e q u a l l y : the l o c a t i o n i n the room of the "no-sky l i n e " 8 6 i s the same i n both i n s t a n c e s . i i i . The r e f l e c t a n c e of the u n d e r s i d e of o b s t r u c t i o n i s a t h i r d parameter a f f e c t i n g d a y l i g h t a c c e s s . I t i s p o s s i b l e t o compensate t o some e x t e n t f o r a reduced d a y l i g h t a c c e s s due t o an o b s t r u c t i o n above the d a y l i g h t i n g a p e r t u r e by i n c r e a s i n g the r e f l e c t a n c e of i t s u n d e r s i d e s u r f a c e . E x p e r i m e n t s by Aschehoug et a l . 8 7 show t h a t w i t h a low r e f l e c t a n c e f o r e g r o u n d , an i n c r e a s e from 30% r e f l e c t a n c e (grey c o n c r e t e ) t o 75% r e f l e c t a n c e , (near w h i t e p a i n t ) i n c r e a s e s the DF by one t e n t h i n the f r o n t of the room and reduces i t by one t e n t h a t the back. i v . Ground r e f l e c t a n c e i s the f o u r t h parameter a f f e c t i n g d a y l i g h t a c c c e s s w i t h a d a y l i g h t i n g a p e r t u r e o b s t r u c t e d overhead. R e f l e c t a n c e of the ground i s v e r y i m p o r t a n t , as i t can m i t i g a t e t o a l a r g e e x t e n t the i n h e r e n t d a y l i g h t i n g d i s a d v a n t a g e s of overhead o b s t r u c t i o n s . I t can be seen i n f i g u r e 37 8 8 , t h a t w i t h an o b s t r u c t i o n over the d a y l i g h t i n g a p e r t u r e , an i n c r e a s e i n ground r e f l e c t a n c e from 5% ( b l a c k t o p ) t o 85% ( l i g h t p a i n t , f r e s h snow) can a p p r o x i m a t e l y t r i p l e the DF a t the back of a room and g e n e r a l l y reduce the DF g r a d i e n t . An i n c r e a s e i n the r e f l e c t a n c e of the u n d e r s i d e of the o b s t r u c t i o n can add a f u r t h e r 10% t o t h e DF a l l a c r o s s the r o o m 8 9 , w i t h even g r e a t e r i n c r e a s e near the window. I t i s im p o r t a n t t o n o t e , t h a t when a d a y l i g h t i n g scheme r e l i e s on h i g h r e f l e c t a n c e f o r the ground s u r f a c e , t h i s 1 1 7 • •to F i g u r e 37 - The e f f e c t of ground r e f l e c t a n c e on d a y l i g h t a c c e s s , w i t h an o b s t r u c t i o n above the d a y l i g h t i n g a p e r t u r e r e f l e c t a n c e v a l u e w i l l need t o be m a i n t a i n e d i n p r a c t i c e t o ensure t h e s u c c e s s of the scheme. Ground r e f l e c t a n c e v a l u e s a r e , however, d i f f i c u l t t o m a i n t a i n f o r the l i f e of the b u i l d i n g , u n l e s s the "ground" i s a r o o f or s i m i l a r s u r f a c e , c o v e r e d w i t h h i g h r e f l e c t a n c e m a t e r i a l which can r e a s o n a b l y be e x p e c t e d t o m a i n t a i n t h i s p r o p e r t y w i t h t i m e . 1 18 3. NOTES 1. Rays of s u n l i g h t a re p a r a l l e l because the source i s v e r y f a r away. 2. T u r b i d i t y i s an index of the haze i n the atmosphere~-e i t h e r due t o n a t u r a l causes (eg. water vapour, fog) or man-made causes (eg. smog). 3. Up t o 120 lumens/Watt. A r t h u r H. R o s e n f e l d and Stephen E. S e l k o w i t z , "Beam D a y l i g h t i n g : An A l t e r n a t i v e I l l u m i n a t i o n t e c h n i q u e , " Energy and B u i l d i n q s , 1 ( 1 9 7 7 ) : 4 4 . 4. IES D a y l i g h t i n g Committee, "Recommended P r a c t i c e of D a y l i g h t i n g , " L i g h t i n g D e s i g n and A p p l i c a t i o n s , F e b r u a r y 1979, p. 33. 5. R. G. Hopkinson, A r c h i t e c t u r a l P h y s i c s : L i g h t i n g (London: Her M a j e s t y ' s S t a t i o n e r y O f f i c e , 1963),- p. .166. 6. IES D a y l i g h t i n g Committee (1979), p. 33. 7. IES D a y l i g h t i n g Committee, Recommended P r a c t i c e of  D a y l i g h t i n g (New York: I l l u m i n a t i n g E n g i n e e r i n g S o c i e t y , 1962), p. 9. 8. W i l l i a m Lam, " S u n l i g h t i n g as Formgiver f o r A r c h i t e c t u r e , " P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l D a y l i g h t i n g  C o n f e r e n c e , 16-18 Feb r u a r y 1983 i n Phoen i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, pp. 77-80. 9. The concept of the D a y l i g h t F a c t o r (DF) i s a u s e f u l index i n a s s e s s i n g the r e l a t i v e ' d a y l i g h t l e v e l s a v a i l a b l e at v a r i o u s p o i n t s i n b u i l d i n g i n t e r i o r s . The DF i s the sum of t h r e e components: the sky component ( S C ) , the e x t e r i o r r e f l e c t e d component (ERC) and the i n t e r n a l l y r e f l e c t e d ' component ( I R C ) . 10. J . A. Lynes, P r i n c i p l e s of N a t u r a l L i g h t i n g (London: E l s e v i e r , 1968), p. 184. 11. Harvey Bryan et a l . , Q u i c k l i t e I : A D a y l i g h t i n g Program  f o r the TI-59 C a l c u l a t o r ( B e r k e l e y , C a l i f o r n i a : Lawrence B e r k e l e y L a b o r a t o r y , 1981). 1 1 9 12. J . W. T. Walsh, The S c i e n c e of D a y l i g h t (New York: Pitman, 1961), p. 233. 13. B u i l d i n g Research Board, The L i g h t i n g of B u i l d i n g s (London: H i s M a j e s t y ' s S t a t i o n e r y O f f i c e , 1944), pp. 22-25. 14. I b i d . , pp. 23. 15. Hopkinson, p. 34. 16. See a l s o Walsh, p. 214-15. 17. B u i l d i n g Research Board, p. 24. 18. Walsh, pp. 233-35. 19. B u i l d i n g Research Board, p. 25. 20. I b i d . , p. 24. 2 1 . I b i d . , p. 27. 22. The performance of 'T' and 'L' shaped b u i l d i n g s i s s i m i l a r t o t h a t of the c r u c i f o r m p l a n s s t u d i e d ( B u i l d i n g Research Board, p. 24). 23. B u i l d i n g Research Board, p. 26. 24. Lynes, p. 156. 25. B u i l d i n g Research Board, p. 26. 26. I b i d . 27. IES D a y l i g h t i n g Committee, Recommended P r a c t i c e of D a y l i g h t i n g , 1962, p. 9. 28. B. H. Reed, " E f f e c t s of Nearby Walks and Co n c r e t e Areas on Indoor N a t u r a l L i g h t i n g , " I l l u m i n a t i n g E n g i n e e r i n g , J u l y , 1956, p. 532. 29. R. G. Hopkinson, A r c h i t e c t u r a l P h y s i c s : L i g h t i n g (London: Her M a j e s t y ' s S t a t i o n e r y O f f i c e , 1963), p. 178. 30. Robert S. H a s t i n g s and R i c h a r d W. Crenshaw, Window Design  S t r a t e g i e s t o Conserve Energy (NBS B u i l d i n g S c i e n c e S e r i e s 104, Washington D.C.: Department of Commerce, 1977), p. 16. 31. R. G. Hopkinson and J . D. Kay, The L i g h t i n g of B u i l d i n g s (London: Faber and F a b e r , 1969), p. 88. 32. Gary 0. R o b i n e t t e , P l a n t s , P e o p l e and E n v i r o n m e n t a l 1 20 Q u a l i t y (Washington, D. C : Department of the I n t e r i o r , 1 972) , pp. 70-7 1. 33. A. Bowen, "Fundamentals of S o l a r A r c h i t e c t u r e , " i n S o l a r  Energy C o n v e r s i o n : An I n t r o d u c t o r y Course, e d i t e d by A. E. Dixon and J~. D. L e s l i e , eds. ( T o r o n t o : Pergamon, 1979), p. 500. 34. P l a n s a r e : A . — G S I S b u i l d i n g , M a n i l a , P h i l l i p i n e s from A r c h i t e c t u r a l Record, " T e r r a c e d Pods I n v i t e D a y l i g h t and B r e e z e s , " A r c h i t e c t u r a l Record, Mid-August 1981, p. 52.; B.--TVA b u i l d i n g , C httanouga, Tenn., from S c o t t Matthews and P e t e r C a l t h o r p e , " D a y l i g h t as a C e n t r a l D eterminant of D e s i g n , " AlA J o u r n a l , September 1979, p. 87. 35. The p l a n s a r e : A.--Wainwright b u i l d i n g , S t . L o u i s , Mo. ( L o u i s S u l l i v a n ) ; B . - - t y p i c a l European o f f i c e b u i l d i n g i n 1950s; C.—UNESCO, P a r i s ( B r euer and Z e h r f u s s ) ; D.--B.P. H e a d q u a r t e r s , Hamburg,(proposal o n l y , A. A a l t o ) ; E.--S h e l l O i l Co. E x p l o r a t i o n and P r o d u c t i o n O f f i c e s , Houston,Texas (CRS, a r c h . ) . 36. Q u a n t r i l l , pp 119-20. 37. F l i e g , K a r l , ed., A l v a r A a l t o (New York: P r a e g e r , 1971), p. 120. 38. AIA Journal-, "Measuring Performance of Energy D e s i g n : DOE s t u d i e s a s e t of Owens-Corning Award Winners over Time," AIA J o u r n a l , January 1983, p. 44. 39. Max H. Leu, "Energy C o n s e r v a t i o n i n O f f i c e B u i l d i n g s , " M a s t e r ' s T h e s i s a t U n i v e r s i t y of B r i t i s h Columbia, 1980, p. 121. 40. Matthews and C a l t h o r p e , p. 87. 41. V l a d i m i r B a z j a n a c , "Energy A n a l y s i s : One Year L a t e r , " P r o g r e s s i v e A r c h i t e c t u r e , A p r i l 1981, p. 154. 42. I b i d . 43. Lynes, p. 159. 44. The p l a n s a r e : A . - - L a r k i n b u i l d i n g , B u f f a l o , N. Y. (F. L. W r i g h t ) ; B.-- Lockheed M i s s i l e s no. 157 b u i l d i n g , S u n n y v a l e , C a l i f . (L. D a l y ) ; C.— A t r i a N o r t h Complex, T o r o n t o (Thorn P a r t n e r s h i p ) ; D.-- E n e r p l e x , P l a i n s b o r o , N. J . (SOM); E . — CIGNA b u i l d i n g , B l o o m f i e l d , Conn. ( A r c h i t e c t s C o l l a b o r a t i v e ) ; F . — S t a t e O f f i c e b u i l d i n g , San J o s e , C a l i f . ( S t a t e of C a l i f * , , A r c h . ) . 45. S c o t t Matthews and Stephen S e l k o w i t z , p l e n n a r y s e s s i o n , The 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 121 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . 46. I b i d . 47. S c o t t Matthews, " P r o v i n g t h e ^ B e n e f i t s of D a y l i g h t i n g , " A r c h i t e c t u r a l R e c o r d , Mid-August, 1981, p. 49. 48. I b i d . 49. Stephen S e l k o w i t z , t a l k g i v e n a t the p l e n n a r y s e s s i o n , The 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . 50. A r c h i t e c t u r a l Record, "Round T a b l e : A R e a l i s t i c Look a t The P a s s i v e Approach--Using N a t u r a l Means t o Conserve Energy," A r c h i t e c t u r a l Record, Mid-August 1983, p. 98. 51. N e s t o r E. Sanchez and W i l l i a m Rudoy, "Energy Impact of the Use of D a y l i g h t i n g i n O f f i c e s , " ASHRAE T r a n s a c t i o n s , 1981, p t . 2 , pp. 145. 52. P e t e r C a l t h o r p e , "More Than J u s t Energy," P r o g r e s s i v e  A r c h i t e c t u r e , A p r i l 1983, p. 119. 53. Lee Stephen Windheim and K y l e V. Davy, "The S u b s t i t u t i o n of D a y l i g h t i n g f o r E l e c t r i c L i g h t i n g i n a Large O f f i c e B u i l d i n g , " P r o c e e d i n g s of the 6th N a t i o n a l P a s s i v e S o l a r  C o n f e r e n c e , September 8-12', 1981 i n P o r t l a n d , Oregon, Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1972, p. 878. 54. A r c h i t e c t u r a l Record, "A P e r s p e c t i v e on D a y l i g h t i n g D e s i g n , " A r c h i t e c t u r a l Record, Midaugust 1981, p. 45. 55. R o s e n f e l d and S e l k o w i t z , p. 44. 56. A. W. Levy, " I n t e r i o r L i g h t i n g D e s i g n and Energy C o n s e r v a t i o n , " D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l Research C o u n c i l of Canada, Canadian B u i l d i n g D i g e s t 192, 1977, p. 3. 57. R o s e n f e l d and S e l k o w i t z , p. 43. 58. M a r i e t t a S. M i l l e t , " D a y l i g h t i n g Design G u i d e l i n e s f o r P a c i f i c Northwest B u i l d i n g s , " P r o c e e d i n g s of ' S o l a r 79  Northwest' C o n f e r e n c e , August 10-12, 1979 i n S e a t t l e . S e a t t l e : P a c i f i c Northwest S o l a r Energy A s s o c i a t i o n , 1979, p. 52. 59. A r c h i t e c t u r a l R e c o r d , " P a r t i t i o n s and L i g h t s Work as a Modular P a i r t o C r e a t e Luminous Space," A r c h i t e c t u r a l  Record, A p r i l 1983, pp. 160-167. 60. Lam, p. 78. 1 22 61. D. Watson, "Johnson C o n t r o l s S a l t Lake C i t y O f f i c e B u i l d i n g D e s i g n : D a y l i g h t i n g s t u d i e s , " P r o c e e d i n g s of the  1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y  1983 i n Phoenix, A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, p. 96. 62. A r c h i t e c t u r a l Record, "On the W i s c o n s i n P r a i r i e a R e p o s e f u l B u i l d i n g w i t h S t r o n g P r e s e n c e , " A r c h i t e c t u r a l  Record, February 1978, pp. 126-132. 63. A r c h i t e c t u r e , " I n g e n i o u s l y D a y l i t S e a s i d e O f f i c e s , " A r c h i t e c t u r e , January 1984, pp. 64-67. 64. S c o t t E l l i n w o o d , " D a y l i g h t i n the Design P r o c e s s , " P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l D a y l i g h t i n g  C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, p. 149. 65. S o l a r Age, "Huzzahs f o r D a y l i g h t i n g , " S o l a r Age, F e b r u a r y , 1984, p. 17. 66. I b i d . 67. Hopkinson and Kay, p. 95. 68. S o l a r Age, p. 17. 69. Dan L e w i s , "Good News on S k y l i g h t Performance," S o l a r Age, pp. 24-25, . 70. Evans, pp. 63-64. 71. F i g u r e a f t e r Benjamin H. Evans, D a y l i g h t i n A r c h i t e c t u r e (New York: M c G r a w - H i l l , 1981), p. 64. 72. However, i t has been shown, both t h e o r e t i c a l l y and e x p e r i m e n t a l l y , t h a t d a y l i g h t i n g w i t h l i g h t w e l l s i s v e r y u n s a t i s f a c t o r y , u n l e s s t h e i r h o r i z o n t a l d i m e n s i o n i s l a r g e compared t o t h e i r depth--Walsh, p. 88. 73. Adapted from Zomeworks C o r p o r a t i o n t r a d e l i t e r a t u r e . 74. F i g u r e s show roof m o n i t o r s i n (top) S o l a r u s Square, Grand J u n c t i o n , C o l o r a d o ( M i l b u r n Sparn, a r c h i t e c t s ) , adapted from J e n n i f e r A. Adams, "A Design Team's Success w i t h Computers," S o l a r Age, March, 1983, pp. 27. A l s o shown (bottom) ro o f m o n i t o r s a t D a l l a s C i t y H a l l ( I . M. P e i , a r c h i t e c t s ) adapted from Evans, p. 174. 75. Lam, p. 80. 76. P l a n views d e r i v e d from: ( l e f t ) A i d A s s o c i a t i o n f o r 1 23 L u t h e r a n s b u i l d i n g , A p p l e t o n , W i s c o n s i n (Warnecke and A s s o c . ) , as d e s c r i b e d i n A r c h i t e c t u r a l R e c o r d , F e b r u a r y 1978, s u p r a ; ( r i g h t ) F i n n i s h N a t i o n a l P e n s i o n s I n s t i t u t e , H e l s i n k i (A. A a l t o ) , as d e s c r i b e d i n F l i e g , p. 120. 77. Walsh, p. 88. 78. Hopkinson, A r c h i t e c t u r a l P h y s i c s , p. 32. 79. Oyvind Aschehoug et a l . , V i n d u , Rom og D a g s l y s - - D e l 11  (Windows, Room and D a y l i g h t - - P a r t I I ) ( i n N o r v e g i a n , Trondheim, Norway: Norges T e k n i s k e H o g s k o l e , 1982), t e x t pp. 5,22; diagrams pp. 19-22. 80. B u i l d i n g Research Board, p. 15. 81. I b i d . 82. Evans, p. 76. 83. Aschehoug, p. 21. F i g u r e s assume 0.75 r e f l e c t a n c e f o r the u n d e r s i d e of overhang and 0.05 r e f l e c t a n c e f o r ground. 84. Walsh, p. 88. 85. B u i l d i n g Research Board, p. 15. 86. The no-sky l i n e i s the l i n e beyond which no sky may be seen. I t i s g e n e r a l l y r e f e r e n c e d a t desk h e i g h t . 87. Aschehoug, diagrams pp. 15-16. 88. I b i d . diagrams pp. 17-18. 89. I b i d . 1 24 IV. PROMOTE DAYLIGHT PENETRATION 1 25 1. INTRODUCTION Once the p o t e n t i a l f o r a c c e s s i n g d a y l i g h t has been maximized, i t i s n e c e s s a r y t o p r o v i d e means t h a t w i l l , i n t u r n , promote d a y l i g h t p e n e t r a t i o n i n t o b u i l d i n g i n t e r i o r s . The term " d a y l i g h t p e n e t r a t i o n " i s a w i d e l y used metaphor d e n o t i n g the phenomenon whereby d a y l i g h t i s r e f r a c t e d and/or r e f l e c t e d by v a r i o u s means i n t o i n t e r i o r s of b u i l d i n g s . D a y l i g h t p e n e t r a t i o n can be p r o v i d e d by: i . t r a d i t i o n a l d a y l i g h t i n g t e c h n i q u e s i i . i n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s 2. TRADITIONAL DAYLIGHTING TECHNIQUES T r a d i t i o n a l d a y l i g h t i n g t e c h n i q u e s f o r l i g h t i n g t a s k a r e a s i n o f f i c e s may be i d e n t i f i e d by two c h a r a c t e r i s t i c s : i . They u t i l i z e o n l y d i f f u s e d a y l i g h t from o v e r c a s t or c l e a r sky; d i r e c t sun i s e x c l u d e d from the i n t e r i o r . T h i s i s because the i n t r o d u c t i o n of s u n l i g h t i n t o t a s k a r e a s of o f f i c e b u i l d i n g s r e q u i r e s methods of d i s t r i b u t i o n and c o n t r o l t h a t are o u t s i d e the scope of t r a d i t i o n a l d a y l i g h t i n g t e c h n i q u e s . i i . Components whose s o l e purpose i s t o promote d a y l i g h t p e n e t r a t i o n are not used. D a y l i g h t i n g a p e r t u r e geometry, 1 26 5 C A L E SITt PLANNING WILDING CONFIGURATUXI BUILDING COMPONENT BUILDING INTERIOR CONFIGURATION AUt> LOCATION OF DAYLIGWTIN6 APERTURE ROOM GEOMETRY GLAZIN6 MATERIAL SLlECTIOh' MTXRIA REFLECTANCES 0 MAINTENANCE FACTOR NET GLAZING AREA tit toi THICK WALLS F i g u r e 38 - Summary of t r a d i t i o n a l t e c h n i q u e s p r o m o t i n g d a y l i g h t p e n e t r a t i o n 1 27 room geometry, and d e t a i l i n g of s u r f a c e s a r e the o n l y means u t i l i z e d t o i n c r e a s e d a y l i g h t p e n e t r a t i o n . A summary of t r a d i t i o n a l d a y l i g h t i n g t e c h n i q u e s i n c l u d e d i n t h i s c h a p t e r i s shown i n f i g u r e 38 . 2.1 C o n f i g u r a t i o n And L o c a t i o n Of D a y l i g h t i n g A p e r t u r e An i m p o r t a n t means of promoting d a y l i g h t p e n e t r a t i o n i s by the a p p r o p r i a t e s i z i n g and l o c a t i o n of the d a y l i g h t i n g a p e r t u r e . In an u n o b s t r u c t e d s i t u a t i o n , d e f i n i t e r e l a t i o n s h i p s can be e s t a b l i s h e d between the s i z e or placement of the d a y l i g h t i n g a p e r t u r e and d a y l i g h t p e n e t r a t i o n . These r e l a t i o n s h i p s a r e m o d i f i e d , t o a g r e a t e r or l e s s e r degree, by e x t e r n a l o b s t r u c t i o n s . U n o b s t r u c t e d s i t u a t i o n The f o l l o w i n g a r e r e s u l t s of p a r a m e t r i c s t u d i e s done by Aschehoug 1 and E v a n s 2 . In t h i s s e r i e s , summarized i n f i g u r e 39 , the c o n f i g u r a t i o n and/or l o c a t i o n of the window on the e x t e r i o r w a l l was v a r i e d , w h i l e the geometry of the room remained c o n s t a n t . i . The s i z e of the d a y l i g h t i n g a p e r t u r e has an o b v i o u s e f f e c t on d a y l i g h t p e n e t r a t i o n . The i n c r e a s e i n the DF w i t h an i n c r e a s e i n a r e a i s n o t , however, l i n e a r s i n c e t h i s depends on s u r f a c e r e f l e c t a n c e s , the l o c a t i o n of the window w i t h r e s p e c t t o the work p l a n e , e t c . T r e a t i n g the window component below the work p l a n e s e p a r a t e l y from the component above the work p l a n e , w i l l e n a b l e e a s i e r 6. 1 2.9 I 1.6 l.