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The application of passive techniques in housing design in hot and dry climates, with special emphasis.. 1988

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c THE APPLICATION OF PASSIVE TECHNIQUES IN HOUSING DESIGN IN HOT AND DRY CLIMATES; WITH SPECIAL EMPHASIS ON INDIA By RAMINDER B. KANETKAR re.ce,+*9 cf-.f^> " B. Arch., Punjab U n i v e r s i t y , I n d i a , 1982 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE.DEGREE OF MASTER OF ADVANCED STUDIES IN ARCHITECTURE in THE FACULTY OF GRADUATE STUDIES School of A r c h i t e c t u r e ( We accept t h i s t h e s i s as c o n f i r m i n g to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1988 © Raminder B. Kanetkar, 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DE-6(3/81) A b s t r a c t T h i s r e s e a r c h focussed on the i d e n t i f i c a t i o n , e v a l u a t i o n and recommendation of p a s s i v e design s t r a t e g i e s s u i t a b l e for housing design i n hot and dry c l i m a t e s i n I n d i a . The term 'passive' r e f e r s to those design techniques which, i n order to enhance thermal comfort, u t i l i z e the favourable and mininimize the unfavourable elements of the l o c a l c l i m a t e . The o b j e c t i v e of the research was to determine means by which r e l i a n c e on mechanical means of a c h i e v i n g comfort and a s s o c i a t e d socio-economic c o s t s can be minimized. The t h e s i s i s d i v i d e d i n t o two p a r t s . The f i r s t p art i d e n t i f i e s and ev a l u a t e s the p a s s i v e design techniques used i n the d w e l l i n g s of p r e - i n d u s t r i a l and p o s t - i n d u s t r i a l c i t i e s l o c a t e d i n hot and dry region i n I n d i a . Climate, environmental problems ( p r i m a r i l y c o o l i n g ) , and indoor comfort c r i t e r i a were analysed to e s t a b l i s h p r e l i m i n a r y c r i t e r i a f o r e v a l u a t i n g the thermal performance of design techniques. The main o b j e c t i v e was to enable d e s i g n e r s to i d e n t i f y those techniques which can be used i n contemporary d w e l l i n g d e s i g n s . The second part proposes s t r a t e g i e s to i n c o r p o r a t e p a s s i v e techniques i n contemporary housing d e s i g n . General s t r a t e g i e s recommended at v a r i o u s l e v e l s of design i n c l u d e the f o l l o w i n g : -minimize s o l a r gain -minimize conductive heat flow -promote v e n t i l a t i o n -minimize i n t e r n a l heat gains -promote r a d i a n t c o o l i n g -delay p e r i o d i c heat flow -promote ev a p o r a t i v e c o o l i n g i i - c o n t r o l h i g h v e l o c i t y wind - c o n t r o l g l a r e These s t r a t e g i e s , which recognize the c o m f o r t - r e l a t e d needs of d w e l l i n g occupants, promote the use of l o c a l c o n s t r u c t i o n p r a c t i c e s . The a p p l i c a t i o n of p a s s i v e techniques presents a r c h i t e c t s with a c o n s i d e r a b l e scope f o r c r e a t i v i t y i n housing d e s i g n . However, at the o u t s e t , i t i s necessary to d e f i n e p r i o r i t i e s i n the s e l e c t i o n of design s t r a t e g i e s , and to ensure these p r i o r i t i e s are addressed through each l e v e l of design. The s t r a t e g i e s s e l e c t e d i n t h i s t h e s i s emphasize the need f o r minimizing heat gain d u r i n g day time, and maximizing heat l o s s at n i g h t . It i s concluded from t h i s r e s e a r c h that the a p p l i c a t i o n of pa s s i v e techniques in contemporary housing design allows f o r maintenance of most thermal comfort needs, thereby reducing r e l i a n c e on mechanical means of c o n t r o l . At the same time, the use of p a s s i v e techniques p r o v i d e s a p o t e n t i a l f o r the housing designs to respond e f f e c t i v e l y to c e r t a i n s o c i o - c u l t u r a l needs of the occupants. TABLE OF CONTENTS page ABSTRACT i i TABLE OF CONTENTS i v LIST OF TABLES v i i LIST OF FIGURES. v i i . i ACKNOWLEDGEMENT x i i INTRODUCTION 1 1. COMFORT AND DWELLINGS 2 2. OBJECTIVES OF THE PROPOSED RESEARCH 8 3. THE RESEARCH METHODOLOGY 10 4. THESIS LAYOUT 12 PART ONE: HISTORICAL REVIEW OF METHODS FOR ACHIEVING COMFORT IN HOUSING IN HOT AND DRY CLIMATE IN INDIA 13 INTRODUCTION 14 SECTION I: PRE-HISTORIC PERIOD 15 1 . INTRODUCTION 2. HOUSING IN MOHANJODARO 2.1. Introduct ion 2.2. L o c a t i o n and Climate 2.3. Indoor comfort C r i t e r i a 2.4. Environmental.Problems 2.5. B u i l d i n g Design Techniques 2.6. Performance of Design techniques SECTION I I : MEDIEVAL PERIOD 28 1. INTRODUCTION 2. HOUSING IN JAISALMER 2.1. Introduct ion 2.2. L o c a t i o n and Climate 2.3. Indoor Comfort C r i t e r i a i v 2.4. Environmental Problems 2.5. B u i l d i n g Design Techniques 2.6. Performance of Design techniques SECTION I I I : MODERN INDUSTRIAL PERIOD 44 1 . INTRODUCTION 2. HOUSING IN CHANDIGARH 2.1. I n t r o d u c t i o n 2.2. L o c a t i o n and Climate 2.3. Indoor Comfort C r i t e r i a and Environmental Problems 2.4. B u i l d i n g Design Techniques 2.5. Performance of Design Techniques SECTION IV: CONCLUSIONS AND CONTEMPORARY ISSUES 64 PART TWO: HOUSING DESIGN STRATEGIES 65 INTRODUCTION 66 SECTION I: SITE SELECTION STRATEGIES 70 SECTION II 1 . INTRODUCTION 2. SITE CLIMATE DATA 3. THERMAL COMFORT CRITERIA 4. MINIMIZE SOLAR GAIN 4.1. Slope O r i e n t a t i o n and Gradient 4.2. E x i s t i n g . V e g e t a t i o n and Topography 5. PROMOTE AIR FLOW 5.1. S i t e A l t i t u d e 5.2. Proximity to Water Bodies SITE PLANNING STRATEGIES 83 1 . INTRODUCTION 2. MINIMIZE SOLAR GAIN 2.1. S t r e e t O r i e n t a t i o n 2.2. S t r e e t Width 2.3. L o c a t i o n and S i z e of Open Spaces 2.4. Landscaping 3. PROMOTE VENTILATION 3.1. D i s t r i b u t i o n of Open Spaces 3.2. B u i l d i n g Heights v 4. PROTECTION FROM HIGH VELOCITY WIND AND DUST 4.1. S h e l t e r b e l t s SECTION I I I : FORM DESIGN STRATEGIES 100 1. INTRODUCTION 2. REFERENCE BUILDINGS 3. MINIMIZE CONDUCTIVE HEAT FLOW 3.1. O r i e n t a t i o n 3.2. Exposed Surface to Volume R a t i o 3.3. Plan Shape 3.4. B u i l d i n g Facade 3.5. Thermal Zoning of Vari o u s Spaces 3.6. L i v i n g Areas Below Grade 4. REDUCE INTERNAL HEAT GAINS 4.1. Heat Generating Areas 5. PROMOTE VENTILATION 5.1. I n t e r i o r Courts and Shafts 5.2. O r i e n t a t i o n 6. PROMOTE RADIANT COOLING 6.1. T e r r a c e s SECTION IV: FABRIC DESIGN STRATEGIES ...129 1. INTRODUCTION 2. MINIMIZE SOLAR GAIN, PROMOTE VENTILATION, CONTROL GLARE 2.1. Windows: I n t r o d u c t i o n 2.2. Window O r i e n t a t i o n 2.3. E x t e r i o r 2.4. E x t e r i o r A c c e s s o r i e s 2.5. The Window 2.6. I n t e r i o r A c c e s s o r i e s 2.7. I n t e r i o r 3. DELAY PERIODIC HEAT FLOW, MINIMIZE CONDUCTIVE HEAT FLOW 3.1. Roof and Wa l l s : Thickness, M a t e r i a l s , Colour SUMMARY AND CONCLUSIONS 159 REFERENCE MATTER 1 66 1 . BIBLIOGRAPHY 1 67 v i L i s t of Tables page No. I. R e f l e c t a n c e values f o r v a r i o u s s u r f a c e s 92 I l a . A c t i v i t y a n a l y s i s of spaces i n a d w e l l i n g 118 l i b . A l l o c a t i o n of spaces with respect to o r i e n t a t i o n 118 I I I . I n t e r n a l heat gain from v a r i o u s sources 123 IV. Performance of e x t e r i o r shading d e v i c e s ....142 V. Time l a g p r o v i d e d by m a t e r i a l s of v a r i o u s thermal p r o p e r t i e s and t h i c k n e s s ....157 VI. Summery of housing design s t r a t e g i e s 162 v i i L i s t of F i g u r e s Page No. 1 . Commercial energy consumed f o r a c h i e v i n g comfort i n b u i l d i n g s i n India 3 2. Shares of country groups i n world commercial energy consumption 3 3. L o c a t i o n of hot and dry c l i m a t e zone i n India 8 1.1. Map of India showing l o c a t i o n of Mohanjodaro 17 1.2. C l i m a t i c data of Mohanjodaro 17 1.3. S t r e e t layout of Mohanjodaro 21 1.4. Plan of t y p i c a l d w e l l i n g u n i t i n Mohanjodaro 21 1.5. Summer Shading mask f o r an eastern w a l l i n a narrow s t r e e t 24 1.6. Time l a g and decrement f a c t o r f o r t h i c k w a l l s 24 1.7. Thermal system of c o u r t y a r d house in Mohanjodaro..... 27 1.8. L o c a t i o n of c i t i e s developed d u r i n g medieval p e r i o d in India .. 29 1.9. C l i m a t i c data of J a i s a l m e r 29 1.10. Town layout of J a i s a l m e r 33 1.11. Plan of a small house i n J a i s a l m e r 33 1.12. Plan of a middle income house i n J a i s a l m e r 35 1.13. Plan and s e c t i o n of a h a v e l i 35 1.14. C o n s t r u c t i o n of the roof of a h a v e l i 37 1.15. S t r u c t u r a l p r o j e c t i o n s and f i n s on the upper l e v e l facade of a h a v e l i 37 1.16. Operation of a wind tower i n summer 41 1.17. The psychrometric p r e s e n t a t i o n of c o o l i n g process through the wind tower 43 1.18. L o c a t i o n of Chandigarh 45 1.19. C l i m a t i c data of Chandigarh 46 1.20. Layout of roads i n Chandigarh 49 v i i i 1.21. 'The s e c t o r layout 49 1.22. Government housing i n Chandigarh 51 1.23. P r i v a t e housing i n Chandigarh 52 1.24. T y p i c a l roof s e c t i o n 54 1.25. Sun path diagram f o r SE facade 54 1.26. Shading d e v i c e s f o r Chandigarh houses 56 1.27. The psychrometric p r e s e n t a t i o n of c o o l i n g through e v a p o r a t i v e c o o l e r s 59 2.1. The elements of e x t e r n a l c l i m a t e and the r e s u l t i n g i n t e r n a l environment i n f l u e n c i n g occupant thermal comfort 71 2.2. B i o - c l i m a t i c chart f o r hot and dry c l i m a t e s 75 2.3. Summer sun path at l a t i t u d e 25°N „... 77 2.4. The s u r f a c e s p e r p e n d i c u l a r to the d i r e c t i o n of sun r e c e i v e more r a d i a t i o n 77 2.5. A mound or t r e e i n the west w i l l reduce few hours of s o l a r r a d i a t i o n on the d w e l l i n g s t r u c t u r e 78 2.6. Suggested l o c a t i o n of houses on a sloped s i t e . . . . 78 2.7. S i t e s e l e c t i o n in a v a l l e y s i t u a t i o n 80 2.8. Raised embankment to enhance the c o o l i n g e f f e c t of a i r 80 2.9. C o o l i n g process due to the p r o x i m i t y of water......... 81 2.10a. Sunpath diagram fo r l a t i t u d e 25°N 86 2.10b. Shadow len g t h for East and West f a c i n g d w e l l i n g block 86 2.11. S t r e e t s running east-west with block f a c i n g south 86 2.12. The e f f e c t of s t r e e t width and block height on shading 88 2.13. An example of a c h i e v i n g narrow s t r e e t width by s e g r e g a t i n g v e h i c l e s from d w e l l i n g f r o n t 88 2.14. Shading in open spaces smaller than surrounding blocks 90 ix 2.15. Deciduous t r e e s and summer and winter s o l a r p e n e t r a t i o n 90 2.16. Solar r a d i a t i o n i n c i d e n t upon ground s u r f a c e and v e r t i c a l s u r f a c e s f a c i n g east, west, south and north at l a t i t u d e 25 N 92 2.17. A i r temperature above v a r i o u s s u r f a c e s 94 2.18. The wind v e l o c i t y i n open country and b u i l t up areas. 94 2.19. A i r v e l o c i t y near the ground around t a l l e r b l o c k s i s more than around lower blocks 96 2.20. Use of s h e l t e r b e l t s f o r summer wind p r o t e c t i o n 98 (Plan) 2.21. (Section) 98 2.22. Modes of heat exchange i n s i d e the d w e l l i n g 101 2.23. The d w e l l i n g forms used f o r a n a l y s i s 103 2.24a. So l a r r a d i a t i o n i n c i d e n t upon s u r f a c e s in v a r i o u s o r i e n t a t i o n s at l a t i t u d e 25 N 107 2.24b. S o l a r r a d i a t i o n i n c i d e n t upon south to south-east f a c i n g s u r f a c e s 107 2.25. Heat gain by conduction f o r v a r i o u s form types 109 2.26. Heat gain by conduction i n v a r i o u s plan shapes as compared with a square plan 114 2.27a. Solar a l t i t u d e d u r i n g summer at l a t i t u d e 25° 116 2.27b. Shading of south f a c i n g s u r f a c e 116 2.28. A comparison between mean monthly a i r and e a r t h temperatures 121 2.29. S i z e of c o u r t y a r d f o r a i r exchange due to thermal f o r c e 126 2.30. T e r r a c e s f o r row housing 126 2.31. F a b r i c as a f i l t e r of e x t e r n a l c l i m a t e 130 2.32. S o l a r heat gain p e r m i t t e d by a 1mx1m window in v a r i o u s o r i e n t a t i o n s 135 2.33. S o l a r a l t i t u d e and windows in v a r i o u s o r i e n t a t i o n s . . 135 x 2.34. R e l a t i v e p r o p o r t i o n of ground r e f l e c t e d , d i r e c t and d i f f u s e d s o l a r r a d i a t i o n Q i n c i d e n t upon a south f a c i n g window at l a t i t u d e 25 N 137 2.35. S o l a r a l t i t u d e and r e f l e c t o r area i n east and west o r i e n t a t i o n s 137 2.36a. Sun path diagram f o r 25°N 140 2.36b. Overheated p e r i o d f o r l a t i t u d e 25°N 140 2.37. V e r t i c l e p r o j e c t i o n s and wind v e l o c i t y i n a room.... 144 2.38a. Fi x e d h o r i z o n t a l p r o j e c t i o n s and a i r flow 146 2.38b. A d j u s t a b l e h o r i z o n t a l l o u v e r s and a i r flow 146 2.39. Heat gain through windows of d i f f e r e n t areas i n south o r i e n t a t i o n 146 2.40. A l a r g e r window area i n c r e a s e s wind v e l o c i t y i n a room with one window e s p e c i a l l y when wind i s o b l i q u e to the window 149 2.41. A higher wind v e l o c i t y i n s i d e a c r o s s v e n t i l a t e d room can be achieved when i t has unequal openings and the o u t l e t i s l a r g e r than the i n l e t 149 2.42. Glare from windows . .. 152 2.43. I n t r i c a t e l y woven j a l i as window m a t e r i a l 153 2.44. Roof f i n i s h e d with earthen pots 157 x i ACKNOWLEDGEMENT I wish to express my g r a t i t u d e to Raymond J . Cole f o r h i s superb guidence. As my ad v i s o r he a l s o deserves the highest c r e d i t f o r m o t i v a t i n g me and g i v i n g me h e l p f u l c r i t i c i s m s at v a r i o u s stages of t h i s study. I a l s o wish to thank Bud Wood f o r h i s continuous support and pa t i e n c e . Without h i s support, e s p e c i a l l y at the i n i t i a l stages, t h i s endeavour would never have reached i t s dest ina t i o n . I s i n c e r e l y a p p r e c i a t e the e f f o r t s of David Rousseou and Gorden Brown i n improving the E n g l i s h of t h i s t e x t , f o r i t i s in E n g l i s h where I need most he l p . There are no words to express my deepest g r a t i t u d e to my parents who provided emotional and f i n a n c i a l support f o r my education i n Canada. I owe more to them than to anyone e l s e . Last but not the l e a s t , as a c l o s e f r i e n d and now as a l i f e p a r t n e r , my husband Vinay deserves the most c r e d i t f o r g i v i n g me enough s t r e n g t h and i n t e l l e c t u a l support in w r i t i n g and f i n i s h i n g t h i s work. INTRODUCTION 1. COMFORT AND DWELLINGS 2. OBJECTIVES OF THE PROPOSED RESEARCH 3. THE RESEARCH METHODOLOGY 4. THESIS LAYOUT 1 1. COMFORT AND DWELLINGS The primary purpose of d w e l l i n g s has always been the p r o v i s i o n and maintenance of human comfort. V a r i o u s methods of a c h i e v i n g comfort i n d w e l l i n g s have been d e v i s e d by d i f f e r e n t s o c i e t i e s a c c o r d i n g to t h e i r needs, resources and and a v a i l a b l e technology. The methods for a c h i e v i n g comfort have g r a d u a l l y changed over time. Before the i n d u s t r i a l r e v o l u t i o n , comfort in d w e l l i n g s was achieved almost e x c l u s i v e l y by the use of n a t u r a l elements l i k e sun and wind which were c o n t r o l l e d through d w e l l i n g form and design . During the i n d u s t r i a l age new sources of f u e l were d i s c o v e r e d and mechanical heating and c o o l i n g d e v i c e s were invented. Where t h i s technology could be a f f o r d e d , t h i s p e r m i t t e d a change in the house form and in the l i f e s t y l e of people. The 1970's brought a temporary shortage of f o s s i l f u e l s , and s o c i e t i e s a l l over the world became concerned about the r i s i n g c o st and l i m i t e d supply of energy. Although developing s o c i e t i e s l i k e India consume l e s s per c a p i t a energy than i n d u s t r i a l i z e d s o c i e t i e s , the cost of energy which was a l r e a d y an issue in the developing world, became a c r i t i c a l development f a c t o r . I n s p i t e of the high c o s t of energy, c o o l i n g , l i g h t i n g and *Dwelling form, as observed by many a r c h i t e c t s (Anderson, 1968), i s an e x p r e s s i o n of the i n t e r a c t i o n of the primary c l i m a t i c , s o c i a l c u l t u r a l and economic needs whereas design i s an e x p r e s s i o n of the i n t e r a c t i o n of b u i l d i n g programme and s i t e c o n d i t i o n s . 2 F i g . 1 . Commercial Energy Consumed f o r A c h i e v i n g Comfort i n B u i l d i n g s i n I n d i a . Source: P a r i k h , 1976. <?1L EXfiJrZTIsKS PLANNEP Q(J>W>- 199 5 • F i g . 2 . Shares of Country Groups i n World Commercial Consumption, 1970-95. Source: F a l v i n , 1980. Energy 3 heating of b u i l d i n g s i n I n d i a , of which r e s i d e n t i a l b u i l d i n g s form a l a r g e p a r t , now consume n e a r l y one q u a r t e r of the t o t a l energy s u p p l i e s of the n a t i o n ( F i g . 1 ) . The r a t e of growth of t o t a l energy consumption in India and other developing c o u n t r i e s i s expected to average 2.3% per year during the p e r i o d 1980-1995 ( F i g . 2 ) . It i s c e r t a i n from the estimated d w e l l i n g u n i t s (4.5 m i l l i o n ) r e q u i r e d to meet the growing demand for housing in India over the next 20 years (Manchanda, 1986) that use of mechanical means of a c h i e v i n g comfort in these b u i l d i n g s w i l l c o n t r i b u t e s i g n i f i c a n t l y to the p r o j e c t e d growth in energy consumption. While the recent r e d u c t i o n of o i l p r i c e s has, t e m p o r a r i l y at l e a s t , reduced the burden of energy imports, a most fundamental issue c o n f r o n t i n g developing n a t i o n s l i k e India remains unchanged: s u s t a i n e d development i s dependent upon minimizing r e l i a n c e on p o t e n t i a l l y high cost energy. An awareness i s growing that a l l b u i l d i n g s can be designed to minimize dependence on c o s t l y non-renewable energy sources. Planners and a r c h i t e c t s , who c o n t r i b u t e the most towards making d e c i s i o n s regarding the use of energy for a c h i e v i n g comfort in b u i l d i n g s , are becoming aware of the need f o r e n e r g y - e f f i c i e n t d e s i g n s . In a r c h i t e c t Charles Correa's words: "In a t h i r d world country l i k e I n d i a , we simply can't a f f o r d to squander the kind of energy r e q u i r e d to c o n s t r u c t and a i r c o n d i t i o n a g l a s s tower in a t r o p i c a l c l i m a t e - and t h i s of course i s an advantage; for i t means that the b u i l d i n g must i t s e l f , through i t s very form, c r e a t e the " c o n t r o l s " which the user needs. Such a response n e c e s s i t a t e s much more than j u s t sun angles and l o u v e r s : 4 i t must i n v o l v e the s e c t i o n , the p l a n , the shape, in s h o r t : the very heart of the b u i l d i n g . To c r o s s a desert and enter a house around a c o u r t y a r d i s a p l e a s u r e beyond mere photogenic making, i t i s the q u a l i t y of l i g h t , and the ambience of moving a i r , that forms the essence of our e xperience. A r c h i t e c t u r e as a mechanism f o r d e a l i n g with the elements ( t r u e l y , a machine for l i v i n g ! ) . T h i s i s the great c h a l l e n g e and o p p o r t u n i t y of our t h i r d world." ( i n Cantacuzino, 1984) U t i l i z a t i o n of n a t u r a l energy sources, by means of the proper design of d w e l l i n g s i s not only b e n e f i c i a l and c o s t - e f f e c t i v e , but i s p s y c h o l o g i c a l l y a p p e a l i n g . T h i s r e a l i z a t i o n has * r e v i v e d i n t e r e s t in t r a d i t i o n a l a r c h i t e c t u r e among many a r c h i t e c t s in developing s o c i e t i e s . T r a d i t i o n a l a r c h i t e c t u r e o f f e r s s e v e r a l techniques of use i n minimizing r e l i a n c e on mechanical means. Poor s o c i e t i e s , which have an abundance of knowledge based on t r a d i t i o n a l methods of b u i l d i n g , f a i l to r e a l i z e that they were once the most s o p h i s t i c a t e d of t h e i r time. The techniques employed by them for a c h i e v i n g comfort were superior' to the techniques used by the i n d u s t r i a l i z e d s o c i e t i e s of today because they responded e f f e c t i v e l y to the l o c a l c l i m a t i c , economic, c u l t u r a l , s o c i a l and t e c h n o l o g i c a l c o n s t r a i n t s . T h i s knowledge can s t i l l be of great value, e i t h e r i n i t s o r i g i n a l form or as a b a s i s f o r renewed design i n t e r p r e t a t i o n . On the other hand, however, many of the c o n d i t i o n s ( f o r example s o c i a l , c u l t u r a l economic and t e c h n o l o g i c a l context) * t r a d i t i o n a l A r c h i t e c t u r e r e f e r s to those s t r u c t u r e s and settlement p a t t e r n s i n which there had been no p r o f e s s i o n a l 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 involvement. 5 under which t r a d i t i o n a l techniques were e f f e c t i v e have changed to the p o i n t where the o r i g i n a l techniques are no longer immediately a p p r o p r i a t e . Furthermore, the m a t e r i a l s u t i l i z e d f o r t r a d i t i o n a l techniques may no longer e a s i l y meet contemporary comfort e x p e c t a t i o n s . These are perhaps a few of the reasons why these techniques are l a r g e l y abandoned. But, i t i s a l s o true that c e r t a i n techniques i n t r o d u c e d by a r c h i t e c t s i n t h i r d world c o u n t r i e s are i n a p p r o p r i a t e for l o c a l c o n d i t i o n s . T herefore, as a r c h i t e c t Hassan Fathy (1986) c o r r e c t l y p o i n t s out that "we must determine what i s basic and constant and thus worth keeping no matter what time p e r i o d i t evolved i n " . I n s p i r e d by the above thought, t h i s t h e s i s i s an attempt to understand, share and propose an a p p l i c a t i o n of t r a d i t i o n a l methods of a c h i e v i n g comfort in the d w e l l i n g s of I n d i a , so that r e l i a n c e on c o s t l y mechanical means of a c h i e v i n g comfort can be minimized. 6 2. OBJECTIVES OF THE THESIS The main o b j e c t i v e of t h i s t h e s i s i s to examine ways to minimize r e l i a n c e on mechanical means of a c h i e v i n g thermal * comfort in r e s i d e n t i a l b u i l d i n g s i n hot and dry region (Fig.3) i n I n d i a . To achieve t h i s g o a l , the f o l l o w i n g s p e c i f i c t o p i c s w i l l be addressed: a. Methods of a c h i e v i n g comfort in r e s i d e n t i a l b u i l d i n g s in India through v a r i o u s p e r i o d s of h i s t o r y . T h i s w i l l be accompli shed: - By i d e n t i f y i n g the design techniques which helped i n a c h i e v i n g thermal comfort, and - By e v a l u a t i n g and o r d e r i n g the design techniques on the b a s i s of t h e i r e f f e c t i v e n e s s in a c h i e v i n g thermal comfort. b. Housing design s t r a t e g i e s f o r a c h i e v i n g thermal comfort in hot and dry region of India with a minimum r e l i a n c e on mechanical means. T h i s w i l l be accomplished by emphasi z i n g : -The use of l o c a l m a t e r i a l s and b u i l d i n g c o n s t r u c t i o n techniques a v a i l a b l e i n the s p e c i f i c r egion, and -The c u l t u r a l and b e h a v i o r a l requirements of the users of the d w e l l i n g s . It should be recognized that although the proposed design s t r a t e g i e s w i l l emphasize non-mechanical means of a c h i e v i n g comfort, the aim here i s not to e l i m i n a t e the power d r i v e n _ Defined as a zone in which hot and dry c l i m a t e predominates fo r a l a r g e time of the year. 7 F i g . 3. L o c a t i o n of Hot and Dry C l i m a t i c Zone i n I n d i a . environmental c o n t r o l systems. I n c o r p o r a t i n g 'modern conveniences', and meeting comfort e x p e c t a t i o n s i n a d w e l l i n g , r e q u i r e that mechanical means cannot be ignored a l t o g e t h e r . 8 3. THE RESEARCH METHODOLOGY The e v a l u a t i o n of v a r i o u s design techniques i n t h i s t h e s i s i s based on t h e i r e f f e c t i v e n e s s i n b r i n g i n g the indoor thermal c o n d i t i o n s w i t h i n the d e s i r e d comfort range. With the inc r e a s e d a v a i l a b i l i t y of computer mod e l l i n g techniques, i t i s now p o s s i b l e to p r e d i c t , reasonably a c c u r a t e l y , the thermal performance of a s t r u c t u r e b u i l t with m a t e r i a l s of known thermo-physical p r o p e r t i e s under given c l i m a t i c c o n d i t i o n s . However, the accuracy of p r e d i c t i o n i s l i m i t e d , not by the model, which can be r e f i n e d to almost any extent, but by the f a c t that the outdoor c l i m a t i c c o n d i t i o n s and the thermal c h a r a c t e r i s t i c s of b u i l d i n g envelope in-use can be p r e d i c t e d only with a l i m i t e d degree of accuracy., In a i r - c o n d i t i o n e d or heated b u i l d i n g s where the i n t e r n a l thermal c o n d i t i o n s are assumed to be maintained at a constant l e v e l with t h e r m o s t a t i c c o n t r o l , the task i s u s u a l l y that of determining the amount of a u x i l i a r y h e a t i n g or c o o l i n g that w i l l be needed (Watson,1973) to maintain that l e v e l over a given p e r i o d of time. T h i s i s a r e l a t i v e l y easy task. However, in the case of non a i r - c o n d i t i o n e d b u i l d i n g s , as in t h i s t h e s i s , where n a t u r a l e n e r g i e s are being used to achieve and maintain thermal comfort, p r e d i c t i n g the p r e c i s e degree of thermal comfort performance that the b u i l d i n g w i l l provide i s a d i f f i c u l t task. In a d d i t i o n to the u n p r e d i c t a b i l i t y of c l i m a t i c c o n d i t i o n s , the v a r i e d a c t i v i t i e s and responses of 9 b u i l d i n g occupants make p r e d i c t i o n more complex. Mathematical models are not very accurate i n a s s e s i n g the human response to v a r y i n g thermal c o n d i t i o n s , p a r t i c u l a r l y when people may be changing some of the assumed b u i l d i n g c h a r a c t e r i s t i c s by opening or c l o s i n g doors and windows. However, computer programes and mathematical models are u s e f u l f o r the b u i l d i n g designer to understand the q u a n t i t a t i v e performance of b u i l d i n g f a b r i c l e a d i n g to the a p p r o p r i a t e c h o i c e between d i f f e r e n t a l t e r n a t i v e s (Gupta,1984). The res e a r c h i n t h i s t h e s i s i s based l a r g e l y on l i t e r a t u r e review, as w e l l as a p p l i c a t i o n of s p e c i f i c mathemetical models and computer programes. The emphasis i s on understanding the theory and the p r i n c i p l e s i n v o l v e d i n a s s e s s i n g the thermal performance of v a r i o u s design techniques, r a t h e r than the q u a n t i t a t i v e r e s u l t s . 10 4. THESIS LAYOUT The t h e s i s i s d i v i d e d i n t o two p a r t s . Part One presents a b r i e f h i s t o r y of the means by which human comfort i n domestic b u i l d i n g s has been achieved in hot and dry c l i m a t i c region in I n d i a , i n the p r e - h i s t o r i c , Medieval and modern i n d u s t r i a l per i o d s . Part Two focuses on developing contemporary design s t r a t e g i e s . There are v a r i o u s l e v e l s of design at which d e c i s i o n s regarding the use of a p p l i e d energy are made by a r c h i t e c t s . These are: s i t e s e l e c t i o n ; s i t e p l a n n i n g ; form design; and f a b r i c d e s i g n . S t r a t e g i e s f o r minimizing the use of a p p l i e d energy are d i s c u s s e d f o r each one of these l e v e l s . A general design p r i n c i p l e a p p l i e d i n each of these s e c t i o n s i s to minimize or modify the adverse e f f e c t s of e x t e r n a l c l i m a t e while u t i l i z i n g the favourable ones. The r e l a t i o n s h i p of e x i s t i n g topography and c l i m a t e to the proposed b u i l d i n g s i s co n s i d e r e d i n the s e c t i o n on s i t e s e l e c t i o n . The s i t e p l a n n i n g d i s c u s s i o n c o n s i d e r s the p o t e n t i a l f o r c r e a t i n g an e f f e c t i v e m i c r o c l i m a t e through s t r e e t l a y o u t , design of open spaces and la n d s c a p i n g . The form design s e c t i o n i n v o l v e s the r o l e of b u i l d i n g volume, shape and c o n f i g u r a t i o n in minimizing the adverse e f f e c t of c1imate. The f i n a l s e c t i o n , i n v o l v i n g the f a b r i c design l e v e l , 1 1 c o n s i d e r s the r o l e of windows, w a l l s and r o o f , and the m a t e r i a l s f o r t h e i r c o n s t r u c t i o n , i n modifying the u n d e s i r a b l e and u t i l i z i n g the favourable e f f e c t s of e x t e r i o r c l i m a t e . 1 2 PART ONE: A HISTORICAL REVIEW OF METHODS FOR ACHIEVING COMFORT IN HOUSING IN HOT AND DRY CLIMATES IN INDIA INTRODUCTION SECTION I: PRE-HISTORIC PERIOD SECTION I I : MEDIEVAL PERIOD SECTION I I I : MODERN INDUSTRIAL PERIOD SECTION IV: CONCLUSIONS AND CONTEMPORARY ISSUES 1 3 INTRODUCTION Part one of t h i s t h e s i s p r e s e n t s a b r i e f h i s t o r y of the techniques by which human comfort i n domestic b u i l d i n g s has been achieved i n I n d i a . The main o b j e c t i v e i s to i d e n t i f y the p o t e n t i a l a p p l i c a t i o n s of these h i s t o r i c a l methods on contemporary domestic a r c h i t e c t u r e . C l i m a t i c f a c t o r s that i n f l u e n c e comfort i n r e s i d e n t i a l b u i l d i n g s , comfort c r i t e r i a , v a r i o u s environmental problems and, most imp o r t a n t l y , the performance of . b u i l d i n g design techniques used in s o l v i n g these problems are examined f o r t y p i c a l examples of housing i n the P r e - h i s t o r i c , Medieval and Modern I n d u s t r i a l p e r i o d s . Part one concludes with o u t l i n i n g the techniques which can be e f f e c t i v e l y used to enhance and maintain thermal comfort in contemporary d w e l l i n g s . 1 4 SECTION I: PRE-HISTORIC PERIOD 1. INTRODUCTION The most s i g n i f i c a n t examples of c i v i l i z a t i o n i n Indi a from p r e - h i s t o r i c times are found in the towns of Mohanjodaro, Harappa and T a x i l a , l o c a t e d i n the hot and dry c l i m a t i c zone. These towns developed d u r i n g the ' C a l c o l i t h i c ' age, i . e . the p e r i o d of t r a n s i t i o n from use of stone to bronze as the m a t e r i a l f o r t o o l s , which i m p l i e s that the knowledge of b u i l d i n g c o n s t r u c t i o n technology, the means of t r a n s p o r t , the urban economy and hence the means of a c h i e v i n g comfort, were l i m i t e d . As a r e s u l t of l e s s d i v e r s i f i e d knowledge of c o n s t r u c t i o n technology, these towns were s i m i l a r i n t h e i r layout and house design (Schoenauer, 1981). This s e c t i o n w i l l examine the methods of a c h i e v i n g comfort in the r e s i d e n t i a l b u i l d i n g s of Mohanjodaro. 2. HOUSING IN MOHANJODARO 2.1. I n t r o d u c t i o n The a r c h e o l o g i c a l r e s e a r c h by Marshal and Wheeler (Schoenauer, 1981) r e v e a l e d that the c i t y of Mohanjodaro e x i s t e d f o r 500 years, from 3250 B.C. to 2750 B.C. Mohanjodaro, now l o c a t e d in P a k i s t a n , i s to the north-west of India ( F i g . 1 . 1 ) . The r i v e r Indus and i t s many t r i b u t a r i e s i n t h i s region i r r i g a t e d the surrounding land and were a source of o c c a s i o n a l f l o o d s * . *The r i v e r Indus has almost d r i e d and t h i s area i s a v i r t u a l d e s ert now. 1 5 2.2. L o c a t i o n and Climate Mohanjodaro i s l o c a t e d at 27° 55'N l a t i t u d e and 69°E l o n g i t u d e (Fig.1.1) and i s 1.7m above mean sea l e v e l . The seasons which predominated i n t h i s area ( i t i s assumed) were summer and winter. During summer the maximum and minimum temperature v a r i e d between 25°C and 45°C. In winter the temperature v a r i e d between 5°C and 25°C. The d i u r n a l range of temperatures was between 15°C and 20°C (Fig.1.2) in both seasons. The sky was mostly c l e a r and d i r e c t s o l a r r a d i a t i o n was intense throughout the year. As the s o i l i n t h i s area was f e r t i l e d u r i n g the p e r i o d under d i s c u s s i o n , the t r e e s and shrubs grew throughout the year and the ground r e f l e c t e d s o l a r r a d i a t i o n was not very i n t e n s e . Wind v e l o c i t y i n t h i s area was u s u a l l y high d u r i n g the months of May and June and the annual r a i n f a l l v a r i e d between 250 and 500 mm. Maximum r e l a t i v e humidity in summer co u l d be as low as 30%. 2.3. Indoor Comfort C r i t e r i a The two important f a c t o r s i n f l u e n c i n g comfort i n b u i l d i n g s are indoor environmental c o n d i t i o n s , and the l i f e s t y l e of the occupants. The way these f a c t o r s i n f l u e n c e d comfort c r i t e r i a i n the d w e l l i n g s of Mohanjodaro are d e s c r i b e d below. Indoor Environmental C o n d i t i o n s The thermal c o n d i t i o n s i n a b u i l d i n g are the r e s u l t of the extent to which the b u i l d i n g m o d i f i e s a i r temperature, r e l a t i v e humidity, s o l a r r a d i a t i o n and a i r movement ( G i v o n i , 1969). The r e s u l t i n g c o n d i t i o n s are experienced by the occupants. 1 6 F i g . 1 . 1 . Map of I n d i a showing L o c a t i o n of Mohanjodaro. Ill 3 M^NT-H- F i g . 1.2. C l i m a t i c Data of Mohanjodaro (Monthly Means). Assumed to be s i m i l a r f o r the p e r i o d under d i s c u s s i o n , 1 7 For p h y s i o l o g i c a l comfort i n a hot and dry c l i m a t e , the a i r temperature r e q u i r e d i n a b u i l d i n g should be between 27°C and 29°C dur i n g the day and 29°C to 32°C at night ( G i v o n i , 1969). The a i r temperature in Mohanjodaro during the summer days was much higher than what i s d e s i r e d . T herefore, reducing the indoor a i r temperature to a comfortable l e v e l was c r i t i c a l . During the day, the entry of o u t s i d e a i r was not d e s i r a b l e because of i t s high temperature which prevents c o n v e c t i v e heat l o s s from the body even when the a i r speed i s high (Olgyay, 1963). T h e r e f o r e , a i r movement was not a d e s i r a b l e s o l u t i o n f o r c o o l i n g f o r such a temperature range. The sweat evaporation r a t e from the body was high even i n s t i l l a i r because of the low humidity. In a d d i t i o n to the high a i r temperature d u r i n g summer, s o l a r r a d i a t i o n was a l s o intense which meant that the w a l l s and the roof of b u i l d i n g s must minimize s o l a r heat g a i n . The d i u r n a l range of temperatures was a l s o high which suggested that the b u i l d i n g s t r u c t u r e should have a high heat storage c a p a c i t y with a time l a g of 12-15hrs. f o r a c h i e v i n g comfortable i n t e r n a l temperatures. D i r e c t p e n e t r a t i o n of s u n l i g h t i n t o b u i l d i n g s was not d e s i r a b l e both f o r thermal reasons and to reduce g l a r e . L i f e S t y l e In a d d i t i o n to i n t e r n a l c o n d i t i o n s , the l i f e s t y l e of people, the way they use the b u i l d i n g and how they dress determines the comfort e x p e c t a t i o n s and i n f l u e n c e s the comfort c r i t e r i a in b u i l d i n g s . Given the l i m i t e d technology, i t can be assumed that b u i l d i n g s of Mohanjodaro were expected to provide comfort i n 1 8 terms of b a s i c p r o t e c t i o n from extreme c l i m a t i c f a c t o r s l i k e h igh summer and low winter temperatures, as w e l l as p r i v a c y and safe storage of goods. Of a l l the areas w i t h i n the house, the c o u r t y a r d was most e x t e n s i v e l y used f o r v a r i o u s a c t i v i t i e s l i k e cooking, s i t t i n g o u t s i d e and s l e e p i n g . The f r o n t part of the house was not used e x t e n s i v e l y for reasons of p r i v a c y . Spinning and weaving were widely p r a c t i c e d d u r i n g t h i s p e r i o d and i t i s known that cotton was used e x c l u s i v e l y f o r t e x t i l e s i n I n d i a . The clothes- worn durin g t h i s p e r i o d were g e n e r a l l y made of c o t t o n which, because of i t s inherent m a t e r i a l p r o p e r t i e s , p r o t e c t s the body from high summer temperature and i s e f f e c t i v e f o r eva p o r a t i v e c o o l i n g . 2.4. Environmental Problems The most important environmental problem i n the d w e l l i n g s of Mohanjodaro was c o o l i n g . Other than c o o l i n g , the b u i l d i n g s a l s o needed p r o t e c t i o n from d i r e c t p e n e t r a t i o n of l i g h t and o c c a s i o n a l f l o o d s . The s e c t i o n s below w i l l examine the b u i l d i n g design f e a t u r e s with a p a r t i c u l a r emphasis on c o o l i n g . 2.5. B u i l d i n g Design Techniques Town Layout A r c h e o l o g i c a l excavations r e v e a l that the s t r e e t s of Mohanjodaro were planned on a g r i d p a t t e r n ( F i g . 1.3). Main s t r e e t s had a north-south o r i e n t a t i o n , which i s di a g o n a l to the predominant wind d i r e c t i o n , and were about 10 m wide. They were l i n e d with shops on both s i d e s (Schoenauer, 1981). 19 The other p a r a l l e l s t r e e t s were much narrower, though r a r e l y l e s s than 3m. in width, which allowed a c a r t to pass through them. Narrow lanes, v a r y i n g from about 1 to 2 m in width, l i n k e d the primary and secondary s t r e e t s . These lanes d i d not n e c e s s a r i l y run in s t r a i g h t l i n e s from one s t r e e t to another because they were mainly used by p e d e s t r i a n s . The l e v e l of these lanes was c o n s i d e r a b l y higher than those of main and secondary s t r e e t s , presumably i n response to the frequent f l o o d s . The r e s i d e n t i a l b u i l d i n g s were of unequal he i g h t s . House Form Most of the excavated areas of Mohanjodaro appear to have been r e s i d e n t i a l . The s i z e of b u i l d i n g s ranged from humble two room d w e l l i n g s to l a r g e multi-room houses that c o u l d be ranked as p a l a c e s . The t y p i c a l d w e l l i n g u n i t of Mohanjodaro was an inward l o o k i n g c o u r t y a r d house ( F i g . 1 . 4 ) . The smaller homes had only one c o u r t y a r d , while the l a r g e r ones had s e v e r a l f o r the purposes of l i g h t and v e n t i l a t i o n . As a r e s u l t of the compact layout of Mohanjodaro, the width of the c o u r t y a r d , u s u a l l y square i n shape, never exceeded the height of surrounding b l o c k s . R e s i d e n t i a l u n i t s had no windows towards the s u b s i d i a r y walkways f o r reasons of p r i v a c y (Grover, 1980). The windows towards the c o u r t y a r d were small and decorated with i n t r i c a t e l a t t i c e work. 20 F i g . 1 . 3 . S t r e e t Layout of Mohanjodaro. Source: Grover, 1980. Fig.1.4. Plan of T y p i c a l D w e l l i n g U n i t i n Mohanjodaro. Source: Grover, 1980. 21 B u i l d i n g C o n s t r u c t i o n and S e r v i c e s The r e s i d e n t i a l b u i l d i n g s were c o n s t r u c t e d with 45cm. or t h i c k e r b r i c k w a l l s and were roofed by b r i c k t i l e s l a i d over timber r a f t e r s with a depth of 30cm. The t o t a l t h i c k n e s s of the roof was approximately 45cm. Water supply to the b u i l d i n g s was through the w e l l s shared by three or four houses. The e n t i r e c i t y was served by an e x t e n s i v e system of drainage. The bathrooms were connected to d r a i n s running under the walkways which in turn were connected to l a r g e sewers l a i d out under the main s t r e e t . Manholes were l o c a t e d at r e g u l a r i n t e r v a l s along the main sewer for i n s p e c t i o n and c l e a n i n g of the d r a i n s . Smaller d r a i n s were covered with b r i c k s l a b s and the l a r g e r main sewers were spanned by c o r b e l l e d b r i c k arches (Grover, 1980). From the above d e s c r i p t i o n of b u i l d i n g s i n the town of Mohanjodaro, i t appears that the design of e x t e n s i v e drainage system, r a i s i n g the p l i n t h of b u i l d i n g s and use of ground f l o o r f o r shops on main s t r e e t s was a response to frequent f l o o d s . C o o l i n g of the indoor environment was achieved by the use of the f o l l o w i n g b u i l d i n g design f e a t u r e s : - Dense c l u s t e r i n g of b u i l d i n g s , - Sun c o n t r o l through o r i e n t a t i o n , - Massive c o n s t r u c t i o n of r o o f s and w a l l s , - Courtyards, - Small openings, and - Use of l a t t i c e work f o r windows. The f o l l o w i n g s e c t i o n w i l l analyse the performance of these f e a t u r e s in moderating the thermal environment. 22 2.5. Performance of Design techniques Dense c l u s t e r i n g of b u i l d i n g s / Sun c o n t r o l through o r i e n t a t i o n In Mohanjodaro, layout of the town was the f i r s t l e v e l of m o d i f i c a t i o n of a harsh summer c l i m a t e . A l l the houses were b u i l t w a l l to w a l l with c e n t r a l c o u r t y a r d s . T h i s meant that only two s i d e s of the b u i l d i n g s were exposed to the sun. The secondary and main s t r e e t s i n the town ran N-S and were 3 to 10m. wide so that the r e s i d e n c e s f a c i n g these s t r e e t s had e i t h e r an east or a west facade exposed to the sun. The summer sun would shine on the east facade u n t i l 11.30 a.m. and the west facade a f t e r 12.30 p.m. The a l t i t u d e of sun d u r i n g these p e r i o d s v a r i e s from 0° to 80° (Fig.1.5) so that the facade f a c i n g the secondary s t r e e t was exposed to the sun fo r no more than 2-3 hours. As shown in F i g u r e 1.4, t h i s was the entrance facade and d i d not have any windows opening towards the s t r e e t . The only door which opened on the s t r e e t had an entry with a v e s t i b u l e which gave the f r o n t facade f u l l p r o t e c t i o n from d i r e c t p e n e t r a t i o n of s u n l i g h t . The f r o n t part of d w e l l i n g s was not e x t e n s i v e l y used for l i v i n g purposes. The bathing area, garbage chutes and w e l l s , which r e q u i r e l e s s c o n s i d e r a t i o n of comfort c o n d i t i o n s , were pl a c e d t h e r e . The e a s t e r n facade f a c i n g a narrow s t r e e t was shaded before 10.30 a.m. and a f t e r 1.30 p.m. as a r e s u l t of the lower a l t i t u d e of the sun ( F i g . 1 . 5 ) . Thus the s o l a r r a d i a t i o n on t h i s facade was e f f e c t i v e f o r no more than an hour and t h i s was p r o t e c t e d by the massive b r i c k wall c o n s t r u c t i o n which 23 A N ^ L S ^ F ALTITUDE AT )WH W WAUL FA^IN£ S T P ^ & T ' F i g . 1 . 5 . Summer Shading Mask f o r an E a s t e r n W a l l i n a Narrow S t r e e t . (Shading Mask f o r Western Wall i s S i m i l a r ) . TIME U £ (y>) Fig.1.6. Time Lag and Decrement F a c t o r f o r Thick W a l l s . Source: Koenigsberger, 1973. 24 ensured high heat storage c a p a c i t y and time l a g of 10-15 hrs ( G i v o n i , 1969). The w a l l s f a c i n g the c o u r t y a r d , in the same o r i e n t a t i o n , remained i n shade f o r most of the day as the width of c o u r t y a r d was l e s s than i t s h e i g h t . These w a l l s r e c e i v e d s o l a r r a d i a t i o n between 11.30a.m. and 12„30p.m. when the a l t i t u d e of sun i s c l o s e to 80°. The i n c i d e n t s o l a r r a d i a t i o n on the v e r t i c a l s u r f a c e i s l e s s intense however due to the steep angle. Massive c o n s t r u c t i o n of r o o f s and w a l l s Because the w a l l s were p r o t e c t e d from s o l a r r a d i a t i o n to a la r g e extent, the main area of s o l a r heat gain was the roof. Roof c o n s t r u c t i o n of about 45cm. i n t h i c k n e s s , made from wood and b r i c k m a t e r i a l s ensured a time l a g of 12- 15 hrs ( G i v o n i , 1969) and were e f f e c t i v e i n reducing heat g a i n . T h i s i m p l i e s that by the time the i n t e r n a l roof s u r f a c e reached i t s highest temperature, i t was a l r e a d y night and the e f f e c t of mean r a d i a n t temperature c o u l d be o f f s e t by the lower temperature of v e n t i l a t i o n a i r ( F i g . 1 . 6 ) . Courtyards At temperatures below 35°C, thermal comfort can be provided by ensuring adequate a i r movement i n the b u i l t space. N a t u r a l a i r movement i n b u i l d i n g s can r e s u l t from wind or temperature d i f f e r e n c e s between i n t e r i o r and e x t e r i o r . As high temperature wind was not d e s i r a b l e d u r i n g the day time, a i r movement was achieved by temperature d i f f e r e n c e s (Koenigsberger, 1971). The c o u r t y a r d s in the houses were e f f e c t i v e i n c o o l i n g the i n t e r i o r spaces through a i r movement ( F i g . 1 . 7 ) . The c o u r t y a r d was shaded dur i n g the day and 25 r e t a i n e d the pool of c o o l night a i r (below 35°C). Because the co o l a i r i s heavier than the surrounding warm a i r (above 40°C), i n the day time when the w a l l s towards the s t r e e t r e c e i v e d i n t e n s e s o l a r r a d i a t i o n and the i n t e r n a l temperature began to r i s e , the c o o l a i r flowed i n from the c o u r t y a r d and re p l a c e d the warm a i r r i s i n g through the i n t e r i o r . Although wind v e l o c i t y i n summer was high, the c o o l a i r i n the co u r t y a r d was l e f t u ndisturbed because of the c o u r t y a r d ' s small s i z e i n comparison to i t s h e i g h t . The c o o l e r a i r , c o o l e r s u r f a c e s and the e a r t h beneath the c o u r t y a r d draw heat from the surrounding areas and r e - r a d i a t e i t to the open sky during the n i g h t . Small openings / Use of l a t t i c e w o r k f o r windows The luminance of the sky near the hor i z o n i s grea t e r than at the z e n i t h under c l e a r sky c o n d i t i o n s and can be a source of g l a r e . In a d d i t i o n , b u i l d i n g s surrounding the d w e l l i n g s i n Mohanjodaro were of a l i g h t c o l o r and were a source of g l a r e in strong s u n l i g h t . On the one hand the small windows helped in reducing s o l a r r a d i a t i o n , but they c o u l d a l s o be a source of g l a r e because of t h e i r small s i z e which c r e a t e d a dramatic c o n t r a s t between the dark i n t e r i o r and the b r i g h t sky outdoors. To p r o t e c t the i n t e r i o r from these sources of g l a r e , the windows at eye l e v e l i n the houses of Mohanjodaro had i n t r i c a t e l a t t i c e work which excluded g l a r e while b r i n g i n g d i f f u s e d l i g h t i n to the i n t e r i o r s . 26 H^T bUSTY WINDS ̂ '/////////7. PAY /t/t/fs 4 H I 6 H T - G R O U N D ' Fig.1.7 . Thermal System of a Courtyard House i n Mohanjodaro In summary, thermal comfort i n the houses of Mohanjodaro was achieved by minimizing the impact of the unfavourable c l i m a t e and by improving the m i c r o - c l i m a t i c c o n d i t i o n s with the help of town l a y o u t , housing form, and c o n s t r u c t i o n of v a r i o u s components l i k e w a l l s , r o o f s , windows. These are termed " p a s s i v e " design techniques. In a d d i t i o n , personal a d a p t a t i o n s were made by people through c l o t h i n g and the use of v a r i o u s areas of the house such as co u r t y a r d s where c o n d i t i o n s were moderated. 27 SECTION I I : MEDIEVAL PERIOD 1. INTRODUCTION The most important Indian c i t i e s which developed i n hot and dry c l i m a t e zone during the e a r l y part of the medieval p e r i o d between 1000A.D.-1800A.D. were o l d D e l h i , Ahmedabad, Udaipur, J a i s a l m e r and J a i p u r ( F i g . 1 . 8 ) . The medieval p e r i o d in i n d i a was marked by many i n v a s i o n s . Most c i t i e s in t h i s region were t h e r e f o r e b u i l t f o r defence purposes and were s i m i l a r i n layout and house form. The c i t y of J a i s a l m e r i s used here to demonstrate methods of ma i n t a i n i n g comfort in houses of the hot and dry c l i m a t i c zone during the medieval per i o d . 2. HOUSING IN JAISALMER 2.1. Introduct ion The town of J a i s a l m e r was founded in 1156 A.D. as a m i l i t a r y f o r t and t r a d i n g post f o r the east-west caravan route c r o s s i n g the Thar d e s e r t . The expansion of the town o u t s i d e the f o r t s t a r t e d i n 1725 A.D. (Agarwal, 1979) with the i n f l u x of p o p u l a t i o n from surrounding areas. During the years 1750-1850 A.D. a d d i t i o n s to the town i n c l u d e d f o r t i f i c a t i o n s around the town and c o n s t r u c t i o n of many l a r g e r r e s i d e n t i a l b u i l d i n g s c a l l e d " H a v e l i s " . J a i s a l m e r i s famous f o r the r i c h l y carved facades of the h a v e l i s and other r e s i d e n t i a l b u i l d i n g s . 28 Fig.1.8. L o c a t i o n of the C i t i e s Developed d u r i n g Medieval P e r i o d i n I n d i a . < z; uil» 1 5 rrr '/A % r77j ' A 77 2 w. 22 n /A V/. C£ — \ 1 < 4o \D D \BQ £ &0 5 (lb He V — < lo S i J F W 1 A M 0 0 A 0 N D- F i g . 1 . 9 . C l i m a t i c Data of J a i s a l m e r (Monthly means). Source: Mani, 1982 29 2.2. . L o c a t i o n and Climate The town of J a i s a l m e r i s s i t u a t e d at 26°55N l a t i t u d e and 75°55E l o n g i t u d e (Fig.1.8) and i s 1.7m above mean sea l e v e l . The c l i m a t e of Jai s a l m e r i s t y p i c a l of the extreme hot and dry re g i o n . Although the summer and winter temperatures are l i k e the town of Mohanjodaro, i . e . , between 25°C and 45°C d u r i n g summer and between 5°C and 25°C during winter, the r e l a t i v e humidity in the month of May and June i s o c a s s i o n a l l y l e s s than 30% ( F i g . 1 . 9 ) . The average annual r a i n f a l l in t h i s area i s l e s s than 25cm and d i r e c t and ground r e f l e c t e d s o l a r r a d i a t i o n i s intense f o r the whole year. In June, which i s the h o t t e s t month, the average s o l a r r a d i a t i o n on a h o r i z o n t a l 2 su r f a c e i s 27.2 MJ/m a day. Wind v e l o c i t y i s u s u a l l y high, i t o f t e n exceeds 4.8 m/sec, and there are severe dust storms d u r i n g the months of May and June. The landscape of the surrounding region i s f l a t , rocky and barren. There are s h i f t i n g sand dunes i n the areas around J a i s a l m e r . S e v e r a l kinds of l i g h t c o l o u r e d limestones and sandstones are a v a i l a b l e as b u i l d i n g m a t e r i a l . 2.3. Indoor Comfort C r i t e r i a Indoor Environmental C o n d i t i o n s Being i n a hot and dry c l i m a t i c zone, the indoor thermal c o n d i t i o n s f o r b u i l d i n g s i n J a i s a l m e r are s i m i l a r to Mohanjodaro. However i n J a i s a l m e r , an a d d i t i o n a l c o n s i d e r a t i o n f o r human comfort i s p r o t e c t i o n from the dust -laden wind. L i f e S t y l e The l i f e s t y l e of the people of J a i s a l m e r was s i m i l a r to 30 other medieval c i t i e s i n t h i s c l i m a t i c zone in India (schoenauer,1981). Given t h e i r t e c h n o l o g i c a l l i m i t a t i o n s , the people of J a i s a l m e r had to l i v e with a s c a r c i t y of water and the severe c l i m a t i c c o n d i t i o n s . People made personal a d a p t a t i o n s i n t h e i r d a i l y indoor and outdoor a c t i v i t i e s to achieve thermal comfort. For example, dur i n g the hot summer day, cooking, s l e e p i n g and other household a c t i v i t i e s were l i m i t e d to the indoors whereas i n the c o o l e r evenings or at nig h t , t e r r a c e s and outdoor spaces were used f o r these a c t i v i t i e s . As the use of most spaces in the house changed d i u r n a l l y and s e a s o n a l l y , with the exception of a few s e r v i c e areas, the v a r i o u s rooms of the house were r a r e l y designed f o r a s i n g l e a c t i v i t y . Most areas of the house were washed and cleaned everyday and w a l l s were whitewashed a n n u a l l y by the r e s i d e n t s . C l o t h e s worn by people in J a i s a l m e r were made of t h i c k c o t t o n . People wore loose garments, and covered t h e i r heads f o r c u l t u r a l reasons, which a l s o gave them p r o t e c t i o n from the strong sun and wind blown dust o u t s i d e . Cotton, as a l r e a d y s t a t e d , i s more e f f e c t i v e f o r ev a p o r a t i v e c o o l i n g than other c l o t h i n g m a t e r i a l s . 2.4. Environmental problems The b a s i c environmental problem i n the b u i l d i n g s of J a i s a l m e r i s c o o l i n g , in a d d i t i o n to which the b u i l d i n g s need p r o t e c t i o n from dust storms. 2.5. B u i l d i n g Design Techniques The Town Layout The town of J a i s a l m e r has an i r r e g u l a r polygon shape and i s 31 surrounded by a 6m. high w a l l . V a r i o u s gates c a l l e d the 'Poles' d e f i n e the entry p o i n t s to the town while the f o r t , which i s w i t h i n the town, i s l o c a t e d on a h i l l surrounded by a second w a l l f o r def e n s i v e purposes (Fig.1.10). The area w i t h i n the f o r t i s t r i a n g u l a r i n shape and c o n t a i n s the r o y a l palace in a d d i t i o n to numerous common d w e l l i n g s . U n l i k e other Indian f o r t s , which are c h a r a c t e r i s e d by strong r e c t i l i n e a r geometry and open spaces, the f o r t in J a i s a l m e r has a winding s t r e e t network, p o s s i b l y f o r s e c u r i t y reasons, and has few community open spaces. The major s t r e e t s in the town o u t s i d e the f o r t have a general E-W o r i e n t a t i o n with minor s t r e e t s at r i g h t angles to these. The " h a v e l i s " , with r i c h l y carved f r o n t s , are l o c a t e d on the E-W s t r e e t s which are wider than other s t r e e t s (Schonauer, 1981). The height of b u i l d i n g s i n general i s one to two times the width of s t r e e t s , the b u i l d i n g s are of unequal h e i g h t s , and the facade a b u t t i n g the s t r e e t has r i c h l y carved b a l c o n i e s and f i n s p r o j e c t i n g at the upper l e v e l . For v a r i o u s socio-economic reasons, the town plan of Jais a l m e r developed i n the form of 'Padas' ( r e s i d e n t i a l d i s t r i c t s ) based on the caste or p r o f e s s i o n of the r e s i d e n t s . The House Form The r e s i d e n t i a l b u i l d i n g s were c o n s t r u c t e d with mutual h e l p by using l o c a l l y a v a i l a b l e m a t e r i a l s and c o n s t r u c t i o n technology. The involvement of occupants with b u i l d i n g c o n s t r u c t i o n and t h e i r s t r u g g l e with c l i m a t i c t e c h n i c a l , p o l i t i c a l and economic c o n s t r a i n t s made them develop a keen design sense which i s evident i n the b u i l d i n g s of J a i s a l m e r . The d w e l l i n g s of 32 ^ 4 GATE TAKH-- F i g . 1.10. Town Layout of J a i s a l m e r . Source: Schoenauer, 1981 Fig.1.11. Plan of a Small House In J a i s a l m e r Source: Schoenauer, 1981 33 J a i s a l m e r are r e a l evidence of the s o p h i s t i c a t e d i n t e r a c t i o n between the above c o n s t r a i n t s , and a m a n i f e s t a t i o n of an e x p r e s s i v e type of a r c h i t e c t u r e . The houses belonging to a l l socio-economic groups were p r i m a r i l y designed to provide p r o t e c t i o n from extreme c l i m a t i c c o n d i t i o n s with a d d i t i o n a l c o n s i d e r a t i o n s for p r i v a c y and the safe storage of p o s s e s s i o n s . However, the f i n a n c i a l s t a t u s of the occupant d i c t a t e d the luxury of the b u i l d i n g in terms of i t s ornamentation and vastness of spaces. There are three types of houses in J a i s a l m e r each belonging to a d i f f e r e n t socio-economic group: a. The f i r s t type c o n s i s t e d of a s i n g l e room, a verandah and a c o u r t y a r d (Fig.1.11). Larger houses of t h i s type had another verandah over the entrance and some had an a d d i t i o n a l room on one s i d e of the c o u r t y a r d . These houses were owned by the poorest people and were b u i l t i n the p e r i p h e r a l areas of the town. b. The second type can be termed the " t y p i c a l " house of J a i s a l m e r and belonged to middle-income people (Fig.1.12). The design and c o n f i g u r a t i o n of t h i s house was s i m i l a r to the f i r s t type, but with a d d i t i o n a l rooms and small enclosed t e r r a c e s l o c a t e d on the upper f l o o r s . The f r o n t of the f i r s t f l o o r had b a l c o n i e s p r o j e c t i n g over the s t r e e t . The t y p i c a l house of J a i s a l m e r was a t t a c h e d to other houses on i t s s i d e and at the back, l e a v i n g only a narrow facade with small openings exposed to the s t r e e t . c. The t h i r d and most complex type, were the " h a v e l i s " ( F i g . 