« 0.8 1) If 1.1 4 A. F i g u r e 39 - The i n f l u e n c e of s i z e and l o c a t i o n of the d a y l i g h t i n g a p e r t u r e on d a y l i g h t p e n e t r a t i o n 1 29 o p t i m i z a t i o n of window s i z e from the p o i n t of view of d a y l i g h t p e n e t r a t i o n , because i t i s the component above t h a t c o n t r i b u t e s most of the l i g h t t h a t reaches the work p l a n e . i i . L o c a t i o n of the window a l s o a f f e c t s d a y l i g h t p e n e t r a t i o n . As measured by the D a y l i g h t F a c t o r , d a y l i g h t p e n e t r a t i o n i n c r e a s e s as the h e i g h t of window i s i n c r e a s e d ( f i g u r e 39 b . ) . T h i s i s due t o the i n c r e a s e d sky component as w e l l as t o the f a c t t h a t more i l l u m i n a n c e i s a v a i l a b l e on the h o r i z o n t a l p l a n e . The amount of i n c r e a s e i s dependent on the sky c o n d i t i o n s , on r e f l e c t a n c e s of e x t e r n a l s u r f a c e s , and on i n t e r n a l s u r f a c e r e f l e c t a n c e s . i i i . A t h i r d parameter a f f e c t i n g d a y l i g h t p e n e t r a t i o n i s c o n f i g u r a t i o n of the window. T a l l windows p r o v i d e more l i g h t p e n e t r a t i o n than l o w e r , wider windows of e q u i v a l e n t a r e a . i v . Windows below the work p l a n e a r e u s e f u l i n b a l a n c i n g the l i g h t w i t h i n a room, e s p e c i a l l y i f f l o o r r e f l e c t a n c e s a r e i n the h i g h e r ranges, but do not c o n t r i b u t e s u b s t a n t i a l l y t o the l i g h t on the work p l a n e 3 . O b s t r u c t e d s i t u a t i o n Under o b s t r u c t e d c o n d i t i o n s , the e f f e c t of d i f f e r e n t d a y l i g h t i n g a p e r t u r e c o n f i g u r a t i o n s must be re-examined. O b s t r u c t i o n s may be c l a s s i f i e d as e i t h e r p r i m a r i l y h o r i z o n t a l or v e r t i c a l . F u r t h e r , as i n d i c a t e d i n the p r e v i o u s c h a p t e r , o b s t r u c t i o n s may o ccur e i t h e r a t the bottom of the d a y l i g h t i n g 1 30 a p e r t u r e ( g e n e r a l l y due t o the presence of nearby b u i l d i n g s or lan d s c a p e elements) or a t the top of the d a y l i g h t i n g a p e r t u r e ( g e n e r a l l y due to elements of the b u i l d i n g i t s e l f ) . i . H o r i z o n t a l o b s t r u c t i o n s a t the bottom of the d a y l i g h t i n g a p e r t u r e have a h o r i z o n t a l s k y - l i n e , r e s u l t i n g , f o r example, from a c o n t i n u o u s row of b u i l d i n g s o p p o s i t e the d a y l i g h t i n g a p e r t u r e . The maximum p e n e t r a t i o n of d a y l i g h t d i r e c t l y from the s k y v a u l t w i l l be d e t e r m i n e d by a l i n e drawn through the t o p of the o b s t r u c t i o n and the head of the a p e r t u r e . Where t h i s l i n e c u t s the w o r k i n g p l a n e , a l i n e can be drawn, beyond which no sky can be seen. T h i s i s c a l l e d the no-sky l i n e . For a p a r a l l e l and h o r i z o n t a l o b s t r u c t i o n , the no-sky l i n e w i l l be p a r a l l e l t o the d a y l i g h t i n g a p e r t u r e , • as shown i n f i g u r e 40 a." A h o r i z o n t a l and p a r a l l e l o b s t r u c t i o n w i l l a f f e c t d a y l i g h t p e n e t r a t i o n more than the l a t e r a l spread of l i g h t . F i g u r e 40 b. shows how the p e n e t r a t i o n of l i g h t i s a f f e c t e d by the i n c r e a s i n g l y h i g h e r o b s t r u c t i o n , but the s i d e spread i s reduced t o a l e s s e r e x t e n t 5 . Because of t h e s e phenomena, v e r t i c a l d a y l i g h t i n g a p e r t u r e s w i l l p r o v i d e b e t t e r d a y l i g h t p e n e t r a t i o n and lower peak i n t e n s i t i e s near the a p e r t u r e , than a h o r i z o n t a l d a y l i g h t i n g a p e r t u r e w i t h e q u a l g l a z i n g a r e a 6 . T h i s i s i n d i c a t e d i n f i g u r e 40 c. i i . H o r i z o n t a l o b s t r u c t i o n s above the d a y l i g h t i n g a p e r t u r e a r e c r e a t e d by elements of the b u i l d i n g i t s e l f (eg. b a l c o n i e s , o v e r h a n g i n g f l o o r s ) . In t h e s e i n s t a n c e s , h o r i z o n t a l a p e r t u r e s w i l l d e l i v e r more l i g h t than v e r t i c a l a p e r t u r e s 131 F i g u r e 40 - D a y l i g h t p e n e t r a t i o n w i t h h o r i z o n t a l o b s t r u c t i o n 1 32 of e q u i v a l e n t a r e a , because the upper p o r t i o n of the sky i s b l o c k e d by the o b s t r u c t i o n . T h i s i s the r e v e r s e of the p r e v i o u s s i t u a t i o n , i i i . V e r t i c a l o b s t r u c t i o n s have a v e r t i c a l s k y - l i n e , such as might be produced, f o r example, by e x t e r n a l r e t u r n w a l l s , l a r g e s c a l e v e r t i c a l s h a d i n g d e v i c e s , or a v e r t i c a l gap between t a l l b u i l d i n g s o p p o s i t e the d a y l i g h t i n g a p e r t u r e . The e f f e c t of a v e r t i c a l o b s t r u c t i o n i s the o p p o s i t e of a h o r i z o n t a l o b s t r u c t i o n o c c u r i n g a t the bottom of the a p e r t u r e , i n t h a t the spread of d a y l i g h t i s reduced, but the d a y l i g h t p e n e t r a t i o n i s not much a f f e c t e d . F i g u r e 41 a . 7 shows the e f f e c t on d a y l i g h t p e n e t r a t i o n of an e x t e r n a l r e t u r n w a l l , w h i l e i n f i g u r e 41 b. the e f f e c t of a v e r t i c a l gap between two b u i l d i n g s o p p o s i t e the d a y l i g h t i n g a p e r t u r e may be seen. The broken d a y l i g h t c o n t o u r s r e p r e s e n t the t h e o r e t i c a l l y u n o b s t r u c t e d c o n d i t i o n ; the s o l i d c o n t o u r , the a c t u a l o b s t r u c t e d c o n d i t i o n 8 . F i g u r e 41 c. shows the e f f e c t on d a y l i g h t p e n e t r a t i o n of d i f f e r e n t window shapes w i t h d a y l i g h t b l o c k e d by a v e r t i c a l o b s t r u c t i o n . In t h i s i n s t a n c e , the v e r t i c a l d a y l i g h t i n g a p e r t u r e s c r e a t e s t r o n g beams of l i g h t a c r o s s a room, whereas the h o r i z o n t a l d a y l i g h t i n g a p e r t u r e p r o v i d e s more u n i f o r m i l l u m i n a n c e 9 . These g e n e r a l o b s e r v a t i o n s s h o u l d be supplemented i n e v e r y p r o j e c t by model s t u d i e s or m a t h e m a t i c a l e x p l o r a t i o n s t h a t a c c u r a t e l y s i m u l a t e the l o c a t i o n of the o b s t r u c t i o n s . Only 1 33 c. F i g u r e 41 - D a y l i g h t p e n e t r a t i o n w i t h v e r t i c a l o b s t r u c t i o n 1 34 thus can more s p e c i f i c i n f o r m a t i o n be o b t a i n e d on the e f f e c t of o b s t r u c t i o n s on d a y l i g h t p e n e t r a t i o n . 2.2 G l a z i n g M a t e r i a l S e l e c t i o n The t h e r m a l and luminous performance of a d a y l i g h t i n g assembly may be d e s c r i b e d by t h r e e c o e f f i c i e n t s , which once known, enable an e v a l u a t i o n of the t o t a l energy performance of t h a t assembly i n a b u i l d i n g , as w e l l as a comparison w i t h o t h e r d a y l i g h t i n g a s s e m b l i e s . i . L i g h t t r a n s m i t t a n c e (T) i s the r a t i o of the amount of l i g h t t r a n s m i t t e d through a m a t e r i a l , or an assembly of m a t e r i a l s , t o the amount of l i g h t s t r i k i n g i t . T h i s c h a r a c t e r i s t i c of the g l a z i n g assembly i n a d a y l i g h t i n g scheme, t h e r e f o r e d i c t a t e s the amount of l i g h t t h a t p e n e t r a t e s i n t o the i n t e r i o r . T a b l e IX 1 0 l i s t s l i g h t t r a n s m i t t a n c e v a l u e s of the more common, as w e l l as of some new, g l a z i n g m a t e r i a l s and a s s e m b l i e s . i i . The sh a d i n g c o e f f i c i e n t (SC) f o r a g l a z i n g assembly i s the r a t i o of the t o t a l s o l a r heat g a i n t h r o u g h i t t o the t o t a l s o l a r heat g a i n t h r o u g h a s t a n d a r d sheet of c l e a r g l a s s under e x a c t l y the same c o n d i t i o n s 1 1 . T a b l e IX i n d i c a t e s SC v a l u e s f o r v a r i o u s g l a z i n g a s s e m b l i e s . I t i s g e n e r a l l y u n d e r s t o o d t h a t the SC v a r i e s a p p r o x i m a t e l y i n i n v e r s e r a t i o t o the l i g h t t r a n s m i t t a n c e ( T ) 1 2 . However, some d a y l i g h t i n g a s s e m b l i e s e x h i b i t a r e l a t i v e l y low SC and h i g h T when compared w i t h o t h e r a s s e m b l i e s . For example, some new p r o d u c t s , such as the "heat m i r r o r " 1 35 GLAZING ASSEMBLY X VISIBLE XTOTAL SOLAR SHADING WINTER V VALUE TRANSMISSION TRANSMISSION COEFFICIENT METRIC(IWTRIAL) SINGLE GLA2ING 3*™ WATER-WHITE CRYSTAL 91.6 91.6 1. 05 6.4G (1.13) 3»m LOW-IRON SHEET 91.1 89.1 1.03 II II 3m» CLEAR FLOAT 91. 85 1. 00 * N 6 * * CLEAR FLOAT 89 BO 0.95 11 H BLUE-GREEN FLOAT 14 48 O.10 M u 6 » * BRONZE FLOAT 50 48 0.68 l l II 6 - * GRAY FLOAT 43 46 0.66 It II 6 « * PYROLYTIC BRONZE . 21 26 0.45 11 II 6m« CHROME Z% CLEAR. <b 10 0.26 5.14 (0.90) 6-M» CHROME b% BRONZE % 9 0.34 5.54 (0.97) POUBLE GLAZING-I3w« AIRSPACE 3»* CLEAR + 3 M CLEAR 81 11 0.88 2.79 (OAS) 6nk *• 6>»i» II 18 (0 0.80 • i II U> BRONZE* 6*1. CLEAR 44- 36 0.54 II It 6 <5fViY •» * • .' 37 34 0.53 II II 6 •»» PYRO. 6R0NZE+ « « 19 20 0.34 II II 6 •*» CLEAR tX CHROME + C CLEAR 1 8 0.18 2.33 (C.+l) 6 » * • 82G0LD + •> 8 3 0.07 1.77 G>.31) 6»m BLUE6REEN + 6mm CLEAR 67 40 0.60 2.10 (0.48) 6 CLEAR «• LOW E. CLEAR** 14 52 0.11 1.80 (0.32) 6m» BRONZE + •• •' 43 32 0.49 ii It 6«m GRAY + » • 98 31 0.46 • H 6»«. GREEN + • * 4 32 0.47 • Ii TR1PL E GLAZING - 1W AIR SPACES CLEAR + CLEAR+3ft» CIEAR 14 60 0.T8 2.10 (0.36) (••> • + 3kn • • 6fc» II 73 53 0.13 1.50 (0.33) 6»« » + HM.55 • » « 48 25 0.39 1.26 (o.ZZ) • • H.M. TT • " • £6 40 0.58 1.31 (0.23) » •• + H.M.88 • " « 63 4 5 0.65 It ii 6»*BLUE-6REEN + H.M. 55 + « 40 16 0.28) 1.26 (0.22) n » * H.M-T7 • " • 56 26 0.41 (0.25) + H.M 88 + » 58 29 0.46 •• II & BRONZE * H.M. 55 • " 27 14 0.Z7 1.26 (o.zz) • • * H.M.71 + « » 31 23 0.38 1.31 (0.23) » • t H.M.gg • » « 39 26 0.42 it II 6*.. GRAY + H.M.55 • » • 40 16 0.2% 1.26 (0.22) • « • M.M.T7 • » « 5* 24 0.41 1.31 • » + H.M.88 + > - 58 29 0.46 II ii * *L0V E.= LOW EMISSIVITY C0ATIN60NKA5) * H. M. -HEAT MIRROR1 FILM T a b l e IX - T a b l e of performance d a t a f o r g l a z i n g a s s e m b l i e s 1 36 m a t e r i a l s , e i t h e r d e p o s i t e d on f i l m 1 3 or on g l a s s 1 " , have s e l e c t i v e t r a n s m i t t a n c e c h a r a c t e r i s t i c s and when used i n g l a z i n g a s s e m b l i e s , e x h i b i t a very low SC, w h i l e m a i n t a i n i n g a r e l a t i v e l y h i g h t r a n s m i t t a n c e . From a l i f e -c y c l e p o i n t of view, these g l a z i n g a s s e m b l i e s can be very c o s t e f f e c t i v e 1 5 . In s t a n d a r d d o u b l e - g l a z e d a s s e m b l i e s as w e l l , d i f f e r e n t l i g h t t r a n s m i t t a n c e s may be o b t a i n e d f o r a g i v e n SC. For example, a d o u b l e - g l a z e d b l u e - g r e e n g l a s s assembly w i l l have about 46% h i g h e r l i g h t t r a n s m i t t a n c e f o r the same SC as a s i m i l a r bronze g l a s s a s s e m b l y 1 6 , i i i . The 'U'-value (U) i s the r a t e a t which heat i s t r a n s f e r r e d through a u n i t a r e a of window when t h e r e i s a d i f f e r e n c e of one degree between the a i r temperature o u t s i d e and the a i r temperature i n s i d e a b u i l d i n g 1 7 . As a v e r y g e n e r a l t r e n d , i t may be observed t h a t the 'U'-v a l u e of g l a z i n g a s s e m b l i e s v a r i e s d i r e c t l y w i t h t h e i r t r a n s m i t t a n c e ; i . e . the lower the heat l o s s of an assembly, the lower i t s l i g h t t r a n s m i t t a n c e . In f a c t , the r e l a t i o n s h i p between these two c o e f f i c i e n t s w i l l v a r y w i d e l y w i t h the g l a z i n g m a t e r i a l s used, t h e i r assembly, t h e i r o r i e n t a t i o n , and t o some e x t e n t w i t h the time of y e a r . The 'U'-value i t s e l f i s a f u n c t i o n of the number and w i d t h of a i r spaces i n a g l a z i n g assembly, as w e l l as of the l i g h t t r a n s m i t t a n c e / r e f l e c t a n c e of the g l a z i n g m a t e r i a l s used. T r a d i t i o n a l methods of l o w e r i n g 'U'-values i n v o l v e the use 1 37 of m u l t i p l e g l a z i n g and of e x t e r i o r or i n t e r i o r a c c e s s o r i e s p a r a l l e l t o the g l a z i n g , such as r o l l e r b l i n d s , f a b r i c shades, V e n e t i a n b l i n d s , . e t c . The advantage of such o p e r a b l e a c c e s s o r i e s i n g e n e r a l , and e s p e c i a l l y of the e x t e r i o r mounted t y p e s , i s t h e i r a b i l i t y t o o p t i m i z e t r a n s m i s s i o n , and the c o n t r o l of s o l a r heat g a i n , g l a r e , and heat l o s s a t d i f f e r e n t times of the day i n response t o changing t h e r m a l and luminous c o n d i t i o n s o u t d o o r s . I d e a l l y , c o n s i d e r i n g l i g h t p e n e t r a t i o n a l o n e , the g l a z i n g assembly s h o u l d have the h i g h e s t t r a n s m i t t a n c e . However, i n o r d e r t o improve the th e r m a l performance r e q u i r e m e n t s , the t r a n s m i t t a n c e must be compromised t o some e x t e n t . The amount w i l l depend on the p a r t i c u l a r d a y l i g h t i n g scheme, as w e l l as on the b u i l d i n g energy l o a d , the l o c a t i o n and o r i e n t a t i o n of the b u i l d i n g , i t s t h e r m a l mass, the c o s t of money, the u t i l i t y r a t e s t r u c t u r e , e t c . In a d a y l i t b u i l d i n g t h e r e f o r e , the aim i s t o o p t i m i z e l i g h t t r a n s m i t t a n c e , s o l a r heat g a i n , c o n d u c t i v e heat l o s s and maintenance, from the p o i n t of view of l i f e - c y c l e c o s t and occupant c o m f o r t . I n t e r i o r and e x t e r i o r appearance and ease of o p e r a t i o n a re o t h e r , l e s s t a n g i b l e , f a c t o r s t o be c o n s i d e r e d . The many t y p e s of g l a s s e s and c o n t r o l d e v i c e s on the m a r k e t 1 8 , 1 9 , a r e the components of c o n v e n t i o n a l d a y l i g h t i n g / s u n c o n t r o l schemes. There are a l s o some new p r o d u c t s , which w i l l soon be, or have j u s t begun t o be, marketed, which may have a pr o f o u n d i n f l u e n c e on d a y l i g h t i n g d e s i g n , s i n c e they do not e x h i b i t the t r a d i t i o n a l t r a d e - o f f s between t r a n s m i t t a n c e and 1 38 heat t r a n s f e r (T and U) or between t r a n s m i t t a n c e and s o l a r heat g a i n r e s i s t a n c e (T and SC). Examples a r e : i . A m a t e r i a l c a l l e d " a e r o g e l " e x h i b i t s h i g h e r t r a n s m i s s i o n c h a r a c t e r i s t i c s than c l e a r g l a s s double g l a z i n g , when used i n 6" t h i c k n e s s - - a t which i t s 'U'-value i s t h a t of an opaque i n s u l a t e d w a l l of same w i d t h 2 0 . i i . An a i r - e n t r a i n e d a c r y l i c p l a s t i c g l a z i n g m a t e r i a l a t t e n u a t e s i n f r a r e d wavelengths w h i l e m a i n t a i n i n g v i s i b l e t r a n s m i t t a n c e , thus r e d u c i n g the SC, and r e s u l t i n g i n reduced s o l a r heat g a i n 2 1 . i i i . Development i s complete on " o p t i c a l s h u t t e r " m a t e r i a l s t h a t change phase, w i t h a change i n outdoor t e m p e r a t u r e , and i n the p r o c e s s v a r y t h e i r t r a n s m i s s i o n t o s o l a r r a d i a t i o n 2 2 . Matthews. 2 3 " has s t a t e d t h a t , i n h i s o p i n i o n , t h e s e phase change m a t e r i a l s w i l l " r e v o l u t i o n i z e d a y l i g h t i n g " . A c c o r d i n g t o S e l k o w i t z 2 " , t h e r e a r e as y e t no s i m p l e methods of c h o o s i n g g l a z i n g o p t i o n s t h a t w i l l be most e f f e c t i v e f o r l a r g e o f f i c e b u i l d i n g s , because the i n t e r r e l a t i o n s h i p of v a r i a b l e s i s complex. However, g u i d e l i n e s f o r g l a z i n g s e l e c t i o n may be g i v e n . The g e n e r a l p r i n c i p l e i s t h a t f o r each fa c a d e o r i e n t a t i o n of a b u i l d i n g , a d i f f e r e n t g l a s s t ype i s r e q u i r e d t o o b t a i n a minimum h e a t i n g , c o o l i n g and l i g h t i n g l o a d 2 5 . i . F or n o r t h - f a c i n g d a y l i g h t i n g a p e r t u r e s , s e l e c t g l a z i n g w i t h h i g h l i g h t t r a n s m i t t a n c e . Shading c o e f f i c i e n t need not be as low as f o r o t h e r o r i e n t a t i o n s . Window a s s e m b l i e s h a v i n g matching c o l o u r s when viewed from o u t s i d e , but PERFORMANCE R E Q U I R E M E N T S ORIENTATION SHADING COEFFIt05 SUN CONT ROL REOt GLARE CWU ROL RE? D LOW V VALUE VISIBLE ENERGY AS * OF TOTAL EKEK.GAIA EXAMPLES OF GLAZING ASSEMBLIES CHOICES OF ASSEMBLIES t VISIBLE TRAN5MI5. ZT8TAL J 50LARTRAN S.C. RANK ,6) MAXIMUM COOLING ftEOUlRED ^ (SHADING ^ IMPORTANT) LOW >ftl-0.5 Y E S POSSIBLY IMPORTANT HIGH )10% I. WJC-6REEN«RH-55+ CLEAR I. • + 10W E. CLEAR 3. CLEAR + H.M.5S+CLEAR 4. BRONZE + CLEAR 5. PYROLVTIC BRONZE 4-CLEAR 6. DOUBLE CLEAR 40 64 43 45 21 IB \6 32. Z5 36 26 60 0.2i> 0-47 0.39 0.54 OAS 0.80 GOOD GOOD GOOD FAIR POOR POOR HI6H >0.T NO RP55IBLY NOT IMfflK: MAY 6E LOW <607» I. SINGLE CLEAR, 1. DOUBLE CLEAR 3. SINGLE BRONZE 0 3 S O 8o 60 48 O.S5 0,#0 O.G8 GOOD FAIR FAIR o BALANCED — SHADING d AND y DAYLIGHTING E ; W , S MEDIUM 0.5 -0.7 YES LIKELY IMPORTAW MEDIUM 60-10% 1. BLUE-GREEN t CLEAR 2. CLEAR + H.M.77+ CLEAR 5. BRONZE + CLEAR 4. PYROLYTIC 6R0NZE 4 CLEAR 61 66 4 4 -2 1 4 0 4 0 36 26 0.60 0.58 454 OAS &O0D 600D FAIR POOR HIGH NO RWSIBLY IHPORTAU' MAY BE LOW <60Vo 1. DOUBLE CLEAR 2. CLEAR + H.M.7T +• CLEAR 3. BLUE-&RCEN + CLEAR 4. BRONZE +CLEAR IS 66 61 4 4 60 AO 40 36 o.go 0.5g> 0.60 0.5+ 6000 600D F A I R POOR U J MAXIMUM £ l HEATIN6 < REOUIREb 2 (S,UN 2; PENETRATION O ACCEPTABLE O WITH CONTROL) HIGH YES VERY LIKELY (IFNIUMI: L*R«E) VERY IMPORTAHt HIGH )10V. 1. C L E A R + LOWE. CLEAR 2. CLEAR 4 H.M.88+CLEAR 3 . TRIPLE CLEAR 4. BROWZE + C L E A R 14 63 7 3 4 4 -51 4-5 5 3 0.71 0. 0.75 0.60 600t> 65\60OD FAIR PA9R HIGH NO VERY LIKELY VERY IMPORTAW MAY BE LOW <60% 1. CLEAR + H.M.88 +CLEAR 2. TRIPLE CLEAfl, 3. DOUBLE CLEAP. 4. B R O W Z E + C L E A R 63 15 IB 4 4 4 S -5 3 60 36 0.£5 |0.73 0.80 0.54 6006 500D FAIR POOR NOTES: I. MAY BE ACHIEVED 6Y 6LA2IN6 ASSEMBLY ALONE OR IM COM&INATIOW V I T H ACCESSORIES. 2. OPTIMUM CONFIGURATION OF SUW CWTftOL MECHANISM VARIES WITH ORIENTATION, LATITUDE & SEASON. 3. RANK INDICATES COMBINED DAYLIGHTING, HEAT LOSS St 501AR HEAT GAIN PERFORMANCE WITHOUT ADDITIONAL GLARE/SOLAR CONTROLS. 4. VVALUE NOT IMPORTANT IF COOLING LOAD INTERNALLY GENERATED. 5. THIS SITUATION Vlli ONLY OCCUR IN HOT CURATES. Table X - Choice of g l a z i n g f o r d a y l i t o f f i c e b u i l d i n g s 1 40 d i f f e r e n t t r a n s m i t t a n c e , have been used on some l a r g e b u i l d i n g s 2 6 . i i . On the e a s t , south and west s i d e s , the g l a z i n g assembly must a c h i e v e low SC w h i l e m a i n t a i n i n g h i g h t r a n s m i t t a n c e . That i s , the percentage of v i s i b l e s o l a r t o t o t a l s o l a r energy must be h i g h e r than on the n o r t h s i d e . T h i s means u s i n g a s s e m b l i e s of c l e a r or bl u e - g r e e n g l a s s w i t h s h a d i n g d e v i c e s , or heat m i r r o r a s s e m b l i e s w i t h o u t s h a d i n g d e v i c e s . I t must be re-emphasized t h a t very low t r a n s m i t t a n c e g l a z i n g a s s e m b l i e s are not an a p p r o p r i a t e s o l u t i o n t o d a y l i g h t i n g : low shading c o e f f i c i e n t s a r e a c h i e v e d o n l y a t the s a c r i f i c e of l i g h t t r a n s m i t t a n c e . T a b l e X summarizes the c r i t e r i a f o r g l a z i n g c h o i c e i n d a y l i t b u i l d i n g s , a t the v a r i o u s o r i e n t a t i o n s . The t a b l e has some l i m i t a t i o n s 2 7 , and the s o l u t i o n s proposed must be und e r s t o o d as f i r s t a p p r o x i m a t i o n s o n l y . 2.3 Maintenance F a c t o r The a c c u m u l a t i o n of d i r t on g l a z i n g produces s c a t t e r i n g of the l i g h t i m p i n g i n g on i t , w i t h a- l o s s i n t r a n s m i t t a n c e f o r h e a v i l y s o i l e d g l a z i n g . In view windows of p r e s t i g e o f f i c e b u i l d i n g s , the s o i l i n g becomes o b j e c t i o n a b l e a e s t h e t i c a l l y l o n g b e f o r e much drop i n l i g h t t r a n s m i t t a n c e can be d e t e c t e d 2 8 , 2 9 . On the o t h e r hand, d a y l i g h t i n g a p e r t u r e s not n o r m a l l y i n view, such as c l e r e s t o r e y s , s k y l i g h t s and roo f m o n i t o r s , can, w i t h poor maintenance s c h e d u l e s , accumulate c o n s i d e r a b l e d i r t , 141 l e a d i n g t o a s u b s t a n t i a l drop i n the amount of l i g h t t r a n s m i t t e d . T able XI 3 0 i n d i c a t e s s u i t a b l e maintenance f a c t o r s f o r d a y l i g h t i n g a p e r t u r e s , f o r v a r i o u s a t m o s p h e r i c c o n d i t i o n s and degrees of ex p o s u r e . LOCATION OF 6UILDIN6 MCUVlATUM 0FGLAZJN6 MAINT. FACTOR NON-INDUSTRIAL OR CLEAN VERTICAL 0.3 INDUSTRIAL AREA SLOPING- 0. t> H0RIX0MTA.L 0.1 DIRTY INDUSTRIAL AREA VERTICAL 0.8 SLOPING 0.1 HORIZONTAL O.Q, T a b l e XI - Maintenance f a c t o r s f o r windows and r o o f l i g h t s i n o f f i c e s In s i z i n g d a y l i g h t i n g a p e r t u r e s , a maintenance (or l i g h t d e p r e c i a t i o n ) f a c t o r i s used t o compensate f o r t h i s l o s s i n t r a n s m i t t a n c e . T h i s f a c t o r (a f r a c t i o n l e s s than u n i t y ) , i s m u l t i p l i e d by the t r a n s m i t t a n c e of c l e a n g l a z i n g , t o a r r i v e a t the a p p r o x i m a t e t r a n s m i t t a n c e of s o i l e d g l a z i n g i n a c t u a l i n s t a l l a t i o n s . The maintenance f a c t o r may be used i n one of two ways: i . The a r e a of g l a z i n g may be i n c r e a s e d p r o p o r t i o n a l l y t o the l o s s i n t r a n s m i t t a n c e i n d i c a t e d by the maintenance f a c t o r . i i . The a r e a of g l a z i n g i s not i n c r e a s e d , but a l l o w a n c e i s made i n c a l c u l a t i n g energy s a v i n g s f o r a c o r r e s p o n d i n g l y l a r g e r 1 42 p r o p o r t i o n . o f l i g h t t o be. s u p p l i e d by the e l e c t r i c a l l i g h t i n g . In t h i s c o n t e x t , H o p k i n s o n 3 1 sounds a note of c a u t i o n c o n c e r n i n g the use of the maintenance f a c t o r . He s u g g e s t s t h a t even i n s i t u a t i o n s when the e x p e c t e d d i r t a c c u m u l a t i o n may reduce l i g h t p e n e t r a t i o n l e v e l s t o l e s s than 80% of the i n i t i a l v a l u e s , the maintenance f a c t o r a l l o w e d f o r s h o u l d be no l e s s than 0.9--and the g l a z e d a r e a i n c r e a s e d o n l y t o t h a t e x t e n t - -w i t h the d e f i c i t made up by e l e c t r i c l i g h t i n g . O t h e r w i s e v e r y l a r g e windows may r e s u l t , w i t h a t t e n d a n t i n c r e a s e i n g l a r e , heat l o s s and c o s t . 