1 . 1 3 ) , owned by r i c h merchants and were l o c a t e d 34 ^ • GROUND FL&SK RR<=,T F L ^ K - Fig.1.12. Plan of a Middle Income House i n J a i s a l m e r Source: Gupta, 1985 STRE-ET- Fig.1.13. Plan and S e c t i o n of a H a v e l i . Source: Gupta, 1985 35 i n s i d e the f o r t . In these four or f i v e s t o r i e d houses, the c o u r t y a r d was surrounded by rooms or verandahs on a l l s i d e s . There were a l s o underground rooms, sometimes on two l e v e l s , one below the other. The uppermost storey was comprised of t e r r a c e s enclosed by wind p a v i l l i o n s and high parapet w a l l s . In some cases, the house was b u i l t around two c o u r t s . In a d d i t i o n to c o u r t y a r d s , a i r ducts were sometimes used f o r v e n t i l a t i o n . B u i l d i n g C o n s t r u c t i o n The most common b u i l d i n g m a t e r i a l s used in J a i s a l m e r were l i g h t y e l l o w i s h sandstone and limestone. The sandstone was used fo r w a l l s which were 0.45m or more in t h i c k n e s s . In b e t t e r q u a l i t y c o n s t r u c t i o n the stone was dressed and j o i n t s were made a c c u r a t e l y without any mortar. The i n d i v i d u a l stones were held together by stone keys cut i n t o the blocks themselves, or by i r o n clamps. In the smaller houses the stone was undressed and the w a l l s were b u i l t i n mud mortar and f i n i s h e d with mud p l a s t e r . On the upper f l o o r l e v e l s of the " h a v e l i s " , where the b u i l d i n g facade p r o j e c t e d out, 50mm t h i c k panels of limestone p r o j e c t e d from the w a l l as f i n s . These were deeply carved i n v a r i o u s geometrical p a t t e r n s . Both the limestone used f o r c a r v i n g , and the sandstone used fo r masonry were l i g h t i n c o l o u r and provided a permanent f i n i s h . Roofs and f l o o r s were b u i l t with timber beams pl a c e d on the w a l l s , spaced c l o s e l y , and covered with a t h i c k l a y e r of grass matting and a t h i c k l a y e r (0.45 to 0.60m) of e a r t h on top (Fig.1.14). Because of the l i m i t e d a v a i l a b i l i t y of timber 36 feA.t2TH FILL.• M A T - F i g . 1 . 1 4 . C o n s t r u c t i o n of the r o o f of a H a v e l i . S o urce: Gupta, 1985 F i g . 1 . 1 5 . S t r u c t u r a l P r o j e c t i o n s and F i n s on the Upper L e v e l Facade of a H a v e l i . Source: Schoenauer, 1981 37 i n t h e d e s e r t , i n some hou s e s t h e t i m b e r beams were r e p l a c e d by s t o n e s l a b s ( t h i s d i d not p r e s e n t a p r o b l e m of water seepage as t h e r e was l i t t l e r a i n f a l l ) . Windows were g e n e r a l l y s m a l l and f i t t e d w i t h s o l i d t i m b e r s h u t t e r s . B e c a u s e of t h e need f o r p r i v a c y , t h e use of windows was l i m i t e d t o upper f l o o r s o n l y . D o o r s were b u i l t w i t h s t o n e frames and a l s o f i t t e d w i t h t h i c k t i m b e r s h u t t e r s . In t h e h o u s e s d e s c r i b e d a b o v e , some of t h e d e s i g n f e a t u r e s t o a c h i e v e c o o l i n g were t h e same as t h o s e d i s c u s s e d i n t h e hous e s of M o h a n j o d a r o ; dense c l u s t e r i n g of b u i l d i n g s , sun c o n t r o l t h r o u g h o r i e n t a t i o n , m a s s i v e c o n s t r u c t i o n of w a l l s and r o o f s , and t h e use of c o u r t y a r d s . However, a d d i t i o n a l d e s i g n f e a t u r e s i n t r o d u c e d h e r e t o enhance c o o l i n g i n c l u d e d : - t h e use of s t r u c t u r a l p r o j e c t i o n s t o c o n t r o l s u n , - u n e q u a l b u i l d i n g h e i g h t s , - c o o l i n g of s u n l i t s u r f a c e s by t h e use of f i n s and c a r v i n g , - a i r d u c t s f o r v e n t i l a t i o n , - basement l i v i n g s p a c e s . 2.6. P e r f o r m a n c e of B u i l d i n g D e s i g n T e c h n i q u e s As t h e b a s i c e n v i r o n m e n t a l p r o b l e m i n b o t h M o h a n j o d a r o and J a i s a l m e r was c o o l i n g , t h e t h e r m a l p e r f o r m a n c e of common d e s i g n t e c h n i q u e s s u c h as dense c l u s t e r i n g of b u i l d i n g s , sun c o n t r o l t h r o u g h o r i e n t a t i o n , m a s s i v e c o n s t r u c t i o n of r o o f and w a l l s , and c o u r t y a r d s c a n be assumed t o have been e q u a l l y e f f e c t i v e f o r b o t h . T h e r e f o r e , o n l y t h e a d d i t i o n a l d e s i g n f e a t u r e s of J a i s a l m e r a r e examined i n d e t a i l f o r t h e i r t h e r m a l p e r f o r m a n c e and p r o t e c t i o n from wind and d u s t . Use of S t r u c t u r a l P r o j e c t i o n s , Unequal Heights, and F i n s f o r C o o l i n g The s t r u c t u r a l p r o j e c t i o n s and f i n s , u n e q u a l h e i g h t s of 38 b u i l d i n g s , and c a r v i n g on the f r o n t facade p r o v i d e d combined thermal p r o t e c t i o n to the b u i l d i n g s at three d i f f e r e n t l e v e l s : a. The unequal b u i l d i n g h e i g h t s , wind p a v i l l i o n s , and high parapet w a l l s c r e a t e d an uneven s k y l i n e , and shaded each other in the process. b. The s t r u c t u r a l p r o j e c t i o n s and f i n s shaded the upper l e v e l facade (Fig.1.15), which would otherwise r e c e i v e intense s o l a r r a d i a t i o n . c. P a r t s of the b u i l d i n g facade and s t r u c t u r a l p r o j e c t i o n s were deeply carved. When the s o l a r r a d i a t i o n was intense and the surface temperature was high, the c o n v e c t i v e heat t r a n s f e r to the a i r from the carved s u r f a c e was more than the f l a t s u r f a c e due to a grea t e r s u r f a c e to volume r a t i o . T h i s enabled the carved s u r f a c e s to c o o l down q u i c k l y when the ambient a i r temperature was low du r i n g the evenings (Gupta, V., 1985). In J a i s a l m e r , carved s u r f a c e s were used at the upper l e v e l where w a l l t h i c k n e s s was between 5-15cm., whereas the ground f l o o r s had f l a t s u r f a c e s and w a l l t h i c k n e s s of grea t e r than 45 cm. The ground f l o o r w a l l s were in shade d u r i n g the day - time because of the narrow width of the s t r e e t s i n r e l a t i o n to the high b u i l d i n g s . The carved s u r f a c e s were u s e f u l only i n t h i n w a l l s as the t h i c k e r w a l l s were capable of reducing heat gain even without t e x t u r e because of t h e i r inherent thermal moderating c h a r a c t e r s t i c s . In a d d i t i o n to c a r v i n g s , the l i g h t c o l o u r of the stones absorbed l e s s r a d i a n t heat (Markus and M o r r i s , 1980) and t h e r e f o r e maintained the e x t e r n a l surface temperature c l o s e r 39 to that of the outdoor a i r , which i n turn reduced the heat flow through the r e l a t i v e l y t h i n w a l l s . Air Ducts for Ve n t i l a t i o n When b u i l d i n g s are t i g h t l y c l u s t e r e d together i t i s g e n e r a l l y d i f f i c u l t to l e t wind i n t o the house through windows and doors, and a i r movement due to temperature d i f f e r e n t i a l s i s u s u a l l y too s l u g g i s h to improve comfort unless i t i s augmented by a d d i t i o n a l design f e a t u r e s . In a d d i t i o n , there were two more important problems r e l a t e d to v e n t i l a t i o n i n J a i s a l m e r : a. The temperature of the o u t s i d e a i r needed to be reduced before i t entered any l i v i n g space, or e l s e i t s c o o l i n g e f f e c t on human s k i n was n u l l i f i e d due to i t s high temperature. b. Due to the dust storms i n summer, the a i r had to be p r e - t r e a t e d to reduce i t s dust p a r t i c l e content. In J a i s a l m e r a i r ducts were used as a s p e c i a l f e a t u r e f o r v e n t i l a t i o n i n a d d i t i o n to the c o u r t y a r d s . The a i r ducts, b u i l t with massive stone w a l l s , temper the a i r before i t entered the l i v i n g space and a l s o reduced the amount of dust in i t (F i g . 1 . 1 6 ) . The o p e r a t i o n of these a i r ducts was s i m i l a r to that of the wind towers used i n hot and a r i d regions l i k e Iran (Bahadori,1979). F i g u r e 1.16 shows the c r o s s s e c t i o n of a t y p i c a l a i r duct. The c i r c u l a t i o n of a i r through night and day, and the r e d u c t i o n of dust p a r t i c l e s in the a i r ducts took p l a c e i n the f o l l o w i n g way: Night Operation When there was no wind blowing at n i g h t , the a i r ducts acted 40 Fig.1.16. Operation of a Wind Tower i n Summer. A i r Flow dur i n g the Day, — ^ ; A i r Flow d u r i n g the Night with no Wind, ̂ . — . Source: Bahadori, 1979. 41 as a chimney. The w a l l s of the duct that were heated during the day t r a n s f e r r e d heat to the c o o l night a i r . The heated a i r was then exhausted at the openings (F i g . 1 . 1 6 ) . T h i s chimney a c t i o n maintained c i r c u l a t i o n of the ambient a i r throughout the b u i l d i n g , and coo l e d the s t r u c t u r e of the b u i l d i n g as w e l l as that of the a i r duct. When there was a wind blowing dur i n g the ni g h t , the a i r c i r c u l a t i o n was i n the d i r e c t i o n opposite to that d e s c r i b e d , but the wa l l s of the tower were coo l e d , and some c o o l i n g of the rooms might have r e s u l t e d . Day Operation When there was no wind blowing dur i n g the day, the duct operated as a reverse chimney. The hot ou t s i d e a i r i n contact with c o l d w a l l s (A) and (B) (cooled d u r i n g the previous night) was co o l e d and sank down through passages (2) and ( 3 ) . Th i s a i r may be l e t out through door (4) or door (6) the dust p a r t i c l e s of which have been l e f t in area (7). When there was a wind, the a i r c i r c u l a t i o n and the rate of c o o l i n g were in c r e a s e d and the c o o l a i r co u l d reach f u r t h e r i n s i d e the house. When a i r went through s e c t i o n (5) and when wa l l (C) was moist, the a i r was f u r t h e r c o o l e d by ev a p o r a t i o n . The psychrometric chart p r e s e n t a t i o n of o r d i n a r y and eva p o r a t i v e c o o l i n g processes through a i r ducts i s shown i n Fig u r e 1.17. Basement L i v i n g Spaces Almost a l l houses in Ja i s a l m e r had basements as l i v i n g spaces. The temperature underground remained almost constant throughout the year due to the absence of any' heat l o a d , and 42 due to rapid decay of the ambient temperature wave in s o i l . Therefore, the rooms in the basement stayed much cooler than the upper floors of the buildings during summer. Source: Bahadori, 1979 43 SECTION I I I : MODERN INDUSTRIAL PERIOD 1. INTRODUCTION In India a f t e r World War I I , the i n t r o d u c t i o n of r a p i d t r a n s p o r t a t i o n systems, the a v a i l a b i l i t y of b u i l d i n g c o n s t r u c t i o n m a t e r i a l s l i k e c o n c r e t e and s t e e l , and the widespread use of e l e c t r i c i t y and f o s s i l f u e l s brought about a s i g n i f i c a n t change in the housing design and c o n s t r u c t i o n methods. The s e r v i c i n g of houses a l s o changed d r a m a t i c a l l y with the i n t r o d u c t i o n of e l e c t r i c l i g h t i n g and modern c o o l i n g and hea t i n g systems. F o l l o w i n g I n d i a ' s independence in 1947, p o l i t i c a l s t a b i l i t y and r a p i d economic development r e s u l t e d i n s i g n i f i c a n t urban sprawl and u n l i m i t e d h o r i z o n t a l expansion of towns and r e s i d e n t i a l neighbourhoods. T h i s a l s o brought an abundance of people to the urban areas r e q u i r i n g new p l a n n i n g c r i t e r i a to solve the problem of housing. New and experimental c i t i e s l i k e Chandigarh, Rourkela, B h i l a i and Gandhinagar were designed and developed with 'modern' design p r i n c i p l e s and c o n s t r u c t i o n methods. The c i t y of Chandigarh, l o c a t e d i n the hot and dry zone, i s d i s c u s s e d in the f o l l o w i n g s e c t i o n s to demonstrate the methods of a c h i e v i n g human comfort i n d w e l l i n g s during the modern i n d u s t r i a l p e r i o d . 44 2. HOUSING IN CHANDIGARH 2 . 1 . I n t r o d u c t i o n Chandigarh was b u i l t s i n c e 195.1 as a c a p i t a l c i t y f o r the s t a t e of Punjab ( S a r i n , 1982), which l o s t i t s c a p i t a l d u r i n g the p a r t i t i o n of I n d i a i n 1947. The c i t y was designed by a team of f o r e i g n a r c h i t e c t s headed by the French a r c h i t e c t Le C o r b u s i e r . A A r ^ 1 r ^ 72* 74' £4-' \<l° Fig.1.18. L o c a t i o n of Chandigarh. 2.2. L o c a t i o n and Climate The c i t y i s l o c a t e d a t 30°43N l a t i t u d e and 76°47E l o n g i t u d e (Fig.1.18). The monthly a i r temperature, r e l a t i v e humidity and s o l a r r a d i a t i o n on a h o r i z o n t a l s u r f a c e (Fig.1.19) i n Chandigarh are t y p i c a l of the hot and dry zones. 45 z: 22 ul Si I I- 777 / / / r 7~7 n LU 2>6 4< E Z 2 22 Z2 72 < J F M A M a a A M/NTH- <2 N t> Fig.1.19. C l i m a t i c Data of Chandigarh (Monthly Means) Source: Mani, 1982 46 The landscape of the surrounding area i s f l a t towards the southwest with o c c a s i o n a l t r e e s and bushes. H i l l s and seasonal r i v e r s form the northeast and southwest boundaries. The s o i l i s c l a y and s u i t a b l e f o r making b r i c k s . 2.3. Indoor Comfort C r i t e r i a and Environmental Problems Indoor Environmental C o n d i t i o n s For the b u i l d i n g s of Chandigarh, the indoor thermal c o n d i t i o n s and the need for c o o l i n g are s i m i l a r to those in other hot dry c l i m a t i c zones l i k e Mohanjodaro or J a i s a l m e r as d i s c u s s e d in the previous s e c t i o n s . L i f e S t y l e Chandigarh was designed a f t e r independence when India was beginning to go through s o c i a l , t e c h n i c a l and economic changes (Bhattacharya, 1979). The c i t y was envisaged as a new experiment a g a i n s t the wide context of t r a d i t i o n a l c i t y p l a n n i n g and house design i n I n d i a . The i n h a b i t a n t s - of the c i t y were expected to adapt to a new 'urban' way of l i f e . The house, as a part of a neighbourhood, was expected to provide a sense of the new s o c i a l i d e n t i t y based upon the general s i m i l a r i t y of income of the occupants r a t h e r than the t r a d i t i o n a l concept based on c a s t e , language and r e l i g i o n (Evenson, 1966). The f u n c t i o n of the house f o r p r o v i d i n g s h e l t e r , p r o t e c t i o n from the extremes of c l i m a t e , safe storage of goods and p r o v i s i o n of p r i v a c y , was not envisaged in the t r a d i t i o n a l sense. Instead i t was argued by the d e s i g n e r s that the house should be a ' l i v i n g machine' (Evenson,1966) where a l l a c t i v i t i e s l i k e cooking, e a t i n g and s l e e p i n g would take plac e i n a e f f i c i e n t and systematic way. 47 The f u n c t i o n a l aspects of the house design were given more importance than the t r a d i t i o n a l s o c i o - c u l t u r a l needs fo r comfort. It was expected by the d e s i g n e r s that the i n c r e a s i n g use of energy i n t e n s i v e s e r v i c e s l i k e a r t i f i c i a l l i g h t i n g and c o o l i n g would help people i n a c h i e v i n g r e q u i r e d environmental c o n d i t i o n s , t h e r e f o r e , a l l houses were provided with an e l e c t r i c i t y supply. The widespread use of e l e c t r i c i t y i n Chandigarh houses has c r e a t e d new h a b i t s and comfort e x p e c t a t i o n s . The occupants, i n s t e a d of adapting t h e i r behavior to achieve comfort, , now expect mechanical means to provide t h e i r comfort requirements. Since the time when Chandigarh was b u i l t , v a r i o u s c l o t h i n g s t y l e s and new c l o t h m a t e r i a l s have developed in India and they change every year with new trends in f a s h i o n . The most popular c l o t h m a t e r i a l worn by the middle c l a s s i n Chandigarh i s a blend of c o t t o n and s y n t h e t i c c a l l e d ' t e r i c o t ' which i s r e l a t i v e l y inexpensive, durable and can be worn without i r o n i n g , but i n h i b i t s e v a p o r a t i v e c o o l i n g . As the need fo r p r i v a c y was not emphasised i n the housing design, t h i c k c u r t a i n s are used on window and door openings for the purpose of p r i v a c y . Although wooden doors and windows are p r o v i d e d i n a l l rooms, they are not f r e q u e n t l y operated by most people (Br.olin, 1976). T e r r a c e s and verandahs are used f o r s l e e p i n g outdoors d u r i n g summer. As expected by the p l a n n e r s , fans and other mechanical means are c o n s i s t e n t l y used f o r c o o l i n g i n s i d e the house. 48 Fig.1.21. The Sector Layout. Source: Evenson, 1966 2.4. B u i l d i n g Design Techniques The C i t y Layout The C i t y of Chandigarh i s planned on a uniform g r i d p a t t e r n (Fig.1.20). A l l major s t r e e t s c a l l e d V2's run SE-NW to p r o t e c t the v e h i c l e d r i v e r s a g a i n s t d i r e c t sun, and secondary s t r e e t s (V3's) run pe r p e n d i c u l a r to them. The t o t a l width of the V2 and V3 roads i s 80 m and 60 m r e s p e c t i v e l y with 9 m of road s u r f a c e . The c i t y i s d i v i d e d i n t o v a r i o u s neighbourhoods c a l l e d ' s e c t o r s ' (Fig.1.21) each of which i s 800x1200 m, and i s surrounded by V2 and V3 roads. Each s e c t o r i s sub- d i v i d e d by V4 roads i n t o four p a r t s with c e n t r a l l y p l a c e d shopping, community and r e c r e a t i o n a l f a c i l i t i e s . A 40 m wide loop road (V5) connects a l l p a r t s of the s e c t o r . The houses face 30 m wide V6 roads and are o r i e n t e d SE-NW or NE-SW. The height of r e s i d e n t i a l blocks does not exceed three s t o r e y s (10 m) for s t r u c t u r a l reasons. A l l s e c t o r s have a s i m i l a r housing layout p a t t e r n . The zoning r e g u l a t i o n s and a r c h i t e c t u r a l c o n t r o l s prepared by planners and a r c h i t e c t s f o r s t a n d a r d i z a t i o n of c o n s t r u c t i o n and u n i f o r m i t y of r e s i d e n t i a l e x p r e s s i o n , s p e c i f y the s i z e of p r o j e c t i o n s on the facade fo r shading, the s i z e of window and door openings, the s i z e of back and f r o n t yards, the height of compound w a l l s and the height of r e s i d e n t i a l b l o c k s . The House Form There are two c a t e g o r i e s of house owners i n Chandigarh (Evenson, 1966): a. Government agencies (used by t h e i r employees) 50 Living A PIHIN6 KM KITCHEN ® J e e p 7 1 PINIH6»- Fig.1.22. Government Housing i n Chandigarh. a. Ground F l o o r Plan of S i n g l e Family Attached House. b. Ground F l o o r Plan of S i n g l e Family Detached House. c. Ground F l o o r P l a n of M u l t i p l e Family Attached House. Source: Evenson, 1966 51 f ^ N T VAV2D ® v&ftAMOA KITSCH T2IL&T tow • N50 DI2AWIH6, V 6 K A N D A Fig.1.23. P r i v a t e Housing i n Chandigarh. a. Ground F l o o r Plan of a S i n g l e Family Attached House b. Ground F l o o r Plan of a S i n g l e Family Detached House. Source: Evenson, 1966 52 b. P r i v a t e homeowners. Each category has two d i f f e r e n t types of houses ( s i n g l e f a m i l y attached and s i n g l e f a m i l y detached) which are used by people of d i f f e r e n t income l e v e l s (Fig.1.22, 1.23). The t y p i c a l form of the s i n g l e f a m i l y detached houses (Fig.1.22b,1.23b) i s the 'bungalow' type. These houses are surrounded by open space on a l l s i d e s and have window openings on two s i d e s . The glazed window openings, as s p e c i f i e d i n the a r c h i t e c t u r a l c o n t r o l s , are l / 6 t h of the t o t a l area of the room and are p r o t e c t e d by a b r i s e s o l e i l or deep veranda. P r o v i s i o n f o r t e r r a c e s i s made in a l l s i n g l e f a m i l y detached houses. The s i n g l e family a t t a c h e d houses (l.22a,c and 1.23a) share side w a l l s and have yards in f r o n t and back. The compound wa l l in the rear yard i s 2 m high f o r the purpose of p r i v a c y , and i s .75 m high at the f r o n t . One bedroom and the l i v i n g r o o m face the f r o n t yard, and the k i t c h e n , the t o i l e t and bathrooms are kept at the rear f o r ease of connection to the main sewer l i n e s . In some cases the t o i l e t s are attached to bedrooms and v e n t i l a t e d by ducts. A l l houses have f l a t r o o f s which are a c c e s s i b l e f o r use as t e r r a c e s . B u i l d i n g C o n s t r u c t i o n and S e r v i c e s As b r i c k was made l o c a l l y , i t became the p r i n c i p a l m a t e r i a l for c o n s t r u c t i o n of a l l houses in Chandigarh. The w a l l s are c o n s t r u c t e d with 20x10x7.5 cm b r i c k s and cement mortar. The e x t e r n a l l o a d bearing w a l l s are 30 cm t h i c k and are p l a s t e r e d and whitewashed on the i n s i d e . The i n t e r n a l load bearing 53 r-^iM- MUt> FUS444- Fig.1.24. T y p i c a l Roof S e c t i o n . S LATITUOe SO* NORTH Fig.1.25. Sun Path Diagram f o r SE Facade. Source: Mani, 1982 54 w a l l s a r e 20cm. t h i c k and are p l a s t e r e d and w h i t e washed on both s i d e s . For roof c o n s t r u c t i o n ( F i g . 1 . 2 4 ) , b r i c k t i l e s of 20x10x5 cm are l a i d over 10 cm t h i c k c o n c r e t e , 5 cm mud fu s k a (mud and hay) and a 3 cm l a y e r of bitumen. The t h i c k n e s s of the roof seldom exceeds 25 cm and i s s u p p o r t e d on the b r i c k w a l l s . The door and window jambs a re made out of l o c a l l y a v a i l a b l e wood, and are f i t t e d w i t h openable, f i x e d g l a s s and wiremesh panes. F i x e d g r i l l s a r e added t o a l l windows f o r the purpose of s e c u r i t y . Shading d e v i c e s l i k e p r o j e c t i o n s and b r i s e s s o l e i l a r e of r e i n f o r c e d c o n c r e t e . The b u i l d i n g f e a t u r e s d e s i g n e d t o p r o v i d e c o o l i n g a r e : - o r i e n t a t i o n , - b r i s e s o l e i l and verandahs, - r o o f c o n s t r u c t i o n w i t h s p e c i a l m a t e r i a l s . In a d d i t i o n , a r t i f i c i a l c o o l i n g d e v i c e s l i k e f a n s and e v a p o r a t i v e c o o l e r s a r e commonly used. 2.5. Performance of B u i l d i n g Design t e c h n i q u e s O r i e n t a t i o n / U s e of b r i s e s - s o l e i l and verandas In the p l a n n i n g of Ch a n d i g a r h , the o r i e n t a t i o n of d w e l l i n g s combined w i t h the use of a b r i s e - s o l e i l i s the p r i m a r y d e s i g n f e a t u r e t h r ough which some c o n t r o l over the sun i s a c h i e v e d . A l l the houses a r e o r i e n t e d SE-NW or NE-SW. In a s i n g l e f a m i l y a t t a c h e d house ( F i g . 1 . 2 2 a & 1.23a) o r i e n t e d SE-NW, ar e a s l i k e the l i v i n g room and bed room f a c e SE and o n l y two w a l l s a r e exposed. The a l t i t u d e of the sun i n the summer months v a r i e s between 0° and 80° (F i g . 1 . 2 5 ) so t h a t the windows f a c i n g SE get s o l a r r a d i a t i o n between 9 a.m. and 12 55 Fig.1.26. Shading Devices f o r Chandigarh Houses. a. B r i s e S o l e i l f o r SE and SW Facades i n the E a r l i e r Houses i n Chandigarh. b. H o r i z o n t a l and V e r t i c a l P r o j e c t i o n s f o r S o l a r P r o t e c t i o n . Source: Evenson, 1966 56 p.m. For t h i s reason, a l l windows f a c i n g SE i n the e a r l i e r , houses of Chandigarh are kept small (45cmx45cm) and are p r o t e c t e d with 45 cm deep b r i s e s o l e i l (Fig.1.26a). In the l a t e r houses the b r i s e s o l e i l i s r e p l a c e d , f o r the purpose of economy and unwanted o b s t r u c t i o n of view, with one h o r i z o n t a l p r o j e c t i o n at the l i n t e l l e v e l combined with v e r t i c a l p r o j e c t i o n s on both s i d e s of the comparatively l a r g e r window openings (Fig.1.26b). T h i s p r o v i d e s p r o t e c t i o n from the sun between 10 a.m. and 12 p.m. when the a l t i t u d e angle v a r i e s between 60° and 80° and the s o l a r i n t e n s i t y i s h i g h . In a d d i t i o n , t h i c k c u r t a i n s are used for windows and doors to o b s t r u c t d i r e c t s o l a r r a d i a t i o n . However, c u r t a i n s are not e f f e c t i v e ways of s o l a r c o n t r o l as they absorb the s o l a r heat and d i s s i p a t e i t to the i n t e r i o r by c o n v e c t i o n and r a d i a t i o n . Half of t h i s r e - r a d i a t i o n i s outwards, but as i t i s of long- wavelength, i t i s stopped by the window g l a s s and the narrow space between the window and the c u r t a i n i s s u b s t a n t i a l l y overheated. The sun p e n etrates the NW facade a f t e r 2.30 p.m. when i t s a l t i t u d e i s below 45°. Solar heat gain on t h i s s i d e i s p a r t i c u l a r l y uncomfortable as i t s maximum i n t e n s i t y c o i n c i d e s with the h o t t e s t part of the day. To prevent the sun from p e n e t r a t i n g i n s i d e , very deep h o r i z o n t a l p r o j e c t i o n s are r e q u i r e d f o r the windows. Therefore a 3 m deep veranda i s p r o v i d e d in f r o n t of the bed rooms in t h i s o r i e n t a t i o n . Roof C o n s t r u c t i o n with S p e c i a l M a t e r i a l s The use of s p e c i a l m a t e r i a l s l i k e bitumen and mud-fuska, 57 because of t h e i r thermo-physical p r o p e r t i e s , p r o v i d e s thermal i n s u l a t i o n f o r the r o o f . Mud-fuska and bitumen are p l a c e d above the s t r u c t u r a l concrete l a y e r (Ref. Fig.1.24) which reduces the amount of heat p e n e t r a t i o n i n t o t h i s l a y e r during the daytime. The heat which does penetrate i s absorbed in the 10 cm mass of concrete and the r e s u l t i n g i n c r e a s e in i n t e r n a l temperature i s s m a l l . In a d d i t i o n to the s p e c i a l m a t e r i a l s , the t e r r a c e s are used f r e q u e n t l y d u r i n g summer and are washed or sprayed with water almost every day which helps i n reducing the e x t e r n a l s u r f a c e temperature w e l l below the a i r temperature through e v a p o r a t i v e c o o l i n g . Use of mechanical c o o l i n g I n s p i t e of the c l i m a t e responsive performance of some b u i l d i n g design f e a t u r e s , there are v a r i o u s f a c t o r s which n e c e s s i t a t e the mechanical c o n t r o l of thermal c o n d i t i o n s i n s i d e the d w e l l i n g s i n Chandigarh: a. Planning the c i t y of Chandigarh with s t a n d a r d i z e d facades, b u i l d i n g h e i g h t s and wide roads was d e t r i m e n t a l with respect to n a t u r a l c o o l i n g . S t a n d a r d i z a t i o n c r e a t e d equal b u i l d i n g heights i n r e s i d e n t i a l s e c t o r s and r e g u l a r facades which, combined with wide roads, d i d not take advantage of mutual shading f o r c o o l i n g as used in the c i t i e s i n p r e - h i s t o r i c and medieval times b. S e l e c t i v e v e n t i l a t i o n ( i . e . v e n t i l a t i o n only d u r i n g the c o o l e r p e r i o d s of the day), i f used, can help i n lowering the indoor temperature dur i n g the day i n summer. However, the windows in Chandigarh houses are normally open 58 throughout the day, with the r e s u l t t h a t the i n t e r n a l a i r temperature r i s e s c o n s i d e r a b l y . c. Heat generated by c e r t a i n a p p l i a n c e s and the occupants themselves r a i s e s the indoor a i r temperature. d. P e r s o n a l a d a p t a t i o n s to thermal comfort through c l o t h i n g are a l s o not very e f f e c t i v e because of the m a t e r i a l p r o p e r t i e s of the popular c o t t o n / s y n t h e t i c b l e n d s . To achieve thermal comfort under these c o n d i t i o n s , the use of e v a p o r a t i v e c o o l e r s and a i r c i r c u l a t i n g fans i s necessary. I t was observed i n Chandigarh t h a t simple and cheap a i r c i r c u l a t i n g fans are a c c e p t a b l e d u r i n g the p e r i o d s when the a i r temperature i s below 32°C. At higher temperatures the use of fans enhances o v e r h e a t i n g due to c i r c u l a t i o n of warm a i r . 4 S U P P L Y A l £ ' 1- )2<*>M c ^ N P I T V H ' N^TB; B=>STW&EN 1 ANP - 2 ' T-HB A l l * I* AB-WfcEJNA •SfeH^I&UB <«»P LAiTBNT 'H6AT A HP M A T U R E RE-UHA-SBp |NT<? ZOOM- Pizy exJLfc TEMPERATURE °C- F i g . 1.27. The Psychrometric P r e s e n t a t i o n pf C o o l i n g Through E v a p o r a t i v e C o o l e r s . 59 E v a p o r a t i v e c o o l e r s with a blower, although r e l a t i v e l y expensive, both c o o l the a i r and provide a d e s i r e d l e v e l of r e l a t i v e humidity, thus c o n t r i b u t i n g c o n s i d e r a b l y to p h y s i c a l comfort i n hot, dry weather ( F i g . 1 . 2 7 ) . In recent times, however, sporadic e l e c t r i c i t y shortages and high energy c o s t s have discouraged the r e l i a n c e on and use of these mechanical methods. U n f o r t u n a t e l y , i n s p i t e of these s o r t s of unforeseen problems, the Chandigarh example was used e x t e n s i v e l y as a model f o r f u t u r e housing developments in I n d i a . Akhtar Chauhan (1986) p o i n t s out the many negative r e p e r c u s s i o n s that r e s u l t e d from the e x t e n s i v e use of Chandigarh p l a n n i n g : "The tragedy of Chandigarh was that i n s t e a d of e v a l u a t i n g i t as an experiment, our t e c h n o c r a t s and bureaucrats accepted i t as a prototype for f u t u r e developments. Le C o r b u s i e r himself was a great student of v e r n a c u l a r a r c h i t e c t u r e and he d i d a l o t to develop a s c i e n t i f i c and a r t i s t i c approach to the housing problem. But in our rush to cope with the f a s t growth of c i t i e s , most of us b l i n d l y accepted the forms of European f u n c t i o n a l a r c h i t e c t u r e . T h i s r e s u l t e d in the mushrooming of boxes, p i l e d up v e r t i c a l l y and h o r i z o n t a l l y as answers to the housing c r i s i s . T h i s approach produced d w e l l i n g s which were expensive to c o n s t r u c t , consumed more energy, were i n d i f f e r e n t to c l i m a t e and non-responsive to user needs." 60 SECTION IV: CONCLUSIONS AND CONTEMPORARY ISSUES P r i o r to the i n t r o d u c t i o n of mechanical means, comfort in domestic b u i l d i n g s was achieved by c l i m a t e responsive or "p a s s i v e " design techniques. They were not based on a d e l i b e r a t e pre-planned concept or a s c i e n t i f i c knowledge of the behavior of c l i m a t e , b u i l d i n g m a t e r i a l s and b u i l d i n g components. Instead they were a r e s u l t of hundreds of years of a c t u a l experimentation w i t h i n the harsh p h y s i c a l context of l i m i t e d n a t u r a l resources and economic, p o l i t i c a l , c u l t u r a l and p h y s i c a l c o n s t r a i n t s . T h i s i s the reason why they performed e f f e c t i v e l y i n p r o v i d i n g comfort and were repe a t e d l y used. The p a s s i v e design techniques, through which thermal comfort in domestic b u i l d i n g s were achieved, were a combination of la y o u t , form, o r i e n t a t i o n , openings, w a l l s , roof and land s c a p i n g . T h i s design o r i e n t e d technology was e f f e c t i v e in b r i n g i n g the i n t e r n a l thermal c o n d i t i o n s w i t h i n the comfort range by shaping the b u i l d i n g to modify or u t i l i z e the c l i m a t i c c o n d i t i o n s . For example, b u i l d i n g form minimized the exposure of wall s u r f a c e s and windows to sun and reduced s o l a r heat g a i n . The c o u r t y a r d s acted as thermal modulators, wind towers enhanced the movement of a i r indoors and the massive b r i c k w a l l s were a good example of s t r u c t u r e s which moderated outdoor temperature i n t o reasonable indoor temperatures. In a d d i t i o n to thermal comfort, the pa s s i v e techniques a l s o 61 provided many other s o c i a l , economic and a r c h i t e c t u r a l b e n e f i t s which can be of p a r t i c u l a r i n t e r e s t to the a r c h i t e c t s d e s i g n i n g housing in a contemporary context. For example, the compact layout of d w e l l i n g s in hot and dry c l i m a t e s allowed a high d e n s i t y which i s necessary in India today (Sengupta, 1986). Furthermore, the use of indigenous m a t e r i a l s and a simple, c o n s t r u c t i o n technology developed by the l o c a l people themselves ensured minimal m a t e r i a l and labour c o s t s . A d d i t i o n a l l y , the houses r e q u i r e d minimal maintenance, other than whitewashing of the i n t e r i o r s once or twice a year. The end of t h i s type of c o n s t r u c t i o n occured as a r e s u l t of the a v a i l a b i l i t y of high technology a l t e r n a t i v e s t r i g g e r e d by sudden i n d u s t r i a l i z a t i o n . The use of expensive m a t e r i a l s l i k e concrete and s t e e l i n b u i l d i n g c o n s t r u c t i o n now r e q u i r e s s p e c i a l i z e d labour, advanced c o n s t r u c t i o n methods and a d d i t i o n a l t r a n s p o r t a t i o n which have r e s u l t e d i n a high cost of c o n s t r u c t i o n . The use of e l a b o r a t e mechanical systems to c o o l the spaces a l s o r e q u i r e s an a d d i t i o n a l maintenance and r e p a i r c o s t and s p e c i a l i z e d t e c h n i c i a n s . In a d d i t i o n , the t r a d i t i o n a l d w e l l i n g s were very w e l l s u i t e d to the user's p h y s i c a l and p s y c h o l o g i c a l needs due to p a r t i c i p a t i o n of the user in design and c o n s t r u c t i o n . T h i s p a r t i c i p a t i o n process has d e c l i n e d in contemporary d w e l l i n g s , e s p e c i a l l y i n mass s c a l e housing p r o j e c t s developed by p r i v a t e and government agencies. The houses are designed and c o n s t r u c t e d by a s i n g l e owner and then bought or occupied by 62 the u s e r s . Many times t h i s p r a c t i c e r e s u l t s i n a design which i s i l l - s u i t e d to user needs. F i n a l l y , the use of p a s s i v e design technology and the l i f e s t y l e of the occupants, formed t r a d i t i o n a l b e h a v i o r a l h a b i t s in the people. For example, a c t i v i t y occured outdoors in the evening, where the temperature i s c o o l e r and comfort i s p r o v i d e d by the n a t u r a l breeze. N a t u r a l f i b r e s i n c l o t h i n g were used to enhance thermal comfort. The minimum r e l i a n c e on p a s s i v e design technology, coupled with a changing l i f e s t y l e of people has c o n t r i b u t e d to e x c l u s i o n of these a d a p t a t i o n s . In a d d i t i o n to the b a s i c comfort requirements, occupants now d e s i r e t h e i r d w e l l i n g s to have thermal c o n t r o l s which can be r e g u l a t e d by them. Although the mechanical c o n t r o l s h e l p in f i n e t u n i n g the occupant comfort and e l e c t r i c i t y i s a widely a v a i l a b l e item, the sporadic e l e c t r i c i t y shortages d u r i n g the peak hours of summer days d e p r e c i a t e the b e n e f i t s of mechanical c o o l i n g systems. A l l these a r c h i t e c t u r a l , economic and s o c i a l i l l - e f f e c t s a s s o c i a t e d with mechanical systems, i n a d d i t i o n to the c o s t of energy and i t s l i m i t e d supply, suggest that t h e i r widespread use i s u n s u i t a b l e , expensive and u n r e l i a b l e in c o u n t r i e s l i k e I n d i a . The mechanical means have t h e r e f o r e become a l i a b i l i t y r a t h e r than an a s s e t . In c o n c l u s i o n , a simple and most e f f e c t i v e way of reducing the i l l - e f f e c t s of r e l i a n c e on mechanical d e v i c e s i s to minimize t h e i r use by i n c o r p o r a t i n g p a s s i v e design 63 technology in d w e l l i n g s . T h i s does not imply that mechanical c o o l i n g or heating should be e l i m i n a t e d , however l e s s r e l i a n c e on i t w i l l be necessary i f more emphasis i s pl a c e d on pa s s i v e design technology. The remainder part of t h i s t h e s i s e x p l o r e s ways of s y s t e m e t i c a l l y and c o n s c i o u s l y i n c o r p o r a t i n g t r i e d and t e s t e d p a s s i v e design techniques i n contemporary d w e l l i n g s . 64 PART TWO: HOUSING DESIGN STRATEGIES INTRODUCTION SECTION I : SITE SELECTION STRATEGIES SECTION II : SITE PLANNING STRATEGIES SECTION III : FORM DESIGN STRATEGIES SECTION IV: FABRIC DESIGN STRATEGIES 65 INTRODUCTION Part two of t h i s t h e s i s focuses on developing p a s s i v e design s t r a t e g i e s f o r housing i n the hot and dry regions of I n d i a . These s t r a t e g i e s can be used f o r a contemporary housing settlement, i n v o l v i n g l a r g e r s i t e development, or f o r a s i n g l e d w e l l i n g on an i s o l a t e d l o t w i t h i n or o u t s i d e the i n h a b i t e d a r e a . The most important o b j e c t i v e s u n d e r l y i n g these s t r a t e g i e s are ; a. to achieve thermal comfort i n s i d e the d w e l l i n g s with the a p p l i c a t i o n of p a s s i v e design techniques and, b. to i n c o r p o r a t e , wherever p o s s i b l e , t r a d i t i o n a l p a s s i v e techniques i n t o a contemporary co n t e x t . T h i s does not mean a l i t e r a l t r a n s l a t i o n but an i n t e r p r e t a t i o n of bas i c p r i n c i p l e s . These o b j e c t i v e s w i l l be accomplished with; a. an emphasis on the a p p l i c a t i o n of l o c a l c o n s t r u c t i o n p r a c t i c e s , m a t e r i a l s and techniques, b. the i n c o r p o r a t i o n of c u l t u r a l and b e h a v i o r a l aspects of occupants, and c. the i n t e g r a t i o n of a r t i f i c i a l systems to f i n e t u n e occupant comfort. As observed i n d w e l l i n g s in v a r i o u s p e r i o d s of h i s t o r y , p a s s i v e means are most accepted and economical i f l o c a l b u i l d i n g c o n s t r u c t i o n p r a c t i c e s , m a t e r i a l s and techniques are 66 used. The i n c o r p o r a t i o n of the c u l t u r a l and b e h a v i o r a l aspects of people i s p a r t i c u l a r l y important i n the design of d w e l l i n g s i n hot and dry r e g i o n s . As the c l i m a t e i s harsh, the occupants spend a s u b s t a n t i a l part of day "trapped" i n s i d e the d w e l l i n g and any f a i l u r e of the house to meet s o c i a l and c u l t u r a l needs i s f e l t more s i g n i f i c a n t l y . To enhance occupant comfort and to meet modern standards of l i v a b i l i t y i n c l u d i n g convenience and h e a l t h , the i n c l u s i o n of a r t i f i c i a l systems i s i n e v i t a b l e . However, in order to use a r t i f i c i a l systems b e n e f i c i a l l y , an understanding of t h e i r design and i n s t a l l a t i o n in the b u i l d i n g system i s r e q u i r e d by the a r c h i t e c t s . The general s t r a t e g i e s s e l e c t e d for a c h i e v i n g thermal comfort with the h e l p of p a s s i v e techniques i n the hot and dry c l i m a t e are: - Minimize s o l a r g a i n , - Minimize conductive heat flow, - Promote v e n t i l a t i o n , - Minimize i n t e r n a l heat gains, - Promote r a d i a n t c o o l i n g , - Delay p e r i o d i c heat flow, - Promote e v a p o r a t i v e c o o l i n g , - C o n t r o l high v e l o c i t y wind and dust and, - C o n t r o l g l a r e . These s t r a t e g i e s are examined in d e t a i l in the f o l l o w i n g s p e c i f i c l e v e l s of d e s i g n : 1. The f i r s t l e v e l of the design s t r a t e g i e s d e a l s with s i t e s e l e c t i o n . S i t e c l i m a t e i s examined with the aim of u t i l i z i n g the favourable and minimizing the unfavourable elements of c l i m a t e on the f u t u r e b u i l d i n g s on a s e l e c t e d s i t e . 67 . 2 . The next l e v e l of s t r a t e g i e s i s concerned with modifying the e f f e c t of u n d e s i r a b l e e x t e r n a l c l i m a t i c elements with the help of s i t e p l a n n i n g . The p o t e n t i a l for s t r e e t l a y o u t , open spaces and landscaping are examined in c r e a t i n g an e f f e c t i v e m i c r o c l i m a t e . 3. The t h i r d l e v e l of design s t r a t e g i e s i s concerned with d w e l l i n g form. These emphasize the r o l e of b u i l d i n g volume, shape and c o n f i g u r a t i o n i n modifying or s e l e c t i n g the elements of e x t e r i o r c l i m a t e . 4. The f o u r t h and f i n a l l e v e l i n v o l v e s c o n s i d e r i n g w a l l s , windows, roof, b u i l d i n g m a t e r i a l s and t h e i r thermal p r o p e r t i e s i n modifying the e f f e c t of e x t e r n a l c l i m a t e on the i n t e r n a l thermal conditions.. As the b a s i c o b j e c t i v e throughout i s to a s s i s t i n a c h i e v i n g thermal comfort, i t should be understood t h a t : a. the s t r a t e g i e s at each l e v e l are i n t e r - r e l a t e d and thus there may be an o v e r l a p p i n g of s t r a t e g i e s a c r o s s d i f f e r e n t l e v e l s . b. to make maximum use of the s t r a t e g i e s , a designer should be c o n s i s t e n t in f o l l o w i n g them at each l e v e l of d e s i g n . I t i s because i f the s t r a t e g i e s are not followed at any one l e v e l i t would r e q u i r e an a d d i t i o n a l emphasis at the next l e v e l as a means of compensation. c. the s t r a t e g i e s at v a r i o u s l e v e l s may become c o n t r a d i c t o r y as design s o l u t i o n s . For example, a design s o l u t i o n f o r promoting a i r flow may c o n t r a d i c t the c o n t r o l of s o l a r heat g a i n . I t i s the r e s p o n s i b i l i t y of the a r c h i t e c t to determine which s t r a t e g y i s more 68 important in t h i s case and to emphasize and r e s o l v e them in that order. d. the s t r a t e g i e s are intended to be a p p l i e d at the s p e c i f i c l e v e l of design and under the circumstances mentioned with them. For example, the s t r a t e g i e s f o r reducing i n t e r n a l heat gain do not apply at the s i t e p l anning l e v e l . S i m i l a r l y the s t r a t e g i e s at the s i t e s e l e c t i o n l e v e l can not be a p p l i e d i n the absence of s p e c i f i e d t o p o g r a p h i c a l f e a t u r e s . Although developed s p e c i f i c a l l y f o r the context of the hot and dry regions i n Ind i a , the s t r a t e g i e s f o r p a s s i v e means of a c h i e v i n g thermal comfort should not be used as a simple set of r u l e s or as a c h e c k l i s t . These s t r a t e g i e s should be used i n s t e a d as a set of b a s i c p r i n c i p l e s . In the process of housing design, an a r c h i t e c t has to s a t i s f y the s o c i a l , f u n c t i o n a l and a e s t h e t i c needs of the occupants by d e a l i n g with many f o r c e s , both economic and t e c h n o l o g i c a l , besides those of c l i m a t e . In 'The Timeless way of B u i l d i n g ' (1979), C h r i s t o p h e r Alexander proposed that one of the c e n t r a l q u a l i t i e s of b e a u t i f u l a r c h i t e c t u r e i s that a l l of these needs and f o r c e s are r e s o l v e d . T h e r e f o r e , the s t r a t e g i e s presented in the f o l l o w i n g s e c t i o n s should be t r e a t e d as a pa r t of the wider context of housing design but not the complete design, with the understanding that t h e i r i n t e g r a t i o n w i l l produce a r i c h e r a r c h i t e c t u r e . 69 SECTION I: SITE SELECTION STRATEGIES 1. INTRODUCTION 2. SITE CLIMATE 3. THERMAL COMFORT CRITERIA 4. MINIMIZE SOLAR GAIN 4.1. Slope O r i e n t a t i o n and Gradient 4.2. E x i s t i n g V e g e t a t i o n and Topography 5. PROMOTE AIR FLOW 5.1. S i t e A l t i t u d e 5.2. Pro x i m i t y to Water Bodies 70 1. INTRODUCTION Although many f a c t o r s u s u a l l y dominate the c h o i c e of b u i l d i n g s i t e , to achieve thermal comfort, an important concern of d e s i g n e r s i s the immediate e x t e r n a l c l i m a t e which surrounds and p e n e t r a t e s the d w e l l i n g through openings, and by heat t r a n s f e r through w a l l s and roof ( F i g . 2 . 1 ) . The i n t e r n a l thermal environment surrounding the occupants r e s u l t s from the immediate e x t e r n a l c l i m a t e (Markus & M o r r i s , 1980). For occupant thermal comfort the impact of e x t e r n a l c l i m a t e on the i n t e r n a l environment can be both f a v o u r a b l e and unfavourable depending upon the month and time of day. A EXItE-NAt CUMAtO" <LNT£KNAl ENyit̂NME-NT-' F i g . 2 . 1 . The elements of E x t e r n a l Climate and the R e s u l t i n g I n t e r n a l Environment I n f l u e n c i n g Occupant Thermal Comfort. 71 primary concern of d e s i g n e r s , t h e r e f o r e , i s to u t i l i z e the favourable and minimize the unfavourable impacts of e x t e r n a l c l i m a t e . In order to understand how the p a r t i c u l a r s of e x t e r n a l c l i m a t e w i l l r e l a t e to the i n t e r n a l environment and b u i l d i n g design, i t i s important to f i r s t understand the s i t e c l i m a t e and comfort c r i t e r i a f o r the occupants. 2. SITE CLIMATE The term s i t e c l i m a t e or mic r o c l i m a t e i s used here to denote the c l i m a t e of the housing s i t e . In order to understand the s i t e c l i m a t e , ' a designer must f i r s t o b t a i n l o c a l c l i m a t i c data. C l i m a t i c i n f o r m a t i o n such as s o l a r r a d i a t i o n , a i r temperature, wind v e l o c i t y and p r e c i p i t a t i o n f o r v a r i o u s l o c a t i o n s in India i s r e p o r t e d i n Mani & Rangarajan (1982). S o l a r r a d i a t i o n data i s p u b l i s h e d for 145 l o c a t i o n s and c o n s i s t s of t a b l e s of g l o b a l , d i f f u s e and d i r e c t s o l a r r a d i a t i o n on h o r i z o n t a l and sloped s u r f a c e s on mean monthly and hourl y b a s i s . I t a l s o i n c l u d e s sun path diagrams f o r l a t i t u d e s 6°N to 36°N and a b r i e f d e s c r i p t i o n of the cl o u d cover of I n d i a . Although a la r g e part of the in f o r m a t i o n i n t h i s work i s on s o l a r r a d i a t i o n , monthly and i n some cases h o u r l y mean values of other c l i m a t i c c h a r a c t e r i s t i c s for 105 l o c a t i o n s i n India have a l s o been covered. T h i s i s the most e x t e n s i v e c o l l e c t i o n of compiled i n f o r m a t i o n on c l i m a t i c c h a r a c t e r i s t i c s at v a r i o u s l o c a t i o n s i n India to date. Although the l o c a l c l i m a t i c data p r o v i d e s i n f o r m a t i o n which may be a u s e f u l guide to the c l i m a t e f o r that l o c a t i o n , c o n d i t i o n s can vary w i t h i n a short d i s t a n c e , from one s i t e to 72 another, or even w i t h i n each s i t e with d i f f e r e n c e s i n s i t e a l t i t u d e , s l o p e , o r i e n t a t i o n , surrounding b u i l d i n g s and e x i s t i n g v e g e t a t i o n (Golany,1980). I t i s o f t e n not r e a l i s t i c f o r an a r c h i t e c t to gather i n f o r m a t i o n about m i c r o c l i m a t e by d i r e c t measurement, e s p e c i a l l y on s i t e s f o r smaller housing schemes. Even f o r l a r g e r p r o j e c t s an a r c h i t e c t i s seldom given an op p o r t u n i t y to c a r r y out s i t e o b s e r v a t i o n s and measurements f o r any length of time. A r e a l i s t i c approach in most p r o j e c t s i s , t h e r e f o r e , to s t a r t with p u b l i s h e d l o c a l c l i m a t e data on mean monthly or hourly b a s i s and p r e d i c t the l i k e l y d e v i a t i o n s . A v i s u a l i n s p e c t i o n of the s i t e or use of survey maps can he l p i n p r e d i c t i n g the v a r i a t i o n of c l i m a t i c c h a r a c t e r i s t i c s i f the designer i s aware of some general r u l e s about t h e i r behaviour with the v a r i a t i o n in topography (the one's a p p l i c a b l e to hot and dry region are d i s c u s s e d i n s i t e s e l e c t i o n s t r a t e g i e s ) . T h i s approach towards a n a l y z i n g s i t e c l i m a t e i s very crude, but i n a d d i t i o n to the time c o n s t r a i n t f o r a r c h i t e c t s , the c o l l e c t i o n and examination of ex t e n s i v e data on s i t e c l i m a t e w i l l a l s o tend to be c o n f u s i n g as the designer i s only i n t e r e s t e d i n c l i m a t i c data u s e f u l f o r the p a r t i c u l a r p r o j e c t (Cole,1979). A v i s u a l i n s p e c t i o n or a s i t e v i s i t i s b e n e f i c i a l i n a l l cases as i t give s the a r c h i t e c t an op p o r t u n i t y to examine the r e l a t i v e importance and i n t e r p l a y of the c l i m a t i c elements which may not be n o t i c e a b l e from the raw c l i m a t i c data. 73 3. THERMAL COMFORT CRITERIA The thermal comfort c r i t e r i a i s i n f l u e n c e d by the i n t e r n a l thermal environment and the a c t i v i t y and c l o t h i n g of occupants. The b i o - c l i m a t i c c h a r t ( F i g . 2 . 2 ) shows an a i r temperature, humidity and a i r v e l o c i t y range w i t h i n which occupants with c e r t a i n type of c l o t h i n g and a c t i v i t y w i l l f e e l c o m f o r t a b l e . The f i n e tuning of comfort for each occupant can only be achieved by making p e r s o n a l a d a p t a t i o n s of c l o t h i n g and a c t i v i t y l e v e l or with the use of mechanical means. However, the c l i m a t i c c h a r a c t e r i s t i c s suggest that the most important general thermal comfort c r i t e r i a for d w e l l i n g s i n hot and dry region r e q u i r e a r e d u c t i o n i n heat gain and promotion of heat l o s s e s . T h i s can be achieved by: - minimizing s o l a r g a i n , - minimizing conductive heat flow, - promoting v e n t i l a t i o n , - promoting r a d i a n t c o o l i n g , - promoting evaporative c o o l i n g , and - d e l a y i n g p e r i o d i c heat flow With these general s t r a t e g i e s i n mind an a r c h i t e c t can develop s p e c i f i c design s t r a t e g i e s at each l e v e l . The s i t e s e l e c t i o n s t r a t e g i e s in the f o l l o w i n g s e c t i o n s are d e r i v e d from general r u l e s about the behaviour of c l i m a t e i n the presence of those t o p o g r a p h i c a l f e a t u r e s which are commonly found in hot and dry r e g i o n s . The extent of c l i m a t i c d e v i a t i o n s due to these f e a t u r e s and t h e i r e f f e c t on s i t e s e l e c t i o n i s e x p l a i n e d in these s t r a t e g i e s . The e f f e c t of s i t e s l ope, a l t i t u d e and waterbodies e t c . on a i r temperature, humidity, wind speed and s o l a r r a d i a t i o n i s d e a l t with 74 I 3 I- a. 4* 3 > fc»L*?UMATI£ £MA£T fz?t2. M^M AT 3 o 5& 7& So Fig.2.2. B i o - c l i m a t i c Chart f o r Hot and Dry Climate Source: Koenigsberger, 1973 i n d i v i d u a l l y i n the f o l l o w i n g s e c t i o n s as the aim here i s to develop s t r a t e g i e s which can be used i n v a r i o u s s i t u a t i o n s . T h e r e f o r e , the s t r a t e g i e s d i s c u s s e d here are a l s o presented i n order of p r i o r i t y . 4. MINIMIZE SOLAR GAIN 4.1. Slope O r i e n t a t i o n and Gradient The d i r e c t i o n and i n c l i n a t i o n of slope can i n f l u e n c e the s i t e c l i m a t e s i g n i f i c a n t l y by r e g u l a t i n g the amount of s o l a r r a d i a t i o n r e c e i v e d by the ground s u r f a c e . T h i s w i l l i n c r e a s e or decrease the temperature of a i r coming i n c o n t a c t with the 75 ground. For in s t a n c e , at l a t i t u d e 25°N, i n the months of May and June, the a l t i t u d e of the sun v a r i e s between 0° to 80° from morning to noon and sun path from s u n r i s e to sunset i s a f u l l 240° ( F i g . 2 . 3 ) . The east, west, and north f a c i n g i n c l i n e d s u r f a c e s r e c e i v e more s o l a r r a d i a t i o n than south. T h e r e f o r e , to achieve maximum c o o l i n g i n summer months, s i t e s on northern, eastern and western slopes should be avoided. However, east f a c i n g slopes are b e t t e r s u i t e d than west f a c i n g s l o p e s , s i n c e the former tend to be c o o l e r on summer even i n g s . In order to evaluate the e f f e c t of s i t e slopes on the mean monthly r a d i a t i o n , the degree of i n c l i n a t i o n of the slop e s i s an important f a c t o r (Mani & Rangarajan,1982). A s u r f a c e that i s p e r p e n d i c u l a r to the d i r e c t i o n of the sun (Fig.2.4) r e c e i v e s the maximum r a d i a t i o n . T h e r e f o r e , given a ch o i c e of s e l e c t i n g a s i t e on south o r i e n t e d slopes with v a r i o u s i n c l i n a t i o n s , the slope i n c l i n a t i o n which faces sun at an obtuse angle rather than at r i g h t angle should be s e l e c t e d . 4.2. E x i s t i n g V e g e t a t i o n and Topography A s i t e with e x i s t i n g v e g e t a t i o n and topography w i l l c r e a t e shade and thus reduce s o l a r r a d i a t i o n and a i r temperature. For i n s t a n c e , presence of a mound on the west sid e can block evening summer sun ( F i g . 2 . 5 ) . Shade can reduce the a i r temperature by 8-10°C (Watson, 1983) i n summer. 76 77 F i g . 2 . 5 . A Mound or Tree i n the West w i l l Reduce few Hours of S o l a r R a d i a t i o n on the D w e l l i n g S t r u c t u r e . 78 5. PROMOTE VENTILATION 5.1. S i t e A l t i t u d e For promoting a i r flow i n a b u i l d i n g , s i t e a l t i t u d e i s an important c o n s i d e r a t i o n as i t a f f e c t s summer a i r v e l o c i t y and temperature. For every 100m of slope e l e v a t i o n , the wind i n c r e a s e s or decreases the temperature by 1°C (Golany,1980). The highest wind v e l o c i t y on a h i l l i s i n the area j u s t below the c r e s t . The lowest v e l o c i t y i s at the bottom and i n the wind shadow (Olgyay, 1963). Therefore, the optimum mi c r o c l i m a t e w i l l u s u a l l y be below the middle but above the foot of a slope. S i t e s s e l e c t e d i n t h i s area w i l l b e n e f i t from c o o l a i r movements in e a r l y evening and warm a i r movements in e a r l y morning ( F i g . 2 . 6 ) . V a l l e y bottoms experience the maximum temperatures on summer days (Geiger, 1950) while s i t e s above the v a l l e y tend to be c o o l e r . Thus, i t i s d e s i r a b l e to a v o i d the v a l l e y bottom s i t e s and s e l e c t the s i t e s above ( F i g . 2 . 7 ) . A r a i s e d embankment, w a l l or impermeable hedge on the lower s i d e of a sloped s i t e can block the c o o l e r a i r which flows slowly down the slope ( F i g . 2 . 8 ) . I t would, of course, be d e s i r a b l e to provide a gate or deciduous hedges so that the flow of a i r i s maintained d u r i n g the c o l d e r p a r t s of the year (Konya,1980). 79 Fig.2.7. Site Selection in a Valley Situation. SECT I ON- Fig.2.8. Raised Embankment to Enhance the cooling Effect of a i r . 80 5.2. Proximity to Water Bodies Water bodies close to s i t e can resu l t in moderating the extreme day time a i r temperature and reducing variations in day and night temperatures during summer. During the summer days, the land surface heats up more than the water. This causes the hot a i r over the land surface to r i s e and cooler a i r over the water flows to replace i t . The shores of lakes, as a r e s u l t , benefit from a daytime breeze blowing from water to land. This cooling e f f e c t can be noted between 400 and 800m inland. During the night the a i r over land cools faster than that over the water and t h i s results in W \GY\J• Fig.2.9. Cooling Process due to the Proximity of Water. Surce: Konya, 1980 81 r e v e r s i n g of the process, with the breeze blowing from land to water ( F i g . 2 . 9 ) . The l a r g e r the body of water the g r e a t e r i t s impact on the m i c r o c l i m a t e . Land surrounding a lake w i l l a l s o be warmer in winter (Robinette, 1983). 82 SECTION I I : SITE PLANNING STRATEGIES 1. INTRODUCTION 2. MINIMIZE SOLAR GAIN 2.1. S t r e e t O r i e n t a t i o n 2.2. S t r e e t Width 2.3. L o c a t i o n and s i z e of Open Spaces 2.4.' Landscaping 3. PROMOTE VENTILATION 3.1. D i s t r i b u t i o n of Open Spaces 3.2. B u i l d i n g Heights 4. PROTECTION FROM HIGH VELOCITY WIND AND DUST 4.1. S h e l t e r b e l t s 83 1 . INTRODUCTION S e l e c t i n g a s i t e with a d e s i r a b l e c l i m a t e may not always be p o s s i b l e or be beyond the c o n t r o l of the a r c h i t e c t . T h i s i s p a r t i c u l a r l y the case f o r housing p r o j e c t s where a c l i e n t or a housing agency approaches the a r c h i t e c t with a p r e s e l e c t e d s i t e . Under such circumstances modifying the unfavourable elements of the m i c r o c l i m a t e and o p t i m i z i n g the favourable ones through s i t e p l a n n i n g , f o r example s t r e e t l a y o u t , design of p u b l i c spaces and lan d s c a p i n g , becomes the primary aim of the a r c h i t e c t . 