2.4 Net G l a z i n g Area D a y l i g h t p e n e t r a t i o n i s o b v i o u s l y a f u n c t i o n of the net t r a n s p a r e n t a r e a , and a l l o w a n c e has t o be made f o r the a r e a taken up by the frame. The frame a r e a f o r me t a l windows i s around 15-25% of the g r o s s window a r e a 3 2 , 3 3 ; w h i l e the frame ar e a f o r wood windows can be 30-50% or more, of the g r o s s window a r e a 3 " , 3 5 . A n o t h e r , r e l a t e d p o i n t i s t h a t nominal s i z e s of windows may be c o n s i d e r a b l y l a r g e r than the a c t u a l frame s i z e . F i g u r e 42 shows the v a r i o u s terms used i n t r a d e l i t e r a t u r e . For d a y l i g h t i n g p u r p o s e s , the ' g l a z e d a r e a ' i s the im p o r t a n t f i g u r e ; however, f o r windows whose frame and g l a z i n g b a r s have s u b s t a n t i a l d e p t h , these w i l l a c t as l o u v e r s t o obscure p a r t of the d a y l i g h t a t o f f - c e n t r e l o c a t i o n s and a p p r o p r i a t e c o r r e c t i o n 143 UNSHADED GLA55 '(?0R 6om HEAT6AIN CALCULATIONS) NET DAYLl6HTItfG APERTURE. (HATcffED AREA) F i g u r e 42 - Terms used i n window t r a d e l i t e r a t u r e f a c t o r s w i l l have t o be used w i t h the ' g l a z e d a r e a ' when d e c i d i n g on the a c t u a l area of the e x t e r i o r v i s i b l e from a p a r t i c u l a r l o c a t i o n . 275 Depth And D e t a i l i n g Of W a l l Around D a y l i g h t i n g A p e r t u r e The w a l l t h i c k n e s s and d e t a i l i n g around the d a y l i g h t i n g a p e r t u r e can have a c o n s i d e r a b l e e f f e c t on the d a y l i g h t p e n e t r a t i o n i n t o the i n t e r i o r . Deep w a l l s , due t o massive c o n s t r u c t i o n or t h i c k i n s u l a t i o n , or b o t h , w i l l reduce d a y l i g h t p e n e t r a t i o n t h rough an o p e n i n g , i f the edge d e t a i l i n g i s kept the same as i t would be f o r t h i n w a l l s . In model t e s t s done by A s c h e h o u g 3 6 , i n c r e a s i n g w a l l t h i c k n e s s from 20 t o 1000mm reduced d a y l i g h t p e n e t r a t i o n a t , the back of rooms t e s t e d by 5 0 % 3 7 . 1 44 F i g u r e 43 - E f f e c t of w a l l t h i c k n e s s on d a y l i g h t p e n e t r a t i o n and examples of t h i c k w a l l s 1 45 ' F i g u r e 44 - P l a n views of s p l a y e d jamb c o n f i g u r a t i o n s F i g u r e 43 a. shows g r a p h i c a l l y the e f f e c t of i n c r e a s i n g the t h i c k n e s s of the e x t e r i o r w a l l . F i g u r e 43 b. shows examples of t h i c k e x t e r i o r w a l l s r e s u l t i n g from the use of p r e c a s t or c a s t -i n - p l a c e c o n c r e t e . I f o p e nings i n a t h i c k w a l l have s p l a y e d jambs w i t h s u r f a c e s of h i g h r e f l e c t a n c e , the d a y l i g h t p e n e t r a t i o n i s e s s e n t i a l l y the same as t h a t f o r the same s i z e opening i n a t h i n w a l l 3 8 , w i t h the a d d i t i o n a l advantage of c o n t r a s t g r a d i n g p r o v i d e d by the s p l a y e d jamb of the t h i c k w a l l 3 9 . F i g u r e 44 1 46 shows t y p i c a l jamb c o n f i g u r a t i o n s . In a l l c a s e s , d a y l i g h t p e n e t r a t i o n i s g r e a t e r f o r s p l a y e d jambs than f o r r i g h t a n g l e d ones.; inward s l o p i n g jambs (b.) g i v e the best spread of l i g h t sideways ( i . e. the w i d e s t e f f e c t i v e window a r e a ) i n a t y p i c a l room, but d a y l i g h t p e n e t r a t i o n f o r c o n f i g u r a t i o n (c.) and (d.) may be g r e a t e r by about 15%"° i f jamb r e f l e c t a n c e s are h i g h ( a p p r o x i m a t e l y 6 0 % ) . 2.6 Room Geometry The f o l l o w i n g are r e s u l t s of p a r a m e t r i c s t u d i e s done by Aschehoug" 1 and E v a n s " 2 . In t h i s s e r i e s , summarized i n f i g u r e 45 , the c o n f i g u r a t i o n and l o c a t i o n of the d a y l i g h t i n g a p e r t u r e on the e x t e r i o r w a l l were kept c o n s t a n t , w h i l e the geometry of the room was changed.' i . An i n c r e a s e i n room w i d t h (and an accompanying i n c r e a s e i n window w i d t h ) , produces no s i g n i f i c a n t change i n l i g h t p e n e t r a t i o n " 3 . i i . W i t h an i n c r e a s e i n room de p t h , the DF i s o b v i o u s l y lower a t the back of the room. However, the deeper rooms have c o n s i d e r a b l y lower d a y l i g h t l e v e l s throughout t h e i r d e p t h " " , " 5 . T h i s i s summarized g r a p h i c a l l y i n f i g u r e 45 a. The d i f f e r e n c e i n d a y l i g h t l e v e l s i s due m o s t l y t o the r e f l e c t e d l i g h t from the back w a l l , which i n the s h a l l o w room c o n t r i b u t e s a g r e a t e r p o r t i o n t o the i n t e r i o r d a y l i g h t than the back w a l l i n the deeper room. i i i . An i n c r e a s e i n c e i l i n g h e i g h t w i t h window h e i g h t r e m a i n i n g c o n s t a n t , reduced th e l i g h t a v a i l a b l e a t the back of the 1 47 F i g u r e 45 - E f f e c t of room geometry on d a y l i g h t p e n e t r a t i o n 1 48 rooms t e s t e d by about 1 5 % " 6 . The e x a c t amount of r e d u c t i o n w i l l depend on room geometry as w e l l as on the r e f l e c t a n c e s of indoor and outdoor s u r f a c e s . The r e d u c t i o n i n d a y l i g h t l e v e l s i s due to s m a l l e r amount of r e f l e c t e d l i g h t a t the work pla n e i n the room w i t h the h i g h e r c e i l i n g . I f , however, advantage i s taken of the g r e a t e r c e i l i n g h e i g h t and the d a y l i g h t i n g a p e r t u r e i s moved h i g h e r up, c o n s i d e r a b l e improvement i n d a y l i g h t p e n e t r a t i o n may be o b t a i n e d " 7 , as seen i n a p r e v i o u s s e c t i o n . F i g u r e 45 b. i n d i c a t e s how added c e i l i n g h e i g h t may be o b t a i n e d , w i t h o u t a d d i n g t o the f l o o r t o f l o o r h e i g h t . i v . A v a r i a t i o n i n c e i l i n g s l o p e has, a c c o r d i n g t o E v a n s " 8 , no e f f e c t on i n t e r i o r d a y l i g h t l e v e l s . 2.6.1 I n t e r i o r R e f l e c t a n c e s One of the more imp o r t a n t parameters d e t e r m i n i n g d a y l i g h t p e n e t r a t i o n - - a n d e s p e c i a l l y d a y l i g h t q u a l i t y — i n a room i s the r e f l e c t a n c e s of i t s v a r i o u s s u r f a c e s . T h i s i n f l u e n c e i s most pronounced f o r u n i l a t e r a l l y s i d e - l i t spaces, s i n c e the l i g h t r e f l e c t a n c e from i n t e r i o r s u r f a c e s i s the major c o n t r i b u t o r t o i l l u m i n a n c e l e v e l s a t the back of the room, as shown i n f i g u r e 46 " 9. A d i r e c t r e s u l t of i n c r e a s e d d a y l i g h t p e n e t r a t i o n w i t h i n t e r i o r s u r f a c e s of h i g h r e f l e c t a n c e i s the c o n s i d e r a b l e s a v i n g i n energy. I t has been e s t i m a t e d by T a m b l y n 5 0 , t h a t a change from dark i n t e r i o r c o l o u r s t o l i g h t ones can r e s u l t i n a 1 49 SO -ftEFLECTANCES: cauu&*i5% WALL* =35% FLOOR = 2 0 % 10 ^ 5 J? •>—. u P »-X I 1 WHS C J c J. CULM* 3 FLOOR s n — <a \ ————— \. O | .5m 3 m 4.5r>. <5M DISTANCE FROM WINDOW (rn) F i g u r e 46 - The c o n t r i b u t i o n of t h e IRC t o t h e i l l u m i n a n c e w i t h i n a room r e d u c t i o n o f power of 10 watt p e r m 2 , o r between 20 and 40% of-) t y p i c a l l i g h t i n g l o a d . M i l l e t has r e p o r t e d even g r e a t e r s a v i n g s i n e n e r g y when d a r k w a l l s were r e p l a c e d by l i g h t o n e s 5 1 . F i g u r e 47 5 2 shows t h e r e l a t i v e c o n t r i b u t i o n of e a c h o f t h e room s u r f a c e s t o t h e d a y l i g h t l e v e l s i n t e s t s c o n d u c t e d by E v a n s . From t h e s e t e s t s , and o t h e r s done by A s c h e h o u g 5 3 , t h e f o l l o w i n g may be o b s e r v e d : i . I n t h e s i m p l e d a y l i g h t i n g schemes t e s t e d , t h e c e i l i n g was f o u n d t o c o n t r i b u t e more t h a n a l l o t h e r room s u r f a c e s t o th e d a y l i g h t i l l u m i n a n c e l e v e l s i n t h e room. C e i l i n g r e f l e c t a n c e i s f o u n d t o be even more i m p o r t a n t i n a c t u a l i n t e r i o r s ( t h a t i n c l u d e f u r n i s h i n g s ) t h a n t h e s e t e s t s i n d i c a t e , s i n c e i t i s g e n e r a l l y t h e l e a s t c l u t t e r e d s u r f a c e 150 ALL SURFACES WHITE ILLUMINANCE AT V = \0O% CEIL1M6 BLACK ILLUMINANCE AT*/ REDUCED TO 33% BACK WALL BLACK ILLUMINANCE AT V REDUCED TO 50% SIDE WALL 6 ILLUMINANCE A T V REDUCED TO (ol% FLOW 6LACK ILLUMINANCE AT'x' REDUCED TO 0>b% F i g u r e 47 - The i n f l u e n c e of room s u r f a c e r e f l e c t a n c e s on d a y l i g h t l e v e l s i n an o f f i c e space, i s u s u a l l y of h i g h r e f l e c t a n c e , and t h e r e f o r e , can be r e l i e d upon t o r e f l e c t d a y l i g h t from the o t h e r s u r f a c e s onto the workplane. i i . H i g h r e f l e c t a n c e f o r the f l o o r i s not as i m p o r t a n t as f o r the c e i l i n g i n a c h i e v i n g d a y l i g h t p e n e t r a t i o n . The reason f o r t h i s i s t h a t the f l o o r , b e i n g below the r e f e r e n c e (work) p l a n e , c o n t r i b u t e s t o the DF o n l y by m u l t i p l e r e f l e c t i o n s o f f w a l l s d and c e i l i n g . I n a c t u a l i n s t a l l a t i o n s , t h e f l o o r i s . a l s o c l u t t e r e d w i t h 151 f u r n i s h i n g s , and because of maintenance r e q u i r e m e n t s , i t g e n e r a l l y has lower r e f l e c t a n c e than o t h e r room s u r f a c e s . I t s p o t e n t i a l as a c o n t r i b u t o r t o the DF i s thus f u r t h e r d e c r e a s e d . i i i . High r e f l e c t a n c e f o r s i d e w a l l s i s c o n s i d e r a b l y more imp o r t a n t than h i g h r e f l e c t a n c e f o r back w a l l as f a r as the DF i s c o n c e r n e d 5 " . High r e f l e c t a n c e f o r the back w a l l i s i m p o r t a n t i n e s t a b l i s h i n g h i g h e r s u r f a c e luminance at the back, and hence b e t t e r b alance of b r i g h t n e s s i n the room. i v . High r e f l e c t a n c e f o r the window w a l l i s h e l p f u l i n g l a r e r e d u c t i o n , but a s s i s t s l i t t l e i n d a y l i g h t p e n e t r a t i o n , s i n c e i t does not r e c e i v e d i r e c t l i g h t from beyond the d a y l i g h t i n g a p e r t u r e . v. A comparative- a n a l y s i s of p a r a m e t r i c s t u d i e s shows t h a t the r e l a t i v e importance of the v a r i o u s i n t e r i o r s u r f a c e s i n promoting d a y l i g h t p e n e t r a t i o n i s a f u n c t i o n of the p r o p o r t i o n s and dimensions of the space. T h e r e f o r e , i n o r d e r t o a s s e s s a c c u r a t e l y d a y l i g h t p e n e t r a t i o n f o r s p e c i f i c room c o n f i g u r a t i o n s , computer s i m u l a t i o n s or model s t u d i e s w i l l be r e q u i r e d . v i . There i s a q u a l i t a t i v e d i f f e r e n c e between some schemes--a d i f f e r e n c e i n the m o d e l l i n g q u a l i t y of the l i g h t i n g — t h a t i s not apparent from the DF p l o t s . For example, schemes w i t h v e r y s i m i l a r v a l u e s of DF ( h o r i z o n t a l i l l u m i n a n c e ) , w i l l , depending on the r e l a t i v e r e f l e c t a n c e s of a d j a c e n t s u r f a c e s , p r o v i d e more or l e s s l i g h t on the s i d e s or the u n d e r s i d e of t h r e e d i m e n s i o n a l o b j e c t s . These l i g h t 1 52 q u a l i t y d i f f e r e n c e s may be m o d e l l e d a n a l y t i c a l l y 5 5 , 5 6 , but must be s t u d i e d w i t h models t o be f u l l y a p p r e c i a t e d . 3. INNOVATIVE DAYLIGHTING TECHNIQUES I n n o v a t i v e d a y l i g h t i n g t echniques--sometimes termed beamed or deep d a y l i g h t i n g t e c h n i q u e s — i n v o l v e the p r o j e c t i o n of d a y l i g h t , and i n some i n s t a n c e s , of s u n l i g h t as w e l l , deep i n t o i n t e r i o r spaces. The i d e a of u s i n g r e f r a c t i n g m a t e r i a l s and r e f l e c t i n g s u r f a c e s t o i n c r e a s e d a y l i g h t p e n e t r a t i o n t h r o u g h view windows i s not new. The use of h i g h r e f l e c t a n c e s u r f a c e s o u t s i d e as w e l l as i n s i d e , near the window, and the l i k e , a r e methods t h a t have l o n g been used t o bounce d a y l i g h t deeper i n t o i n t e r i o r s paces. However, i n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s i n c o r p o r a t e components t h a t are shaped and l o c a t e d - - a n d i n d e e d , whose main purpose i s — t o i n c r e a s e d a y l i g h t p e n e t r a t i o n . When p r o p e r l y d e s i g n e d , beamed d a y l i g h t i n g t e c h n i q u e s can p e r f o r m s u b s t a n t i a l l y b e t t e r f o r a g i v e n a r e a of d a y l i g h t i n g a p e r t u r e than t r a d i t i o n a l systems. T h i s improved performance has two a s p e c t s : i . I n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s p r o v i d e i n c r e a s e d d a y l i g h t p e n e t r a t i o n over t r a d i t i o n a l d a y l i g h t i n g t e c h n i q u e s . With the l a t t e r , i t i s p o s s i b l e t o d a y l i g h t a room a d e q u a t e l y , and w i t h b r i g h t n e s s r a t i o s t h a t a r e w i t h i n c o m f o r t a b l e l e v e l s , t o a d e pth e q u i v a l e n t t o 2 1/2 t i m e s the h e i g h t of the d a y l i g h t i n g a p e r t u r e 5 7 , 5 8 , 5 9 . Assuming t h a t the head of the d a y l i g h t i n g a p e r t u r e i s a t the c e i l i n g , and the c e i l i n g h e i g h t i s i n the range of 2.5-3.0m 153 found i n contemporary o f f i c e s , the maximum d a y l i g h t p e n e t r a t i o n t h a t can be a c h i e v e d by t r a d i t i o n a l means i s 6.0-7.5m. TRADITIONAL 1 INNOVATIVE F i g u r e 48 - Comparison of d a y l i g h t p e n e t r a t i o n a c h i e v e d by t r a d i t i o n a l and i n n o v a t i v e t e c h n i q u e s F i g u r e 48 shows c o m p a r a t i v e d a y l i g h t p e n e t r a t i o n a c h i e v e d by a t y p i c a l t r a d i t i o n a l and an i n n o v a t i v e t e c h n i q u e . A s u r v e y by E a c r e t 6 0 has i n d i c a t e d t h a t deep d a y l i g h t i n g systems can p r o v i d e a t a room depth of 6m, f o r example, between 50% and 300% more d a y l i g h t than a s t a n d a r d d a y l i g h t i n g a p e r t u r e of the same a r e a and a t the same l o c a t i o n . i i . I n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s a c h i e v e b e t t e r b a l a n c e of b r i g h t n e s s i n i n t e r i o r s than t r a d i t i o n a l d a y l i g h t i n g t e c h n i q u e s . F i g u r e 48 a l s o shows t h a t the deep d a y l i g h t i n g scheme p r o v i d e s more even i l l u m i n a n c e l e v e l s • t h r o u g h o u t the d e pth of the space (meeting both ambient and 1 54 t a s k l i g h t i n g n e e d s ) , whereas i n the t r a d i t i o n a l system, t h e r e i s a h i g h maximum l i g h t l e v e l near the a p e r t u r e , and a sharp drop towards the back of the room. I f the room s u r f a c e s have h i g h r e f l e c t a n c e , then the DF c u r v e i s a good i n d i c a t o r of the g e n e r a l l e v e l of b r i g h t n e s s a c r o s s the room. By p r o j e c t i n g a l a r g e p a r t of the a v a i l a b l e l i g h t towards the back, s u r f a c e luminances are i n c r e a s e d at the back, and r e s u l t i n a b a l a n c e of b r i g h t n e s s throughout the room, l e s s p e r c e i v e d g l a r e ( s i n c e the eye a d a p t a t i o n l e v e l i s h i g h e r ) , and s o f t e r m o d e l l i n g c h a r a c t e r i s t i c s ( s i n c e the l i g h t from the window s i d e i s no l o n g e r as d o m i n a n t ) . Hence, both q u a n t i t a t i v e and q u a l i t a t i v e a s p e c t s of the d a y l i g h t i n g scheme show improvement. A summary of i n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s i n c l u d e d i n t h i s c h a p t e r i s shown i n f i g u r e 49 . 3.1 Deep D a y l i g h t i n g Through View Windows Where view windows are used f o r beamed d a y l i g h t i n g , t h r e e t y p e s of s o l u t i o n s may be i d e n t i f i e d : i . In the f i r s t t y p e , the d a y l i g h t i n g mechanism i s i n c o r p o r a t e d i n the window head and s i l l , or i n the window s i l l a l o n e . F i g u r e 50 shows the s e r e s p o n s e s . The f i r s t d e s i g n response u t i l i z e s a r e f l e c t i n g s i l l and head, as e x e m p l i f i e d by the IBM r e g i o n a l o f f i c e b u i l d i n g i n S o u t h f i e l d , M i c h i g a n 6 1 ( a . ) , and by a d e s i g n c a l l e d " v i s i o n window" by A s h l e y e t a l . 6 2 ( b . ) Another d e s i g n response \ ! S C A L E S I T E PLANNIN6 BUILDING CONflGURATION BUILDING C O M P O N E N T BUILDING INTERIOR DEEP DWUfiHTING THROUGH VIEW WNDOW DEEP DAYLIGHTING THOUGH APERTURES A&OVE EYE LEVEL DEEP DAYL1GUTIN6 THROUGH ROOF APERTURES F i g u r e 4 9 - Summary of i n n o v a t i v e t e c h n i q u e s d a y l i g h t p e n e t r a t i o n promot i n g 1 56 F i g u r e 50 - D a y l i g h t beaming mechanisms i n t e g r a t e d i n t o the b u i l d i n g envelope 157 u t i l i z e s an e n l a r g e d , r e f l e c t i v e s i l l t o bounce d a y l i g h t onto the c e i l i n g , as e x e m p l i f i e d by the EG&G W i l l o w Creek o f f i c e b u i l d i n g i n Idaho F a l l s 6 3 ( f i g u r e 50 c.) In t h i s b u i l d i n g , l i g h t i n g from the windows p r o v i d e s a l l ambient l i g h t i n g f o r the p e r i m e t e r 9m. A f o l l o w - u p study has a l s o i n d i c a t e d t h a t on a c l e a r day, d a y l i g h t reduces the energy used f o r m e c h a n i c a l s e r v i c e s and e l e c t r i c a l l i g h t i n g by 20%, compared t o a b u i l d i n g w i t h same-sized windows and no advantage taken of d a y l i g h t i n g p o t e n t i a l 6 " . The double r e f l e c t i o n a t the window a c h i e v e d i n the f i r s t d e s i g n t y p e s e n a b l e s d a y l i g h t t o be r e f l e c t e d deeper i n t o the i n t e r i o r than w i t h the s i n g l e r e f l e c t i o n a c h i e v e d i n the p r e v i o u s scheme. However, the s i n g l e r e f l e c t i v e s i l l ( w i t h no r e f l e c t i v e , head) i s a s i m p l e r c o n c e p t , and i s t h e r e f o r e more e c o n o m i c a l i n f i r s t c o s t . In a l l t h e s e d e s i g n s , g l a r e c o n t r o l i s a c h i e v e d by s l o p i n g the g l a z i n g downward. In the second type of s o l u t i o n , the d a y l i g h t i n g mechanism i s an e x t e r i o r a c c e s s o r y . T h i s may c o n s i s t of p i v o t i n g and r e t r a c t a b l e l o u v r e s , p i v o t i n g but n o n - r e t r a c t a b l e l o u v r e s , or s m a l l s t a t i o n a r y 1 i g h t s h e l v e s , as shown i n f i g u r e 51 6 5 . Operable l o u v r e s , when a u t o m a t i c , have the advantage of p r o v i d i n g s o l a r c o n t r o l as w e l l as enhanced d a y l i g h t i n g . The f i x e d l o u v r e s , on the o t h e r hand, cannot respond t o changing sun a n g l e s and p r o v i d e s o l a r c o n t r o l a t some s a c r i f i c e t o d a y l i g h t a c c e s s . In the t h i r d type of s o l u t i o n , the d a y l i g h t i n g mechanism i s l o c a t e d between the g l a z i n g or on the i n t e r i o r . These 1 58 OFF- uJHfTE A. AIRFOIL TYPE BLINDS B. TYPICAL EXTERIOR VE«TMNWE BL/W05 UdMT axsvut MMI-4HO.VB C. TVnCAL 50k!