2. MINIMIZE SOLAR GAIN Shading i s an e f f e c t i v e technique f o r reducing s o l a r heat g a i n . The shadows c r e a t e d by b u i l d i n g s on s i t e reduce the a i r temperature by about 25% i n the summer months (Watson, 1983). In order to maximize the b e n e f i t of shading i n the m i c r o c l i m a t e , the o r i e n t a t i o n and width of s t r e e t s , the s i z e and l o c a t i o n of open spaces and la n d s c a p i n g are important c o n s i d e r a t i o n s . 2.1. S t r e e t O r i e n t a t i o n S t r e e t o r i e n t a t i o n , i f d w e l l i n g blocks are f a c i n g the s t r e e t , a f f e c t s the shadow l e n g t h . For c a l c u l a t i n g shadow le n g t h s , s o l a r a l t i t u d e and azimuth angles f o r d i f f e r e n t hours of the day can be taken from the sun path diagram f o r a p a r t i c u l a r l a t i t u d e (Fig.2.10a), and can be t r a n s l a t e d i n t o shadow l e n g t h (Fig.2.10b). 84 East and west f a c i n g b u i l d i n g blocks a b u t t i n g the s t r e e t c a s t l a r g e r shadows i n the afternoons and mornings throughout the year. The len g t h of the shadow ca s t by south f a c i n g blocks i n c r e a s e s i n summer ( A p r i l - J u n e ) mornings and a f t e r n o o n s . A d d i t i o n a l l y , during t h i s p e r i o d , the sun shines f o r l e s s e r hours on south f a c i n g blocks and at a much steeper angle than on east and west f a c i n g b l o c k s . T h i s i m p l i e s that the layout of s t r e e t s p a r a l l e l to an east-west a x i s , which can maximize south f a c i n g b l o c k s , w i l l e f f e c t i v e l y (Fig.2.11) u t i l i z e shading by b u i l d i n g b l o c k s . 2.2. S t r e e t Width S t r e e t width i s another design f a c t o r which an a r c h i t e c t can employ to modify excess s o l a r r a d i a t i o n . Narrow s t r e e t s with b u i l d i n g s on both s i d e s w i l l i n c r e a s e the shadows c r e a t e d by surrounding b l o c k s . The s t r e e t width i n housing design, a c c o r d i n g to zoning r e g u l a t i o n s (1984) i n hot and dry regions i n I n d i a , depends on two f a c t o r s : the requirements f o r v e h i c u l a r t r a f f i c , and the height of surrounding r e s i d e n t i a l b l o c k s . In g e n e r a l , s t r e e t s f o r v e h i c u l a r access have to be much wider than p e d e s t r i a n s t r e e t s . The summer s o l a r a l t i t u d e at l a t i t u d e 25°N (Fig.2.10a) i s high so that paved surface of v e h i c u l a r s t r e e t s (Fig.2.12a,b) running east-west remains unshaded f o r a s i g n i f i c a n t amount of time and can r a i s e the surrounding a i r temperature c o n s i d e r a b l y . One g e n e r a l l y accepted method of reducing the width of s t r e e t s c a r r y i n g v e h i c u l a r t r a f f i c i s to remove the t r a f f i c from the 85 9A-M 4s, ® tA4T ANP W&rT F&^fcES Fig.2.10. a. Sun Path Diagram f o r L a t i t u d e 25°N. b. Shadow Length f o r East and West F a c i n g D w e l l i n g B l o c k s . Source: Mani, 1982 Fig.2.11. S t r e e t s running east-west with b l o c k s f a c i n g south, 86 d w e l l i n g f r o n t a g e . T h i s i s p a r t i c u l a r l y advantageous f o r l a r g e housing p r o j e c t s where the whole scheme can be d i v i d e d i n t o s m a l l e r r e s i d e n t i a l segments, each surrounded by p e r i p h e r a l parking and access roads (Fig.2.13). Within each segment, a network of narrow p e d e s t r i a n s t r e e t s i s then c r e a t e d . Because of t h e i r c l o s e p r o x i m i t y , the b u i l d i n g b l o c k s can then shade from each other and the ground s u r f a c e . In a d d i t i o n to maximizing the e f f e c t of shading, the narrow s t r e e t width r e s u l t s i n a compact housing l a y o u t , with shaded space through which people from v a r i o u s p l a c e s w i t h i n the r e s i d e n t i a l and s e r v i c e u n i t can move on a human s c a l e adapted to c l i m a t e . A narrow s t r e e t network a l s o helps i n a c h i e v i n g more ground coverage, higher d e n s i t i e s , and reduces the u t i l i t y networks (water supply, sewerage l i n e s e t c . ) , maintenance and energy consumption f o r s t r e e t l i g h t i n g . The narrow s t r e e t network, however, reduces p r i v a c y and i n d i v i d u a l r e s i d e n t i a l i d e n t i t y and may i n c r e a s e noise p o l l u t i o n . T h e r e f o r e , the s t r e e t width should be kept to a minimum compatiable with these problems or by t a k i n g a d d i t i o n a l measures to r e c t i f y them. 2.3. S i z e and L o c a t i o n of Open Spaces In hot and dry c l i m a t e s , open spaces are used f r e q u e n t l y and t h i s i s p o s s i b l e only when open spaces are shaded. I s o l a t e d l a r g e open spaces which are not p r o t e c t e d from s o l a r r a d i a t i o n are uncomfortable. Instead of a few l a r g e open spaces, a number of small open spaces i n the compact layout can b e n e f i t from shading by the surrounding r e s i d e n t i a l 87 Fig.2.12. The E f f e c t of S t r e e t Width and Block Height on Shading. a. S t r e e t Wider than Block Height. b. S t r e e t Width Equal to Block Height. ocxoooooo oooooooooo Fig.2.13. An Example of A c h i e v i n g Narrow S t r e e t Width by Segregating V e h i c l e s from D w e l l i n g F r o n t . Source: K e s s l e r , 1979. 88 blocks and can a l s o improve wind movement around d w e l l i n g s , s i m i l a r to the c o u r t y a r d e f f e c t . Open spaces which are smaller i n len g t h and width than the height of surrounding blocks (Fig.2.14) w i l l b e n e f i t from f u l l or p a r t i a l shading i n summer i n the morning and afternoon hours. Smaller open spaces d i s t r i b u t e d throughout the r e s i d e n t i a l segments, in a d d i t i o n to reducing the e f f e c t of s o l a r r a d i a t i o n , are e a s i e r to maintain. Furthermore, l o c a t i o n of open spaces towards south and south- east o r i e n t a t i o n i s most e f f e c t i v e as i t can b e n e f i t from shade i n the aft e r n o o n , the time when most outdoor a c t i v i t y i n hot and dry c l i m a t e s g e n e r a l l y takes p l a c e ( S a i n i , 1980). 2.4. Landscaping V e g e t a t i o n can reduce the e x t e r n a l a i r temperature by b l o c k i n g d i r e c t s o l a r r a d i a t i o n and by f i l t e r i n g and c o o l i n g the a i r (Davis & Schuburt, 1974). Trees can a l s o speed up the c o o l i n g process in the evening by heat r a d i a t i o n to the open sky (Robinette, 1983). Passive c o o l i n g by the p l a n t s i s in many ways s u p e r i o r to c o o l i n g with the h e l p of b u i l d i n g . envelope or form. Bowen (1980) has c h a r a c t e r i z e d the a l t e r n a t i v e s : 1 "The most s i g n i f i c a n t r e s u l t i n g d i f f e r e n c e between the c o o l i n g e f f e c t s of p l a n t s and manmade s t r u c t u r e s i s that the s t r u c t u r e i s made of non- l i v i n g (concrete) or dead (lumber) m a t e r i a l s and t h e r e f o r e o f f e r s l i m i t e d c o o l i n g c a p a b i l i t i e s determined by the thermal performance of the m a t e r i a l s ; while a p l a n t - which i s a l i v i n g organism w i l l c o n s t a n t l y p o s i t i o n and arrange i t s canopy and leaves to take maximum advantage of the sun's rays, thus maximizing t h e i r c o o l i n g e f f e c t s . " In a d d i t i o n p l a n t s f i l t e r p o l l u t a n t s from the a i r , reduce 89 eo A T H^H fWVt <S><5° A T 3 P M ' 2*7° A T * " ' M - Fig.2.14. Shading i n Open Spaces Smaller than Surrounding B l o c k s . SUMMER- Fig.2.15. Deciduous Trees and Summer and Winter S o l a r P e n e t r a t i o n . 90 noise l e v e l s and can a l s o be used to d i r e c t a i r flow, reduce g l a r e , screen u n d e s i r a b l e s i g h t s and c o n t r o l c i r c u l a t i o n . They in r e a l sense provide p s y c h o l o g i c a l and s p i r i t u a l s o l a c e i n a d d i t i o n to p r o v i d i n g c o o l i n g . T h e r e f o r e , t h e y are nature's most a t t r a c t i v e p a s s i v e c o o l i n g d e v i c e . Deciduous Trees Deciduous v e g e t a t i o n should be c o n s i d e r e d , not only where shade i s r e q u i r e d to a v o i d e x c e s s i v e heat gain d u r i n g the overheated times of the year (May and June), but a l s o when s o l a r exposure i s d e s i r e d d u r i n g the underheated p e r i o d s (December and January). I t i s d e s i r a b l e to p l a n t more t r e e s towards the west so that they can provide shade d u r i n g the afternoons when the maximum a i r temperature (40-45^C) in summer c o i n c i d e s with the heat gain from s o l a r r a d i a t i o n . Important measures of the c o o l i n g p o t e n t i a l s of t r e e s are t h e i r s i z e and form and the shading d e n s i t y c o e f f i c i e n t s of t h e i r canopies. A design matrix f o r deciduous t r e e s should a l s o i n c l u d e t h e i r l e a f out and f u l l l e a f drop dates. Because the l e a f drop and r e f o l i a t i o n of most n a t i v e p l a n t s and t r e e s in hot and dry regions corresponds very c l o s e l y to the times of the year when s o l a r exposure and shade, r e s p e c t i v e l y , are needed, i t i s u s e f u l to take advantage of the n a t u r a l rhythms of these p l a n t s (Fig.2.15). Ground Cover and Shrubs Around the D w e l l i n g The s o l a r r a d i a t i o n r e c e i v e d by the ground s u r f a c e (Fig.2.16) at l a t i t u d e 25°N during the month of June i s about twice that r e c e i v e d by east or west w a l l s . T h e r e f o r e , the s o l a r 91 J0-, <M 1 , 1 , 1 1 . p , . : 1 J F M A M J J A S O N D Fig.2.16. S o l a r R a d i a t i o n I n c i d e n t Upon Ground Sur f a c e and V e r t i c a l S u r faces f a c i n g E a s t , West, South and North at L a t i t u d e 25 N. fe^&NTA^e ^LAV2 V2ADIA1W RE-FL&cVTS-D MAT&2IAL5- Ll^HT (ZED t>m\< rz&p Wo AFT££ TZAIH U*HT <5£A£9 DKY t>AV2K- <̂ J2A4><5 w e ^ H ,fv1AV2&Cg- PATKK: 6r2&eN •5ANP Pt2Y W H I T E . ^% ASPHALT 2<5% W E T •1*3 £ T a b l e I . R e f l e c t a n c e Values f o r v a r i o u s S u r f a c e s . Source: E l Bannany, 1984 92 r a d i a t i o n r e f l e c t e d from the ground onto b u i l d i n g facades w i l l add s i g n i f i c a n t l y to the c o o l i n g requirements of the d w e l l i n g . The r e f l e c t a n c e values f o r paved s u r f a c e s are much higher than that of landscaped or green s u r f a c e s (Table I ) . Although a s p h a l t s u r f a c e s f o r roads keep the r e f l e c t e d r a d i a t i o n at a minimum, the heat absorbed by them i n c r e a s e s the surrounding a i r temperature (Geiger, 1969). T h e r e f o r e , for summer c o o l i n g , i t i s d e s i r a b l e to minimize the paved s u r f a c e s around the d w e l l i n g s and to re p l a c e them (wherever p o s s i b l e ) with grass or v e g e t a t i v e ground cover. P l a n t s , shrubs, and v e g e t a t i v e ground cover around the dwe l l i n g s a l s o reduce the a i r temperature due to t h e i r a b s o r p t i o n and ev a p o r a t i o n . The measured summer c o o l i n g e f f e c t has shown 10-14°C c o o l e r (Fig.2.17.) temperatures f o r grass s u r f a c e s as compared to paved or a s p h a l t s u r f a c e s (Olgyay, 1963). In a d d i t i o n to daytime c o o l i n g , p l a n t cover w i l l a l s o reduce d i u r n a l temperature f l u c t u a t i o n s by t r a p p i n g and r e f l e c t i n g thermal r a d i a t i o n from the ground at night ( M i l l e r , 1980). 3. PROMOTE VENTILATION Wind v e l o c i t y at the ground l e v e l i s reduced c o n s i d e r a b l y by dw e l l i n g s or settlement c l u s t e r s . Fig.2.18 shows that the wind v e l o c i t y i n a b u i l t up area at ground l e v e l i s much lower than in open country (Koenigsberger,1973). The most important design f a c t o r s i n f l u e n c i n g the wind v e l o c i t y in a b u i l t up area a re: o r i e n t a t i o n and width of s t r e e t s , d i s t r i b u t i o n and 93 1 ? bvv&U-lrfc$\- A S P H A L T - Fig.2.17. A i r Temperature Above V a r i o u s Surfaces, - fe?UHPAV2Y \— — ^ <lot>- ul \et>- O - - © l « r V » - - * - J a « <2>e>~j VYIWD / r 7 W ?-/ I 1 ' LATTSI^. • em WIND C ^ u N T r 2 Y - Fig.2.18. The Wind V e l o c i t y i n Open Country and B u i l t up Areas. Source: Koenigsberger, 1973. 94 s i z e of open spaces, and the s i z e and height of surrounding b u i l d i n g s . In determining the o r i e n t a t i o n and width of s t r e e t s in hot and dry r e g i o n , the c o n s i d e r a t i o n s f o r minimizing s o l a r r a d i a t i o n are more important than f o r a i r movement. The dilemma f a c i n g the designer i n t h i s region i s , t h e r e f o r e , to minimize s o l a r heat gain while s t i l l a l l o w i n g adequate a i r movement. 3.1. D i s t r i b u t i o n and s i z e of Open Spaces The p r e v a i l i n g wind d i r e c t i o n s d u r i n g the summer i n India's hot and dry regions are from east and west. The o r i e n t a t i o n of s t r e e t s in an east-west d i r e c t i o n with the d w e l l i n g b l o c k s f a c i n g south i s the most d e s i r a b l e f o r maximizing summer shading. In a g r i d l a y o u t , however, t h i s o r i e n t a t i o n a l s o prevents wind movement through the b l o c k s . A s l i g h t t i l t of blocks towards the east w i l l improve the wind movement i n d w e l l i n g i n t e r i o r s , but t h i s e f f e c t i s p a r t i a l l y o f f s e t due to the narrow width of s t r e e t s , again d e s i r a b l e fo r m i n i mizing s o l a r g a i n . T h e r e f o r e , the most e f f e c t i v e way to improve wind movement i n a block i s with the p r o v i s i o n of small open spaces d i s t r i b u t e d throughout the whole compact settlement. The open spaces w i l l p r ovide wind movement as long as they are shaded ( s i m i l a r to c o u r t y a r d e f f e c t ) or at l e a s t s i x times l a r g e r than the height of surrounding b u i l d i n g s (Koenigsberger, 1973). 95 3.2. B u i l d i n g Heights When the b u i l d i n g s i n a compact settlement are approximately the same h e i g h t , t h e r e i s a s e p a r a t i o n between the f r e e a i r flow above the b u i l d i n g s and that i n the b u i l t up zone so that wind v e l o c i t y near the ground i s much lower. A s i n g l e b u i l d i n g p r o j e c t i n g above the he i g h t of the neighbouring b u i l d i n g s i n such cases can modify the p a t t e r n and v e l o c i t y of the a i r flow near the ground. The a i r v e l o c i t y at the ground l e v e l of a t a l l e r b l o ck i s found to be much more than around b l o c k s s m a l l e r i n h e i g h t (Koenigsberger,1973). T h i s can serve a u s e f u l purpose i n a hot and dry c l i m a t e , e s p e c i a l l y i n the F i g . 2 . 1 9 . A i r V e l o c i t y Near the Ground Around T a l l e r Blocks i s More Than Around Lower b l o c k s . Source: Koenigsberger, 1973 6 96 c e n t r a l p a r t of a compact settlement where wind v e l o c i t y at the ground l e v e l i s found to be the lowest. A t a l l e r b u i l d i n g l o c a t e d there w i l l improve the a i r movement for the surrounding b l o c k s as long as i t s h o r i z o n t a l dimensions are not much l a r g e r than those of the lower blocks (Fig.2.19). 4. PROVIDE PROTECTION FROM HIGH VELOCITY WIND AND DUST 4.1. S h e l t e r b e l t s In I n d i a ' s hot and dry r e g i o n s , the afternoon wind, p a r t i c u l a r l y in the months of May and June, can be troublesome fo r thermal comfort. The average wind v e l o c i t y d u r i n g t h i s time of the day i s high (above 4.8m/sec), and the a i r i s g e n e r a l l y dust laden. The l a r g e r p u b l i c open spaces, p e r i p h e r y blocks and d w e l l i n g s in open areas are more l i k e l y to be a f f e c t e d by dust and high winds and w i l l need p r o t e c t i o n . S h e l t e r b e l t s or p l a n t s i n groups p l a c e d p e r p e n d i c u l a r to the wind d i r e c t i o n are an e f f e c t i v e way of c o n t r o l l i n g wind v e l o c i t y in these areas. The height of s h e l t e r b e l t s i s the most important f a c t o r in determining the zones of p r o t e c t i o n behind them (Fig.2.20). The wind v e l o c i t y on the leeward s i d e of the s h e l t e r b e l t s may be reduced by as much as 30-50% (Melaragno, 1982) f o r a d i s t a n c e of 10-20 times the height of the b a r r i e r (Fig.2.21). The i n f l u e n c e of a s h e l t e r b e l t i n reducing wind v e l o c i t y may extend as f a r as 25-35 times i t s height depending on i t s p e n e t r a b i l i t y and width. C o n t r o l l i n g dust with s h e l t e r b e l t s i s not e q u a l l y e f f e c t i v e because dust p a r t i c l e s can be l i f t e d to a c o n s i d e r a b l e height 97 Fig.2.20. Use of S h e l t e r b e l t s f o r Summer Wind p r o t e c t i o n . ( P l a n ) . M I N I M U M z ^ H E M a x i m u m Fig.2.21. ( S e c t i o n ) . Source: Melaragno, 1982 98 and are c a r r i e d f o r long d i s t a n c e s before r e t u r n i n g to the ground ( S a i n i , 1 9 7 3 ) . For maximum p r o t e c t i o n from dust in the b u i l d i n g blocks the b a r r i e r s need to be at l e a s t as high as the b u i l d i n g i t s e l f and l e s s than 2 m away from the facade, but t h i s arrangement has the disadvantage of e x c l u d i n g the p o s s i b i l i t y of f u l l y u t i l i z i n g the c o o l evening breezes. T h e r e f o r e , window s h u t t e r s and other p a r t s of the b u i l d i n g f a b r i c d i s c u s s e d in l a t e r s e c t i o n s can be used more e f f e c t i v e l y to c o n t r o l dust. Only sand, because of i t s tendency to bounce along the ground, can be stopped e f f e c t i v e l y by low v e g e t a t i o n of about 1.7 m in height ( S a i n i , 1973). Because of the need for con s e r v i n g the water r e q u i r e d to grow new p l a n t s i n t h i s r e g i o n , e x i s t i n g v e g e t a t i o n , earthforms and waterbodies should be used as an i n t e g r a l p a r t of s i t e p l a n n i n g and not t r e a t e d as an expendable element. As d i s c u s s e d i n s i t e s e l e c t i o n , a p a r t i c u l a r e f f o r t should be made to use e x i s t i n g t r e e s and mounds ( i f any) i n the west or east o r i e n t a t i o n to provide p r o t e c t i o n from hot winds and s o l a r r a d i a t i o n . 99 SECTION I I I : FORM DESIGN STRATEGIES 1. INTRODUCTION 2. REFERENCE BUILDINGS 3. MINIMIZE CONDUCTIVE HEAT FLOW 3.1. O r i e n t a t i o n 3.2. Exposed Surface/Volume r a t i o 3.3. Plan Shape 3.4. B u i l d i n g Facade 3.5. Thermal Zoning of v a r i o u s Spaces 3.6. L i v i n g Areas Below Grade 4. REDUCE INTERNAL HEAT GAINS 4.1. Heat Generating Areas 5. PROMOTE VENTILATION 5.1. I n t e r i o r Courts and Shafts 5.2. O r i e n t a t i o n 6. PROMOTE RADIANT COOLING 6.1. T e r r a c e s 100 1. INTRODUCTION The i n t e r n a l thermal environment i n a the i n f l u e n c e of e x t e r n a l c l i m a t e and d w e l l i n g i s a r e s u l t of the i n t e r n a l heat gains Fig.2.22. Modes of Heat exchange I n s i d e the D w e l l i n g . (Fig.2.22). . The more s i g n i f i c a n t of these i n domestic b u i l d i n g s i s the e x t e r n a l c l i m a t e . The main o b j e c t i v e of form design i n t h i s t h e s i s i s to u t i l i z e the favourable and modify the unfavourable elements of e x t e r n a l c l i m a t i c through b u i l d i n g shape, volume, c o n f i g u r a t i o n and o r i e n t a t i o n . The s t r a t e g i e s f o l l o w e d at the 101 form design l e v e l are p a r t i c u l a r l y important as any i n a p p r o p r i a t e d e c i s i o n s regarding o r i e n t a t i o n , b u i l d i n g shape e t c . are d i f f i c u l t to r e c t i f y and any e f f o r t to compensate for them at f a b r i c design l e v e l w i l l i n v o l v e more design time and e x t r a b u i l d i n g m a t e r i a l s . I t i s important, t h e r e f o r e , to follow these s t r a t e g i e s c r i t i c a l l y . 2. THE REFERENCE BUILDINGS For the purpose of heat gain a n a l y s i s , four most commonly used forms for s i n g l e and m u l t i p l e f a m i l y d w e l l i n g s are examined (Fig.2.23). These are: - Detached, - Row Housing, - High Rise and - C l u s t e r . a. Detached In t h i s arrangement ( l a , l b ) the d w e l l i n g s are separated from each other and are surrounded by open space. S i n g l e f a m i l y d w e l l i n g s i n t h i s arrangement are t y p i c a l l y l i m i t e d to three s t o r e y s . The s i d e setbacks, a c c o r d i n g to b u i l d i n g r e g u l a t i o n s , are kept equal to or more than the mean height of the s t r u c t u r e s f o r the reasons of p r i v a c y . b. Row Housing In t h i s arrangement ( I I a , I I b ) , the d w e l l i n g s share common side w a l l s and u s u a l l y do not exceed three s t o r e y s i n h e i g h t . They do have f r o n t and back setbacks, however. c. High Rise The r e q u i r e d setbacks between h i g h r i s e b u i l d i n g s ( I I I ) vary according to t h e i r h e i g h t . The height r e s t r i c t i o n s f o r m u l t i p l e f a m i l y h i g h r i s e b u i l d i n g s vary from four to f i f t y or 1 02 Fig.2.23. The D w e l l i n g Forms used f o r A n a l y s i s . U T £ Y A N D X A Vt> I H A TJIrb- M Lew^T+i -(MO 1-6, 7 - ^ V2.-IA i WIDTH ( M ) 7- £ i 0 | 7- ̂ i t W ^ H T CM)- <*-4 V O L U M E ( c U M) RAJF A U S A N- H • M ) 1*7-^4 E A 4 T FACADE 4 ^ . £ S H ts N • it,-? 43> -^5 M- N- [ e ^ U T H FA^APE 4% Ko-g> 4%>-<£>E N FACADE H • 4-UKFAC6 AREA ( e x F a c e p ) [ e - U R P A C E / /V/5L- •2.4 •<24 • 1 03 more s t o r e y s , depending upon the zoning i n the area, d. C l u s t e r Housing S i n g l e or m u l t i p l e f a m i l y d w e l l i n g s i n hot and dry regions of India were arranged t r a d i t i o n a l l y in small c l u s t e r s , around common open spaces, f o r s o c i a l and c u l t u r a l reasons. The c l u s t e r form i s s i m i l a r to row housing ( l l a , l l b ) , only the back and f r o n t yards of the d w e l l i n g s are omitted and they are grouped c l o s e l y around a common open space. T h i s p r o v i d e s more f l e x i b i l i t y i n the o r i e n t a t i o n as compared with the row arrangement. The height of the d w e l l i n g s can vary from one to three s t o r e y s . F i g u r e 2.23 give s the d e t a i l s on the forms used f o r a n a l y s i s in t h i s s e c t i o n . Each of the four d w e l l i n g forms has d i f f e r e n t heat t r a n s f e r c h a r a c t e r i s t i c s which are important to c o n s i d e r in c l i m a t e responsive d e s i g n . Before d i s c u s s i n g the form design s t r a t e g i e s i t i s important to examine ways by which heat exchange in the d w e l l i n g takes p l a c e : - through c o n d u c t i o n / f a b r i c - s o l a r radiation/windows and, - v e n t i l a t i o n / i n f i l t r a t i o n . The r a t e at which heat i s conducted through the opaque s u r f a c e s i n a b u i l d i n g i s a f u n c t i o n o f : -the temperature d i f f e r e n c e between i n s i d e and o u t s i d e a i r . -the exposed areas of b u i l d i n g f a b r i c . -the i n s u l a t i n g p r o p e r t i e s of the f a b r i c (U-values) The s o l a r r a d i a t i o n i n c i d e n t upon exposed s u r f a c e s i n c r e a s e s the a i r temperature surrounding the b u i l d i n g . To c a l c u l a t e t h i s i n c r e a s e in a i r temperature, the e f f e c t of s o l a r 1 0 4 r a d i a t i o n i n c i d e n t on b u i l d i n g s u r f a c e s can be combined with the outdoor a i r temperature and the f r a c t i o n of heat absorbed by the s u r f a c e s , by using the s o l - a i r temperature concept. T h i s t h e o r e t i c a l e x t e r n a l a i r temperature can be used f o r c a l c u l a t i n g heat gain by conduction ( G i v o n i , 1981). For a constant U-value of b u i l d i n g f a b r i c and a given indoor a i r temperature, heat gain by conduction through opaque su r f a c e s becomes a d i r e c t f u n c t i o n of the area of exposed s u r f a c e s and t h e i r o r i e n t a t i o n . In terms of form design, t h i s f a c t o r i s d e s c r i b e d as the exposed surface/volume r a t i o . In g e n e r a l , a r e d u c t i o n i n exposed surface/volume r a t i o w i l l reduce the heat gain by conduction. A gr e a t e r source of heat gain i n s i d e b u i l d i n g s however i s from the s o l a r r a d i a t i o n e n t e r i n g through windows. Glas s windows are transparent f o r the short wave r a d i a t i o n emitted by sun but are opaque f o r long wave r a d i a t i o n emitted by the o b j e c t s in a room. As a r e s u l t , s o l a r heat heat, once i t has entered through a window, i s trapped i n s i d e the b u i l d i n g . T h e r e f o r e , the presence of windows in f a b r i c can s i g n i f i c a n t l y i n f l u e n c e the t o t a l heat gain i n s i d e a b u i l d i n g and depends upon: - the s o l a r r a d i a t i o n i n c i d e n t upon the window, - the Window area, - shading d e v i c e s and, - g l a s s type. Heat gain by v e n t i l a t i o n r e s u l t s from : - the a i r exchange r a t e , - the temperature d i f f e r e n c e between i n s i d e and o u t s i d e a i r , and - the s p e c i f i c heat of the a i r A i r exchange rate i s a m u l t i p l e of the number of a i r changes per hour i n a p a r t i c u l a r volume of space. For a given 105 temperature d i f f e r e n c e and s p e c i f i c heat of the a i r , the heat gain by v e n t i l a t i o n i s mainly determined by the volume of space and the number of a i r changes per hour. As there i s a l i m i t to the a l l o w a b l e r e d u c t i o n of a i r exchange rate f o r h e a l t h reasons, the volume of space becomes the most important f a c t o r which determines heat g a i n . A r e d u c t i o n i n the volume w i l l t h e r e f o r e reduce heat gain by v e n t i l a t i o n . As v e n t i l a t i o n r a t e i n hot and dry c l i m a t e s i s g e n e r a l l y kept low d u r i n g the day time, reducing heat gain by conduction becomes more c r i t i c a l at form design l e v e l . 3. MINIMIZE CONDUCTIVE HEAT FLOW 3.1. Or i e n t a t ion O r i e n t a t i o n i s the most important f a c t o r i n determining s o l a r heat g a i n . The f o l l o w i n g f i g u r e s (Fig.2.24a,b) show the d i s t r i b u t i o n of s o l a r r a d i a t i o n on v e r t i c a l s u r f a c e s in v a r i o u s o r i e n t a t i o n s at l a t i t u d e 25°N. The e f f e c t of o r i e n t a t i o n on form design, from these c a l c u l a t i o n s , can be summarized as f o l l o w s ; a. During the summer months ( A p r i l - J u l y ) n e a r l y 50% of the t o t a l heat load from s o l a r r a d i a t i o n i s on the roof (Fig.2.24a). East and west f a c i n g s u r f a c e s r e c e i v e a heat load of around 19-20% each, north f a c i n g s u r f a c e s 6-13% and south f a c i n g s u r f a c e s only 2%. T h i s i m p l i e s that optimum o r i e n t a t i o n f o r l a r g e r s u r f a c e s (opaque or g l a s s ) in any form i s due south because the heat l o a d due to s o l a r r a d i a t i o n i s minimum. However, f i g u r e 2.24b demonstrates that s o l a r r a d i a t i o n i n c i d e n t upon 1 06 30-, Fig.2.24a. S o l a r R a d i a t i o n I n c i d e n t upon Su r f a c e s i n V a r i o u s O r i e n t a t i o n s at L a t i t u d e 25 N. J F M A M J J A S O N B Fig.2.24b. S o l a r R a d i a t i o n I n c i d e n t upon South to South-east F a c i n g S u r f a c e s . 1 0 7 s u r f a c e s f a c i n g up to 25° east of south does not r i s e s i g n i f i c a n t l y . T h i s i m p l i e s that a s l i g h t d e v i a t i o n of l a r g e r s u r f a c e s from south o r i e n t a t i o n does not in c r e a s e the heat gain s i g n i f i c a n t l y . Consequently the exposure of l a r g e r s u r f a c e s i n any b u i l d i n g form upto 25° east of south i s accept a b l e from the p o i n t of view of minimizing heat l o a d . A major d e v i a t i o n from south o r i e n t a t i o n , however, w i l l cause e x c e s s i v e heat g a i n . b. Both east and west f a c i n g s u r f a c e s r e c e i v e maximum i n c i d e n t s o l a r r a d i a t i o n d u r i n g summer. However, l a r g e r g l a s s and opaque s u r f a c e s (with time l a g l e s s than 2 hrs.) i n east are more e f f e c t i v e than in the west because they r e c e i v e s o l a r r a d i a t i o n in the morning when the a i r temperature i s below comfort l e v e l . c. Larger s u r f a c e s can a l s o be o r i e n t e d to the north where the heat load i s l e s s than east and west o r i e n t a t i o n s . The problem with north o r i e n t a t i o n , however, i s that s u r f a c e s r e c e i v e minimum s o l a r r a d i a t i o n in winter when some he a t i n g may be r e q u i r e d . 3.2. Exposed S u r f a c e / Volume R a t i o Heat gain by conduction takes p l a c e through the e x t e r n a l w a l l s and roof of d w e l l i n g s . In the f o l l o w i n g example (Fig.2.25), heat gain by conduction i s compared f o r the four d i f f e r e n t d w e l l i n g forms a l r e a d y i n t r o d u c e d in t h i s s e c t i o n . The d w e l l i n g s of each form have the same f l o o r area and volume, but exposed s u r f a c e area i n each case v a r i e s and consequently so does the exposed surface/volume r a t i o (Ref. Fig . 2 . 2 3 ) . 1 0 8 {0 t— 30 - 85- g£ - 75-Z. 7<2 - o (gO - u 59- Q CO  4*- y 3*5- 30- 25-< i — <c 15-ui 10- 5. 4 1 KW/w2' IA l b UA FO£M TYPE- n & i n a m e ? - N̂ >HTH r 1191. 6>U w/vvp' W B ^ T = " S A M E - q = • g>£ U = '2- , 5' 11- = <2«3"C Fig.2.25. Heat gain by Conduction f o r D i f f e r e n t Form Types, 1 0 9 The heat gain c a l c u l a t i o n s i n t h i s example are f o r d w e l l i n g s l o c a t e d at l a t i t u d e 25°N i n the month of June. The average d a i l y o u t s i d e a i r temperature (To) i s 37°C and a c c e p t a b l e indoor a i r temperature ( T i ) i s assumed to be 25°C. For the purpose of c a l c u l a t i n g s o l - a i r temperature ( T s ) , mean d a i l y r a d i a t i o n i n t e n s i t y (I) f o r s u r f a c e s f a c i n g v a r i o u s o r i e n t a t i o n s has been taken from the a v a i l a b l e c l i m a t i c data (Mani, 1981). The absorptance of the s u r f a c e ( a ) , s u r f a c e conductance (fo) and a i r to a i r transmittance (U-value) are those f o r 228mm b r i c k w a l l s (Koenigsberger, 1973), p l a s t e r e d on the i n s i d e only and s u b j e c t e d to a wind speed of 4m/s. Heat gain by a i r exchange and s o l a r r a d i a t i o n through the windows i s not i n c l u d e d i n these c a l c u l a t i o n s . The l a r g e r s u r f a c e s of each form are o r i e n t e d towards the north-south. The f o l l o w i n g p o i n t s regarding form design emerge from these c a l c u l a t i o n s : a. F i g . 2.25 demonstrates that forms with l e s s e r exposed su r f a c e have l e s s e r heat g a i n . T h i s i m p l i e s that a compact form l i k e a cube or d w e l l i n g s arranged i n row or m u l t i s t o r e y , which share the sid e w a l l s , are more e f f e c t i v e i n reducing heat gain in comparison with detached houses. However, these i m p l i c a t i o n s must be evaluated in c o n j u n c t i o n with the a b i l i t y of each form to i n c r e a s e heat l o s s through outgoing r a d i a t i o n at night and to provide v e n t i l a t i o n c o o l i n g during the evening. Both f u n c t i o n s are a l s o important f o r thermal comfort at night and i n the evening. 1 10 For i n s t a n c e , a compact form l i k e the d w e l l i n g s arranged in a m u l t i s t o r e y ( I I I ) has the minimum exposed w a l l s u r f a c e and thus the l e a s t heat g a i n . T h i s a p p l i e s i n p a r t i c u l a r to i n t e r n a l u n i t s with a d j o i n i n g neighbours on each s i d e , above and below. In the above a n a l y s i s , t o t a l heat gain by conduction i n a m u l t i s t o r e y d w e l l i n g ( I I I ) i s 65% l e s s than a two s t o r e y detached ( l b ) house and 48% l e s s than a two s t o r e y row ( l i b ) house. However, t h i s form a l s o has l e s s p o t e n t i a l for the use of n a t u r a l e n e r g i e s , e s p e c i a l l y f o r summer c o o l i n g by outgoing longwave r a d i a t i o n and n a t u r a l v e n t i l a t i o n . The c o o l i n g of the i n t e r i o r i n t h i s form w i l l be very slow in the evenings and at n i g h t . T h e r e f o r e , although t h i s form i s u s e f u l f o r minimizing heat during the day, i t w i l l h a r d l y achieve any comfort at n i g h t . On the other hand, the heat gain i n row and c l u s t e r houses (I I a , I I b ) i s only 21-40% l e s s than detached houses ( l a , l b ) . Evening and night time heat l o s s i n a row house, although l e s s than a detatched house, occurs through the exposed roof r e s u l t i n g i n r a p i d c o o l i n g by r e - r a d i a t i o n to the c l e a r sky. Heat l o s s i n t h i s form can be f u r t h e r enhanced by the use of c o u r t y a r d s and s h a f t s (the thermal behavior of c o u r t y a r d s has a l r e a d y been d i s c u s s e d ) . As a r e s u l t , row and c l u s t e r houses b e n e f i t from both r e d u c t i o n in e x c e s s i v e day time he a t i n g and r a p i d night time c o o l i n g . T h i s form, t h e r e f o r e , i s r e l a t i v e l y more e f f e c t i v e i n hot and dry c l i m a t e . 1 1 1 Row and c l u s t e r form, as a general e x p r e s s i o n of an e f f e c t i v e response to heat gain problem, can be f u r t h e r t r a n s l a t e d i n t o v a r i o u s design s o l u t i o n s responding to d e s i r e d arrangement of spaces and s i t e c l i m a t e of s p e c i f i c housing p r o j e c t s . Since the roof c o n t r i b u t e s to a l a r g e extent in heat exchange, the above a n a l y s i s (Fig.2.25) a l s o demonstrates that roof area i s a c r i t i c a l p art of form d e s i g n . A comparison between two detached houses ( l a &Ib) shows that i n a s i n g l e s t o r e y detached house ( l a ) , only the roof c o n t r i b u t e s 55% of the t o t a l heat g a i n . In a two s t o r e y detached house ( l b ) , where the roof area i s reduced by 50% f o r the same volume and f l o o r area, the t o t a l heat gain of the b u i l d i n g i s reduced by 15%. F u r t h e r , in row houses ( I I a , I I b ) , where s i d e w a l l s are shared, the roof c o n t r i b u t e s to 70% of the t o t a l heat gain by conduction. I f the roof area i n t h i s form i s reduced by 50% ( l i b ) , the t o t a l b u i l d i n g heat gain decreases by 30%. T h i s comparison suggests that two or three storey houses of the same f l o o r area and volume are more e f f e c t i v e i n reducing heat gain by conduction than s i n g l e s t o r e y houses because of l e s s e r roof a r e a . Although heat gain by conduction and s o l a r r a d i a t i o n through windows i s not i n c l u d e d i n the above c a l c u l a t i o n s , i t i s important to mention here that even with a minimum exposed surface/volume r a t i o , the presence of windows can s i g n i f i c a n t l y c o n t r i b u t e to the t o t a l heat gain by the form. T h e r e f o r e , a r e d u c t i o n i n exposed 1 1 2 surface/volume r a t i o w i l l be e f f e c t i v e only when the p r o p e r t i e s of f a b r i c , most imp o r t a n t l y the windows, have been designed for minimizing heat g a i n . 3.3. Plan Shape In a s i n g l e f a m i l y detached house, where the s i d e w a l l s are not shared and the exposed surface/volume r a t i o i s high, the plan shape becomes an important f a c t o r i n reducing heat gain by conduction. In the f o l l o w i n g c a l c u l a t i o n s (Fig.2.26), heat gain by conduction in a square plan i s compared with v a r i o u s other plan shapes. A l l these plan shapes have s i m i l a r roof areas and volumes and t h e i r l a r g e r s u r f a c e s face north or south o r i e n t a t i o n . These c a l c u l a t i o n s do not i n c l u d e heat gain by i n f i l t r a t i o n and s o l a r r a d i a t i o n through windows. S o l - a i r temperatures f o r v a r i o u s o r i e n t a t i o n s , i n s i d e a i r temperature and - U-value are s i m i l a r to the c a l c u l a t i o n s i n the previous sect i o n . These c a l c u l a t i o n s demonstrate t h a t : a. A square plan may not minimize heat gain during summer even though i t has the minimum exposed surface/volume r a t i o . The reason for t h i s i s the unequal d i s t r i b u t i o n of s o l a r r a d i a t i o n on v a r i o u s o r i e n t a t i o n s . b. A r e d u c t i o n in east west facades reduces conductive heat gai n , however, there i s a l i m i t at which i t i s no longer e f f e c t i v e . Plans with a r a t i o between 1:1.6 to 1:2.5 are most e f f e c t i v e i n reducing conductive heat g a i n . The optimum shape i s a 1:2 r a t i o of s i d e s . An optimum plan shape, however, cannot be g e n e r a l i s e d f o r 1 1 3 30-i 29 28 27 23 22 H 21 20 N- 1.5 Plan Ra t i o Fig.2.26. Heat Gain by Conduction i n V a r i o u s Plan Shapes as Compared with a Square P l a n . 1 1 4 a l l l o c a t i o n s because of the d i f f e r e n c e s i n the r a d i a t i o n i n t e n s i t y . In any case an optimum plan shape i s not c r i t i c a l , and plans with 1:1.6 to 1:2.5 r a t i o of i t s s i d e s w i l l give a c c e p t a b l e performance. 3.4. B u i l d i n g Facade Shading of the w a l l s and surrounding spaces reduces the e x t e r n a l a i r temperature by about 25%. Th e r e f o r e , i t i s an e f f e c t i v e and simple way of c o n t r o l l i n g heat gain to the d w e l l i n g i n t e r i o r . In order to maximise the shade on b u i l d i n g facade, o r i e n t a t i o n , and d i s t a n c e between b u i l d i n g b l o cks are important f a c t o r s . The e f f e c t of o r i e n t a t i o n on the shading of b u i l d i n g facade i s as f o l l o w s : a. As sun path i s n o r t h e r l y d u r i n g summer and shines at higher a l t i t u d e s f o r c o n s i d e r a b l e time (Fig.2.27a), the south facade remains i n shade f o r long part of the day. During mid day, when sun i s at a steep angle to south w a l l s , a s l i g h t p r o j e c t i o n of the b u i l d i n g i n h o r i z o n t a l d i r e c t i o n c r e a t e s an ex t e n s i v e shadow. As a r e s u l t , i n two or three s t o r e y d w e l l i n g s , shade can be c r e a t e d by p r o j e c t i n g or receding each f l o o r (Fig.2.27b).* b. East and west facades each r e c e i v e sun i n the morning and in the afternoon f o r 4-5 hours. As the sun shines on these facades at a d i r e c t angle, they are d i f f i c u l t to shade with the v a r i a t i o n s in b u i l d i n g facade. T h e r e f o r e , the exposure of east and west facades should be avoided (wherever p o s s i b l e ) by sh a r i n g the side w a l l s or with l a n d s c a p i n g . 1 1 5 Fig.2.27. S o l a r A l t i t u d e and Shading of South facade a. S o l a r A l t i t u d e During Summer at L a t i t u d e 25°N. b. Shading of South F a c i n g facade by p r o j e c t i n g each f l o o r . The e f f e c t of d i s t a n c e between b l o c k s on shading has been d i s c u s s e d under s i t e p l a n n i n g s t r a t e g i e s . T h i s a n a l y s i s suggests that compact forms l i k e two to three s t o r e y housing b l o c k s arranged i n rows or c l u s t e r s , with exposed s u r f a c e s f a c i n g n o r t h south o r i e n t a t i o n , b e n e f i t from maximum mutual shading i f they are separated by d i s t a n c e s l e s s than t h e i r h e i g h t s . 3.5. Thermal Zoning of v a r i o u s Spaces Thermal zoning of v a r i o u s spaces a c c o r d i n g to t h e i r thermal comfort requirements u s i n g warm and c o o l areas i n the d w e l l i n g i s an e f f e c t i v e way of enhancing thermal comfort. 1 1 6 Domestic b u i l d i n g s o f f e r many p o s s i b i l i t i e s f o r thermal zoning due to the v a r i e d use of spaces, and d i f f e r e n t time and frequency of use. As a r e s u l t , with only a l i t t l e e f f o r t by the designer, thermal comfort can be enhanced. The main f a c t o r s which should be co n s i d e r e d i n making d e c i s i o n s about thermal zoning (Cole, 1979) and the r e s u l t i n g a l l o c a t i o n of spaces are showed i n t a b l e s I l a and l i b . It i s assumed that l i g h t weight c o t t o n c l o t h i n g i s worn by the occupants. Some important c o n s i d e r a t i o n s r e g a r d i n g the thermal zoning of va r i o u s spaces are: a. In a hot and dry c l i m a t e , because of afternoon r e s t p e r i o d s e s p e c i a l l y during the peak summer months (May- J u l y ) , bedrooms are used d u r i n g the afternoon as w e l l as at n i g h t . T h e r e f o r e , m a i n t a i n i n g c o o l e r indoor temperatures f o r afternoon and night comfort i s the prime concern i n a l l o c a t i n g bedrooms. The morning a i r temperature i s below comfort range and p e n e t r a t i o n of sun at t h i s time does not c r e a t e as much di s c o m f o r t as in the evenings. Because of these c o n s i d e r a t i o n s , a south or southeast o r i e n t a t i o n i s most d e s i r a b l e f o r bedrooms. North or northeast o r i e n t a t i o n i s a l s o a c c e p t a b l e as i t keeps the room c o o l e r i n the af t e r n o o n . In the forms l i k e row houses which allow l e s s f l e x i b i l i t y i n zoning spaces, p r e f e r e n c e should be given to l o c a t i n g the master bedroom in south or southeast and the remaining bedrooms i n north or n o r t h e a s t . S p l i t l e v e l planning in such cases 1 17 A C T I V I T Y T r l £ K M A L C ^ V W T £ £ i T £ £ l A VENTILATION- TIM'S ^ F U S B H^AT- NlGfJT/AFTBKN- L<?W R £ 4 T ^ U6-HT ACTIVITY . R?T>fcgAT& Mfep- U>W WA-V2M 7 INTERMITTENT M E p - HI&H ItttejZMJTP&HT |VttSD- unv- iNT^MITTeKT Table I l a . A c t i v i t y A n a l y s i s of Spaces i n a D w e l l i n g . ACTIVITY- 0\?I£NT-AT1£N f A u ^ w ^ (<=>fA^) N w V V V V ACTIVITY-(UYI14&/P1H ) V V V V V s/ V P=-ATH>N<<i V V V N/ V V Table l i b . A l l o c a t i o n of Spaces with Respect to O r i e n t a t i o n . T18 w i l l achieve the best p o s s i b l e o r i e n t a t i o n for a l l the bedrooms. L i v i n g and d i n i n g spaces are used throughout the day and in the evening. As the evening a c t i v i t y in hot and dry c l i m a t e s i s o f t e n outdoors, a l i v i n g r o o m a b u t t i n g a t e r r a c e or an open space with a south or south-east o r i e n t a t i o n w i l l be most d e s i r a b l e . Western exposures should be avoided f o r l i v i n g rooms because of the evening over h e a t i n g . In a compact layout where the s i d e w a l l s are shared, and the block i s narrow, a s p l i t l e v e l p l a n n i n g w i l l be u s e f u l . In s p l i t l e v e l houses, p r e f e r e n c e should be given to p l a c i n g bedrooms on upper f l o o r s to improve comfort by r a p i d c o o l i n g at n i g h t . T o i l e t s are separated from main l i v i n g areas f o r hygenic purposes and moisture g e n e r a t i o n . T h i s space i s used i n t e r m i t t e n t l y and does not r e q u i r e thermal c o n t r o l . Only a higher v e n t i l a t i o n r a t e and adequate l i g h t i n g c o n d i t i o n s are necessary. A west and southwest o r i e n t a t i o n w i l l enable the t o i l e t to act as a b u f f e r zone fo r the l i v i n g areas. Kitchen spaces generate heat and i t i s d e s i r a b l e to segregate them from the main l i v i n g areas in order to reduce i n t e r n a l heat g a i n . The k i t c h e n i s used i n t e r m i t t e n t l y d u r i n g the daytime but c o n t i n u o u s l y i n the morning and evening. A south-eastern exposure f o r a k i t c h e n w i l l provide c o o l e r thermal c o n d i t i o n s i n the evening. The heat l o s s r a t e i n the evening w i l l a l s o i n c r e a s e with the n a t u r a l v e n t i l a t i o n whereas, d u r i n g 1 1 9 daytime, n a t u r a l v e n t i l a t i o n w i l l i n c r e a s e the heat g a i n . A mechanical exhaust system can be used to augment or as a s u b s t i t u t e f o r n a t u r a l v e n t i l a t i o n and to help c o n t r o l heat gain d u r i n g day time. e. Many a c t i v i t i e s normally a s s o c i a t e d with indoor spaces in a c o l d c l i m a t e are performed out of doors i n a hot dry c l i m a t e . T h i s e s p e c i a l l y a p p l i e s to a c t i v i t i e s l i k e s l e e p i n g , washing, cooking, p l a y i n g , e a t i n g e t c . The r e f o r e , the area a d j o i n i n g the b u i l d i n g s becomes an extension of the indoor space and should be t r e a t e d with equal c a r e . For indoor spaces, p a s s i v e means f o r thermal c o n t r o l are p r e f e r a b l e to mechanical c o n t r o l s ; f o r outdoor spaces t h i s i s the only form of c o n t r o l p o s s i b l e . Outdoor spaces l i k e t e r r a c e s , b a l c o n i e s , e t c . are l i k e l y to be used i n the evening or at n i g h t . A south or south -eastern exposure f o r these spaces w i l l keep them c o o l f o r evening use. 3.6. L i v i n g Areas Below Grade The s o i l can be used as a heat source i n c o l d c l i m a t e , a heat sink i n hot c l i m a t e or as i n s u l a t i o n (Morelan,1980). An approximate a i r temperature compared with e a r t h temperature at a depth of 3m. i n the hot and dry regions on a vegetated s i t e i n North America (Fig.2.28) i l l u s t r a t e s t h a t : a. The e a r t h reaches a temperature of approximately 19°C(65°F) i n summer and a high of 21°C(70°F) i n winter, with an annual average of 20°C(66°F). b. The d a i l y range of e a r t h temperatures i s much smaller than the d a i l y range of a i r temperatures. 1 20 3 < Mi 4 14- 2* b H - PEL <• — / \ • • • / \ • , — V -#— • —» • — - — - Alte & X T K E M B £ - eAV2TH B^TKEMEJ- efuV&A turner- (a A N O G?UNEO C ^ L t ^ T H^TTES-T- ( M A X T U M ^ («&rr>$crO A\£ T&Mtf£V2AT|# Altf AT AV6KA66 ^F. £ A K T H AT AV£KA<^£ T H « ^ & pevo^ps? • 3^'^ ^>4°£ - Fig.2.28. A Comparison Between Mean Monthly A i r and E a r t h Temperatures. Source: Moreland, 1980 T h e r e f o r e , the s o i l surrounding a below grade space serves to r a d i c a l l y reduce e x t e r n a l c l i m a t i c h e a t i n g and c o o l i n g ef f e c t s . 1 2 1 At the form design l e v e l , a designer can l o c a t e one or two l i v i n g areas l i k e bedrooms or l i v i n g rooms i n the basement. These areas w i l l remain c o o l e r than above grade spaces. The basement spaces, i n a d d i t i o n to p r o v i d i n g a comfortable thermal environment, i n c r e a s e the f l o o r area of the house without adding to the ground coverage. 4. REDUCE INTERNAL HEAT GAINS In r e s i d e n t i a l b u i l d i n g s , the i n t e r n a l heat gains by body heat, a p p l i a n c e s and e l e c t r i c l i g h t i n g are not as s i g n i f i c a n t as in commercial b u i l d i n g s . Thermal comfort i n r e s i d e n t i a l b u i l d i n g s i s p r i m a r i l y c l i m a t e r e l a t e d (Mara, 1984). However, in hot and dry regions, where e x t e r n a l a i r temperature i n summer i s a l r e a d y 8-10°C above the comfort l e v e l , even a small amount of heat generated indoors w i l l be u n d e s i r a b l e f o r a c h i e v i n g and m a i n t a i n i n g thermal comfort. The amount of i n t e r n a l heat gains i n a given area depends on the number and power of l i g h t b ulbs, the heat generating c a p a c i t y of a p p l i a n c e s and the occupancy rate of the d w e l l i n g s . Heat generated by the occupants depends upon t h e i r a c t i v i t y l e v e l . Table I I I . shows the average heat gain from v a r i o u s sources i n a d w e l l i n g with an occupancy rate of f i v e . 4.1. Heat Generating Areas The k i t c h e n i s the major area i n r e s i d e n t i a l b u i l d i n g s where a s i g n i f i c a n t amount of heat i s generated by cooking and the use of a p p l i a n c e s . 1 22 F a c t o r s Amount of Heat Gain - Human bodies between 130-160 Watts f o r each body (Sedentary a c t i v i t y ) . L i g h t s Incandescent 95% Of Wattage F l u o r e s c e n t 79% of Wattage for each Lamp (when in use). Appliances Gas stove 1500-2000 Watts each E l e c t r i c i r o n 500-1OOOWatts Washing machine 500-800Watts (when in use) . Table I I I . I n t e r n a l Heat Gain from V a r i o u s Sources. L i v i n g rooms and study rooms r e q u i r e suppliment l i g h t i n g due to t h e i r continuous use and f u n c t i o n . At the form design l e v e l , there are two ways of c o n t r o l l i n g i n t e r n a l heat gains in r e s i d e n t i a l b u i l d i n g s ; 1. By keeping heat generating areas l i k e the k i t c h e n and u t i l i t y room e t c . away from the areas of main use l i k e l i v i n g r o o m s or bedrooms. A b u f f e r space l i k e a veranda, c o u r t y a r d or passage can be p l a c e d in between. 2. By i n c r e a s i n g the d a y l i g h t p o t e n t i a l of some spaces. T h i s may be done by the p r o v i s i o n of c o u r t y a r d s and l i g h t s h a f t s i n a compact l a y o u t . The design of c o u r t y a r d s and s h a f t s f o r v e n t i l a t i o n , d i s c u s s e d i n the f o l l o w i n g s e c t i o n , i s e q u a l l y e f f e c t i v e f o r d a y l i g h t i n g . 5. PROMOTE VENTILATION N a t u r a l v e n t i l a t i o n i s most d e s i r a b l e during evenings when the o u t s i d e a i r temperature i s c o o l e r than i n s i d e . N a t u r a l 1 23 v e n t i l a t i o n c o n t r i b u t e s to thermal comfort i n s i d e the dw e l l i n g s i n two ways: a. By c o o l i n g the s t r u c t u r e when the indoor temperature i s above the outdoors. T h i s may be termed as ' s t r u c t u r a l c o o l i n g ' . b. By i n c r e a s i n g heat l o s s from the body when the surrounding a i r i s c o o l e r than body temperature, and by evaporation of moisture from s k i n . T h i s may be termed as 'comfort c o o l i n g ' . S t r u c t u r a l c o o l i n g i s a f u n c t i o n of number of a i r changes per hour i f the outdoor a i r temperature i s c o o l e r than indoor whereas Comfort c o o l i n g , f o r an a i r temperature lower than body (37°C), r e s u l t s from a i r movement and i t s adequate d i s t r i b u t i o n i n occupied zone. At the form design l e v e l n a t u r a l v e n t i l a t i o n f o r s t r u c t u r a l and comfort c o o l i n g may be enhanced by i n t e r i o r c o u r t s and s h a f t s and by p r o v i s i o n f o r c r o s s v e n t i l a t i o n . 5.1. I n t e r i o r Courts and Shafts In compact forms such as c l u s t e r or row housing, due to the the p r o x i m i t y of surrounding b u i l d i n g s , the o u t s i d e a i r v e l o c i t y decreases before i t e n t e r s the spaces i n s i d e the d w e l l i n g . As a r e s u l t , the p o t e n t i a l for both comfort and s t r u c t u r a l c o o l i n g by n a t u r a l v e n t i l a t i o n i s reduced c o n s i d e r a b l y . An improvement i n a i r movement and exchange ( G i v o n i , 1977) i n such forms can be achieved by i n c o r p o r a t i n g c o u r t y a r d s and s h a f t s . The f o l l o w i n g f a c t o r s are important f o r a c h i e v i n g s t r u c t u r a l and comfort c o o l i n g with c o u r t y a r d s and s h a f t s : a. the temperature d i f f e r e n c e between i n s i d e and o u t s i d e a i r , and b. the v e r t i c a l d i s t a n c e between two openings. 1 2 4 The c o u r t y a r d s reduce the incoming a i r temperature by p r o v i d i n g shade. T h i s pool of c o o l e r a i r stays i n a c o u r t y a r d because of being heavier than the surrounding warm a i r . For maximizing shading and r e s u l t i n g c o o l i n g of a i r , the l e n g t h and width of a c o u r t y a r d should be l e s s than the height of surrounding s t r u c t u r e s . When openings are provided at a higher and a lower l e v e l i n a w a l l f a c i n g the c o u r t y a r d (Fig.2.29), a c o n v e c t i v e loop i s s t a r t e d with the c o o l e r a i r coming i n at the lower l e v e l and hot a i r r i s i n g and going out at the higher l e v e l . A minimum v e r t i c a l d i s t a n c e of 2 m i s r e q u i r e d between openings to s t a r t and maintain t h i s c o n v e c t i v e loop. A l a r g e r v e r t i c a l d i s t a n c e between two openings w i l l i n c r e a s e a i r movement d e s i r a b l e for comfort c o o l i n g , but w i l l a l s o i n v o l v e more b u i l d i n g m a t e r i a l and a d d i t i o n a l c o s t . T h e r e f o r e , c o u r t y a r d s may be more e f f e c t i v e for p r o v i d i n g s t r u c t u r a l r a t h e r than comfort c o o l i n g . A higher a i r movement in a occupied zone w i t h i n the d w e l l i n g can be achieved with c r o s s v e n t i l a t i o n . In the evening, when o u t s i d e a i r i s c o o l e r than i n s i d e , a i r movement w i l l be c r e a t e d by c r o s s v e n t i l a t i o n i f windows of the room on both windward and leeward s i d e s are opened. In order to achieve d e s i r e d a i r movement and d i s t r i b u t i o n i n a room, the f o l l o w i n g f a c t o r s are important: - o r i e n t a t i o n of i n l e t and o u t l e t windows with respect to wind d i r e c t i o n and, - t h e i r p o s i t i o n and s i z e . P o s i t i o n and s i z e of windows i s c o n s i d e r e d at f a b r i c design 125 Fig.2.29. S i z e of Courtyard f o r A i r Exchange due to Thermal Force. Fig.2.30. T e r r a c e s f o r Row Housing. 126 l e v e l whereas t h e i r o r i e n t a t i o n i s decided at form design l e v e l . 5.2. O r i e n t a t i o n The wind movement in summer i s from the east to west. O r i e n t i n g windows towards the wind d i r e c t i o n i s not very e f f e c t i v e because the a i r i n t h i s case w i l l flow s t r a i g h t through the rooms, v e n t i l a t i n g only a l i m i t e d s e c t i o n (Givoni,1981). On the other hand i f the windows are o r i e n t e d o b l i q u e to the wind d i r e c t i o n , a l a r g e r indoor area w i l l be a f f e c t e d by the a i r flow, and average v e l o c i t i e s w i l l be h i g h e r . Based on these c o n s i d e r a t i o n s , a south to south- east o r i e n t a t i o n of form w i l l f u l f i l r e q u i r e d c o n d i t i o n s f o r comfort c o o l i n g more e f f e c t i v e l y than east-west. In a hot and dry c l i m a t e , where ambient temperature has a g r e a t e r p h y s i o l o g i c a l i n f l u e n c e than v e n t i l a t i o n , the o r i e n t a t i o n of l a r g e r s u r f a c e s between 15 and 30° east of south w i l l a l s o minimize heat gain from s o l a r r a d i a t i o n . 6. PROMOTE RADIANT COOLING 6.1. T e r r a c e s At n i g h t , long wave r e - r a d i a t i o n to the c l e a r sky causes the temperature of h o r i z o n t a l s u r f a c e s to drop below ambient a i r temperature. T h i s phenomenon can be used f o r c o o l i n g some spaces in d w e l l i n g s at night with the help of an exposed roof s u r f a c e ( G i v o n i , 1981). In m u l t i p l e storey row houses, where ground and middle f l o o r r o o f s are not exposed, i t i s advantageous to have t e r r a c e s on these l e v e l s (Fig.2.30). T e r r a c e form housing, i n a d d i t i o n to p r o v i d i n g r a d i a n t c o o l i n g 1 27 f o r the spaces under t e r r a c e s , a l s o p r o v i d e s outdoor space s u i t a b l e f o r use i n the evening and at n i g h t . T e r r a c e s , however, c r e a t e the problem of heat gain during daytime. As a remedy to to t h i s problem v a r i o u s methods of shading the roof during the daytime can be co n s i d e r e d . Some of these methods are: a. Use of movable shades made of canvas or some i n s u l a t i n g mater i a l b. F i x e d shades made of l i g h t weight m a t e r i a l s c. Shading by deciduous c r e e p e r s F i x e d shades are l e a s t e f f e c t i v e because they o b s t r u c t r a d i a n t c o o l i n g at n i g h t . Movable shades made of canvas, timber and some i n s u l a t i n g m a t e r i a l s have maintenence problems and a short l i f e span. Shading by deciduous creepers t r a i n e d on to wiremesh, about 2 m above the roof s u r f a c e i s an e f f e c t i v e method of c o n t r o l l i n g heat gain on the roof. The creepers do not i n t e r f e r e with r a d i a n t c o o l i n g as l e a f temperatures are lower than the ambient temperature. 1 28 SECTION IV: FABRIC DESIGN STRATEGIES 1. INTRODUCTION 2. MINIMIZE SOLAR GAIN, PROMOTE VENTILATION, CONTROL GLARE 2. 1 . Windows: I n t r o d u c t i o n 2. 2. Window O r i e n t a t i o n 2. 3. Exter i o r 2. 4. E x t e r i o r A c c e s s o r i e s 2. 5. The Window 2. 6. I n t e r i o r A c c e s s o r i e s 2. 7. I n t e r i o r 3. DELAY PERIODIC HEAT FLOW, MINIMIZE HEAT FLOW 3.1. Roof and W a l l s : Thickness, Colour CONDUCTIVE M a t e r i a l s , 129 1. INTRODUCTION The f a b r i c of a d w e l l i n g comprises of windows, w a l l s and ro o f , b u i l t with d i f f e r e n t b u i l d i n g m a t e r i a l s and t h i c k n e s s . Each of these elements a c t s as a f i l t e r that r e j e c t s , r e c e i v e s or moderates the e x t e r n a l c l i m a t e ( F i g . 