-SHADE UGH*SHELF C O M 81 WATIOU ( 5 » H f c ~ L o.A,) F i g u r e 51 - D a y l i g h t beaming mechanism as an e x t e r i o r a c c e s s o r y 1 59 s i ( v / e r e d u p p e r " j>urf.ace.-b i <3 CONCAVE SURFACE DAVLI6HT1N6 6L!WDf, CONVEX SURFACE DAYLIGHTING BLINDS F i g u r e 52 - D a y l i g h t beaming mechanism as an i n t e r i o r a c c e s s o r y mechanisms c o n s i s t of h o r i z o n t a l b l i n d s of v a r i o u s p r o f i l e s . S t a n d a r d (1-1/2") or t h i n (1") V e n e t i a n b l i n d s , s - i l v e r e d on the convex s i d e , a re used, as shown i n f i g u r e 52 ( r i g h t ) . Some d e s i g n s use b l i n d s w i t h the concave s i d e up, as f o r example the R e f l e c t i v e I n s u l a t i n g B l i n d s (RIB) d e v e l o p e d by the Oak Ridge N a t i o n a l L a b o r a t o r y , as shown i n f i g u r e 52 ( l e f t ) 6 6 . The o r i g i n a l p r o p o s a l by S e l k o w i t z and R u b i n s t e i n 6 7 , as w e l l as the " M o d u l a t o r " b l i n d s used a t the MIT s o l a r b u i l d i n g 6 8 , a l s o had concave r e f l e c t i v e s u r f a c e s . The major d i s a d v a n t a g e of the concave type b l i n d seems to be t h e appearance of "hot s p o t s " of l i g h t on the c e i l i n g due t o the s l i g h t f o c u s i n g n a t u r e of the system. 160 In summary, the use of beamed d a y l i g h t i n g t e c h n i q u e s w i t h view windows has the f o l l o w i n g a d vantages: i . The use of the window f o r both view and d a y l i g h t i n g " e l i m i n a t e s the c o s t of e x t r a , s e p a r a t e d a y l i g h t i n g a p e r t u r e s . i i . When compared t o deep d a y l i g h t i n g t e c h n i q u e s through c l e r e s t o r e y s , the e l e v a t i o n i s r e l a t i v e l y s i m p l e , w i t h no e x t r a d a y l i g h t i n g a p e r t u r e s t o i n t e g r a t e i n t o the e l v a t i o n rhythm. i i i . For an e q u i v a l e n t d a y l i g h t p e n e t r a t i o n , s m a l l e r d a y l i g h t i n g a p e r t u r e s a r e f e a s i b l e w i t h the beamed d a y l i g h t i n g mechanisms than would be w i t h o u t them. The mechanisms may be i n t e g r a t e d i n t o the b u i l d i n g e n v e l o p e , may be a p a r t of the g l a z i n g system, or may be e x t e r n a l or i n t e r n a l a c c e s s o r i e s - - a n d t h e i r main f u n c t i o n i s t o p r o j e c t d a y l i g h t deeper i n t o the i n t e r i o r . 3.2 Deep D a y l i q h t i n g - - T h r o u g h W a l l A p e r t u r e s Above Eye L e v e l 3.2.1 C l a s s i f i c a t i o n When the f u n c t i o n of d a y l i g h t i n g i s s e p a r a t e d from the o t h e r f u n c t i o n s of windows, i t then becomes p o s s i b l e t o l o c a t e and d e t a i l a p e r t u r e s so as t o maximize d a y l i g h t p e n e t r a t i o n . Deep d a y l i g h t i n g schemes of the s p l i t f u n c t i o n type may be c l a s s i f i e d by t h e i r h e i g h t above f l o o r l e v e l , w i t h t h r e e l o c a t i o n s d i s t i n g u i s h e a b l e : 161 F i g u r e 53 - Beamed d a y l i g h t i n g d e s i g n s a t d i f f e r e n t l o c a t i o n s i n e x t e r i o r w a l l s i . The d a y l i g h t i n g a p e r t u r e may be l o c a t e d below the 2m h e i g h t above the f l o o r l e v e l . A t y p i c a l scheme, o r i g i n a t i n g from A u s t r i a , i s shown i n f i g u r e 53 a 6 9 . I t u t i l i z e s p r i s m a t i c g l a s s , and the d a y l i g h t i n g a p e r t u r e s a l t e r n a t e w i t h view windows. T h i s l o c a t i o n f o r d a y l i g h t i n g a p e r t u r e s of the s p l i t f u n c t i o n t y pe i s not common. Advantages a r e : the p o s s i b i l i t y of lower f l o o r t o c e i l i n g h e i g h t ; f e a s i b i l i t y of r e t r o f i t i n s t a l l a t i o n and the avo i d a n c e of a t i e r e d • window l o o k on e l e v a t i o n . D i s a d v a n t a g e s a r e : view windows 1 62 ar e r e p l a c e d by the d a y l i g h t i n g mechanism, w i t h a r e s u l t a n t l o s s of view; some systems may have a problem of g l a r e ( b e i n g more i n the l i n e of s i g h t ) and p r o t r u d i n g d a y l i g h t i n g mechanisms may c r e a t e window washing problems f o r t a l l b u i l d i n g s . The d a y l i g h t i n g a p e r t u r e may a l s o be l o c a t e d above the 2m h e i g h t , and below the c e i l i n g , as shown i n f i g u r e 53 b. T h i s i s the most common l o c a t i o n f o r s p l i t f u n c t i o n beamed d a y l i g h t i n g c o n c e p t s . Advantages of t h i s t e c h n i q u e a r e : g l a r e c o n t r o l i s s i m p l e r than f o r openings t h a t double as view a p e r t u r e s ; l i t t l e i n t e r f e r e n c e w i t h the use of e x t e r i o r w a l l below the d a y l i g h t i n g a p e r t u r e and p o t e n t i a l f o r good d a y l i g h t p e n e t r a t i o n i n c r e a s e d due t o h e i g h t of opening above f l o o r . D i s a d v a n t a g e s a r e : more complex e l e v a t i o n , r e q u i r i n g c a r e f u l p r o p o r t i o n i n g and d e t a i l i n g and p o s s i b l e c l e a n i n g problem f o r the d a y l i g h t i n g mechanism ( f o r l o u v r e and l i g h t s h e l f s y s t e m s ) . Beamed d a y l i g h t i n g systems may a l s o be l o c a t e d above the c e i l i n g and below the s l a b of the f l o o r above, as shown i n f i g u r e 53 c. These systems are c a l l e d plenum d a y l i g h t i n g 7 0 . The d e s i g n shown i s based on a scheme f o r the P r i n c e t o n F o r r e s t a l C e n t e r , a s p e c u l a t i v e o f f i c e complex, i n P l a i n s b o r o , N. J . 7 1 Advantages w i t h t h i s t y p e of scheme a r e : s i n c e g l a r e i s not a problem, the d a y l i g h t i n g a p e r t u r e can be d e s i g n e d t o maximize d a y l i g h t p e n e t r a t i o n ; the plenum space which i s seldom f u l l y u t i l i z e d , can be put t o u s e , s a v i n g i n f l o o r t o f l o o r h e i g h t 1 63 by a p o t e n t i a l r e d u c t i o n of the f l o o r t o c e i l i n g h e i g h t . D i s a d v a n t a g e s a r e : the c e i l i n g needs t o be a b l e t o t r a n s m i t the d a y l i g h t e i t h e r t h r ough h o l e s or by b e i n g . t r a n s p a r e n t - -and no r e a d i l y a v a i l a b l e systems a r e on the market; s u r f a c e s i n the plenum need to be s p r a y - p a i n t e d a l i g h t c o l o u r ; p i p i n g and d u c t s have t o be r o u t e d more c a r e f u l l y , so as not t o b l o c k the d a y l i g h t near the e x t e r i o r w a l l s . D a y l i g h t i n g systems of the s p l i t f u n c t i o n t y pe can a l s o be c l a s s e d a c c o r d i n g t o the type of d a y l i g h t i n g mechanism, as f o l l o w s : i . l i g h t s h e l f systems, c o n s i s t i n g of a s i n g l e l a r g e element or s e v e r a l s m a l l e r s t a t i o n a r y l o u v r e - l i k e elements i i . p r i s m a t i c systems, c o n s i s t i n g of r e f r a c t i v e g l a s s b l o c k s , r e f r a c t i v e g l a s s or t h i n - f i l m p r i s m a t i c s i i i . l o u v r e systems, c o n s i s t i n g of a d j u s t a b l e elments on the e x t e r i o r , between window panes or on the i n t e r i o r 3.2.2 L i g h t s h e l v e s  D e s c r i p t i o n As P h i l l i p s 7 2 and H o p k i n s o n 7 3 have documented, l i g h t s h e l v e s have been used i n h o s p i t a l s and s c h o o l s as e a r l y as the 1950s, and the concept has been known p o s s i b l y 50 y e a r s e a r l i e r 7 4 . P h i l l i p s c a l l s them " h o r i z o n t a l r e f l e c t i n g b a f f l e s " 7 5 - - a d e s c r i p t i v e term. F i g u r e 54 shows the components of a l i g h t s h e l f system. 164 DIRECT 51>U \ \ V \ ( S I -CK, DIFFU5E. / \ X > r ^ - ' D A Y L I G H T ^ r ^ ^ i P ||__ --PAYLI6HTIW6 APERTURE -X \ \z ^-REFLECTIVE, CEILING EXTERIOR LI6HT5HELF ; INTERIOR LIGHT 5HELF —OPTIONAL VIEW WJIND^V F i g u r e 54 - The components of a l i g h t s h e l f system The major component, i s the e x t e r i o r l i g h t s h e l f ( 1 ) . I t s pr i m a r y f u n c t i o n i s t h a t of a l a r g e r e f l e c t o r , b o u n c i n g s k y l i g h t and s u n l i g h t from the e x t e r i o r onto the c e i l i n g ; i t a l s o a c t s as a shading' d e v i c e f o r any view window d i r e c t l y beneath. H o r i z o n t a l p r o j e c t i o n of e x t e r i o r l i g h t s h e l v e s w i l l v a r y w i t h the geometry of the d a y l i g h t i n g a p e r t u r e above and the view window below, as w e l l as w i t h the o r i e n t a t i o n of the f a c a d e , the geo g r a p h i c l a t i t u d e of the b u i l d i n g , s t r u c t u r a l r e q u i r e m e n t s , e t c . The r e f l e c t a n c e of the upper s u r f a c e i s an im p o r t a n t parameter, s i n c e i t d e t e r m i n e s the amount of d a y l i g h t the s h e l f w i l l be a b l e t o "bounce" i n t o the i n t e r i o r . T h i s s u r f a c e may be s p e c u l a r , s e m i - s p e c u l a r , or matte. S p e c u l a r s u r f a c e s , such 1 65 as a l u m i n i z e d mylar or p o l i s h e d s t a i n l e s s s t e e l , have the h i g h e s t r e f l e c t a n c e (>80°). T h e i r d i s a d v a n t a g e i s t h a t d i r e c t i o n a l r e f l e c t a n c e may c r e a t e "hot s p o t s " of l i g h t on the c e i l i n g and a l s o s u f f e r r e d u c t i o n i n r e f l e c t a n c e w i t h t i m e , even w i t h good m a i n t e n a n c e 7 6 . S e m i s p e c u l a r r e f l e c t i n g s u r f a c e s (such as a n o d i z e d aluminum, h i g h g l o s s p a i n t , e t c . ) have somewhat lower r e f l e c t a n c e s (peak at 70 t o 80°) but t h e i r maintenance i s e a s i e r . N o n s p e c u l a r r e f l e c t i n g s u r f a c e s (such as matte p a i n t , p r e f i n i s h e d e n a m e l l e d or p o r c e l a i n p a n e l s ) can have r e f l e c t a n c e s of up t o 80°. M a t e r i a l and f i n i s h of the e x t e r i o r l i g h t s h e l f must be e v a l u a t e d not o n l y on the b a s i s of d a y l i g h t i n g performance, but a l s o i n terms of i n i t i a l c o s t , maintenance, a e s t h e t i c s , e t c . The t i l t of the r e f l e c t i n g (top) s u r f a c e w i l l v a r y from d e s i g n t o d e s i g n , depending on v a r i o u s parameters t h a t d e t e r m i n e i t s o p t i c a l performance as w e l l as r e q u i r e m e n t s f o r good w e a t h e r i n g , r a i n shedding, e t c . O p t i m i z e d s o l u t i o n s g e n e r a l l y have a s l i g h t 5-10% upward t i l t 7 7 , ( e .g. f i g u r e 55 a . 7 8 ) but d e s i g n s have been b u i l t h a v i n g a t i l t of 0° from h o r i z o n t a l ( e . g . f i g u r e 55 b . 7 9 ) t o about 40° from h o r i z o n t a l ( e . g . f i g u r e 55 c . 8 0 ) I t appears t h e r e f o r e t h a t optimum t i l t v a r i e s w i t h the degree of s p e c u l a r i t y of the top s u r f a c e , g e o g r a p h i c l a t i t u d e , s t r u c t u r a l s o l u t i o n and s p a t i a l c h a r a c t e r i s t i c s of the i n t e r i o r . The p r i m a r y f u n c t i o n of the i n t e r i o r l i g h t s h e l f (2. on the diagram) i s t o reduce the b r i g h t n e s s g r a d i e n t between a r e a s near the d a y l i g h t i n g a p e r t u r e and those f u r t h e r removed. I t a l s o 1 66 F i g u r e 55 - T y p i c a l l i g h t s h e l f c o n f i g u r a t i o n s i n c r e a s e s d a y l i g h t p e n e t r a t i o n somewhat, and a c t s as a b a f f l e t o reduce d i r e c t g l a r e . A e s t h e t i c s , performance and i n t e g r a t i o n L i g h t s h e l v e s a r e s t r o n g e l e v a t i o n d e s i g n e l e m e n t s . G e n e r a l l y , they w i l l i m p a r t a s t r o n g h o r i z o n t a l i t y t o the e l e v a t i o n . However, i t i s p o s s i b l e t o reduce the h o r i z o n t a l emphasis of l i g h t s h e l v e s by u s i n g the window s u r r o u n d as a frame f o r them. L i g h t s h e l v e s can be i n t e g r a t e d i n t o e l e v a t i o n s of 1 67 c o n c r e t e b u i l d i n g s w i t h r e l a t i v e ease, s i n c e c o n c r e t e l e n d s i t s e l f t o m a s s i v e , t h r e e - d i m e n s i o n a l e l e v a t i o n a l t r e a t m e n t 8 1 . Some e l e v a t i o n s o l u t i o n s a r e shown i n f i g u r e 56 8 2 . L i g h t s h e l v e s ( i n t e r i o r and e x t e r i o r ) can be massive s t r u c t u r a l l y and, because of t h e i r a r e a , e x t e r i o r l i g h t s h e l v e s can be exposed to s u b s t a n t i a l wind l o a d s . They can pose maintenance problems and may i n t e r f e r e w i t h window washing. These and o t h e r secondary e f f e c t s need t o be c o n s i d e r e d i n t h e i r d e s i g n and i n a s s e s s i n g t h e i r c o s t e f f e c t i v e n e s s . 3.2.3 P r i s m a t i c Systems  D e s c r i p t i o n P r i s m a t i c systems f o r beaming d a y l i g h t and s u n l i g h t were used i n N o r t h American s c h o o l s and o f f i c e s i n the 1 9 5 0 s 8 3 and many p a t e n t s f o r beamed d a y l i g h t i n g u t i l i z i n g the p r i n c i p l e s of r e f r a c t i o n have been t r a c e d back t o the 1890s 8*. F i g u r e 57 shows the components of a p r i s m a t i c beamed d a y l i g h t i n g system. The main component i s the t r a n s p a r e n t or t r a n s l u s c e n t p r i s m a t i c m a t e r i a l (1) t h a t "bends" the l i g h t r a y s and r e d i r e c t s them upward onto the h i g h l y r e f l e c t i v e c e i l i n g ( 2 ) , whence the l i g h t i s d i f f u s e d i n the i n t e r i o r . The r e f r a c t i n g element may c o n s i s t of p r i s m a t i c g l a s s b l o c k s , p r i s m a t i c s h eet g l a s s , l i n e a r f r e s n e l l e n s e s ( s i m i l a r t o p r i s m a t i c g l a s s , but h a v i n g f o c u s i n g c h a r a c t e r i s t i c s ) , or l i n e a r t h i n f i l m p r i s m a t i c s . An enlargement of the p r i s m a t i c element i s a l s o shown. U s u a l l y two p a r a l l e l p r i s m a t i c elements a r e 1 68 F i g u r e 56 - E l e v a t i o n a l t r e a t m e n t s of l i g h t s h e l v e s 169 TYPICAL PRl6.t1ATIC 6LAZIH6S PRISMATIC 6LA66 PRISM AND -STANDARD WINDOW DOUBLE PRISMATIC T H I N - F I L M P R I S M A T I C • S H E E T ON 5 T A W D A P . D DOUBLE 6 L A Z I N 6 F i g u r e 57 - The components of a p r i s m a t i c beamed d a y l i g h t i n g system used, both t o bend the l i g h t f u r t h e r than would be p o s s i b l e w i t h — a s i n g l e element, as w e l l as t o ease maintenance by p r o v i d i n g two f l a t o u t e r s u r f a c e s . In an o b s t r u c t e d s i t u a t i o n , the v a r y i n g r e f r a c t i n g p r o p e r t i e s of d i f f e r e n t l y shaped p r i s m s may be used t o advantage, by l o c a t i n g p r i s m s w i t h the a p p r o p r i a t e r e f r a c t i o n c h a r a c t e r i s t i c s on d i f f e r e n t f l o o r s of a b u i l d i n g . Thus, as shown i n f i g u r e 58 8 5 , p r i s m s of h i g h e s t r e f r a c t a n c e (no. 3 i n the diagram) can be u t i l i z e d on lower f l o o r s , w h i l e p r i s m s of lower r e f r a c t a n c e can be used on i n t e r m e d i a t e and upper f l o o r s . The d a y l i g h t p e n e t r a t i o n on each of thes e f l o o r s w i l l be comparable, even though the lower f l o o r s a r e s u b s t a n t i a l l y more o b s t r u c t e d . 1 70 CD g © TYPES OF PRISMATIC 6LAS5  Figure 58 - Use of prismatic daylighting system in an obstructed si t u a t i o n Aesthetics, performance and integration P h i l l i p s 8 6 , Bartenbach 8 7 and E a c r e t 8 8 have a l l published performance data on prismatic systems. Typical examples exhibit considerable improvement in daylight penetration over non-beamed daylighting solutions. This i s true e s p e c i a l l y at the back of the d a y l i t spaces. The r e l a t i v e l y uniform d i s t r i b u t i o n of l i g h t w i l l also result in balanced brightness in the room. Because prismatics redirect most of the l i g h t upward onto the c e i l i n g , there i s l i t t l e l i g h t transmitted below the horizontal, and the glass surfaces appear of much lower brightness than the unobstructed sky would appear when viewed 171 from t a s k p o s i t i o n s i n the s p a c e 8 9 . B a r t e n b a c h 9 0 r e p o r t s t h a t the luminance of the p r i s m a t i c g l a s s i s w i t h i n the range of the luminance of s u r r o u n d i n g s u r f a c e s , when seen from the i n t e r i o r . Thus the p r i s m a t i c type of system can, by i t s i n h e r e n t w o r k i n g c h a r a c t e r i s t i c s , e l i m i n a t e g l a r e a t the d a y l i g h t i n g a p e r t u r e . The i n t e g r a t i o n of p r i s m a t i c systems i n e l e v a t i o n s i s a s i m p l e r d e s i g n e x e r c i s e , than t h a t i n v o l v i n g l i g h t s h e l f systems. Because i n most i n s t a n c e s the p r i s m s w i l l not p r o t r u d e from the p l a n e of the f a c a d e , they can be t r e a t e d v i s u a l l y as c l e r e s t o r e y windows. Two p o s s i b l e e l e v a t i o n a l r e s o l u t i o n s are shown i n f i g u r e 59 9 1 . The r e c e n t a v a i l a b i l i t y of t h i n - f i l m p r i s m a t i c s e l i m i n a t e s the weight and bulk a s s o c i a t e d w i t h p r i s m a t i c g l a s s . These new f i l m s may be g l u e d t o the i n t e r i o r f a c e s of double g l a z i n g , thus e l i m i n a t i n g maintenance and e n a b l i n g s t a n d a r d g l a z i n g frames t o be u t i l i z e d . Most r e f r a c t i n g systems have no d i u r n a l or s e a s o n a l a d j u s t m e n t , but t h i s may be p r o v i d e d i f they a r e i n c o r p o r a t e d i n t o o p e r a b l e windows or j a l o u s i e type e l e m e n t s 9 2 , i n which case s e a s o n a l adjustment or d i u r n a l t r a c k i n g can d i r e c t the r e f r a c t e d l i g h t a c c u r a t e l y , f o r the best d a y l i g h t i n g advantage. In s p i t e of t h e i r r e l a t i v e s i m p l i c i t y , i n h e r e n t freedom from g l a r e problems, low maintenance, and i n some i n s t a n c e s , of low f i r s t c o s t 9 3 , p r i s m a t i c beamed d a y l i g h t i n g systems have not been e x t e n s i v e l y used i n r e c e n t d a y l i t b u i l d i n g s . There a r e s e v e r a l reasons f o r t h i s : 172 F i g u r e 59 - E l e v a t i o n a l t r e a t m e n t s of p r i s m a t i c systems 1 73 i . A r c h i t e c t s a r e not f a m i l i a r w i t h the f i e l d of o p t i c s and the laws of r e f r a c t i o n . T h e r e f o r e , they a re not a b l e t o custom d e s i g n p r i s m a t i c beamed d a y l i g h t i n g systems f o r each p r o j e c t . What i s needed i s some s t e p by s t e p g r a p h i c method of d e s i g n i n g w i t h r e f r a c t i n g m a t e r i a l s . Because these d e s i g n t o o l s are u n a v a i l a b l e t o a r c h i t e c t s i n a form they can r e a d i l y use, t h e r e i s a s c a r c i t y of r e c e n t examples u s i n g these methods, i n s p i t e of t h e i r g r e a t p o t e n t i a l and s i m p l i c i t y . i i . P r i s m a t i c g l a s s b l o c k and sheet g l a s s , though a v a i l a b l e i n Europe and Japan, appear t o have been d i s c o n t i n u e d by N o r t h American m a n u f a c t u r e r s , and l i t e r a t u r e d e s c r i b i n g t h e i r u s e 9 " i s no l o n g e r a v a i l a b l e . R e c e n t l y , however, imported r e f r a c t i v e g l a s s b l o c k s have become a v a i l a b l e 9 5 . i i i . L i n e a r t h i n f i l m p r i s m a t i c s a r e a v a i l a b l e 9 6 but p r o t o t y p e s and t e c h n i c a l l i t e r a t u r e d e s c r i b i n g t h e i r use i s l a c k i n g 9 7 . These systems, however, have g r e a t p o t e n t i a l i n d a y l i g h t i n g which w i l l be r e a l i z e d when i n f o r m a t i o n d e s c r i b i n g and d e t a i l i n g t h e i r use w i l l be a v a i l a b l e . 3.2.4 Louvre Systems  D e s c r i p t i o n Louvre systems u t i l i z e s m a l l s c a l e , a d j u s t a b l e d e v i c e s t o r e f l e c t d a y l i g h t deeper i n t o the i n t e r i o r . The l o u v r e s p i v o t and, i n many i n s t a n c e s , r e t r a c t as w e l l . L o u v r e s such as V e n e t i a n b l i n d s , have been used f o r decades t o c o n t r o l g l a r e and 1 74 e x c e s s i v e s o l a r heat g a i n . However, t h e i r p u r p o s e f u l use f o r d a y l i g h t i n g i s r e c e n t . Louvre d e v i c e s f o r beaming d a y l i g h t p r o v i d e an i n t e g r a t e d s o l u t i o n t o f o u r i n t e r r e l a t e d problems: two of t h e r m a l t r a n s f e r - - c o n t r o l of unwanted s o l a r heat g a i n and of c o n d u c t i v e heat l o s s e s ; and two of d a y l i g h t i n g — d a y l i g h t p e n e t r a t i o n and c o n t r o l of g l a r e . The v a r i o u s t e c h n i q u e s and p r o d u c t s a v a i l a b l e were h i g h l i g h t e d i n the p r e v i o u s s e c t i o n d e s c r i b i n g beamed d a y l i g h t i n g systems t h r o u g h view a p e r t u r e s . A e s t h e t i c s , performance and i n t e g r a t i o n E x t e r i o r l o u v r e s p r o v i d e the b e s t t h e r m a l p e r f o r m a n ce--both i n b l o c k i n g unwanted s o l a r heat g a i n and r e d u c i n g heat l o s s . They a l s o p r o v i d e s e c u r i t y when c l o s e d . T h e i r e f f e c t on the e l e v a t i o n i s more pronounced than the e f f e c t of l o u v r e s on the i n t e r i o r . Because of the h o u s i n g r e q u i r e d when they a r e r e t r a c t e d , and because of the s i d e t r a c k s needed t o s t a b i l i z e most models, d a y l i g h t i n g a p e r t u r e s d e s i g n e d w i t h e x t e r i o r l o u v r e s u s u a l l y have a r t i c u l a t e d shapes, w i t h a s p e c t ( h e i g h t t o l e n g t h ) r a t i o c l o s e t o u n i t y , as shown i n f i g u r e 60 9 B . Louvres may a l s o be l o c a t e d between the e x t e r i o r and the i n t e r i o r g l a z i n g of d o u b l e - g l a z e d windows, and h a v i n g w i d t h s of 1" or l e s s . T h e i r t h e r m a l p e r f o r m a n c e , as i n d i c a t e d by the sh a d i n g c o e f f i c i e n t , i s i n t h i s c a s e somewhat p o o r e r , but t h e i r i n i t i a l c o s t and maintenance i s l e s s than t h a t of e x t e r i o r l o u v r e s . L o u v r e s on the i n t e r i o r a r e the l e a s t e x p e n s i v e of the t h r e e p o s s i b l e l o c a t i o n s . As d e s c r i b e d i n the p r e v i o u s 175 F i g u r e 60 - Examples of e l e v a t i o n a l t r e a t m e n t s w i t h e x t e r i o r l o u v r e s 176 s e c t i o n , many systems a r e a v a i l a b l e . Louvres on the i n t e r i o r or between the g l a z i n g have l i t t l e i n f l u e n c e on the e l e v a t i o n a l t r e a t m e n t s i n c e they they can adapt t o the rhythm s e t up by the g l a z i n g m u l l i o n s . 3.3 Deep D a y 1 i g h t i n g - - t h r o u g h Roof A p e r t u r e s D a y l i g h t p e n e t r a t i o n through a p e r t u r e s on r o o f s may be i n c r e a s e d by mechanisms s i m i l a r t o those a v a i l a b l e f o r w a l l a p e r t u r e s . The p r i m a r y aims of beaming mechanisms are t o i n c r e a s e i l l u m i n a n c e l e v e l s i n the a r e a s away from d a y l i g h t i n g a p e r t u r e s and t o smooth out the b r i g h t n e s s g r a d i e n t i n the i n t e r i o r . U s u a l l y , the secondary aim of g l a r e r e d u c t i o n i s s i m u l t a n e o u s l y a c h i e v e d . F i g u r e 61 shows the t e c h n i q u e employed i n beaming l i g h t from the a t r i u m i n t o work spaces, i n the TVA b u i l d i n g , Chattanooga, T e n n e s s e e " . At a s m a l l e r s c a l e , f i g u r e 62 shows a s t a n d a r d s k y l i g h t , f i t t e d w i t h s e a s o n a l l y a d j u s t a b l e r e f l e c t o r / s h a d e on the e x t e r i o r , as w e l l as a f a b r i c r e f l e c t o r / d i f f u s e r on the i n t e r i o r 1 0 0 . T h i s i s an e l e g a n t s o l u t i o n , u s i n g mass-produced, and r e a d i l y a v a i l a b l e components. F i g u r e 63 shows two h i g h l y o p t i m i z e d , beamed d a y l i g h t i n g systems d e v e l o p e d by A s h l e y e t a l . 1 0 1 These u t i l i z e d i r e c t s u n l i g h t as w e l l as d i f f u s e d a y l i g h t and, a c c o r d i n g t o the d e s i g n e r s , have u n i f o r m l i g h t d i s t r i b u t i o n c h a r a c t e r i s t i c s . The a r e a of the g l a z i n g i s reduced t o a minimum, t o c u t down on heat l o s s and s o l a r heat g a i n . These d e s i g n s n e c e s s i t a t e s p e c i a l l y f a b r i c a t e d r e f l e c t o r s and l i g h t w e l l s . T h e i r c o s t e f f e c t i v e n e s s i s not known. 177 BEAMED DAYLIGHTING FOR ATRIUM OF JVA Bu.'U.Vg F i g u r e 61 - L a r g e - s c a l e beamed d a y l i g h t i n g from the t o p The above examples u t i l i z e t he p r i n c i p l e of l i g h t r e f l e c t i o n t o i n c r e a s e d a y l i g h t p e n e t r a t i o n and s p r e a d . However, the p r i n c i p l e of r e f r a c t i o n may a l s o be used t o a c h i e v e the same ends. L e m o n s 1 0 2 has made model s t u d i e s w i t h c o m m e r c i a l l y a v a i l a b l e t h i n - f i l m p r i s m a t i c s and f r e s n e l l e n s e s t o a c h i e v e i n c r e a s e d l i g h t p e n e t r a t i o n f o r s k y l i g h t s . He r e p o r t s t h a t l i n e a r l e n s e s , both of the concave and the convex t y p e , produce d i f f u s e , l a r g e p o o l s of l i g h t w i t h o v e r c a s t s k y ; and d i f f u s e s t r i p s of l i g h t w i t h a c l e a r sky. S i n g l e and double l i n e a r p r i s m s bend the l i g h t a t p r e d i c t a b l e a n g l e s . Obvious a p p l i c a t i o n s appear t o be c o r r i d o r s p a c e s , as w e l l as w a l l washers, e t c . 1 0 3 The use of l i g h t r e f r a c t i o n p r i n c i p l e s , and • e s p e c i a l l y of t h i n - f i l m p r i s m a t i c s , t o i n c r e a s e d a y l i g h t 178 F i g u r e 62 - Example of beaming mechanism added t o s t a n d a r d s k y l i g h t p e n e t r a t i o n has much p o t e n t i a l i n beamed d a y l i g h t i n g . 1 79 5IW6LE DIRECTION 4KVL16HT REFLECTOH • I510 u)i*iW S u n ( ^ kC^ U s u m m t C - s u n TWO DIRECTION 6KVLI6HT RErlECTOR, F i g u r e 63 - H i g h l y o p t i m i z e d s k y l i g h t d e s i g n s 4. NOTES 1. O y v i n d Aschehoug e t a l . , V i n d u , Rom og D a g s l y s (Trondheim, Norway: Norges T e k n i s k e H o g s k o l e , 1980). 2. Benjamin H. Evans, D a y l i g h t i n A r c h i t e c t u r e (New York: M c G r a w - H i l l , 1981), p. 57. 3. R. G. Hopkinson and J . D. Kay, The L i g h t i n g of B u i l d i n g s (London: Faber and F a b e r , 1969), p. 90. 4. B u i l d i n g R esearch B o a r d , The L i g h t i n g of B u i l d i n g s (London: H i s M a j e s t y ' s S t a t i o n e r y O f f i c e , 1944), pp. 16,17,18. 5. I b i d . , p. 17. 6. I b i d . , p. 18. 7. I b i d . , pp. 17,18,19. 180 8. I b i d . , p. 18. 9. I b i d . , p. 19. 10. T able assembled from: ir"C. W. C l a r k s o n and M. L. L i l l y , " S i n g l e and M u l t i p l e G l a s s G l a z i n g Media i n P a s s i v e S o l a r Energy C o n s t r u c t i o n , " P r o c e e d i n g s of the 3rd N a t i o n a l  P a s s i v e S o l a r C o n f e r e n c e , January 11-13, 1979 i n San J o s e ,  C a l i f . , Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1979, p. 342. 2. G uardian G l a s s . "Guardian A r c h i t e c t u r a l G l a s s " , 1984. Trade l i t e r a t u r e . 3. The S o u t h w a l l C o r p o r a t i o n . "Look i n t o Heat M i r r o r " , 1982. Trade l i t e r a t u r e . 11. D. G. Stephenson, " R e f l e c t i v e G l a z i n g U n i t s , " D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l Research C o u n c i l of Canada, Canadian B u i l d i n g D i g e s t 101, May 1968, p. 1. 12. R. Johnson e t . a l , " G l a z i n g Energy Performance and D e s ign o p t i m i z a t i o n w i t h D a y l i g h t i n g , " Energy and B u i l d i n g s , 6(1984):30. 13. The S o u t h w a l l C o r p o r a t i o n , s u p r a . 14. J e r r y Germer, " S w i t c h a b l e G l a z i n g s , " S o l a r Age, October 1984, pp. 20-23. 15. I b i d . 16. C a l c u l a t e d from performance data shown i n S o u t h w a l l C o r p o r a t i o n t r a d e l i t e r a t u r e . 17. Stephenson, p. 1. 18. R i c h a r d Rush, " G l a s s o l i n e , " P r o g r e s s i v e A r c h i t e c t u r e , September, 1981, pp. 233-241. 19. P i l a r V i l a d a s , "Through a G l a s s B r i g h t l y , " P r o g r e s s i v e  A r c h i t e c t u r e , November, 1981, pp. 138-43. 20. S o l a r Age, "Marvel M a t e r i a l s , " S o l a r Age, December, 1983, p. 41 . 21. M. C. Varshneya and V. V. Varma, "A new F e n e s t r a t i o n M a t e r i a l f o r Heat P r o t e c t i o n , " Energy and B u i l d i n g s , 1(1977):383-91. 22. J e r r y Germer, " S w i t c h a b l e G l a z i n g s , " S o l a r Age, October 1984, pp. 20-23. 23. Matthews, S c o t t . " L i g h t i n g from the Top". T a l k g i v e n a t The 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . 181 24. Rush, p. 238. 25. S. A. J u r o v i c s , " D a y l i g h t G l a z i n g and B u i l d i n g Energy M i n i m i z a t i o n , " ASHRAE T r a n s a c t i o n s , 1982, pp. 375. 26. Rush, p. 241. 27. The t a b l e assumes t h a t d a y l i g h t i n g i s a dominant d e s i g n parameter. The r a n k i n g of the g l a z i n g a s s e m b l i e s c o n s i d e r s t h e i r performance i n terms of d a y l i g h t i n g , heat l o s s , and s o l a r heat g a i n . I t does not c o n s i d e r c o s t s or a e s t h e t i c s . 28. Hopkinson and Kay, pp. 88 and 117. 29. J . A. Lynes, P r i n c i p l e s of N a t u r a l L i g h t i n g (London: E l s e v i e r , 1968), p. 134. 30. Adapted from Lynes, p. 183, t a b l e A . 8 . I I I . See a l s o Harvey Bryan, D a y l i g h t i n g Design T o o l s Workshop Workbook (The 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n Phoen i x , A r i z o n a ), p. 107. 31. Hopkinson and Kay, pp. 258-59. 32. I b i d . , p. 88. 33. Lynes, p. 107. 34. I b i d . 35. Hopkinson and Kay, pp. 88 and 117. 36. Oyvind Aschehoug et a l . , V i n d u , Rom og D a g s l y s — D e l I I (Windows, Room and D a y l i g h t - - P a r t 11, i n N o r v e g i a n J Trondheim, Norway: Norges T e k n i s k e H o g s k o l e , 1982), t e x t pp. 19; diagrams pp. 5-8. 37. I b i d . , diagrams p. 6-8. 38. I b i d . , diagrams pp. 10-12; t e x t p. 6. 39. M a r i e t t a S. M i l l e t , " D a y l i g h t i n g D e s i gn G u i d e l i n e s f o r P a c i f i c Northwest B u i l d i n g s , " P r o c e e d i n g s of ' S o l a r 79  Northwest' C o n f e r e n c e , August 10-12, 1979 i n S e a t t l e . S e a t t l e : P a c i f i c Northwest S o l a r Energy A s s o c i a t i o n , 1979, p. 53. 40. Aschehoug et a l . , P a r t I I , pp. 9-12. 41. Aschehoug et a l . 42. Evans, pp. 57-59. 43. Aschehoug e t a l . , t e s t s e r i e s A1. 182 44. I b i d . , t e s t s e r i e s C, 45. I b i d . , t e s t s e r i e s H, 46. I b i d . 47. I b i d . 48. Evans, p. 61. 49. F i g u r e a f t e r Hopkinson and Kay, p. 87. 50. Roger T. Tamblyn, "Towards Zero Energy i n B u i l d i n g s " , t a l k g i v e n a t the Conference "Energy E f f i c i e n c y and the Bottom L i n e " , October 25, 1979, Vancouver, B. C , as quoted i n Leu, Max H, "Energy C o n s e r v a t i o n i n O f f i c e B u i l d i n g s , " M a s t e r ' s T h e s i s a t U n i v e r s i t y of B r i t i s h C o lumbia, 1980, p. 180. 51. M i l l e t , p. 54. 52. Evans, p. 75. 53. Aschehoug et a l . , P a r t I I . 54. Evans, p. 75. 55. Aschehoug et a l . , P a r t I , pp. 11-12 t e x t . 56. D. P. T u r n e r , ed, Windows and Environment (Newton-le-W i l l o w s : P i l k i n g t o n E n v i r o n m e n t a l A d v i s o r y S e r v i c e , 1969), pp. 54-61. 57. Evans_,_.p. 58. 58. Hopkinson and Kay, p. 95. 59. M i c h a e l D. Shanus, "Deep D a y l i g h t i n g : I n n o v a t i v e L i g h t i n g Concepts f o r a Large O f f i c e B u i l d i n g , " 1982 IES Combined  P a c i f i c Northwest and South P a c i f i c C o a s t a l R e g i o n a l  C o n f e r e n c e , Santa B a r b a r a , C a l i f . , 1982, p. 3. 60. Kreg M. E a c r e t , "Beamed . D a y l i g h t i n g : H i s t o r i c a l R e view,Current 2 t e s t i n g and A n a l y s i s and Design O p t i o n s , " P r o c e e d i n g s of the 5th N a t i o n a l P a s s i v e S o l a r C o n f e r e n c e ,  October 19-26, 1980 i n Amherst, Mass., Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1980, p. 1176. 61. W a l t e r F. Wagner, J r . , E n e r g y - E f f i c i e n t B u i l d i n g s (New York: M c G r a w - H i l l , 1980), p. 143. 6.2. C a r l y l e M. A s h l e y , e t a l , " I n n o v a t i v e , E f f i c i e n t 183 D a y l i g h t i n g D e s i g n s , " P r o c e e d i n g s of the 5th N a t i o n a l  P a s s i v e S o l a r C o n f e r e n c e , October 19-26, 1980 i n Amherst,  Ma s s., Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1980, p. 1180. 63. L i g h t i n g D e s i gn and A p p l i c a t i o n s , " W i l l o w Creek O f f i c e B u i l d i n g , Idaho F a l l s , " L i g h t i n g Design and A p p l i c a t i o n s , March 1981, pp. 14-18. 64. AIA J o u r n a l , "Measuring Performance of Energy D e s i g n : DOE s t u d i e s a s e t of Owens-Corning Award Winners over Time," AIA J o u r n a l , J a n u a r y 1983, p. 45. 65. P i v o t i n g a i r f o i l l o u v r e s shown, drawn a f t e r J i m Murphy, "Rainbow's End," P r o g r e s s i v e A r c h i t e c t u r e , A p r i l 1980, p. 104. E x t e r i o r V e n e t i a n b l i n d s drawn from Baumann b l i n d s t r a d e l i t e r a t u r e . 66. R e f l e c t i v e I n s u l a t i n g B l i n d s (RIB) drawn a f t e r Hanna B. S h a p i r a and P a u l k. Barnes, " R I B - - R e f l e c t i v e I n s u l a t i n g B l i n d s , " P r o c e e d i n g s of the 4th N a t i o n a l P a s s i v e S o l a r  C o n f e r e n c e , October 3-5, 1979 i n Kansas C i t y , M i s s o u r i , Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1979, p. 394. 67. A r t h u r H. R o s e n f e l d and Stephen E. S e l k o w i t z , "Beam D a y l i g h t i n g : An A l t e r n a t i v e I l l u m i n a t i o n t e c h n i q u e , " Energy and B u i l d i n g s , 1 ( 1 9 7 7 ) : 4 4 . 68. R a l p h M. Lebens, " D e t e r m i n i n g the Optimum Design of the S o l a r M o d u l a t o r , " P r o c e e d i n g s of the 3rd N a t i o n a l P a s s i v e  S o l a r C o n f e r e n c e , January 11-13, 1979 i n San J o s e , C a l i f . , Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1979, p. 100. 69. C h r i s t i a n B a r t e n b a c h and M a r t i n K l i n g l e r , D a y l i g h t i n g  Through S u n - P r o t e c t i o n (Munich: L i c h t p l a n u n g Ch. B a r t e n b a c h ) , f i g u r e i~2, n. p.. 70. H a r r i s o n F r a k e r i n A r c h i t e c t u r a l Record, "Round T a b l e : A R e a l i s t i c Look a t The P a s s i v e Approach--Using N a t u r a l Means t o Conserve Energy," A r c h i t e c t u r a l Record, Mid-August 1983, p. 98. 71. A r c h i t e c t u r a l R e c o r d , " E n e r p l e x : O f f i c e Complex E x p l o r i n g S o p h i s t i c a t e d Energy S o l u t i o n s , " A r c h i t e c t u r a l Record, May, 1982, p. 13.1 . 72. P h i l l i p s , Derek, L i g h t i n g i n A r c h i t e c t u r a l Design ( T o r o n t o : M c G r a w - H i l l ) , 1964. 73. Hopkinson, p. 31. 74. E a c r e t , p. 1174. 184 75. P h i l l i p s , p. 101 . 76. P e r s o n a l communication from s t u d e n t s of the S c h o o l of P l a n n i n g , U n i v e r s i t y of A r i z o n a , a t the model d i s p l a y s of deep d a y l i g h t i n g systems, The 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f erence, 16-18 F e b r u a r y 1983 i n Phoenix, A r i z o n a . 77. S. S e l k o w i t z , S. Navvab and S. Matthews, "Design and-Performance of L i g h t S h e l v e s , " P r o c e e d i n g s of the 1983  I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983  i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f erence, 1983, p. 268. 78. V e n t u r a C o a s t a l C o r p o r a t i o n b u i l d i n g , V e n t u r a , C a l i f . , i n S. E l l i n w o o d , " D a y l i g h t i n the Design P r o c e s s , " P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l D a y l i g h t i n g  C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, p. 151. 79. The Water Resources C o n t r o l Board b u i l d i n g , Sacramento, C a l i f . , i n H. Bryan and V. B a z j a n a c , " D a y l i g h t i n g Design f o r New C a l i f o r n i a S t a t e O f f i c e B u i l d i n g - S i t e 1-C," P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l D a y l i g h t i n g  C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, p. 195. 80. The Lockheed M i s s i l e s #157 b u i l d i n g i n Lee Stephen Windheim and K y l e V. Davy, "The S u b s t i t u t i o n of D a y l i g h t i n g f o r E l e c t r i c L i g h t i n g i n a Large O f f i c e B u i l d i n g , " P r o c e e d i n g s of the 6th N a t i o n a l P a s s i v e S o l a r  C o n f e r e n c e , September 8-12, 1981 i n P o r t l a n d , Oregon, Newark, Delaware: American S e c t i o n of the I n t e r n a t i o n a l S o l a r Energy S o c i e t y , 1972, pp. 877. 81. Frame and s t u c c o b u i l d i n g s , may i m i t a t e c o n c r e t e i n t h e i r m assing. Examples a r e : the Water Resources C o n t r o l Board b u i l d i n g ( S i t e 1-C), Sacramento, C a l i f . and the V e n t u r a C o a s t a l C o r p o r a t i o n b u i l d i n g , i n V e n t u r a , C a l i f . Both of these were d e s i g n e d as c o n c r e t e b u i l d i n g s , but b u i l t as frame and s t u c c o . Harvey B r y a n , p r e s e n t a t i o n a t the D a y l i g h t i n g Design T o o l s Workshop; and S c o t t E l l i n w o o d , p e r s o n a l communication, both a t The 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f erence, 16-18 F e b r u a r y 1983 i n Phoenix, A r i z o n a . 82. E l e v a t i o n s and s e c t i o n s show, from t o p : CIGNA b u i l d i n g , B l o o m f i e l d , Conn. (TAC, a r c h . ) from M i c h a e l J . C r o s b i e , " L i g h t i n g S t r a t e g i e s : Case Study," A r c h i t e c t u r e , October 1984, pp. 62-63; GSIS b u i l d i n g , M a n i l a , P h i l i p p i n e s (TAC, a r c h . ) from A r c h i t e c t u r a l Record, " T e r r a c e d Pods I n v i t e 1 85 D a y l i g h t and B r e e z e s , " A r c h i t e c t u r a l R e c o r d , Mid-August 1981, p. 55; Lockheed M i s s i l e s #157 b u i l d i n g , ***, C a l i f . (L. D a l y ) d e v e l o p e d from A r c h i t e c t u r a l R e c o r d , "Technology P u r s u e s , C a t c h e s , D a y l i g h t ," A r c h i t e c t u r a l Record, Mid-August 1981, pp. 58-59. 83. Nancy C. Rodgers, "The P o t e n t i a l of Beam S u n l i g h t i n g , " L i g h t i n g Design and A p p l i c a t i o n s , November, 1979, p. 35. 84. E a c r e t , p. 1174. 85. P i l k i n g t o n G l a s s , t r a d e l i t e r a t u r e [ e a r l y 1960s] 86. R. 0. P h i l l i p s , "Making the Best Use of D a y l i g h t i n B u i l d i n g s , " i n S o l a r Energy A p p l i c a t i o n s i n the Design of  B u i l d i n g s , e d i t e d by Henry Cowan (London: A p p l i e d S c i e n c e , 1980), p. 109. 87. B a r t e n b a c h , S e c t i o n 2.3.2., n.p. 88. E a c r e t , p. 1175. 89. Derek P h i l l i p s , p. 102. 90. B a r t e n b a c h , s e c t i o n 2.3.1. 91. E l e v a t i o n s adapted from: ( t o p ) S o c i a l s e c u r i t y A d m i n i s t r a t i o n , NE Program S e r v i c e C e n t r e b u i l d i n g , J a m a i c a , N.Y. ( E h r e n k r a n t z Group) as d e s c r i b e d i n Magnusson, M, "Window C o n f i g u r a t i o n : D e s i g n i n g f o r D a y l i g h t i n g and P r o d u c t i v i t y , " P r o c e e d i n g s of the 1983  I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 Feb r u a r y 1983  i n P h o e n i x , A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, pp. 155-57; (bottom) e l e v a t i o n adapted from p r o t o t y p e b u i l d i n g d e s c r i b e d i n Ba r t e n b a c h ( s u p r a ) , i n s e r t pages. 