2 . 3 1 ) . At the f a b r i c d e sign l e v e l an a r c h i t e c t can design v a r i o u s elements which can b r i n g the i n t e r n a l thermal c o n d i t i o n s to a d e s i r e d l e v e l . However, the p a r t i c u l a r Fig.2.31. F a b r i c as a F i l t e r of E x t e r n a l C l i m a t e . emphasis and design e f f o r t r e q u i r e d f o r each element of the f a b r i c i s dependent on s t r a t e g i e s f o l l o w e d at. e a r l i e r l e v e l s of desi g n . The s t r a t e g i e s f o r windows w a l l s and roof design f o r enhancing thermal comfort are d i s c u s s e d i n the f o l l o w i n g ( W A L L S , W I N K W S, l& M F ) 130 s e c t i o n s . 2. MINIMIZE SOLAR GAIN, PROMOTE VENTILATION, CONTROL GLARE 2.1. Windows: I n t r o d u c t i o n T r a d i t i o n a l d w e l l i n g s i n the hot and dry regions i n India were b u i l t with a minimum window area to reduce the adverse e f f e c t of extreme c l i m a t e . A window, however, in a contemporary d w e l l i n g i s expected to serve the f o l l o w i n g func t i ons: a. to permit d a y l i g h t , b. to promote v e n t i l a t i o n f o r comfort and s t r u c t u r a l c o o l i n g , c. to provide view, d. to minimize s o l a r gain i n summer, e. to allow winter heat gai n , f. to give p r o t e c t i o n from g l a r e , g. to provide noise i n s u l a t i o n , and h. to f u l f i l l the a e s t h e t i c s of facade. Because of t h e i r a b i l i t y to transmit s o l a r r a d i a t i o n , windows permit s e v e r a l times g r e a t e r heat gain than w a l l areas (Givoni,1981,). However, the o v e r a l l thermal performance of windows i s not based only on heat gain by s o l a r r a d i a t i o n . With respect to thermal comfort the important f u n c t i o n s of windows are to provide p r o t e c t i o n from summer s o l a r g a i n , g l a r e , and to promote n a t u r a l v e n t i l a t i o n f o r comfort and s t r u c t u r a l c o o l i n g . Window design i s a c a r e f u l b a l a n c i n g of a l l these f u n c t i o n s . For i n s t a n c e , the need to decrease heat gain i n the room may lead to d e s i g n i n g a small window which c o u l d , i n t u r n , r e s u l t i n d e p r i v i n g the i n t e r i o r of v e n t i l a t i o n f o r comfort c o o l i n g . T h e r e f o r e , a l l f u n c t i o n s important f o r a c h i e v i n g thermal comfort must be c o n s i d e r e d c o l l e c t i v e l y so that the emphasis on one f u n c t i o n does not 131 r e s u l t in d e p r i v i n g the occupants of the o t h e r s . The window design becomes even more complicated when a d d i t i o n f u n c t i o n s such as p r o v i d i n g view are a l s o c o n s i d e r e d . The s o l a r g a i n , v e n t i l a t i o n and g l a r e permitted by windows are r e g u l a t e d by s e v e r a l design f a c t o r s which are w i t h i n the c o n t r o l of a desig n e r . The most s i g n i f i c a n t of these are the window area, i t s o r i e n t a t i o n , i t s v e r t i c a l and h o r i z o n t a l p o s i t i o n i n g and the g l a z i n g m a t e r i a l s . However, the c o n t r a d i c t o r y f u n c t i o n s of windows make i t d i f f i c u l t to achieve d e s i r a b l e thermal performance with only these f a c t o r s and r e q u i r e a d d i t i o n a l p a r t s and window a c c e s s o r i e s to improve each f u n c t i o n s e p a r a t e l y . T h e r f o r e , the design of window a c c e s s o r i e s such as shading p r o j e c t i o n s , canopies and landscaping around the window becomes e q u a l l y important. On account of the c o n t r a d i c t o r y f u n c t i o n s and s e v e r a l design f a c t o r s , window design i s the most complex part of the f a b r i c d e s i g n . In order to s i m p l i f y the complexity of the o v e r a l l window system, i t i s u s e f u l to d i f f e r e n t i a t e i t i n terms of e x t e r i o r p a r t s i d e n t i f i e d with e x t e r i o r c l i m a t e , and i n t e r i o r p a r t s i d e n t i f i e d with i n t e r i o r environment (Leu, 1980).' The h i e r a r c h y of p a r t s i n the o v e r a l l window system i s as f o l l o w s : a. Exter i o r b. E x t e r i o r Accessor l e s c . The Window d. I n t e r i o r Accessor l e s e. I n t e r i o r 1 32 Each of these p a r t s of the window system can he l p i n modifying the i n f l u e n c e of e x t e r i o r c l i m a t e on i n t e r n a l thermal c o n d i t i o n s . The s p e c i f i c a r c h i t e c t u r a l design of these p a r t s i s dependent on the elements of e x t e r n a l c l i m a t e , the time of the day and the month. A general i n t r o d u c t i o n of a l l these p a r t s i s given below. a. E x t e r i o r The e x t e r i o r of the window system c o n s t i t u t e s the surrounding s u r f a c e s , v e g e t a t i o n , screens e t c . The e x t e r i o r elements are the f i r s t f a c t o r s in window design by which the adverse e f f e c t s of c l i m a t e can be reduced. b. E x t e r i o r A c c e s s o r i e s These c o n s t i t u t e shading d e v i c e s , r o l l e r b l i n d s , e x t e r i o r s h u t t e r s , awnings, and screens, a l l of which are p a r t l y or f u l l y a t t a c h e d to windows. The ba s i c purpose of e x t e r i o r a c c e s s o r i e s i s to c o n t r o l s o l a r gain and to modify wind movement. c. The Window The window i t s e l f i s an important part of o v e r a l l window system as i t i n f l u e n c e s the i n t e r n a l thermal c o n d i t i o n s by p e r m i t t i n g heat gain and v e n t i l a t i o n . The window area, i t s p o s i t i o n , and the type of window m a t e r i a l used are the most important design f a c t o r s . d. I n t e r i o r a c c e s s o r i e s I n t e r i o r a c c e s s o r i e s such as drapes, b l i n d s and s h u t t e r s , p r o v i d e c o n t r o l over the s o l a r r a d i a t i o n that i s permitted through the window. Although they are not e f f e c t i v e f o r 1 3 3 reducing heat gai n , they can reduce g l a r e . e. I n t e r i o r The c o l o u r s and m a t e r i a l of the w a l l s can be used to supplement the thermal performance of windows. T h i s i s e s p e c i a l l y u s e f u l f o r reducing g l a r e which can be accomplished with c a r e f u l s e l e c t i o n of c o l o r . 2.2. Window O r i e n t a t i o n An important c o n s i d e r a t i o n i n window design i s i t s o r i e n t a t i o n because i t d i c t a t e s the design of both the e x t e r i o r and i n t e r i o r p a r t s of the o v e r a l l window system. F i g u r e 2.32 shows the s o l a r heat gain p e r m i t t e d by a 1mx1m window i n v a r i o u s o r i e n t a t i o n s . The window i s without any shading d e v i c e s and i s u n v e n t i l a t e d . The e f f e c t of o r i e n t a t i o n on heat gain and i t s i m p l i c a t i o n s on window system design are summarized below: a. The heat gain through windows f a c i n g south to 30° east of south i s .lower than other o r i e n t a t i o n s d u r i n g summer. Th i s o r i e n t a t i o n a l s o allows wind movement i n the evening as the d i r e c t i o n of wind flow i s east-west. T h e r e f o r e , l a r g e r window area i n t h i s o r i e n t a t i o n w i l l b e n e f i t from both minimum heat gain and comfort v e n t i l a t i o n . In a d d i t i o n , due to a higher a l t i t u d e of sun in south during summer i t i s e a s i e r to provide e f f e c t i v e shading with l e s s complicated shading d e v i c e s . b. Heat gain through east and west f a c i n g windows i s the maximum, hence r e l a t i v e l y smaller and fewer windows 1 34 3? 2: V> o IH \ \ H I' \ \ 1 E : / 'OTH / / / • ̂ . mi ^ , - T^TAL THINNESS * 4-5M*1 - piFPUSB = -SK^UHPKEFLfccT&P 12.AP1ATWNS' 10 • -WlKp^>w WITHOUT Fig.2.32. S o l a r Heat Gain P e r m i t t e d by a 1mx1m Va r i o u s O r i e n t a t i o n s . Window i n Fig.2.33. S o l a r A l t i t u d e and Windows i n v a r i o u s O r i e n t a t i o n s . a. S o l a r A l t i t u d e d u r i n g Summer and Windows i n South b. S o l a r A l t i t u d e d u r i n g Summer and Windows i n East and West. 1 35 should be p l a c e d i n these facades. In a d d i t i o n , the design of f i x e d shading i s most c r i t i c a l i n these o r i e n t a t i o n s . Windows f a c i n g east or west r e c e i v e summer sun f o r more hours and at a more d i r e c t angle than southern exposures (Fig.2.33a,b). T h e r e f o r e , these windows are more d i f f i c u l t to shade and r e q u i r e more complicated h o r i z o n t a l and v e r t i c a l overhangs. c. East f a c i n g windows are b e t t e r than west f a c i n g ones for thermal comfort, s i n c e the former r e c e i v e summer sun i n the evening when the a i r temperature i s maximum. Thi s i m p l i e s that the window area in the east can be l a r g e r than the west. d. North f a c i n g windows allow l e s s heat gain than east and west. Larger window area in north i s b e n e f i c i a l i n summer but can cause some discomfort d u r i n g winter due to the absence of d i r e c t sun. Heat gain i n v a r i o u s o r i e n t a t i o n s can be a l t e r e d , however, with the degree and e f f i c i e n c y of shading d e v i c e s and with the presence of v e n t i l a t i o n c o n d i t i o n s (Givoni 1981). 2.3. E x t e r i o r In a d d i t i o n to d i r e c t r a d i a t i o n , the b u i l d i n g s r e c e i v e d i f f u s e and r e f l e c t e d r a d i a t i o n . F i g u r e 2.34 shows the r e l a t i v e p r o p o r t i o n of these components upon a south f a c i n g window at l a t i t u d e 25°N. The r e f l e c t e d r a d i a t i o n i n c i d e n t upon a window v a r i e s with the r e f l e c t a n c e value of s u r f a c e m a t e r i a l s surrounding the window and i t s o r i e n t a t i o n . With the lower a l t i t u d e of the sun, such as i n east and west 1 36 Fig.2.34. R e l a t i v e P r o p o r t i o n of Ground R e f l e c t e d , D i r e c t and D i f f u s e d S o l a r R a d i a t i o n I n c i d e n t upon a South f a c i n g Window at L a t i t u d e 25 N RESULT aV- HI*W AlT'TUPg- i n t e r n - Fig.2.35. S o l a r A l t i t u d e and R e f l e c t o r Area i n East , West and South O r i e n t a t i o n s . 1 37 o r i e n t a t i o n s , the r e f l e c t o r area surrounding the window in c r e a s e s (Fig.2.35) which in turn i n c r e a s e s the s o l a r r a d i a t i o n i n c i d e n t upon the window. The g r e a t e s t concern in these o r i e n t a t i o n s i s the m a t e r i a l used for the r e f l e c t o r area surrounding the window. The use of landscaping o u t s i d e the window w i l l be e f f e c t i v e i n reducing the r e f l e c t e d r a d i a t i o n . Landscaping w i l l a l s o reduce the temperature of incoming a i r i f the windows are open. The shrubs, hedges and p l a n t s , however, should be lower than the window s i l l so that they do not d e f l e c t d e s i r e d a i r movement. 2.4. E x t e r i o r A c c e s s o r i e s The b a s i c purpose of e x t e r i o r a c c e s s o r i e s i s to c o n t r o l s o l a r heat gain during the summer and to permit i t i n winter. Another f u n c t i o n of e x t e r i o r a c c e s s o r i e s i s to promote v e n t i l a t i o n to enhance thermal comfort. The a c c e s s o r i e s designed f o r s o l a r c o n t r o l and comfort v e n t i l a t i o n , however, a l s o a f f e c t d a y l i g h t , g l a r e , and view. A c c e s s o r i e s f o r s o l a r c o n t r o l There are two types of e x t e r i o r a c c e s s o r i e s f o r s o l a r c o n t r o l : f i x e d and a d j u s t a b l e shading d e v i c e s . The f i x e d shading d e v i c e s i n c l u d e h o r i z o n t a l , v e r t i c a l and eggcrate p r o j e c t i o n s whereas the a d j u s t a b l e d e v i c e s i n c l u d e wood s h u t t e r s and a v a r i e t y of l o u v e r s : v e r t i c a l , h o r i z o n t a l and combinations of both. The a d j u s t a b l e shading d e v i c e s can be moved at w i l l to f u l f i l l changing requirements, but f i x e d d e v i c e s exert t h e i r e f f e c t in a predetermined f a s h i o n . 1 38 In order to design f i x e d shading d e v i c e s the a r c h i t e c t must f i r s t know the s o l a r a l t i t u d e and the s o l a r azimuth an g l e s . Both can be found, f o r any date of the year and any hour of the day, by using the sun-path diagram f o r the p a r t i c u l a r l a t i t u d e . Fig.2.36a shows the sun path diagram f o r 25°N l a t i t u d e . The next step i s to d e f i n e and mark the overheated p e r i o d on the sun path diagram. Using the mean hourly temperatures f o r each month, the overheated p e r i o d can be d e f i n e d and marked on the sun path diagram (Fig.2.36b). Once the overheated p e r i o d i s determined, with a s o l a r shading mask placed on the sun path diagram, v e r t i c a l and h o r i z o n t a l shadow angles can be found. With t h i s i n f o r m a t i o n the depth and shape of v e r t i c a l and h o r i z o n t a l p r o j e c t i o n s can be determined f o r any o r i e n t a t i o n . Due to d i f f e r e n t s o l a r a l t i t u d e and azimuth, the shape and s i z e of s o l a r c o n t r o l devices may be d i f f e r e n t f o r v a r i o u s o r i e n t a t i o n s . T h e r e f o r e , s o l a r c o n t r o l s , i n a d d i t i o n to p r o v i d i n g p r o t e c t i o n from sun can g i v e a strong a r c h i t e c t u r a l c h a r a c t e r to a facade. An a r c h i t e c t can u t i l i z e t h i s a e s t h e t i c p o t e n t i a l i n a p o s i t i v e way by g i v i n g an i n d i v i d u a l c h a r a c t e r to each facade. The f i x e d shading d e v i c e s are a l s o easy to i n t e g r a t e i n t o the c o n v e n t i o n a l b u i l d i n g c o n s t r u c t i o n methods i n I n d i a . The s i m p l i c i t y of t h e i r i n t e g r a t i o n makes them an a t t r a c t i v e o p t i o n , e s p e c i a l l y f o r south f a c i n g windows. On the negative s i d e , the performance of f i x e d shading d e v i c e s , 1 39 © 2.36. a. Sun Path Diagram f o r L a t i t u d e 25°N b. Overheated P e r i o d f o r L a t i t u d e 25°N 1 4 0 designed to c o n t r o l s o l a r gain d u r i n g the pe r i o d s with maximum temperature, may not be as e f f e c t i v e as d e s i r e d . T h i s i s i l l u s t r a t e d by Gi v o n i (1981): "The f u n c t i o n a l requirements f o r s o l a r c o n t r o l d i f f e r widely with r e g i o n a l c l i m a t e s and, w i t h i n each r e g i o n , with seasonal c l i m a t i c v a r i a t i o n s . T h i s problem i s f u r t h e r complicated because of the d i f f e r e n t y e a r l y p a t t e r n s of temperature and s o l a r r a d i a t i o n . While the i n t e n s i t y of s o l a r r a d i a t i o n ( i n the nothern hemisphere) has i t s maximum on June 22nd and ' i t s minimum on December 22nd, the temperature y e a r l y wave i s delayed on account of the heat c a p a c i t y of the earth's s u r f a c e and reaches i t s maximum i n July-August and i t s minimum in January-Feburary. Therefore when the sun i s excluded i n the hot l a t e summer by some f i x e d arrangement i t w i l l be excluded too i n the c o o l s p r i n g , so that some compromise i s r e q u i r e d in t h i s case." In a d d i t i o n , f i x e d shading d e v i c e s , due to the use of m a t e r i a l s l i k e s t e e l and concrete f o r t h e i r c o n s t r u c t i o n , are an expensive s o l u t i o n to the problem of heat g a i n . For such c o n d i t i o n s , a d j u s t a b l e shading d e v i c e s w i l l p r ovide more s a t i s f a c t o r y performance and w i l l be r e l a t i v e l y inexpensive to c o n s t r u c t . With a d j u s t a b l e shading d e v i c e s l i k e wooden s h u t t e r s and l o u v e r s , i t i s p o s s i b l e to e l i m i n a t e upto 90% of the heating e f f e c t by s o l a r r a d i a t i o n during the per i o d s with maximum temperature in summer. Table IV l i s t s the thermal performance of some commonly used e x t e r i o r shading d e v i c e s i n hot and dry c l i m a t e s . The i n f l u e n c e of these de v i c e s on d a y l i g h t , g l a r e and view i s a l s o i n c l u d e d i n t h i s t a b l e . I t i s i n d i c a t e d i n t h i s t a b l e that h o r i z o n t a l p r o j e c t i o n s i n south o r i e n t a t i o n are more e f f e c t i v e than v e r t i c a l to c o n t r o l s o l a r r a d i a t i o n . V e r t i c a l p r o j e c t i o n s on the east and west are e f f e c t i v e in 141 IV. Performance of E x t e r i o r Shading D e v i c e s . D e v i c e - T H E R M A L vimm/wcb P&PUC& -U>UKYi GAIN &FE£TlVfcLY IN 9 , < S W , S E . (l^VCB (9LAtfE- P & F L 6 £ T IA/IHP A P V A N T A d e ^ L S L Y L f e A ^ T E F F E C T I V E <2>N & 4 w F A C A D E S • - R S D U C S D A Y U 6 H T POTENTIAL- - p<? N<2T B'U^CK V I E W _ C O L L E C T PUST- P^3&CTI<?NS- S<»LA|£ (SAIN IN A N Y ^KIGNTATWN IMPK^^& W I N D VELOCITY' s£ D I S . T ^ 1 6 » U T ^ N • IN lNTt=Mau>yi- - iREDL^-e DA.YLIG.HT RSTfeNTlAU- - P » L < ? c K l / I B W P A K T I A U - Y - PAV2TICULAYlLY fepPECTlV& IN <5B A M D S Y V - ^ R l B N T A T l ^ N ^ F<?l? K E D - U i - i ^ -S^WUK. « - A l N - • tfepi^B i/erHTlL-AT'^N ^ A f A K^DUC-e D A Y U 6 H fcT&HTlAL <3-u6.<5.TANTlAu_Y- • g . X P e N S l v & S^LUTWN T̂> s<5LA^ • B ' U ^ C l i V I E W P A R T I A L L Y ' LATTICE (3ALl) K B P t / i S WIND V E L O C I T Y feUTALUJVV VfcNTlUATi-oN.- ^ L - A r Z S - - P E P U C & P U S T - - R e d u c e D A Y U ^ H T P;?TSNTIAL- . A f e'S - T H e - n ^ A t - L Y P L E A ^ I H S - • P*wa*5dTO?NS AT 4e>* AN6L&- ' p»L^<s.|<. W M P "SUfesTANTlAU-Y- * U B S T A N Tl A L L Y - fcSATBNT- r ^ T S N T l A l - McOVBAfoLE W ^ P ^ H U T m ^ S (CUSEDJ 11 •yatPUC-e S<?LAW. dAtM ^Ufe»TANTlAU* -fe=L-<*£.K W 1 N P -SUBSTANTIALLY- • | a B D « * = e D A Y LJf iHT «.U&srAVTl*LOf * . & U » < ^ < VIPVV Stfe.STANnALL.Y- V E R T I C A L ujuv&tes; (SAtW IN ALL tfKlBNTAIWNS • M A y <SS*/FUCT WtTH Wl ivp M ^ V B M t e N T - H^BPlfclEi <sLA£e-1  », -tiFVfes^TlV&L.'Y V2BD1/CB -SdL-ArZ. « A i N IN ALL. <9Y21B NTATU»N£ • - p l R B C T W I N D N A W & M E N T VN T H f e p l r a e c T I / W H5« IT l^H-SD T V <2<ary"trtiL 4^LAl4 dfiilW. DEDUCE G.L-A»2.e • .RteT>U<iE P A Y U 6 H T W-&NTIAL • • VJuSCJf. V l & Y V P A R T I A L L Y ' - fZE?t>y^a p a y U 6 H T P^TENTIAL- . p.L<JCK VVEJW P A R T I A L L Y - 1 4 2 p r o v i d i n g adequate shading only i f they are t i l t e d at 45 to the south. T h i s p o s i t i o n , however, e l i m i n a t e s comfort vent i l a t i o n . The thermal performance of both f i x e d and a d j u s t a b l e e x t e r n a l shading d e v i c e s improves i f they are of darker c o l o u r s and the room i s u n v e n t i l a t e d ( G i v o n i , 1981). T h i s i s because darker c o l o u r s r e f l e c t l e s s e r s o l a r r a d i a t i o n towards the i n t e r i o r and an i n c r e a s e in e x t e r n a l a i r temperature, from the heat absorbed by shading d e v i c e s , does not e l e v a t e the a i r temperature of the u n v e n t i l a t e d room. A c c e s s o r i e s to promote v e n t i l a t i o n The a c c e s s o r i e s designed f o r c o n t r o l l i n g s o l a r r a d i a t i o n may a l s o promote v e n t i l a t i o n . In row houses or other compact forms, where only two facades are exposed, i t i s not always p o s s i b l e to provide c r o s s v e n t i l a t i o n by keeping windows in both windward and leeward d i r e c t i o n . The e x t e r i o r a c c e s s o r i e s are advantageous for such cases as they a c c e l e r a t e the wind v e l o c i t y and enhance comfort c o o l i n g p a r t i c u l a r l y i n rooms with windows only i n windward d i r e c t i o n . F i g u r e 2.37 i l l u s t r a t e s t h i s : a. A room with one window in.windward d i r e c t i o n has a much lower wind v e l o c i t y than a c r o s s v e n t i l a t e d room (Fig.2.37a,b). T h i s i s because the i n t e r n a l e x t e r n a l pressure g r a d i e n t a c r o s s the opening i s very small (Melaragno,1983). b. By p r o v i d i n g two windows (with a t o t a l area equal to the s i n g l e window in f i r s t case) in windward d i r e c t i o n (Fig.2.37c) the wind v e l o c i t y i n the same room improves, 1 43 Fig.2.37. V e r t i c a l P r o j e c t i o n s and Wind V e l o c i t y i n a Room. a. Wind V e l o c i t y i n a Cross V e n t i l a t e d Room. b. Wind V e l o c i t y i n a Room with One Window. c. Wind V e l o c i t y i n a Room with Two Windows on the Same Wall d. Wind V e l o c i t y with the A d d i t i o n of V e r t i c a l P r o j e c t i o n s . Sources: Chandra, Subrato, 1983. Melaragno, 1982 1 44 but only moderately as the pressure g r a d i e n t i s s t i l l s m a l l . c. However, when v e r t i c a l p r o j e c t i o n s are added to these windows (Fig.2.37d) the wind v e l o c i t y i n the same room in c r e a s e s d r a m a t i c a l l y . The i n t e r i o r wind v e l o c i t y i n t h i s case i n c r e a s e s almost three times the f i r s t case but only i f the wind d i r e c t i o n i s o b l i q u e to the i n l e t windows. T h i s improvement in wind v e l o c i t y i s achieved because, with the a d d i t i o n of v e r t i c a l p r o j e c t i o n s , a pressure region i s formed in f r o n t of the i n l e t window and a s u c t i o n at the o u t l e t window r e s u l t i n g in improved c r o s s v e n t i l a t i o n . The depth of v e r t i c a l p r o j e c t i o n s i s not an important f a c t o r f o r improving v e n t i l a t i o n c o n d i t i o n s (Givoni,1981). However, i f v e r t i c a l p r o j e c t i o n s are provided f o r windows of 2-3 rooms in the same o r i e n t a t i o n , the depth of p r o j e c t i o n s should not be more than one h a l f the d i s t a n c e between two openings. The p r o j e c t i o n s l a r g e r than t h i s may o b s t r u c t the wind movement in the adjacent room. H o r i z o n t a l p r o j e c t i o n s do not i n f l u e n c e the v e l o c i t y of a i r , but have s i g n i f i c a n t impact on the a i r flow p a t t e r n i n a room. For i n s t a n c e , 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 e l i m i n a t e the e f f e c t of pressure b u i l d - u p above the window, thus the pressure below the window d i r e c t s the a i r flow upwards l e a v i n g the occupied zone without a i r f l o w (Fig.2.38a). A gap between the h o r i z o n t a l p r o j e c t i o n and the b u i l d i n g face can ensure a downward p r e s s u r e . There may be a c o n f l i c t between d e s i r a b l e a i r flow p a t t e r n and 1 45 Fig.2.38. a. 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 and A i r Flow. b. A d j u s t a b l e H o r i z o n t a l Louvers and a i r Flow, Source: Fathy, 1986 A L L W I N D O W S . Fig.2.39. Heat g a i n Through Windows of D i f f e r e n t South O r i e n t a t i o n . Areas i n 1 46 c o n t r o l of s o l a r r a d i a t i o n i n p o s i t i o n i n g a d j u s t a b l e h o r i z o n t a l l o u v e r s . For i n s t a n c e , l o u v e r s angled downward w i l l d i r e c t the a i r flow i n t o the occupied zone (Fig.2.38b) in a room, but w i l l not prevent the sun to pe n e t r a t e . 2.5. The Window Window Area A s i g n i f i c a n t amount of heat gain through the c l o s e d g l a s s windows takes p l a c e by s o l a r r a d i a t i o n . For a constant r a d i a t i o n heat flow and s o l a r gain f a c t o r of the window g l a s s , window area i s the most important c o n s i d e r a t i o n in determining heat gain by s o l a r r a d i a t i o n (Fig.2.39). Window area i s a l s o an important c o n s i d e r a t i o n f o r s t r u c t u r a l and comfort c o o l i n g as i t determines the a i r exchange r a t e (m /h) and wind v e l o c i t y in a space, when the windows are opened i n the evening. For a given outdoor wind v e l o c i t y , the a i r exchange rate i n a space i n c r e a s e s p r o p o r t i o n a t e l y with the window area. Whereas, from the p o i n t of view of reducing heat g a i n , a minimum area of window i s d e s i r a b l e even in south o r i e n t a t i o n , a c o n s i d e r a b l e decrease i n window area w i l l a l s o reduce comfort and s t r u c t u r a l c o o l i n g i n the evening r e s u l t i n g i n an i n c r e a s e d dependence on mechanical c o o l i n g . T h e r e f o r e , window area should be kept to a minimum compatible with adequate comfort and s t r u c t u r a l c o o l i n g r e q u i rements. When the window area i s 25-30% of the corresponding w a l l area in north and south o r i e n t a t i o n s , and i s designed with proper shading and minimum v e n t i l a t i o n , the room a i r temperature and 1 47 requirements f o r mechanical c o o l i n g are minimum durin g the day time in summer ( S h r i f t e i l i g , 1980). In the evening and at night (between 9 p.m. to 7 a.m.), i f the windows are open and the room has between 12-30 a i r changes per hour, the indoor a i r temperature drops w i t h i n the comfort range (22-30°C). A high a i r change rate during the n i g h t , achieved by 25-30% window area, a l s o improves the room a i r temperature during the day due to s t r u c t u r a l c o o l i n g and keeps i t w i t h i n an a c c e p t a b l e range of thermal comfort (Golneshan,1985). Window area i s an important f a c t o r for determining a i r v e l o c i t y f o r comfort c o o l i n g in a space. In a room with one window the i n f l u e n c e of window area on a i r v e l o c i t y i s a p p r e c i a b l e (Fig.2.40), e s p e c i a l l y when d i r e c t i o n of a i r flow i s o b l i q u e to the window. The wind v e l o c i t y in t h i s case i n c r e a s e s p r o p o r t i o n a t e l y with window area and a l s o i s d i s t r i b u t e d over a l a r g e r space (Givoni,1981). If a room i s c r o s s v e n t i l a t e d , an i n c r e a s e i n the s i z e of windows has a g r e a t e r e f f e c t on i n t e r n a l a i r v e l o c i t y , but only when the i n l e t and o u t l e t openings are i n c r e a s e d s i m u l t a n e o u s l y . When a room has unequal openings, and the o u t l e t i s l a r g e r than the 5 i n l e t , higher average speeds and much higher maximum v e l o c i t i e s are obtained (Fig.2.41). However, a combination of a small i n l e t with l a r g e r o u t l e t produces a concentrated a i r f l o w , l i m i t e d to a small s e c t i o n of the room. Such an arrangement i s d e s i r a b l e when the a i r stream i s to be d i r e c t e d at a given part of the room. On the other hand, when the i n l e t i s l a r g e r than the o u t l e t , maximum v e l o c i t i e s are much lower but the average indoor v e l o c i t y i s •1 48 Fig.2.40. A Larger Window Area Increases Wind V e l o c i t y i n a Room with One Window E s p e c i a l l y When Wind i s Oblique to the Window. Fig.2.41. Higher Wind V e l o c i t y I n s i d e a Cross v e n t i l a t e d Room Can be Achieved When i t Has Unequal Openings and the O u t l e t i s Larger than the I n l e t . Source: G i v o n i , 1981 149 not a f f e c t e d much. When a i r flow through the whole space i s r e q u i r e d , a l a r g e i n l e t opening w i l l be d e s i r a b l e . Window p o s i t i o n i n g A s i g n i f i c a n t e f f e c t of window p o s i t i o n i s on a i r d i s t r i b u t i o n and v e l o c i t y i n a space. The v e r t i c a l p o s i t i o n of a window, with respect to the a i r d i s t r i b u t i o n , v a r i e s with space usage in a d w e l l i n g . For in s t a n c e i n the l i v i n g room, where most of the area i s occupied by seated people, the main a i r flow w i l l be d e s i r e d at the head and shoulder height (70 to 120cm.) of the seated people ( G i v o n i , 1969). In bedrooms the main a i r f l o w i n the evening should be at a height a l i t t l e above bed l e v e l (50 to 80cm.). Windows kept below these l e v e l s w i l l not be e f f e c t i v e i n p r o v i d i n g comfort c o o l i n g i n these rooms and w i l l only i n c r e a s e the heat g a i n . In the k i t c h e n space, requirement f o r adequate a i r changes i s more important than proper a i r d i s t r i b u t i o n and v e l o c i t y due to cooking odours and moisture. A i r changes in k i t c h e n are best achived through windows placed c l o s e r to the c e i l i n g . A l i g h t breeze i n k i t c h e n may be r e q u i r e d below the counter top l e v e l , whereas a i r d i s t r i b u t i o n above or at the work top l e v e l w i l l be d i s r u p t i v e to cooking a c t i v i t y . However, windows above the counter top l e v e l are r e q u i r e d f o r d a y l i g h t i n g i n k i t c h e n . If the room i s c r o s s v e n t i l a t e d , the height of the o u t l e t window has a small e f f e c t on the d i s t r i b u t i o n and v e l o c i t y of the a i r , but there i s an abrupt drop i n a i r v e l o c i t y below the s i l l l e v e l of an i n l e t window. T h i s i m p l i e s that a proper 150 v e r t i c a l p o s i t i o n of an i n l e t window i s more important than the o u t l e t window i n a c r o s s v e n t i l a t e d space. In a d d i t i o n to a i r d i s t r i b u t i o n and v e l o c i t y , window p o s i t i o n a l s o a f f e c t s g l a r e . G l a r e i s a f u n c t i o n of the c o n t r a s t between the window and window wa l l (Fig.2.42a). A room with windows on one wa l l only w i l l always have t h i s problem. However, such problem can be r e c t i f i e d by p o s i t i o n i n g windows on opposite or adjacent w a l l s (Fig.2.42b). The g l a r e can a l s o be reduced by p o s i t i o n i n g windows with the s i l l above eye l e v e l which a l s o concentrates ground r e f l e c t e d l i g h t on to the c e i l i n g . A l i g h t c o l o u r c e i l i n g can i n t h i s way ensure adequate and w e l l d i f f u s e d i n t e r i o r l i g h t i n g , through a comparatively small window (Fig . 