92. B a r t e n b a c h , s e c t i o n 2.1.2., n.p. 93. E a c r e t , p. 1177. 94. The Owens I l l i n o i s g l a s s p r o d u c t s c a t a l o g u e , p u b l i s h e d i n the e a r l y 1960's, showed a s e l e c t i o n of s e v e r a l p r i s m a t i c g l a s s e s , as w e l l as p r i s m a t i c g l a s s b l o c k s , w i t h s p e c i f i c a t i o n s and i n s t a l l a t i o n i n s t r u c t i o n s . A c c o r d i n g t o i n f o r m a t i o n by m a n u f a c t u r e r s ' r e p r e s e n t a t i v e s i n B. C , a l l t he major N o r t h American g l a s s m a n u f a c t u r e r s have stopped the manuf a c t u r e and d i s t r i b u t i o n of t h e s e p r o d u c t s . 95. N.E.G. C o r p o r a t i o n , Japan, g l a s s b l o c k p r o d u c t s , d i s t r i b u t e d by Ce r c o I n d u s t r i e s L t d . 96. 3-M C o r p o r a t i o n , f o r example, manufacture a range of t h i n -1 86 f i l m p r i s m a t i c s . 97. P e r s o n a l communication by 3-M r e p r e s e n t a t i v e a t the m a n u f a c t u r e r s ' d i s p l a y s , The 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 February 1983 i n P h o e n i x , A r i z o n a . 98. Sources f o r e l e v a t i o n s : (top) O f f i c e b l o c k , H a h n s t r a s s e , and (bottom) South German C e n t r a l Bank b u i l d i n g , both i n F r a n k f u r t , W. Germany, shown i n Faber " M a x i m a t i c " e x t e r n a l b l i n d s , t r a d e l i t e r a t u r e . 99. L i g h t i n g D e s i gn and A p p l i c a t i o n s , "TVA O f f i c e Complex - A Teamwork Approach t o Energy E f f i c i e n c y , " L i g h t i n g D e s i g n  and A p p l i c a t i o n s , November 1980, pp. 34-37. 100. D. F e l t s , "Case Study f o r New C o n s t r u c t i o n : The Window Rock Elementary S c h o o l A d d i t i o n , " P r o c e e d i n g s of the 1983  I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983  i n P h o e n i x , A r i z o n a . Washington, D. C.: 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, p. 187. 101. A s h l e y et a l . , p. 1182. 102. Thomas M. Lemons, "Lenses Which Improve S k y l i g h t Performance," P r o c e e d i n g s of the 1983 I n t e r n a t i o n a l  D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x ,  A r i z o n a . Washington, D. C : 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 1983, pp. 255-60. 103. I b i d . 187 V. INTERIOR SPACE PLANNING IN DAYLIT BUILDINGS 188 1. INTRODUCTION The t e c h n i q u e s i n c l u d e d i n t h i s c h a p t e r comprise the t h i r d p a r t i n the o v e r a l l o b j e c t i v e of m a x i m i z i n g the p o t e n t i a l f o r d a y l i g h t i n g w i t h i n a b u i l d i n g : i n t e r i o r space p l a n n i n g . The t e n a n t of a d a y l i t o f f i c e b u i l d i n g has t o be s e n s i t i v e t o the d a y l i g h t i n g i m p l i c a t i o n s of v a r i o u s o f f i c e l a y o u t s and the l i g h t i n g needs of v a r i o u s o f f i c e a c t i v i t i e s , and must a l s o work i n harmony w i t h the p a t t e r n of luminous zones n a t u r a l l y o c c u r i n g i n d a y l i t b u i l d i n g s . O t h e r w i s e , the d a y l i g h t p e n e t r a t i o n a c h i e v e d i n the d e s i g n of the b u i l d i n g may be i m p a i r e d . T h i s c h a p t e r o u t l i n e s a range of t e c h n i q u e s t h a t can a s s i s t i n a c h i e v i n g the main g o a l of d a y l i g h t i n g : l o c a t i n g p e o p l e and a c t i v i t i e s i n such a way t h a t advantage i s taken of a v a i l a b l e i n t e r i o r d a y l i g h t . 2. TECHNIQUES FOR SPACE PLANNING The t e c h n i q u e s i n c l u d e d i n t h i s c h a p t e r a r e summarized i n f i g u r e 64 . 189 S C A L E SITE P L A N N I N G BUILDING CoNFlSUfJOHl BUILDING COMPONENT BUILDING. INTERIOR*. LOCATION OF ACTIVITIES J OPEN PLAN INTERIOR LOCATION OF CELLULAR OFTICZS D D E T A I L I N G OF CEUULAR OFFICES DAYU6HTIN6 & ACOUSTICS F i g u r e 64 - Summary of t e c h n i q u e s f o r i n t e r i o r space p l a n n i n g 1 90 2.1 L o c a t i o n Of A c t i v i t i e s In o r d e r t o t a k e advantage of a v a i l a b l e d a y l i g h t , a c t i v i t i e s w i t h i n a d a y l i t b u i l d i n g s h o u l d be l o c a t e d a c c o r d i n g t o t h e i r v i s u a l performance r e q u i r e m e n t s . In a t y p i c a l s i d e l i t o f f i c e space, t h r e e zones of v a r y i n g d a y l i g h t p e n e t r a t i o n , shown i n f i g u r e 65 , may be i d e n t i f i e d : F i g u r e 65 - The t h r e e zones of d a y l i g h t p e n e t r a t i o n i . Zone A, the p e r i m e t e r zone, extends t o about 3.5-4.5m from the d a y l i g h t i n g a p e r t u r e i n t r a d i t i o n a l d a y l i g h t i n g systems and t o about 6-8m u s i n g deep d a y l i g h t i n g systems. The a c t u a l d i s t a n c e s w i l l be g r e a t l y dependent on sky c o n d i t i o n s , o r i e n t a t i o n of the d a y l i g h t i n g a p e r t u r e , and the e x t e n t of o b s t r u c t i o n s , as w e l l as on the i n t e r i o r d e t a i l i n g 1 . T h i s zone i s c h a r a c t e r i z e d by the a v a i l a b i l i t y of view outdoors,, an exposure t o f l u c t u a t i n g 191 c l i m a t i c c o n d i t i o n s and e x c e l l e n t d a y l i g h t i n g p o t e n t i a l . D a y l i g h t i n g i n t h i s zone has low v e i l i n g r e f l e c t i o n f o r most p o s i t i o n s 2 , p r o v i d e s good i l l u m i n a n c e on the v e r t i c a l s u r f a c e s 3 , w e l l b a l a n c e d s p e c t r a l c o m p o s i t i o n , good m o d e l l i n g c h a r a c t e r i s t i c s " and g e n e r a l l y , ESI v a l u e s s u b s t a n t i a l l y h i g h e r than raw i l l u m i n a t i o n measurements 5. i i . Zone C, the c o r e zone, i s t y p i c a l l y beyond 7m from the d a y l i g h t i n g a p e r t u r e s i n t r a d i t i o n a l d a y l i g h t i n g systems and beyond 12m i n d e s i g n s u t i l i z i n g deep d a y l i g h t i n g t e c h n i q u e s . T h i s zone cannot b e n e f i t from d a y l i g h t and i s l a r g e l y independent of the e x t e r n a l c l i m a t e . In o f f i c e s , t h i s zone i s permanently l i t by a r t i f i c i a l l i g h t i n g and r e q u i r e s c o o l i n g f o r much of the y e a r 6 . Any d a y l i g h t i n g t h a t reaches t h i s zone i s more of p s y c h o l o g i c a l h e l p than an a i d t o v i s u a l t a s k p e r f o r m a n c e 7 . i i i . The i n t e r m e d i a t e a r e a , Zone B, i s c h a r a c t e r i z e d by d a y l i g h t i n g adequate f o r ambient l i g h t i n g , w i t h t a s k l i g h t i n g s u p p l e m e n t a t i o n . I t s t h e r m a l b e h a v i o u r , as i t s luminous c h a r a c t e r i s t i c s , i s somewhere between t h a t of the c o r e and the p e r i m e t e r zone. T h i s i n t e r m e d i a t e zone i s found a t 3.5-12m from the d a y l i g h t i n g a p e r t u r e . The a c t u a l l o c a t i o n and e x t e n t of t h i s zone w i l l v a r y w i t h the d e s i g n . T a b l e X I I shows a comprehensive l i s t of o f f i c e a c t i v i t i e s , w i t h t h e i r approximate v i s i b i l i t y r e q u i r e m e n t s and p r e f e r r e d zone l o c a t i o n . I t i s p o s s i b l e t o c a p i t a l i z e on the c h a r a c t e r i s t i c s of the luminous environment a v a i l a b l e i n each of 192 A C T I V I T Y COLOUR ILLUMINANCE ILLUMINANCE SCALAR Z O N E ON H0RI7. aiff. ON VERT. 5URF. ILLUMIN. LOCATION WRITING-HANDWRITING PEN O 1 0 0 A , & n PENCIL 0 Z 0 0 A TYPEWRITING 0 z z 0 A , B WORD PROCESSING 0 z \ 0 A , B , G * DRAFTING - LARGE SCALE WORK 0 2 2 1 A , 6 MEDIUM « » . 0 Z 1 1 A FINE 0 1 1 1 A READING - TVPE WRITTEN MTL.GOOD 0 1 0 0 A , & * " " POOR 0 2 1 0 A HANDWRITTEN MTL. GOOD 0 1 0 0 A, B * a II POOR 0 2 1 0 A 5 0 R T / F I L E - SORTING (HORIZ.) O 2 1 1 A , & FILING (VERT.) 0 1 Z 1 E> 6T0RA6E ACTIVE \ 1 1 1 E> « DEAD 0 1 1 0 C INSPECTION - COLOUR MATCHING 2 1 1 1 A TEXTURE MATCHING t 1 / 2 A INSPECT 3D MATl. 1-2 1 1 2 A PHOTOCOPYING O 2 1 0 A,&,G * DIBCU&6I0N - TELEPHONE 0 0 0 1 B , G INTERVIEW 1 1 0 2 A, & CONFERENCE SMALL 1 1 0 2 A , B LARGE 2 1 1 2 A A / V PRESENTATION - GRAPHICS 1 0 1 0 A , 6 SLIDES X X X C T V X X X X C V. D.T. X 1 X. X A , B , C » SECONDARY ACTNITES - LUNCH \ 1 1 1-2 A , B &REAK 1 1 1 1 B WA6HRO0M 1 1 1 1 C BULLETIN 6 . 0 0 2 0 B,C "•• LEGEND: * ADDITIONAL TASK 2 - VERY IMPORTANT 0- NOT IMPORTANT LIGHTING MAY BE 1 - IMPORTANT X - NOT APPLICABLE NEEDED T a b l e X I I - I l l u m i n a t i o n r e q u i r e m e n t s and p r e f e r r e d zone l o c a t i o n of v a r i o u s o f f i c e a c t i v i t i e s 1 93 t h e s e t h r e e zones, by g i v i n g c o n s i d e r a t i o n t o l o c a t i n g the v a r i o u s a c t i v i t i e s i n the a p p r o p r i a t e zone, a c c o r d i n g t o t h e i r v i s u a l performance r e q u i r e m e n t s . Thus, a c t i v i t i e s such as t e x t u r e and c o l o u r m a t c hing, d r a f t i n g , and o t h e r s i m i l a r , v i s u a l l y demanding a c t i v i t i e s , w i l l b e n e f i t from b e i n g l o c a t e d i n Zone A. A c t i v i t i e s such as g r a p h i c p r e s e n t a t i o n s t o a group, i n t e r v i e w s and c o n f e r e n c e s , v e r t i c a l f i l i n g and o t h e r work r e q u i r i n g good m o d e l l i n g and v e r t i c a l i l l u m i n a t i o n , w i l l b e n e f i t from b e i n g l o c a t e d i n Zones A or B. C i r c u l a t i o n , s t o r a g e and o t h e r low use and v i s u a l l y non-c r i t i c a l s p a c e s , as w e l l as equipment rooms, washrooms and s i m i l a r spaces t h a t r e q u i r e c o m p a r t m e n t a t i o n , a c c e s s t o m e c h a n i c a l s e r v i c e s , or s p e c i a l l i g h t i n g needs, are best l o c a t e d , from the . p o i n t of view of d a y l i g h t i n g , i n the c o r e zone. L o c a t i n g these secondary spaces i n the c o r e zone l i b e r a t e s f l o o r a rea near the p e r i m e t e r zone f o r p r i m a r y o f f i c e a c t i v i t i e s and i n c r e a s e s the chances t h a t d a y l i g h t i n g w i l l be used f o r t h e s e p r i m a r y a c t i v i t i e s . In low r i s e o f f i c e b u i l d i n g s , s k y l i g h t s or l i g h t w e l l s can e f f e c t i v e l y b r i n g d a y l i g h t i n t o some secondary s p a c e s ~ - s u c h as c o r r i d o r s or washrooms--to p r o v i d e a sense of f o c u s , and a s s i s t i n o r i e n t a t i o n . In many deep space o f f i c e b u i l d i n g s , i t w i l l not be p o s s i b l e t o l o c a t e a c t i v i t i e s i n t h e i r p r e f e r r e d l o c a t i o n s on the p e r i m e t e r , due t o i n s u f f i c i e n t space i n the s e zones. F u r t h e r m o r e , t h e r e a r e o t h e r c r i t e r i a , o v e r l a i d on d a y l i g h t i n g c o n s i d e r a t i o n s , t h a t may o v e r r i d e the above g u i d e l i n e s . 194 N e v e r t h e l e s s , i t i s im p o r t a n t t o u n d e r s t a n d the d a y l i g h t r e q u i r e m e n t s of d i f f e r e n t t a s k s and attempt t o l o c a t e these i n the a p p r o p r i a t e luminous environment: t h i s i s an im p o r t a n t a s p e c t of e f f i c i e n t r e s o u r c e a l l o c a t i o n . 2.2 Open P l a n I n t e r i o r Where the type of o f f i c e work and the management s t y l e p e r m i t s , the use of an open p l a n i n t e r i o r w i l l f a c i l i t a t e d a y l i g h t p e n e t r a t i o n . I t i s now t e c h n i c a l l y and e c o n o m i c a l l y f e a s i b l e t o p r o v i d e workspace d e f i n i t i o n , e n v i r o n m e n t a l comfort c o n d i t i o n s and a c o u s t i c a l p r i v a c y f o r the r e q u i r e m e n t s of most o f f i c e a c t i v i t i e s , i n open p l a n , " l a n d s c a p e d o f f i c e s " 8 . .When opaque, f u l l - h e i g h t p a r t i t i o n s a re used t o d e f i n e s h a l l o w depth o f f i c e s a l o n g the p e r i m e t e r , r e s u l t i n g i n open a r e a s on the i n t e r i o r , view and d a y l i g h t a re t o t a l l y b l o c k e d and the open a r e a must r e l y e n t i r e l y on e l e c t r i c l i g h t i n g f o r i t s i l l u m i n a t i o n . Without such p a r t i t i o n s , d a y l i g h t i n the i n t e r i o r zones might o t h e r w i s e be s u f f i c i e n t t o save e l e c t r i c energy, but i n any case would p r o v i d e improved m o d e l l i n g and a f e e l i n g of i n c r e a s e d s p a c i o u s n e s s . E v a n s 9 has argued t h a t i d e a l l y "the whole s t r u c t u r e of the i n t e r i o r must a l l o w f o r and complement ... [ t h e ] h o r i z o n t a l f l o w of d a y l i g h t from windows f o r best e f f e c t " . 195 2.3 L o c a t i o n Of C e l l u l a r O f f i c e s In c u r r e n t N o r t h American p r a c t i c e , c e l l u l a r o f f i c e s , when r e q u i r e d , a r e l o c a t e d a t the p e r i m e t e r . Such space a l l o c a t i o n ^0 4 3 1 SO! S3sD L i J f U M U f c ^ L l s T L , ) ' t>P» j D • i • i 5 s • i f 3 _ . J I J L>0 L>D» j L> D° j r>r»»! 3 i il j EH u° L b F i g u r e 66 - A r e c e n t example of o f f i c e f l o o r p l a n h a v i n g c e l l u l a r o f f i c e s on t h e i n t e r i o r d e c i s i o n s a r e the r e s u l t not of f u n c t i o n a l r e q u i r e m e n t s , but a r e f l e c t i o n of the s o c i a l v a l u e system h e l d by the o r g a n i z a t i o n and the l a r g e r s o c i a l s t r u c t u r e . T h i s f a c t can be a p p r e c i a t e d when i t i s r e a l i z e d t h a t c e l l u l a r o f f i c e s i n European p r a c t i c e of today, and even i n N o r t h American p r a c t i c e of t h r e e decades ago, have not n e c e s s a r i l y been l o c a t e d a l o n g the p e r i m e t e r of the " b u i l d i n g . For example., i n t h e 1950's the concept of 1 96 " e x e c u t i v e c o r e p l a n " was p o p u l a r i n the USA 1 0. In t h i s l a y o u t , e x e c u t i v e s were l o c a t e d i n the c e n t r e of the space, i n i n d i v i d u a l o f f i c e s , w i t h s t a f f a l o n g the p e r i m e t e r of the b u i l d i n g , i n an open p l a n arrangement. From a f u n c t i o n a l p o i n t of view, t h i s i s s t i l l c o n s i d e r e d s u p e r i o r 1 1 . A r e c e n t d a y l i t b u i l d i n g i n the U. S. A., has d e f i e d s o c i a l c o n v e n t i o n and p r o v i d e s c e l l u l a r o f f i c e s f o r management p e r s o n n e l a t the i n t e r i o r , l e a v i n g , as shown i n f i g u r e 66 1 2 , p e r i m e t e r a r e a s open. To g i v e i n t e r i o r c e l l u l a r o f f i c e s a m e n i t i e s and p r e s t i g e , g l a z e d or p a r t l y g l a z e d p a r t i t i o n s w i t h c u r t a i n s may be used; g r e a t e r amount of p l a n t m a t e r i a l can a l s o be i n t r o d u c e d . I n t e r i o r o f f i c e s on lower f l o o r s may be d a y l i t through l i g h t w e l l s and, on the upper f l o o r , t h r o u g h s k y l i g h t s 1 3 . I f the i n t e r i o r placement of c e l l u l a r o f f i c e s w i t h i n a l a r g e r open p l a n i s not a c c e p t a b l e , i n t e r m i t t e n t b reaks i n the l i n e of c e l l u l a r o f f i c e s at the p e r i m e t e r may be c o n s i d e r e d , so t h a t the open a r e a s have views t o the e x t e r i o r and some a c c e s s to d a y l i g h t . T h i s i s shown i n f i g u r e 67 . I n t e r m i t t e n t b r e a k s i n a l i n e of c e l l u l a r o f f i c e s a r e of added importance i n deep p l a n s , because the s u b j e c t i v e sense of e n c l o s u r e i n deep l a y o u t s g r e a t l y i n c r e a s e s i f more than two e x t e r i o r w a l l s a r e b l o c k e d by c e l l u l a r o f f i c e s 1 " . I f c e l l u l a r o f f i c e s a re l o c a t e d a l o n g t h r e e e x t e r i o r w a l l s of a d e e p space o f f i c e f l o o r , as many as 90% of the p e o p l e working on the f l o o r w i l l be i n open a r e a s b e h i n d these c e l l u l a r o f f i c e s and most of them w i l l have n e g l i g i b l e d a y l i g h t i l l u m i n a n c e a t t h e i r w o r k s t a t i o n s 1 5 . 1 97 <3AP5 IN ROWS' O F C E L L U L A R O F F I C E S A L L O W S D A Y L I G H T T O ' 5 P I L L 1 T O A R E A S B E V O N D F i g u r e 67 - Layout of c e l l u l a r o f f i c e s a t b u i l d i n g p e r i m e t e r t o e n a b l e some d a y l i g h t p e n e t r a t i o n There are f u n c t i o n a l l y and t e c h n i c a l l y w o r k a b l e a l t e r n a t i v e s t o c e l l u l a r o f f i c e s . The " l a n d s c a p e d o f f i c e " c oncept i s one a l t e r n a t i v e , but t h e r e a r e o t h e r f e a s i b l e c o n c e p t s , such as the f l e x i b l e , s e m i - p r i v a t e o f f i c e c o m p a r t m e n t a t i o n , based on work group u n i t s , proposed by A l e x a n d e r e t a l . 1 6 2 . 4 D e t a i l i n g Of C e l l u l a r O f f i c e s F u l l h e i g h t , opaque p a r t i t i o n s , e n c l o s i n g c e l l u l a r o f f i c e s a t the p e r i m e t e r of a deep o f f i c e space, b l o c k a l l a c c e s s t o view and d a y l i g h t f o r the open p l a n a r e a s beyond. A l t e r n a t e d e t a i l i n g of th e s e p a r t i t i o n s w i l l e n a b le d a y l i g h t p e n e t r a t i o n : 198 F i g u r e . 68 - D e t a i l i n g of g l a z e d p a r t i t i o n s f o r c e l l u l a r o f f i c e s a t b u i l d i n g p e r i m e t e r i . Use f u l l y g l a z e d p a r t i t i o n s . P a t t e r n e d g l a s s or c l e a r g l a s s w i t h c u r t a i n s may be used below door head h e i g h t ; above t h i s h e i g h t c l e a r g l a s s may be used (see f o r example the C o n n e c t i c u t G e n e r a l L i f e I n s u r a n c e Company b u i l d i n g , i n B l o o m f i e l d , C o n n e c t i c u t , by SOM A r c h i t e c t s 1 7 ) . A l t e r n a t e l y , c l e a r g l a s s may be used i n some c a s e s w i t h o u t a c u r t a i n . An e l e g a n t l y d e t a i l e d example i s shown i n f i g u r e 68 , which i s a r e c e n t l y (1983) c o m p l e t e d b u i l d i n g f o r the same c l i e n t s as the p r e v i o u s l y mentioned b u i l d i n g 199 (re-named CIGNA Corp. , A r c h i t e c t s C o l l a b o r a t i v e A r c h i t e c t s 1 8 ) . The owners were p l e a s e d w i t h the s p a c i o u s n e s s of the e a r l i e r b u i l d i n g and r e q u e s t e d t o have the d a y l i g h t i n g concept r e t a i n e d - - o r i m p r o v e d - - i n t h e i r newer b u i l d i n g 1 9 . A t t e n t i o n t o d e t a i l i n g and c l o s e c o - o r d i n a t i o n between a r c h i t e c t , l i g h t i n g c o n s u l t a n t and a c o u s t i c a l c o n s u l t a n t e s p e c i a l l y are n e c e s s a r y f o r t h i s type of work t o s u c c e e d 2 0 . i i . Use p a r t i t i o n s w i t h opaque lower p o r t i o n and g l a z e d upper p o r t i o n t o a l l o w r e f l e c t e d l i g h t t o s p i l l i n t o the i n t e r i o r zones, beyond the c e l l u l a r o f f i c e s a t the p e r i m e t e r , and thus p r o v i d e ambient d a y l i g h t i n g 2 1 , 2 2 . B e s i d e s t h e i r f u n c t i o n i n " b o r r o w i n g " l i g h t - - b o t h e l e c t r i c and d a y l i g h t - -t h e r e i s an i n c r e a s e i n the sense of s p a c i o u s n e s s 2 3 . In o f f i c e s , t h i s g l a z e d p o r t i o n i s u s u a l l y above the door head h e i g h t . Examples of t h i s type of p a r t i t i o n s a r e commonplace 2 1 1. W h i l e the q u a n t i t y and q u a l i t y of d a y l i g h t on the i n t e r i o r i s i n f e r i o r w i t h t h i s l e s s e r amount of g l a z i n g , the a c o u s t i c a l performance of the p a r t i t i o n ( i n both a b s o r b t i o n and t r a n s m i s s i o n ) i s improved and f l e x i b i l i t y i n l o c a t i o n of f u r n i t u r e and f i l i n g / s t o r a g e i s g r e a t e r . i i i . Even w i t h f u l l y opaque p a r t i t i o n s f o r p e r i m e t e r c e l l u l a r o f f i c e s , i t may be p o s s i b l e t o b r i n g i n d a y l i g h t t o i n t e r i o r s beyond. T h i s may be done by b r i n g i n g d a y l i g h t t hrough l i g h t w e l l s , s k y l i g h t s or t h r o u g h the c e i l i n g , 2 0 0 where plenum l i g h t i n g i s used, as i n f i g u r e 69 . F i g u r e 69 - A t e c h n i q u e f o r i n d i r e c t l y d a y l i g h t i n g i n t e r i o r a r e a s o b s t r u c t e d from d a y l i g h t i n g a p e r t u r e s by s o l i d p a r t i t i o n s 2 . 5 D a y l i g h t i n g And A c o u s t i c s Both a c o u s t i c a l and d a y l i g h t i n g s o l u t i o n s i n v o l v e c h o i c e s r e g a r d i n g i n t e r i o r b u i l d i n g s u r f a c e s , i n t e r i o r geometry and c o m p a r t m e n t a t i o n . As s u c h , s o l u t i o n s t o one can i n f l u e n c e t h e e f f e c t i v e n e s s of the o t h e r . T h i s s e c t i o n o u t l i n e s how d a y l i g h t i n g d e t a i l s may a f f e c t a c o u s t i c s and v i c e v e r s a and f i g u r e 7 0 p r o v i d e s a summary of t y p i c a l d e t a i l s which i n t e g r a t e r e q u i r e m e n t s of a c o u s t i c s and d a y l i g h t i n g . D a y l i g h t i n g s o l u t i o n s a f f e c t i n g a c o u s t i c s The r e q u i r e m e n t f o r r e l a t i v e l y l a r g e e x t e r i o r g l a z i n g a r e a s , f o r e i t h e r d a y l i g h t i n g or v i e w , can a d v e r s e l y a f f e c t 201 F i g u r e 70 - D e t a i l s t h a t i n t e g r a t e a c o u s t i c a l and d a y l i g h t i n g r e q u i r e m e n t s a c o u s t i c a l performance of o f f i c e i n t e r i o r s . The g l a s s a c t s as a s o u n d - r e f l e c t i n g s u r f a c e , which i s u n d e s i r a b l e i n open p l a n o f f i c e s . T h i s may be r e s o l v e d by t i l t i n g the g l a z i n g t o d e f l e c t sound onto e i t h e r the f l o o r or the c e i l i n g 2 5 " , or by the use of l i g h t - c o l o u r e d , v e r t i c a l sound-absorbent b a f f l e s , a t r i g h t a n g l e s t o the windows, t o absorb some of the sound b e f o r e i t s t r i k e s the g l a s s 2 6 . A f o r t u i t o u s e f f e c t of both these s o l u t i o n s i s a r e d u c t i o n i n p e r c e i v e d g l a r e from the window. Another a c o u s t i c a l problem may a r i s e when f u l l y g l a z e d p a r t i t i o n s a r e used t o enable d a y l i g h t t o p e n e t r a t e beyond compartmented a r e a s a t the b u i l d i n g p e r i m e t e r . To reduce unwanted sound r e f l e c t a n c e , s e m i - g l a z e d p a r t i t i o n s , or a c o m b i n a t i o n of f u l l y g l a z e d and s e m i - g l a z e d , a c o u s t i c a l l y 202 a b s o r b e n t p a r t i t i o n s 2 7 , may be used i n s t e a d . D a y l i g h t i n g s o l u t i o n s may a l s o a f f e c t a c o u s t i c s a d v a n t a g e o u s l y . Pendant type c e i l i n g l a m p s 2 8 , i n d i r e c t l i g h t i n g , and f u r n i t u r e mounted t a s k l i g h t i n g , l e a v e the c e i l i n g f r e e of l u m i n a i r e s , thus e l i m i n a t i n g the s o u n d - r e f l e c t i v e s u r f a c e s c r e a t e d by the l e n s e s of r e c e s s e d f l u o r e s c e n t f i x t u r e s , and i m p r o v i n g a c o u s t i c s i n open p l a n o f f i c e s . The s t e p p e d 2 9 or s l o p e d c e i l i n g s 3 0 i n some d a y l i t b u i l d i n g s a r e a l s o advantageous t o a c o u s t i c s , as they reduce m u l t i p l e r e f l e c t i o n s of sound between the f l o o r and c e i l i n g . A c o u s t i c a l s o l u t i o n s a f f e c t i n g d a y l i g h t i n g A d e t a i l which may a d v e r s e l y a f f e c t d a y l i g h t i n g i s the use of a g r i d of v e r t i c a l , . s o u n d - a b s o r b e n t b a f f l e s , hung from the c e i l i n g , t o i n c r e a s e sound a b s o r p t i o n i n open p l a n o f f i c e s . One s o l u t i o n which may not compromise d a y l i g h t i n g i n v o l v e s the use of b a f f l e s h a v i n g h i g h l i g h t r e f l e c t a n c e , a r r a n g e d o n l y i n one d i r e c t i o n , p e r p e n d i c u l a r t o the e x t e r i o r w a l l . Some a c o u s t i c a l d e t a i l s may enhance d a y l i g h t i n g . S o f t , porous c e i l i n g s u r f a c e s , f o r example, are i d e a l f o r a c o u s t i c a l a b s o r p t i o n and these same s u r f a c e s , i f of h i g h l i g h t r e f l e c t a n c e , a r e h e l p f u l i n r e d u c i n g g l a r e 3 1 . 203 3. NOTES 1. H. Max Leu, "Energy C o n s e r v a t i o n i n O f f i c e B u i l d i n g s , " M a s t e r ' s T h e s i s a t U n i v e r s i t y of B r i t i s h C olumbia, 1980, p. 118 . 2 . James W. G r i f f i t h , " B e n e f i t s of D a y l i g h t i n g : Energy and Cost S a v i n g s , " ASHRAE J o u r n a l 2 0 , J a n u a r y 1978, p. 55. 3. E r n e s t Wotton, "Some C o n s i d e r a t i o n s A f f e c t i n g the I n c l u s i o n of Windows i n O f f i c e Facades," L i g h t i n g Design  and A p p l i c a t i o n s , F e b r u a r y 1976, p. 34. 4. J . A. Lynes, P r i n c i p l e s of N a t u r a l L i g h t i n g (Amsterdam: E l s e v i e r , 1968), p. 48-50. 5. E r i c Thrun and Robert J e n n i n g s , " L e v e l s of Performance R e l a t e d I l l u m i n a t i o n A v a i l a b l e from D a y l i g h t i n T y p i c a l O f f i c e S c hool I n t e r i o r s , " J o u r n a l of IES, October 1 9 8 1 , p. 14. 6 . Leu, pp. 119 - 2 0 . 7. Wotton, p. 33. 8 . D a v i d A. H a r r i s e t a l . , P l a n n i n g and D e s i g i n q the O f f i c e  Environment ( T o r o n t o : Van N o s t r a n d R e i n h o l d , 1981). 9 . Benjamin H. Evans, D a y l i g h t i n A r c h i t e c t u r e (New York: M c G r a w - H i l l , 1981), p. 40. 10. H a r r i s et a l . , p. x i . 1 1 . Frank D e S e r i o , i n A r c h i t e c t u r a l R e c o r d , "Round T a b l e : A R e a l i s t i c Look a t The P a s s i v e Approach--Using N a t u r a l Means t o Conserve Energy," A r c h i t e c t u r a l Record, M i d -August 1983, p. 98. 1 2 . M a n u f a c t u r e r s ' Hanover T r u s t World H e a d q u a r t e r s (SOM), a f t e r S. D a r y a n a n i , "Design C o n s i d e r a t i o n s f o r the D a y l i g h t i n g of New Commercial B u i l d i n g s , " Energy and  B u i l d i n g s , 6(1984): 1 1 5, f i g u r e 1 0 . 13. D e S e r i o , p. 98. 14. Frank D u f f y et a l . , e d i t o r s , P l a n n i n g O f f i c e Space ( London: A r c h i t e c t u r a l P r e s s , 1 9 7 6 7 ^ p~. 43. 15. I b i d . 204 16. C h r i s t o p h e r A l e x a n d e r et a l . , A P a t t e r n Language (New York: O x f o r d , 1977), p a t t e r n no. 146, " f l e x i b l e O f f i c e Space", pp. 690-95. 17. Juergen J o e d i c k e , O f f i c e B u i l d i n g s (New York: P r a e g e r , 1962) , p. 21. 18. A r c h i t e c t u r a l Record, " P a r t i t i o n s and L i g h t s Work as a Modular P a i r to C r e a t e Luminous Space," A r c h i t e c t u r a l  R e c o r d , A p r i l 1983, pp. 160-67. 19. I b i d . , p. 160. 20. I b i d . 21. M a r i e t t a S. M i l l e t , " D a y l i g h t i n g Design G u i d e l i n e s f o r P a c i f i c Northwest B u i l d i n g s , " P r o c e e d i n g s of ' S o l a r 79  Northwest' C o n f e r e n c e , August 10-12, 1979 i n S e a t t l e . S e a t t l e : P a c i f i c Northwest S o l a r Energy A s s o c i a t i o n , 1979, p. 53. 22. J . Longmore, "The E n g i n e e r i n g of D a y l i g h t , " i n Developments i n L i g h t i n q - - P a r t J_, e d i t e d by J . A. Lynes (London: A p p l i e d S c i e n c e , 1978) , p. 178. 23. A l e x a n d e r et a l . , p a t t e r n no. 194, " I n t e r i o r Windows", pp. 897-99. 24. See f o r example, M a c M i l l a n B l o e d e l b u i l d i n g , i n Vancouver, B. C. and the CIGNA b u i l d i n g ( s u p r a ) . 25. D e S e r i o , p. 98. 26. H a r r i s e t a l . , p. 57. A c t u a l l y , these b a f f l e s would have t o be l a r g e r , or c l o s e l y spaced, t o be e f f e c t i v e a c o u s t i c a l l y - - p e r s o n a l communication, P r o f e s s o r C h a r l e s T i e r s , UBC School of A r c h i t e c t u r e . 27. As f o r example, i n the CIGNA b u i l d i n g , A r c h i t e c t u r a l R e c o r d , s u p r a , pp. 160-67. 28. As i n the Water Resources C o n t r o l Board b u i l d i n g ( S i t e 1-C ) , Sacramento, C a l i f . Harvey Bryan, s l i d e p r e s e n t a t i o n a t the D a y l i g h t i n g Design T o o l s Workshop, The 1983 I n t e r n a t i o n a l D a y l i g h t i n g C o n f e r e n c e , 16-18 F e b r u a r y 1983 i n P h o e n i x , A r i z o n a . 29. As f o r example, i n the Water Resources C o n t r o l Board b u i l d i n g , Sacramento, C a l i f . See Bryan, s u p r a . 30. As f o r example, i n the V e n t u r a C o a s t a l C o r p o r a t i o n b u i l d i n g , V e n t u r a , C a l i f . See A r c h i t e c t u r e , " I n g e n i o u s l y D a y l i t S e a s i d e O f f i c e s , " A r c h i t e c t u r e , January 1984, 205 pp. 64-67. 31. DeSerio, p. 98. 206 VI . CONTROL OF BRIGHTNESS EXTREMES 207 1. INTRODUCTION The c o n t r o l of b r i g h t n e s s extremes i n a b u i l d i n g i n t e r i o r may be a c c o m p l i s h e d by two means: i . i n c r e a s i n g the b r i g h t n e s s l e v e l of s u r f a c e s away from d a y l i g h t i n g a p e r t u r e s i i . d e c r e a se the p e r c e i v e d b r i g h t n e s s of the d a y l i g h t i n g a p e r t u r e . The methods used t o a c c o m p l i s h t h e s e a r e d i f f e r e n t f o r t r a d i t i o n a l d a y l i g h t i n g t e c h n i q u e s and f o r i n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s . i . In t r a d i t i o n a l t e c h n i q u e s , the two b r i g h t n e s s c o n t r o l s t r a t e g i e s — i n c r e a s i n g b r i g h t n e s s of s u r f a c e s away from the d a y l i g h t i n g a p e r t u r e s and d e c r e a s i n g p e r c e i v e d b r i g h t n e s s of d a y l i g h t i n g a p e r t u r e s — a r e c o n c e i v e d i n i s o l a t i o n , and a r e d e s i g n e d t o a c h i e v e e i t h e r the one g o a l , or the o t h e r . Because of t h i s , a r e d u c t i o n i n g l a r e a t the d a y l i g h t i n g a p e r t u r e , a c h i e v e d w i t h t r a d i t i o n a l t e c h n i q u e s , always e n t a i l s a p r o p o r t i o n a t e r e d u c t i o n i n d a y l i g h t p e n e t r a t i o n . i i . By c o n t r a s t , i n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s may a c c o m p l i s h s i m u l t a n e o u s l y s e v e r a l g o a l s : i n c r e a s i n g d a y l i g h t p e n e t r a t i o n , r e d u c i n g p e r c e i v e d b r i g h t n e s s of the d a y l i g h t i n g a p e r t u r e , i n c r e a s i n g the b r i g h t n e s s of s u r f a c e s 208 remote from d a y l i g h t i n g a p e r t u r e s . F i g u r e 71 i l l u s t r a t e s examples of t h e s e two approaches. F i g u r e 71 - Reducing b r i g h t n e s s extremes u s i n g t r a d i t i o n a l and i n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s F i g u r e 71 a. shows a t r a d i t i o n a l response t o c o n t r o l of b r i g h t n e s s extremes. The s u n / g l a r e c o n t r o l d e v i c e reduces the p e r c e i v e d b r i g h t n e s s of the d a y l i g h t i n g aperture_^_-but i n e v i t a b l y a l s o reduces d a y l i g h t p e n e t r a t i o n t o some e x t e n t , the amount depending on t h e c o n f i g u r a t i o n of the s h a d i n g d e v i c e . H i g h r e f l e c t a n c e v a l u e s f o r i n t e r i o r s u r f a c e s tends somewhat t o o f f s e t t h i s l o s s by i n c r e a s i n g the IRC. D e s i g n t r a d e - o f f s a r e i n v o l v e d between the s e competing r e q u i r e m e n t s . The i n n o v a t i v e -d a y l i g h t i n g t e c h n i q u e i n f i g u r e 71 b. shows: the p e r c e i v e d b r i g h t n e s s of the d a y l i g h t i n g a p e r t u r e i s reduced by t i l t i n g of the g l a s s t o reduce the t r a n s m i t t a n c e of l i g h t from h i g h e r a n g l e s ; r e f l e c t i v e s u r f a c e s away from view a r e used t o bounce 209 S C A L E SITE PLANNING WILMN6 CONFI6URATI0* BUILDING, COMPONENT BUILDING INTERIOR r LANDSCAPING FOR. GLARE CONTROL - I t DAYLIGHTING FROM MORE THAN ONE DIRECTION GLARE/SOLAR HEAT CONTROL - E & W INTERIOR L16HT SHELVES GLARE/50LAR HEAT CONTROL - SOUTH GLARE CONTROL - NORTH GLAZING TILT CONTRAST GRADING LIGHT COLOURED SURFACES F i g u r e 72 - Summary of t e c h n i q u e s f o r b r i g h t n e s s extremes c o n t r o l l i n g 210 s u n / s k y - l i g h t deeper i n t o the i n t e r i o r , t h e r e b y e n a b l i n g a s m a l l e r d a y l i g h t i n g a p e r t u r e f o r a g i v e n d a y l i g h t p e n e t r a t i o n ; the use of h i g h r e f l e c t a n c e c e i l i n g t o i n c r e a s e luminance of s u r f a c e s away from the d a y l i g h t i n g a p e r t u r e . The same c h a r a c t e r i s t i c s of i n n o v a t i v e d a y l i g h t i n g t e c h n i q u e s t h a t enable them t o d i s t r i b u t e , r a t h e r than r e j e c t , e x c e s s s u n / d a y l i g h t , a l s o p r o v i d e the means of c o n t r o l l i n g b r i g h t n e s s extremes. 2. TECHNIQUES FOR BRIGHTNESS CONTROL F i g u r e 72 g i v e s a summary of the t e c h n i q u e s examined i n t h i s c h a p t e r . 2.1 L a n d s c a p i n g For G l a r e C o n t r o l L a n d s c a p i n g — p l a n t i n g i n p a r t i c u l a r - - m a y be d e s i g n e d w i t h a view t o i t s a r c h i t e c t u r a l and e n g i n e e r i n g u s e s 1 ; s a v i n g energy i n b u i l d i n g s 2 , 3 ; p r o v i d i n g a g e n e r a l l y more c o m f o r t a b l e t h e r m a l environment"; and w i t h the aim of promoting d a y l i g h t p e n e t r a t i o n and c o n t r o l of g l a r e 5 . However, beyond the s t r i c t l y f u n c t i o n a l , the use of p l a n t s i n and around our b u i l d i n g s s a t i s f i e s s y m b o l i c , a e s t h e t i c and e m o t i o n a l n e e d s 6 , 7 . T h i s means t h a t , more than any o t h e r a s p e c t i n the b u i l t environment, the use of p l a n t s cannot be c o n s i d e r e d s o l e l y from a n a r r o w l y f u n c t i o n a l v i e w p o i n t : the l e s s t a n g i b l e b e n e f i t s must a l s o be c o n s i d e r e d . P a r t of the purpose of a d a y l i t b u i l d i n g i s t o e s t a b l i s h a s e n s i t i v e r e l a t i o n s h i p between i t s e l f and i t s s u r r o u n d i n g s . 2 1 1 P l a n t s , when used as elements of the d a y l i g h t i n g scheme, n a t u r a l l y tend to strengthen that r e l a t i o n s h i p , as w e l l as the awareness of that r e l a t i o n s h i p . The c o n t r o l of g l a r e from d a y l i g h t and s u n l i g h t by the use of land forms, s t r u c t u r e s , or v e g e t a t i o n may be accomplished e i t h e r by f i l t e r i n g or by reducing r e f l e c t i o n . G l a r e c o n t r o l by f i l t e r i n g WINTER SUMMErS F i g u r e 73 - Gl a r e r e d u c t i o n by f i l t e r i n g d u r i n g summer and winter Trees may be used i n l o w - r i s e o f f i c e b u i l d i n g s , or on the lower f l o o r s of h i g h - r i s e b u i l d i n g s , to c o n t r o l g l a r e by f i l t e r i n g of s u n / d a y l i g h t . A problem a r i s e s with deciduous t r e e s t h a t , i f they f i l t e r s u f f i c i e n t amount of l i g h t i n the summer, then they w i l l a llow too much g l a r e i n the winter, when they are l e a f l e s s . One s o l u t i o n i s shown i n f i g u r e 73 : the 212 l o w e r , w i n t e r sun i s b l o c k e d by low c o n i f e r s and the h i g h e r , summer sun by h i g h e r d e c i d u o u s t r e e s . The use of t r e e s and shrubs on the wes t / e a s t s i d e s f o r heat and g l a r e c o n t r o l i s e s p e c i a l l y advantageous because the low angl e sun can be b l o c k e d r e l a t i v e l y e a s i l y by younger, or lower mature t r e e s and by t r e e s a t v a r y i n g d i s t a n c e s from a b u i l d i n g . By c o n t r a s t , f i l t e r i n g of s u n l i g h t on south f a c a d e s cannot be a c c o m p l i s h e d beyond the second or t h i r d f l o o r , u n l e s s mature t r e e s a r e a l r e a d y p r e s e n t on the s i t e or o t h e r g l a r e c o n t r o l d e v i c e s a re used f o r many y e a r s u n t i l newly p l a n t e d t r e e s mature. On the n o r t h s i d e , the ta s k i s t h a t of r e d u c i n g sky g l a r e and, s i n c e t h e r e i s l i t t l e p roblem w i t h sun s h a d i n g , the r e q u i r e m e n t s a re not as s t r i n g e n t as on the s o u t h s i d e . T r e l l i s e s of c l i m b i n g p l a n t s a r e a p p r o p r i a t e f o r west w a l l s , where they can be q u i t e dense. One such s o l u t i o n i s shown i n f i g u r e 74 . On the so u t h s i d e t r e l l i s e s must be h o r i z o n t a l i n or d e r t o keep the sun o u t ; and t h e r e f o r e , both the t r e l l i s s t r u c t u r e and the t r i m m i n g of the p l a n t s may r e q u i r e a d d i t i o n a l maintenance on t h i s f a c a d e . P l a n t s c l i m b i n g d i r e c t l y on b u i l d i n g f a c e s c r e a t e a s o f t e n e d , " o l d c o u n t r y " a p p e a l 8 , but i n o f f i c e b u i l d i n g s — e s p e c i a l l y d a y l i t ones, r e q u i r i n g c o n s t a n t view and u n o b s t r u c t e d windows--they may p r e s e n t maintenance problems. As m a t e r i a l f o r g l a r e c o n t r o l , p l a n t s of open, l o o s e f o l i a g e a r e most u s e f u l ; t hey f i l t e r the l i g h t , whereas denser p l a n t s o b s t r u c t i t 9 . T a b l e X I I I 1 0 i n d i c a t e s l i g h t i n t e n s i t i e s found under mature s t a n d s of v a r i o u s t r e e s . 213 F i g u r e 74 - G l a r e c o n t r o l a t west or e a s t w a l l s w i t h t r e l l i s e s TYPE OF TREE (OLD STAND) NO FOLIAGE FOLIAGE DECIDUOUS RED BEECH 2 3 - 2. - 40 OAK 43 • • 69 3 -• 35 A5H 33 -- $>0 S --GO BIRCH 20 - 30 EVERGREEN SILVER FIR Z- • ZO SPRUCE A- • 40 PIKJE zz- - 4 0 T a b l e X I I I - L i g h t i n t e n s i t i e s (% of t h a t o u t s i d e ) under mature s t a n d s of v a r i o u s t r e e s G l a r e c o n t r o l by r e f l e c t i o n As i s the case w i t h o t h e r l i g h t s o u r c e s , the ground as a secondary l i g h t source may r e q u i r e b r i g h t n e s s c o n t r o l 1 1 . P o t e n t i a l g l a r e problems may be reduced by s t u d y i n g t h e a n g u l a r 214 r e l a t i o n s h i p between the occupant, the window and the- r e f l e c t i v e s u r f a c e s ( s p e c u l a r and n o n - s p e c u l a r ) , and i n l o c a t i n g t h e s e s u r f a c e s out of d i r e c t l i n e of s i g h t as much as p o s s i b l e . I \i^ -^ ^^ %<TC V ( J JlllllllllllllllllllM F i g u r e 75 - Optimum p o s i t i o n i n g of p l a n t i n g and of the e x t e r i o r r e f l e c t i n g s u r f a c e F i g u r e 75 shows t h a t g e n e r a l l y , f o r l o c a t i o n s a t or near the ground f l o o r , r e f l e c t i v e s o u r c e s c l o s e r t o the f e n e s t r a t i o n ( i . e . seen from w o r k s t a t i o n s a t a s t e e p e r a n g l e below the h o r i z o n t a l ) a re l e s s l i k e l y t o cause g l a r e than s o u r c e s f a r away. There i s a range of a n g l e s from the h o r i z o n t a l (between 15° and 45°) t h a t causes l e a s t g l a r e and s t i l l a s s i s t s w i t h d a y l i g h t p e n e t r a t i o n . The use of s p e c u l a r l y r e f l e c t i v e s u r f a c e s must be s t u d i e d c a r e f u l l y s i n c e t h e s e may cause g l a r e and/or s o l a r heat g a i n a t c e r t a i n sun a n g l e s 1 2 . S u r f a c e s which ar e n o n - s p e c u l a r r e f l e c t o r s a r e p r e f e r r a b l e , s i n c e they make luminous and t h e r m a l c o n t r o l e a s i e r . I t can a l s o be seen i n f i g u r e 75 t h a t i t i s b e t t e r , from the p o i n t of view of summer 215 heat g a i n , t o l o c a t e a s p h a l t d r i v e w a y s , or c o n c r e t e s u r f a c e s some d i s t a n c e away from the b u i l d i n g . I n s t e a d , low growing p l a n t s and shrubs s h o u l d be used immediately a d j a c e n t t o i t , s i n c e they do not heat up as h i g h d e n s i t y , man-made m a t e r i a l s do. The r e d u c t i o n , of g r o u n d - r e f l e c t e d g l a r e can a l s o be a c c o m p l i s h e d by t r e e s . To t h i s end, dark p l a n t s w i t h a s m a l l e r l e a f s u r f a c e , a re most e f f e c t i v e i n r e d u c i n g r e f l e c t i o n 1 3 . 2.2 D a y l i g h t From More Than One D i r e c t i o n O N E S I D E D A Y L I T TWO S I D E S D A V U T P L A N V I E W O F bmx6n RCoW F i g u r e 76 - D a y l i g h t i n g a p e r t u r e s on more than one s i d e reduces b r i g h t n e s s g r a d i e n t s The p r o v i s i o n of d a y l i g h t i n g a p e r t u r e s on more than one s i d e of a space reduces b r i g h t n e s s extremes, improves m o d e l l i n g and r a i s e s i l l u m i n a n c e . Whenever the c o n f i g u r a t i o n of t h e b u i l d i n g a l l o w s , i t i s t h e r e f o r e advantageous t o p r o v i d e 216 d a y l i g h t from more than one d i r e c t i o n . In p r a c t i c e , however, u n i l a t e r a l l i g h t i n g w i l l p r e v a i l f o r o f f i c e b u i l d i n g s due t o economic and o r g a n i z a t i o n a l f o r c e s t h a t r e q u i r e deep o f f i c e space. In the l a t t e r type of s p a c e s , any t e c h n i q u e s used t o i n c r e a s e i l l u m i n a n c e l e v e l s by secondary d a y l i g h t i n g a p e r t u r e s (such as a t r i a , l i g h t w e l l s , s k y l i g h t s , e t c . ) w i l l s e r v e t o b a l a n c e the i n t e r i o r b r i g h t n e s s . Even r e l a t i v e l y s m a l l d a y l i g h t a p e r t u r e s i n w a l l s a d j a c e n t t o the main source of d a y l i g h t can p r o v i d e a s o f t e n i n g of the h a r s h m o d e l l i n g of u n i d i r e c t i o n a l l i g h t 1 " , and by r e f l e c t i n g l i g h t back onto the i n t e r i o r s u r f a c e of the window w a l l , can l e s s e n the c o n t r a s t between the window and i t s s u r r o u n d s 1 5 . Windows from two o p p o s i t e s i d e s w i l l a l s o reduce g l a r e , but the l i g h t i n g q u a l i t y i s somewhat poorer because of c r o s s s h a d i n g 1 6 ( f i g u r e 76 ). 2.3 G l a r e And S o l a r Heat C o n t r o l -- East And West There a r e t h r e e d e s i g n responses t o the c o n f l i c t between sun-shading and d a y l i g h t i n g on the e a s t and west o r i e n t a t i o n s : i . a r e d u c t i o n i n the s i z e of windows, or t h e i r t o t a l e l i m i n a t i o n on th e s e e l e v a t i o n s i i . the i n c o r p o r a t i o n , i n p l a n , of z i g - z a g e a s t and west e x t e r i o r w a l l s , w i t h the openings i n these f a c i n g s o u t h and/or n o r t h i i i . p r o v i s i o n of s h a d i n g and g l a r e c o n t r o l d e v i c e s f o r e a s t and west f a c i n g d a y l i g h t i n g a p e r t u r e s 217 In s i t u a t i o n s i n which c o n s i d e r a t i o n s o t h e r than d a y l i g h t i n g r e q u i r e windows f a c i n g e a s t or west, the f o l l o w i n g r e sponses f o r g l a r e / s h a d i n g c o n t r o l a r e a p p r o p r i a t e f o r d a y l i t b u i l d i n g s : i . Use r e f l e c t i v e or heat a b s o r b i n g g l a s s i n s p e c i f i c l o c a t i o n s to reduce g l a r e and s o l a r heat g a i n w i t h o u t u ndermining d a y l i g h t i n g . The p r e v a l e n t way of u s i n g these g l a s s e s u n i f o r m l y i n a l l windows of a b u i l d i n g , i m p a i r s d a y l i g h t p e n e t r a t i o n s i n c e t h e s e g l a z i n g s s u b s t a n t i a l l y reduce the amount of l i g h t t r a n s m i t t e d t o the i n t e r i o r f o r a g i v e n window a r e a 1 7 . R e f l e c t i v e or heat a b s o r b i n g g l a s s may, however, be u t i l i z e d w i t h o u t p e n a l t y i n terms of d a y l i g h t i n g i n two i n s t a n c e s . F i r s t , i n d e s i g n s which u t i l i z e s e p a r a t e a p e r t u r e s f o r d a y l i g h t i n g and view, the view window can have t i n t e d g l a s s f o r g l a r e and s o l a r heat c o n t r o l . Many d a y l i t b u i l d i n g s employ t h i s s o l u t i o n 1 8 . A second type of g l a r e / s h a d i n g c o n t r o l u t i l i z e s heat a b s o r b i n g g l a s s as a sun shade, as shown i n f i g u r e 77 . The heat a b s o r b i n g g l a s s i s h e l d i n a frame above and i n f r o n t of c l e a r g l a s s windows, a l l o w i n g a f r e e c i r c u l a t i o n of a i r between i t and the window, d i s s i p a t i n g the heat g a i n . Depending on the r e l a t i v e l o c a t i o n of the shade w i t h r e s p e c t t o the window, t h i s concept may be used on the e a s t / w e s t or s o u t h e a s t / s o u t h w e s t f a c a d e s . In f i g u r e 77 ( l e f t ) 1 9 , t h i s a c c e s s o r y i s used t o g e t h e r w i t h s l a t t e d h o r i z o n t a l , opaque s h a d i n g s l a t s (a c o n f i g u r a t i o n t h a t w i l l s e r v e s o u t h , 218 HOCUOklTAL F i g u r e 77 - Heat a b s o r b i n g g l a s s as a sunshade s o u t h e a s t and southwest o r i e n t a t i o n s ) . F i g u r e 77 ( r i g h t ) 2 0 shows a shade d e s i g n e d f o r e a s t and west o r i e n t a t i o n s . Here, the g l a s s shade i s u t i l i z e d a l o n e , w i t h o u t the s l a t s , i i . Use opaque, f i x e d , v e r t i c a l p r o j e c t i o n s s u i t a b l y p r o p o r t i o n e d t o s c r e e n t h e sun out a t the low a n g l e s e n c o u n t e r e d on e a s t and west f a c a d e s . A c c o r d i n g t o W a l s h 2 1 and M i l l e t et a l . 2 2 , d i f f e r e n t c o n f i g u r a t i o n s of s h a d i n g d e v i c e s h a v i n g the same t h e r m a l performance ( i . e . d e r i v e d from the same s h a d i n g m a s k 2 3 , and t h e r e f o r e e q u a l l y e f f e c t i v e i n b l o c k i n g out t h e s u n ) , do not n e c e s s a r i l y have the same luminous e f f i c a c y . M i l l e t e t a l . have s t u d i e d the luminous e f f e c t i v e n e s s of the v e r t i c a l sun c o n t r o l 219 d e v i c e s shown i n f i g u r e 78 2" . A l l f o u r d e v i c e s shown a r e of e q u i v a l e n t t h e r m a l e f f e c t i v e n e s s . F i g u r e 78 shows the r e s u l t s of e x p e r i m e n t s on both sunny and o v e r c a s t " ^ days. Under both c o n d i t i o n s , the m u l t i p l e s o l i d v e r t i c a l l o u v r e s o f f e r e d the h i g h e s t luminous performance. For i s o l a t e d windows on the e a s t or west f a c a d e s , as shown i n f i g u r e 79 2 5 , a r e t u r n w a l l some d i s t a n c e from the window can p r o v i d e s c r e e n i n g from unwanted s u n l i g h t , w i t h o u t s e r i o u s l y a f f e c t i n g d a y l i g h t i n g . i i i . V e r t i c a l , o p e r a b l e l o u v r e s a v o i d some of the drawbacks of f i x e d sun c o n t r o l d e v i c e s , s i n c e t h e i r o r i e n t a t i o n may be a d j u s t e d t o maximize s o l a r s h a d i n g at some hours of the day, w h i l e a t o t h e r times they may be s e t t o maximize d a y l i g h t i n g . F i g u r e 80 2 6 shows.such an i n s t a l l a t i o n . L i k e a l l s h a d i n g d e v i c e s , o p e r a b l e l o u v r e s a re most e f f e c t i v e t h e r m a l l y when they a r e l o c a t e d on the b u i l d i n g e x t e r i o r . However, i n t e r i o r v e r t i c a l b l i n d s may a l s o be used: they a re l e s s e f f e c t i v e i n b l o c k i n g s o l a r h e a t , but serv e w e l l i n r e d u c i n g g l a r e from sun and sky. They r e q u i r e l e s s m e c h a n i c a l maintenance, have much lower i n i t i a l c o s t and, s i n c e they a r e a v a i l a b l e i n a wide range of c o l o u r s and t e x t u r e s , they can a l s o c o n t r i b u t e t o the i n t e r i o r d e c o r a t i o n c o n c e p t . V e r t i c a l i n t e r i o r b l i n d s r e t r a c t as w e l l as p i v o t , t h u s p r o v i d i n g a c l e a r view. By c o n t r a d i s t i n c t i o n , e x t e r i o r l o u v r e s of the v e r t i c a l type can u s u a l l y o n l y p i v o t , w i t h o u t r e t r a c t i n g . A c o m b i n a t i o n of f i x e d a r c h i t e c t u r a l p r o j e c t i o n s f o r sun 220 9 \ \ \ Fig '-. window plan shoving v e r t i c l e sun control devices decomposed by "form" and " d e t a i l " SECTION 10 L0 osc .5, .1, .2, unobstructed wlndov no shading device; overcast sky SECTION PLAN 10 0 OSC F i g multiple s o l i d v e r t i c l e louvre; overcast sky SECTION PLAN 10 0 DBC A \ \ . 1i1: \ / / / ! -' / / : 50 Fig . so l i d v e r t i c l e louvre; direct beam 9 22° altitude 62 azimuth SECTION PLAN 10 0 DBC \\\\\ tr. Fig . slatted v e r t i c l e louvre; direct beam fi 22 altitude 62 azimuth SECTION Fig . multiple s o l i d v e r t i c l e louvre; e-direct beam t? 22 e altitude 62 azimuth F i g u r e 78 - Luminous performance of v a r i o u s v e r t i c a l s h a d i n g d e v i c e s h a v i n g e q u i v a l e n t t h e r m a l performance 221 F i g u r e 79 - R e t u r n w a l l s on e a s t or west f a c a d e s can p r o v i d e s u n s c r e e n i n g w h i l e a l l o w i n g d a y l i g h t i n s h a d i n g and i n t e r i o r v e r t i c a l h o r i z o n t a l - - f o r a d d i t i o n a l g l a r e e c o n o m i c a l l y a p p r o p r i a t e r e s p o n s e . b l i n d s - - v e r t i c a l or c o n t r o l may be an 222 i v . Where b u i l d i n g f a c a d e s o r i e n t towards s o u t h e a s t and southwest, n e i t h e r v e r t i c a l , nor h o r i z o n t a l s h a d i n g d e v i c e s a l o n e can p r o v i d e s u f f i c i e n t s o l a r s h a d i n g . E g g c r a t e type l o u v r e s (a c o m b i n a t i o n of v e r t i c a l and h o r i z o n t a l s hading elements) are a p p r o p r i a t e i n these c a s e s . Evans has g i v e n an example of t h i s s o l u t i o n , used i n a s p e c u l a t i v e h i g h r i s e o f f i c e b u i l d i n g i n Southwestern U.S.A. As shown i n f i g u r e 81 2 7 , e g g c r a t e - t y p e l o u v r e s between the g l a z i n g s c r e e n out d i r e c t sun, but r e f l e c t d a y l i g h t i n t o the space, s i m u l t a n e o u s l y b l o c k i n g the view of a b r i g h t sky. The l o w e r , view window, u t i l i z e s r e f l e c t i v e g l a z i n g t o reduce the b r i g h t n e s s of the e x t e r i o r . . v. H o r i z o n t a l b l i n d s or l o u v r e s may a l s o be used on e a s t and west f a c i n g windows. They can be m a n u a l l y — a n d p r e f e r a b l y a u t o m a t i c a l l y — c l o s e d t o b l o c k d i r e c t sun when t h i s can p e n e t r a t e i n t o the work space. The Hooker Chemical B u i l d i n g i n N i a g a r a F a l l s , N.Y., i s an example of t h i s r e s p o n s e : a l l f o u r e l e v a t i o n s have h o r i z o n t a l l o u v r e s t h a t a r e c o n t r o l l e d by s e n s o r s i n d e p e n d e n t l y on each f a c a d e 2 8 . W h i l e t h e s e l o u v r e s do not r e t r a c t , they do respond t o the d i f f e r e n t luminous and t h e r m a l c o n d i t i o n s a t each facade. V e n e t i a n - t y p e b l i n d s , t h a t r e t r a c t as w e l l as p i v o t , are o t h e r examples of h o r i z o n t a l g l a r e / s u n c o n t r o l d e v i c e s . These may be on the e x t e r i o r or i n t e r i o r and be e i t h e r of the manual or the a u t o m a t i c t y p e . The use of f a b r i c shades — the Gregory Bateson b u i l d i n g i n Sacramento, C a l i f o r n i a , i s an example of t h i s — i s a l s o an a p p r o p r i a t e 223 F i g u r e 81 - E g g c r a t e l o u v r e s b e i n g used on s o u t h e a s t f a c i n g windows response f o r v a r i o u s o r i e n t a t i o n s , i n c l u d i n g the e a s t and w e s t 2 9 . One advantage of a u t o m a t i c h o r i z o n t a l d e v i c e s i s t h e i r a b i l i t y t o c l o s e over the d a y l i g h t i n g a p e r t u r e , t h e r e b y r e d u c i n g heat l o s s when d a y l i g h t i s u n a v a i l a b l e . A d i s a d v a n t a g e i n t h e i r use on e a s t or west f a c i n g a p e r t u r e s i s t h a t , s i n c e they must cover most or a l l of the a p e r t u r e when the sun i s i n o f f e n d i n g p o s i t i o n , they w i l l r e s t r i c t , and i n some cases e l i m i n a t e , the a v a i l a b i l i t y of d a y l i g h t a t t h e s e t i m e s . 224 2.4 G l a r e And S o l a r Heat C o n t r o l — South S o l a r s h a d i n g of s o u t h f a c i n g d a y l i g h t i n g a p e r t u r e s i s a r e l a t i v e l y s i m p l e m a t t e r , when compared t o the i n t r i c a c i e s of s i m u l t a n e o u s s o l a r s h a d i n g and d a y l i g h t i n g on e a s t and west f a c i n g a p e r t u r e s . A l t h o u g h the c o n f i g u r a t i o n s f o r s h a d i n g / g l a r e c o n t r o l d e v i c e s on s o u t h f a c i n g a p e r t u r e s a r e d i f f e r e n t from those f a c i n g e a s t / w e s t , the c a t e g o r i e s of responses a r e the same as o u t l i n e d i n the p r e v i o u s s e c t i o n : i . Use heat a b s o r b i n g or r e f l e c t i v e g l a s s i n s p e c i f i c l o c a t i o n s t o reduce g l a r e and s o l a r heat g a i n w i t h o u t i m p a i r i n g d a y l i g h t i n g . These g l a s s e s a re o n l y a p p r o p r i a t e - - a s mentioned i n the p r e v i o u s section--when used i n windows which s e r v e o n l y f o r view ( i n d e s i g n s where d a y l i g h t i n g i s p r o v i d e d by o t h e r a p e r t u r e s ) and when they a r e used as sunshades i n f r o n t of d a y l i g h t i n g a p e r t u r e s . i i . Use opaque, f i x e d , h o r i z o n t a l p r o j e c t i o n s c o n f i g u r e d t o b l o c k unwanted s o l a r p e n e t r a t i o n t h r ough the d a y l i g h t i n g a p e r t u r e . As noted p r e v i o u s l y , s o l a r s h a d i n g d e v i c e s h a v i n g i d e n t i c a l t h e r m a l performance but d i f f e r e n t c o n f i g u r a t i o n , w i l l d i f f e r i n t h e i r luminous performance. M i l l e t et a l . 3 0 have s t u d i e d the e f f e c t of the h o r i z o n t a l sun c o n t r o l d e v i c e s shown i n f i g u r e 82 . The t h r e e d e v i c e s t e s t e d a r e of e q u i v a l e n t t h e r m a l e f f e c t i v e n e s s but of v e r y d i f f e r e n t luminous performance. The m u l t i p l e s o l i d v e r t i c a l l o u v r e s o f f e r e d the best luminous p e r f o r m a n c e 3 1 . W a l s h 3 2 a l s o s u g g e s t s t h i s " t i e r e d 225 www VS.N W\ NXV. Fig 3A. v a i l section shoving horizontal sun control devices decomposed by "torn" and " d e t a i l " SECTION r 10 0 OSC Fig 10. multiple s o l i d overhang; overcast sky SECTION 10 - 0 FLAN DBC ..2j.l t ' / Fig *. s o l i d overhang; direct beam $ 50° altitude 4° azimuth SECTION 10 -.0 DBC PLAN '•• ,_- r-,\ \ \ \ *\ \ \ \ \ X M \ \ \ \ V 2 1 .U.'3 .2 .1' J)J I'll/ I ]y J / i l ! / / / ; Fig 5. slatted overhang; direct beam g 50° altitude 4 azimuth SECTION l n J r L L n PLAN DBC \ \ W W W)j /// / A.l.i , ^ /' / i f / Fig 6. sol i d multiple overhang; direct beam t> 50 altitude 4 azimuth F i g u r e 82 - Luminous performance of v a r i o u s h o r i z o n t a l s h a d i n g d e v i c e s h a v i n g e q u i v a l e n t t h e r m a l performance 226 sunbreak" as a s o l u t i o n t o the sun s h a d i n g / d a y l i g h t i n g c o n f 1 i c t - - e s p e c i a l l y f o r t a l l windows, f o r which a s i n g l e , l a r g e o~verhang, h i g h above the opening i s not f e a s i b l e . Of two sh a d i n g d e v i c e s h a v i n g i d e n t i c a l t h e r m a l p erformance, the one h i g h e r above the window head has g r e a t e r luminous e f f e c t i v e n e s s ( i . e . a l l o w s i n more d a y l i g h t ) . I t s p r o j e c t i o n from the b u i l d i n g must, however, be c o r r e s p o n d i n g l y g r e a t e r and thus a t r a d e - o f f i s i n v o l v e d between the c o s t due t o the e x t r a depth of the sh a d i n g d e v i c e and s a v i n g s due t o d a y l i g h t i n g 3 3 . i i i . H o r i z o n t a l o p e r a b l e l o u v r e s , b l i n d s and shades a v o i d some of the drawbacks of f i x e d sun c o n t r o l d e v i c e s , s i n c e they can, i f p r o p e r l y c o n t r o l l e d , maximize s o l a r s h a d i n g when needed and maximize d a y l i g h t i n g a t o t h e r t i m e s . H o r i z o n t a l l o u v r e s on south f a c a d e s can p o t e n t i a l l y p r o v i d e g l a r e / s o l a r heat g a i n c o n t r o l a t a l l sun a n g l e s and s i m u l t a n e o u s l y p r o v i d e d a y l i g h t i n g . I f the o p e r a t i n g mechanism i s a u t o m a t i c , then such d e v i c e s can p r e d i c t a b l y p r o v i d e energy s a v i n g s . i v . A u t o m a t i c , sensor a c t i v a t e d f a b r i c shades--on the e x t e r i o r or i n t e r i o r - - a r e a n o ther s o l u t i o n t o the g l a r e / s o l a r heat g a i n problem encountered a t south f a c i n g d a y l i g h t i n g a p e r t u r e s . F a b r i c s come i n many c o l o u r s , p r o v i d i n g an o p p o r t u n i t y f o r c o l o u r h i g h l i g h t s on e l e v a t i o n s 3 " . F a b r i c s a l s o come i n s e v e r a l d e n s i t i e s , p r o v i d i n g a c h o i c e of s h a d i n g c o e f f i c i e n t most a p p r o p r i a t e f o r the p a r t i c u l a r b u i l d i n g and o r i e n t a t i o n . Even when drawn, f a b r i c shades, 227 e s p e c i a l l y the l e s s dense weaves, can p r o v i d e some view o u t s i d e and l i m i t e d d a y l i g h t p e n e t r a t i o n 3 5 . 2.5 G l a r e C o n t r o l — N o r t h G l a r e c o n t r o l on n o r t h e l e v a t i o n s can be more e a s i l y a c c o m p l i s h e d than f o r o t h e r o r i e n t a t i o n s because s o l a r c o n t r o l i s not n e c e s s a r y . Thus the luminous c o n d i t i o n s on the n o r t h s i d e a re r e l a t i v e l y s t a t i c , w i t h luminance d i s t r i b u t i o n of both the c l e a r and the o v e r c a s t sky r e l a t i v e l y c o n s t a n t , o n l y a b s o l u t e luminance b e i n g c hangeable. Because of t h i s , the amount of p o t e n t i a l g l a r e can be r e a d i l y p r e d i c t e d and s i m p l e d e s i g n r e s p o n s e s , t h a t reduce sky luminance t o a c c e p t a b l e l e v e l s , can be d e v e l o p e d . L i g h t c u r t a i n s , l o o s e weave i n t e r i o r f a b r i c shades (of a p p r o p r i a t e l i g h t t r a n s m i t t a n c e ) or i n t e r i o r V e n e t i a n b l i n d s , can be u t i l i z e d as s i m p l e s o l u t i o n s t o the g l a r e problem a t t h i s o r i e n t a t i o n . 2.6 G l a z i n g T i l t Requirements f o r sun s h a d i n g and g l a r e c o n t r o l on the south e l e v a t i o n s , and t o a l e s s e r e x t e n t on the e a s t and west as w e l l , may be r e s o l v e d by i n c r e a s i n g the a n g l e of i n c i d e n c e 3 6 of the s u n l i g h t on the g l a z i n g a t a g i v e n t i m e , i . e . by t i l t i n g the g l a s s downward. A downward t i l t f o r the g l a z i n g reduces s o l a r heat g a i n w i t h o u t o b s t r u c t i n g view out and a u t o m a t i c a l l y reduces g l a r e by a l l o w i n g l e s s d a y l i g h t i n , p r i m a r i l y because of i n c r e a s e d r e f l e c t i o n a t g r e a t e r a n g l e s of i n c i d e n c e . F i g u r e 83 228 FOR SOUTH WALL AT 4 5 ' LATITUDE WINTER EQUINOX SUMMER SOLSTICE SOLSTICE 1-00 •60 ABSORPTION 0 20 40 60 80 100 ANGLE OF INCIDENCE, DEGREES F i g u r e 83 - R e f l e c t a n c e v a l u e s t h rough g l a s s a t v a r i o u s a n g l e s of i n c i d e n c e a . 3 7 shows the r e l a t i o s h i p between r e f l e c t a n c e and a n g l e of i n c i d e n c e . I t . c a n be seen t h a t r e f l e c t a n c e v a l u e s r i s e s h a r p l y above i n c i d e n t a n g l e s of 57 d e g r e e s 3 8 . S o l a r h e a t g a i n and g l a r e a r e f u r t h e r reduced, because t h e outward p r o j e c t i o n of the t i l t r educes the a r e a of g l a s s exposed t o t h e sun. The geometry i s e q u i v a l e n t t o a comparable v e r t i c a l overhang s h a d i n g v e r t i c a l g l a s s 3 9 . F i g u r e 84 shows a t y p i c a l s o l u t i o n t o s o l a r s h a d i n g i n v o l v i n g t i l t e d f e n e s t r a t i o n . The energy f a l l i n g on t h i s window i s the same as i f the window were v e r t i c a l and had a 1'-4" p r o j e c t i n g shade a l o n g the l i n t e l 4 0 . The energy t r a n s m i t t e d i s , however, l e s s than f o r the comparable v e r t i c a l window w i t h overhang, because of the g l a s s t i l t w hich reduces t r a n s m i s s i o n by a f u r t h e r 2 2 % * 1 . 229 S i n c e the t r a j e c t o r y of the sun i n w i n t e r i s l o w e r , the a n g l e of i n c i d e n c e of s u n l i g h t i s lower and the e f f e c t i v e n e s s of t i l t as a s h a d i n g d e v i c e i n w i n t e r i s much reduc e d . In the morning and l a t e a f t e