2 . 4 2 c ) . Low l e v e l windows w i l l be g l a r e f r e e i f they open i n t o a shaded and p l a n t e d c o u r t y a r d . V e r t i c a l strip-windows p l a c e d in the corners of room w i l l a l s o be e f f e c t i v e i n reducing g l a r e i f the adjacent w a l l i s p a i n t e d a l i g h t c o l o u r (Fig.2.42d). T h i s w i l l throw l i g h t onto the wa l l s u r f a c e thus p r o v i d i n g a l a r g e r apparent source of a l e s s e r luminance. Window m a t e r i a l s The choice of a p p r o p r i a t e m a t e r i a l f o r a window i s important in minimizing heat gain and promoting v e n t i l a t i o n through a window. Wood and g l a s s are the two most commonly used m a t e r i a l s f o r windows i n I n d i a . Wooden s h u t t e r s , used before g l a s s became popular, were e f f e c t i v e i n c o n t r o l l i n g heat gain f o r the c l o s e d windows during the daytime. However, the c l o s e d wooden s h u t t e r s a l s o o b s t r u c t d a y l i g h t and view completely. 151 Fig.2.42. G l a r e From Windows. a. G l a r e due to C o n t r a s t between Window and Window Wa l l . b. Reduced G l a r e by P o s i t i o n i n g Windows on Adjacent W a l l s . c. A high L e v e l Window with L i g h t Colour C e i l i n g Reduces G l a r e . d. Corner windows Reduce G l a r e . Source: Gupta, 1984 1 52 Windows f i t t e d with wooden l o u v e r s perform b e t t e r than wooden s h u t t e r s , s i n c e they not only p r o v i d e c o n t r o l over heat gain but a l s o allow f o r l i g h t p e n e t r a t i o n . However, as d i s c u s s e d e a r l i e ' r ( s e c t i o n 2.4.), the p o s i t i o n of l o u v e r s with r e s p e c t to the a i r flow p a t t e r n may c o n f l i c t with c o n t r o l of s o l a r r a d i a t i o n . A window f i t t e d with a wooden l a t t i c e (Fig.2.43) i s the most e f f e c t i v e s o l u t i o n i n terms of the thermal performance of a windov; i f wood i s to be used as window m a t e r i a l . An i n t r i c a t e l y woven wood l a t t i c e ( j a l i ) , i n a d d i t i o n to p r o v i d i n g p r o t e c t i o n from d i r e c t sun, a l s o p r o v i d e s a i r flow and g l a r e f r e e l i g h t i n a s i n g l e a r c h i t e c t u r a l s o l u t i o n (Fathy, 1986). With l a n d s c a p i n g around the j a l i , the incoming a i r can be c o o l e d and h u m i d i f i e d d u r i n g the daytime. Fig.2.43. I n t r i c a t e l y Woven Wood J a l i as Window M a t e r i a l . Source: Fathy, 1986 153 Although c l e a r g l a s s , as a window m a t e r i a l , has the advantage of p r o v i d i n g maximum l i g h t and view, i t a l s o admits s o l a r r a d i a t i o n . The heat gain through a window can be reduced with the h e l p of i n t e r i o r and e x t e r i o r shading devices and r e p l a c i n g c l e a r g l a s s with s o l a r absorbing g l a s s , but a l l these r e q u i r e a d d i t i o n a l c o s t . A 4mm c l e a r g l a s s window with shading d e v i c e s admits 1/3 of impinging r a d i a t i o n in a south o r i e n t a t i o n ( S t r a a t e n , 1967). The r e f o r e , i f c l e a r g l a s s i s to be used as window m a t e r i a l , an emphasis should be placed on adequate design of shading d e v i c e s . 2.6. I n t e r i o r A c c e s s o r i e s The purpose of i n t e r i o r a c c e s s o r i e s i s to r e g u l a t e s o l a r r a d i a t i o n and to provide p r o t e c t i o n from g l a r e . Although i n t e r i o r a c c e s s o r i e s o b s t r u c t s o l a r r a d i a t i o n , e x t e r n a l shading d e v i c e s are more e f f e c t i v e i n p r o v i d i n g p r o t e c t i o n from s o l a r heat g a i n . The reason f o r t h i s i s that part of heat absorbed by i n t e r n a l d e v i c e s i s d i s s i p a t e d towards the i n t e r i o r which adds to i n t e r n a l heat g a i n . The c o l o u r of i n t e r i o r a c c e s s o r i e s i s an important f a c t o r . The l i g h t c o l o u r a c c e s s o r i e s w i l l absorb l e s s heat and a l s o reduce g l a r e . 2.7. I n t e r i o r The windows i n hot and dry c l i m a t e s need to be smaller and fewer i n number, with the r e s u l t the i n t e r i o r l i g h t i n g l e v e l w i l l be low. The use of a l i g h t c o l o u r on the wa l l s i n c r e a s e s the r e f l e c t i o n of d a y l i g h t and the o v e r a l l b r i g h t n e s s i n a room. T h i s i n turn reduces the c o n t r a s t between the window and the window w a l l , which i n turn reduces g l a r e . 1 54 3. DELAY PERIODIC HEAT FLOW, MINIMIZE CONDUCTIVE HEAT FLOW 3.1. Roof and Walls: Thickness, M a t e r i a l s and Colour Hot and dry c l i m a t e s p o t e n t i a l l y have a high d i u r n a l range, normally between 10 and 15°C. T h i s temperature f l u c t u a t i o n causes d i s c o m f o r t d u r i n g v a r i o u s times of day and n i g h t . E x t e r n a l w a l l s and the roof should t h e r e f o r e have p r o p e r t i e s which moderate t h i s high e x t e r n a l temperature range and minimize conductive heat flow. Roof and w a l l s with high thermal c a p a c i t y and r e s i s t a n c e w i l l reduce t h i s e x t e r n a l temperature range by d e l a y i n g the p e r i o d i c heat flow to the i n t e r i o r (Givoni,1981). T h i s delay in p e r i o d i c heat flow i s a s s o c i a t e d with an advantageous time l a g . The time l a g f o r an exposed roof should be at l e a s t 12 to 15 hours so that the r e l e a s e of heat to the i n t e r i o r , which i s absorbed dur i n g the day, i s delayed u n t i l the c o o l e r hours of the n i g h t . The r e q u i r e d time l a g f o r w a l l s depends upon t h e i r o r i e n t a t i o n . For i n s t a n c e , east f a c i n g w a l l s r e q u i r e a time l a g of 12 to 14 hours as they r e c e i v e t h e i r maximum hea t i n g between 10 and 11a.m. A time l a g of only 10 hours f o r east w a l l s w i l l allow the i n s i d e s u r f a c e temperature to reach i t s maximum at 8p.m., when the ambient a i r temperature i s s t i l l l i k e l y to be above the comfort l e v e l . West f a c i n g w a l l s r e q u i r e a r e l a t i v e l y smaller time l a g , normally 8 to 10 hours, as they r e c e i v e t h e i r maximum hea t i n g between 3 and 4 p.m. South and north f a c i n g w a l l s do not r e q u i r e a l a r g e time l a g , because t h e i r t o t a l maximum heating in summer i s much lower. 1 55 i n order to achieve a g r e a t e r time l a g and low thermal c o n d u c t i v i t y , the t h i c k n e s s and thermal p r o p e r t i e s ( d e n s i t y and s p e c i f i c heat) of roof and w a l l s are important c r i t e r i a ( G i v o n i , 1981). The t o t a l t h i c k n e s s of roof and w a l l s i s a combination of l a y e r s of v a r i o u s m a t e r i a l s i n c l u d i n g e x t e r i o r and i n t e r i o r f i n i s h e s , each l a y e r of which c o n t r i b u t e s i n modifying and d e l a y i n g the heat conduction from e x t e r n a l to i n t e r n a l s u r f a c e . One of the reasons f o r combining v a r i o u s m a t e r i a l s i n roof and w a l l c o n s t r u c t i o n i s to reduce the s t r u c t u r a l load and m a t e r i a l c o s t . As roof c o n s t r u c t i o n i n hot and dry regions i n India i s u s u a l l y done with c o n c r e t e , a s l a b of 300 mm (Table V) would be r e q u i r e d to achieve a time l a g of 12 hours. T h i s i s u n l i k e l y to be economical, s i n c e not only i s the volume of m a t e r i a l e x c e s s i v e , but a l s o the weight would r e q u i r e l a r g e r s t r u c t u r a l members to support i t . Use of an i n s u l a t i n g l a y e r on the o u t s i d e of a t h i n n e r concrete s l a b can provide the same time l a g (Koenigsberger,1973) without i n c r e a s i n g the weight of the t o t a l s t r u c t u r e . E a r t h pots with an a i r gap (Fig.2.44), foam con c r e t e , or expanded p o l y s t y r e n e are some of the recommended i n s u l a t i n g m a t e r i a l s (Sodha and Bansal,1984). Inverted, c l o s e l y packed earthen pots on a ro o f , i n a d d i t i o n to p r o v i d i n g a time l a g of above 12 hours and low thermal c o n d u c t i v i t y , provide i n c r e a s e d s u r f a c e area f o r r a d i a t i o n emission to the c l e a r sky at n i g h t , and c o o l f a s t e r than a f l a t r o o f . However, t h i s kind of roof i s not s u i t a b l e for frequent occupancy. Foam concre t e or p o l y s t y r e n e 1 56 20 15 10 / y * TlVl' feffANDgp fi?AM6P •5TB BU ALUM1HIUM- 11 (TO 0>0?.<\ 0-0 til tit* 0-15 0-30 0-45 Thickness: m 0-60 Table V. Time Lag Prov i d e d by the M a t e r i a l s of V a r i o u s Thermal P r o p e r t i e s and Th i c k n e s s . Source: E l Bannany, 1984 RADIATE "G? SKY- Fig.2.44. Roof F i n i s h e d with Earthen Pots. Source: Sodha and Bansal, 1984 1 57 f i n i s h e d with b r i c k t i l e s are, t h e r e f o r e , more s u i t a b l e f o r a roof which i s f r e q u e n t l y used. These m a t e r i a l s , however, are more expensive than the cheap earthen pots. The w a l l s in hot and dry c l i m a t e s are b u i l t with b r i c k s as they are l o c a l l y a v a i l a b l e . The t h i c k n e s s of w a l l s depends upon the a v a i l a b l e s i z e of the b r i c k s . For f u r t h e r r e d u c t i o n of conductive heat flow and a l a r g e r time l a g , double w a l l s can be b u i l t with a a i r gap in between. As d i s c u s s e d e a r l i e r , the t h i c k n e s s of w a l l s i n v a r i o u s o r i e n t a t i o n s should be d i f f e r e n t depending upon the time l a g r e q u i r e d . For east o r i e n t a t i o n s , where the maximum time l a g i s r e q u i r e d , the e x t e r n a l w a l l s should not be l e s s than 300 mm. and should p r e f e r a b l y have a c a v i t y . For west o r i e n t a t i o n s 300 mm t h i c k w a l l s without a c a v i t y w i l l provide the r e q u i r e d time l a g . For north and south o r i e n t a t i o n s , 220 mm t h i c k w a l l s would be s u f f i c i e n t , but the b u i l d i n g codes in India s p e c i f y that a l l e x t e r n a l w a l l s must be 300 mm t h i c k to prevent the seepage of moisture dur i n g the r a i n y season and f o r s t r u c t u r a l reasons. The w a l l t h i c k e s s e s mentioned here do not i n c l u d e the e x t e r i o r and i n t e r i o r f i n i s h e s . The p e r i o d i c heat flow and'conductive. heat gain through w a l l s w i l l be f u r t h e r a f f e c t e d by e x t e r i o r f i n i s h e s and t h e i r c o l o u r . If the e x t e r n a l c o l o u r of the w a l l s i s white, that i s with an a b s o r p t i v i t y of l e s s than 0.4, the flow of heat w i l l decrease f u r t h e r but, only i f w a l l s are l e s s than 220 mm t h i c k ( G i v o n i , 1981). The i n f l u e n c e of e x t e r i o r c o l o u r i n reducing conductive heat flow through t h i c k e r w a l l s (above 220 mm) i s not c r i t i c a l . 1 58 SUMMARY AND CONCLUSIONS T h i s r e s e a r c h set out to i d e n t i f y , evaluate and recommend pa s s i v e design s t r a t e g i e s s u i t a b l e f o r housing design in hot and dry region of I n d i a . Passive design s t r a t e g i e s were i n v e s t i g a t e d because they allow e f f e c t i v e thermal c o n t r o l w i t h i n r e s i d e n c e s with the minimal use of modern mechanical c o o l i n g d e v i c e s . Passive design s t r a t e g i e s a d d i t i o n a l l y p r ovide the p o t e n t i a l to c r e a t e a r e s i d e n t i a l environment which i s v i s u a l l y and p s y c h o l o g i c a l l y more ap p e a l i n g than that a s s o c i a t e d with modern, m e c h a n i c a l l y - c o n t r o l l e d r e s i d e n c e s . A q u a l i t a t i v e a n a l y s i s of the thermal performance of v a r i o u s p a s s i v e design techniques used i n t r a d i t i o n a l d w e l l i n g s i n Part One demonstrates t h a t , in a d d i t i o n to p r o v i d i n g thermal comfort, p a s s i v e techniques responded e f f e c t i v e l y to the c u l t u r a l , economic and t e c h n o l o g i c a l c o n s t r a i n t s under which people designed and c o n s t r u c t e d t h e i r d w e l l i n g s . On the other hand, mechanical c o o l i n g d e v i c e s widely used in the contemporary d w e l l i n g s , although e f f e c t i v e i n p r o v i d i n g thermal comfort, are expensive to use, u n r e l i a b l e as a long term s o l u t i o n to the c o o l i n g problem and encourage d w e l l i n g designs which are i l l - s u i t e d to user needs. T h i s a n a l y s i s , in a d d i t i o n to s h a r i n g the knowledge and p r o v i d i n g a r a t i o n a l b a s i s f o r the use of p a s s i v e design techniques, enables a r c h i t e c t s to c r i t i c a l l y s e l e c t those techniques which are u s e f u l i n the contemporary c o n t e x t . In Part Two, a conceptual framework for i n c o r p o r a t i n g p a s s i v e techniques at v a r i o u s l e v e l s of design has been presented. V a r i o u s c l i m a t e - r e s p o n s i v e s t r a t e g i e s are s e l e c t e d at a 1 6 0 general l e v e l by c o n s i d e r i n g l o c a l c l i m a t e and comfort c i t e r i a and then t r a n s l a t e d i n t o the s p e c i f i c s of s i t e s e l e c t i o n , s i t e p l a n n i n g , form and f a b r i c d e s i g n . A general o b j e c t i v e of the s t r a t e g i e s at a l l l e v e l s i s to minimize the adverse e f f e c t s of c l i m a t e and maximize i t s b e n e f i t s . Table VI presents a l l these s t r a t e g i e s i n the order of t h e i r p r i o r i t y i n a p p l i c a t i o n . In hot and dry c l i m a t e s the need f o r reducing heat gain d u r i n g daytime and promoting heat l o s s at night o v e r r i d e s other comfort requirements and becomes a d e c i s i v e f a c t o r at v a r i o u s l e v e l s of d e s i g n . T h i s t h e s i s a l s o shows that i n c l u s i o n of p a s s i v e design techniques i n t o the wider context of housing design does not r e s t r i c t the a r c h i t e c t s from e v o l v i n g d i v e r s e design s o l u t i o n s . In f a c t , s t r a t e g i e s at each l e v e l give a r c h i t e c t s a c o n s i d e r a b l e scope f o r c r e a t i v i t y . As s i t e c o n d i t i o n s and programming requirements f o r each p r o j e c t are d i s t i n c t , each s t r a t e g y which addresses a p a r t i c u l a r thermal comfort problem w i l l respond d i f f e r e n t l y to the needs of each p r o j e c t , and can be t r a n s l a t e d i n t o d i v e r s e design s o l u t i o n s and a r c h i t e c t u r a l e x p r e s s i o n s . However, a designer should c l e a r l y d e f i n e the problem and be c o n s i s t e n t in f o l l o w i n g i t at each l e v e l of d e s i g n . The use of p a s s i v e techniques p r o v i d e s thermal comfort and v a r i o u s other b e n e f i t s to a l l types of d w e l l i n g s and these b e n e f i t s can be s u b s t a n t i a l when a p p l i e d i n mass s c a l e developments l i k e m u l t i f a m i l y housing. According to the cu r r e n t housing trends i n I n d i a , the great bulk of new d w e l l i n g u n i t s are m u l t i - f a m i l y s t r u c t u r e s c r e a t e d by 161 If s § 2 J US i f * h IS « y in ± -o I 9. z # I 2 V 111 >- 2 - f - ill 3 01 Till <L < " f t a * Hi 3 J " HI m m * * - a m i M i s * ! > <7) i i _ i <u0 > (U I—I J3 (0 E- V t- at •"2) V - le*-^ ^A\±Z>C)<iH<?'=> 1V3H TVN2l3±Nl •aavne 1 62 > 2 2 o ILJ o DQ -< I i f ! ? £ • * • • a is £ VJ 2-f § s § - x a w}» S i t fiS-* if 11 vi Eft. o 41 JFT H P ^ . 3 > • SI TE  PL AN NI NG  IB*.?*- 0 O, i i L • • • • t "T ul j 3 OL A x ft X • • \k St § 111 §* i l l J > IFC £ p t ? M • • SI TE  S EL EC TI ON  V . t * « 4 a £ Z ii. — • N^HVn I J . N 3 A •9Nn«*c iNviqvzi 1 6 3 government or p r i v a t e b u r eaucracies (Chauhan, 1986). T h i s c e n t r a l i z a t i o n of d w e l l i n g developments i s compatible with mass s c a l e a p p l i c a t i o n of p a s s i v e techniques and b r i n g s the b e n e f i t s of c l i m a t e responsive design to a l a r g e r number of people at a low per u n i t c o s t . Given the estimated d w e l l i n g u n i t s r e q u i r e d to meet the growing demand for housing in I n d i a , i t i s a b s o l u t e l y e s s e n t i a l that housing designs based on p a s s i v e techniques are implemented, widely used and accepted by the d w e l l i n g occupants. In order to implement the housing designs based on p a s s i v e techniques, i t i s imperative f o r the government p o l i c i e s and housing r e g u l a t i o n s to r e f l e c t t h e i r o b j e c t i v e s . The c l i m a t e responsiveness of d w e l l i n g s should, t h e r e f o r e , form an important b a s i s for housing r e g u l a t i o n s and government p o l i c i e s , e s p e c i a l l y in regions with extreme c l i m a t e s . F i n a l l y , p a s s i v e design techniques can be s u c c e s s f u l and b e n e f i c i a l only when they are widely used and accepted by d w e l l i n g occupants. In a r a p i d l y i n d u s t r i a l i z i n g country such as I n d i a , the use of mechanical c o o l i n g i n r e s i d e n c e s i s c o n s i d e r e d by many to be a modern n e c e s s i t y ensuring maximum comfort i n contemporary d w e l l i n g s . Besides changing a t t i t u d e s l i k e t h i s , i t w i l l be necessary to convince o p i n i o n l e a d e r s , i n p a r t i c u l a r contemporary a r c h i t e c t s , about the b e n e f i t s of p a s s i v e design technology. An emphasis on the r e s e a r c h and development of p a s s i v e techniques, and making t h i s knowledge widely a v a i l a b l e are the two extremely important i n i t i a l steps which can be instrumental in 1 64 encouraging use and acceptance of housing designs based p a s s i v e techniques. 1 65 REFERENCE MATTER BIBLIOGRAPHY: SOURCES CITED AND CONSULTED Adamson and E f t r i n g . "Influence of Window S i z e , P r o p e r t i e s and Shading on Annual Heat Consumption and Indoor Temperatures." In Johnsen, K j e l d ( e d i t o r ) , Energy Conservation i n the B u i l t Environment, Session 2: Methods to Improve B u i l d i n g Envelope. Copenhagen: Danish B u i l d i n g Research I n s t i t u t e , 1979, pp. 241- 254. Alexander, C h r i s t o p h e r . The Timeless Way of B u i l d i n g . New York: Oxford U n i v e r s i t y Press, 1979. Anderson, Standford. Planning f o r D i v e r s i t y and Choice: P o s s i b l e Futures ' and t h e i r R e l a t i o n s to the Man C o n t r o l l e d Environment. MIT p r e s s . 1968. A r a t a n i , N. " U t i l i z a t i o n of Thermal Capacity of the Ground Under the F l o o r f o r C o o l i n g the Dwelling i n Summer." In Johnsen, K j e l d ( e d i t o r ) , Energy Conservation i n the B u i l t Environment, Session 4: Design f o r Low Energy Consumption. Copenhagen: Danish B u i l d i n g Research I n s t i t u t e , 1979, pp. 209-218. Arnol d , George W. and Bach, Charles L. "Weather Cycle I d e n t i f i c a t i o n f o r E v a l u a t i o n in Climate Responsive Design." Passive C o o l i n g . AS/ISES, 1981, pp.397-401. Aughenbangh, Nolan B. "Underground Houses." In Golany, Gideon ( e d i t o r ) , Housing i n A r i d Lands: Design and Pl a n n i n g . London: The A r c h i t e c t u r a l Press, 1980, pp. 151-157. Baes, Steve. "C o o l i n g with Night Time A i r . " A l t e r n a t ive Sources of Energy (Jan/Feb 1980), pp.22-25. Bahadori, Mehdi N. "Natural C o o l i n g i n Hot A r i d Regions." In Sayigh, A.A.M. ( e d i t o r ) , S o l a r Energy A p p l i c a t i o n i n B u i l d i n g s . London: Academic Press, 1979. Bar, Avram. "Space C o o l i n g and Thermal C o n t r o l by Skyward R a d i a t i o n . " In Golany Gideon ( e d i t o r ) , A r i d Zone Settlement Planning: The I s r a e l i Experience. New York: Pergamon Press, 1979, pp. 164-196. Baxter, A.J. "Windows and Energy." In Johnsen, K j e l d ( e d i t o r ) , Energy Conservation i n the B u i l t Environment, Session 2: methods to Improve B u i l d i n g Envelope, pp. 269-280. 167 B e c h t e l , R.B., I t t e l s o n , W.H., and Wheeler, L. "Environmental Psychology and Housing Design i n A r i d Urban Areas." In Golany, Gideon ( e d i t o r ) , Urban Planning f o r A r i d Zones: American Experiences and D i r e c t i o n s . New York: John Wiley and Sons, 1978, pp.75-86. Bernatzky, A. "The C o n t r i b u t i o n of Trees and Green Spaces to a Town Climate." In B i t a n , A . ( e d i t o r ) , The Impact of Climate On Planning and B u i l d i n g . Lansanne, S w i t z e r l a n d : E l s e v i e r Sequoia, S.A., 1980, pp. 301- 310. Bhattacharya, B. Urban Development in I n d i a . I n d i a : Shree P u b l i s h i n g House, 1979. B i l l i n g t o n , N. "Comfort." B u i l d i n g S e r v i c e s (October 1978), pp. 37-38. Bowen, Arthu r . Passive C o o l i n g Handbook Addenda: F i f t h N a t i o n a l Passive Conference. Amherst, Mass: Lawrence Berkeley Laboratory, 1980. B r o l i n , Brent C. The F a i l u r e s of Modern A r c h i t e c t u r e . New York: Van Nostrand Reinhold, 1976. Burberry, P. and A l d r i d g e , L. "Conserving Energy in B u i l d i n g s - The Choices f o r Designers." A r c h i t e c t ' s J o u r n a l (Sept.1974), pp. 615-628. Burberry, P. B u i l d i n g f o r Energy C o n s e r v a t i o n . New York: John Wiley and Sons, 1978. Cain, A., Daraie and N.John. "Indigenous Development and Housing." In D a k h i l , U r a l and Tewfik ( e d i t o r s ) , Housing Problems i n Developing C o u n t r i e s : Proceedings of IAHS I n t e r n a t i o n a l Conference, Volume 1. New York: John Wiley and Sons, 1978, pp. 3-12. Cantacuzino, Sherban. C h a r l e s Correa- An Essay. Singapore: Mimar P u b l i c a t i o n , 1984. Center f o r Renewable Resources. Renewable Energy i n C i t i e s (Report). New York: Van Nostrand Reinhold Company Inc., 1984, pp. 162-178. Chandra, Prakash. "Simulation of Thermal Design of B u i l d i n g s . " In Gupta, Vinod ( e d i t o r ) , Energy and H a b i t a t . New D e l h i : Wiley Eastern L i m i t e d , 1984, pp.74-79. 1 68 Chandra, Subrato and Houston, M i c h a e l . "Wingwalls to Improve N a t u r a l V e n t i l a t i o n : F u l l S c a le R e s u l t s and Design S t r a t e g i e s . " In Hayes, John and Andrejko, Dennis A. ( E d i t o r s ) , Progress i n Passive Solar Energy Systems. ASES, 1983, pp.855-860. Chauhan, Akhtar. "Urban Housing: Issues in H i s t o r i c a l P e r s p e c t i v e . " J o u r n a l of Indian I n s t i t u t e of A r c h i t e c t s . ( A p r i l - J u n e 1986), Vol.51, pp.18-20. Cheetam, D.W. "An Assessement of the E f f e c t s of High Rise Housing on Urban Density with P a r t i c u l a r Reference to the Inf l u e n c e of C o n s t r u c t i o n Technology." In D a k h i l , U r a l and Tewfik ( e d i t o r s ) , Housing Problems i n Developing C o u n t r i e s : Proceedings of IAHS I n t e r n a t i o n a l Conference, Volume 1. New York: John Wiley and Sons, 1978, pp. 90-101. C l a r k e , J.A. Energy S i m u l a t i o n i n B u i l d i n g Design. B r i s t o l , U.S.A.: Adam H i l g e r L t d . , 1985. C l a r k , K. N. "Design C r i t e r i a f o r Desert Housing." In Clark and Paylor ( e d i t o r s ) , Desert Housing - Balancing Experience and Technology f o r Dwellings i n Hot A r i d Zones. A r i z o n a : O f f i c e of A r i d Land S t u d i e s , The U n i v e r s i t y of A r i z o n a , 1980, pp. 315-320. Cole, Ray. "Energy Conscious Design F i l e . " AIBC Forum (May/1979), pp. 11-18. . "Energy Conscious Design F i l e . ' (June/1979), pp. 9-16. . "Energy Conscious Design F i l e . ' (July/1979), pp. 9-14. . "Energy Conscious Design F i l e . ' (Sepember/1979), pp. 9-16. . "Energy Conscious Design F i l e . " AIBC Forum (January/1980), pp. 11-18. Cook, J e f f e r e y . "Landscaping f o r M i c r o c l i m a t i c Advantage i n A r i d Zone Housing." In Golany, Gideon ( e d i t o r ) , Housing i n A r i d Lands: Design and Planning. London: The A r c h i t e c t u r a l Press, 1980, pp. 225-233. . "Cooling as the Absence of Heat: S t r a t e g i e s for the Prevention of Thermal Gain." P a s s i v e C o o l i n g . AS/ISES, 1981, pp.612-621. Cowan, Henry J . Energy Conservation i n the Design of M u l t i s t o r e y B u i l d i n g s . Sydney: Pergamon Press, 1983. AIBC Forum AIBC Forum AIBC Forum 169 Crowther, R.L. "The Use of So l a r Energy i n Arid-Zone Houses." In Golany, Gideon ( e d i t o r ) , Urban Planning f o r A r i d Zones: American Experiences and D i r e c t i o n s . New York: John Wiley and Sons, 1978, pp. 154-160. Danby, M i l e s . " B u i l d i n g Design Golany Gideon ( e d i t o r ) I n t e r n a t i o n a l Lessons. in Hot Dry C l i m a t e s . " In Desert P lanning: New York: N i c h o l s P u b l i s h i n g Danz Co., 1982, pp. 113-122. E r n s t . Sun P r o t e c t i o n ; An I n t e r n a t i o n a l a r c h i t e c t u r a l Survey. 1967. New York: F r e d e r i c k A. Praegar P u b l i s h e r , Davis, Sam. The Form of Housing. New York: Van Nostrand Reinhold Company, 1977. Davis and Schudert. A l t e r n a t i v e N a t u r a l Energy Sources i n B u i l d i n g Design. New York: Van Nostrand Reinhold Company, 1974. Dickson, D.J. " V e n t i l a t i o n with Open Windows." In Johnson, K j e l d ( e d i t o r ) , Energy Conservation i n the B u i l t Environment, Session 2: Methods to Improve B u i l d i n g Envelope. Copenhagen: Danish B u i l d i n g Research I n s t i t u t e , 1979, pp. 141-152. D o x i a d i s , C.A. "Energy and Human Settlements." E k i s t i c s (November, 1968). pp.455-459. E l Bannany, S h e r i f Abdel Raouf. Energy-Conscious Design G u i d e l i n e s f o r Egyption Housing. Unpublished Ph.d T h e s i s , The C a t h o l i c U n i v e r s i t y of America, School of A r c h i t e c t u r e , Washington, D.C. 1984. Evans, M. "Chapter 9: Required Thermal Performance f o r Walls and Roofs." i n Housing, Climate and Comfort. New York: H a l s t e d Press/John Wiley & Sons Inc., 1980, pp. 88-100. Evenson, Norma. Chandigarh. Berkeley: U n i v e r s i t y of C a l i f o r n i a Press, 1966. F a l v i n , C h r i s t o p h e r . Energy and A r c h i t e c t u r e : The So l a r and Conservation P o t e n t i a l . World Watch Paper 40, November 1980. F a i r e y , V i e i r a and K e r e s t e c i o g l n . " A u x i l i a r y Latent C o o l i n g Loads i n p a s s i v e l y Cooled B u i l d i n g s - An Experimental Research Study." In F i r s t Annual Symposium: E f f i c i e n t U t i l i z a t i o n of Energy i n R e s i d e n t i a l and Commercial B u i l d i n g s . Texas: A & M U n i v e r s i t y , 1984, pp.22-28. 1 70 Fathy, Hassan. N a t u r a l Energy and Vernacular A r c h i t e c t u r e . Chicago: U n i v e r s i t y of Chicago Press, 1986. . A r c h i t e c t u r e f o r the Poor: An Experiment i n Rural Egypt. Chicago: U n i v e r s i t y of Chicago Press, 1973. . The Arab House. London: Longman Press, 1972. F r i e d , Kana. "Methods fo r Climate C o n t r o l in A r i d Zones." In Golany, Gideon ( e d i t o r ) , Housing i n A r i d Lands: Design and P l a n n i n g . London: The A r c h i t e c t u r a l Press, 1980, pp. 181-189. Fry and Drew. T r o p i c a l A r c h i t e c t u r e . New York: Reinhold P u b l i s h i n g C o r p o r a t i o n , 1982. Geddes, Robert. "Nature of the B u i l t Environment; R e l a t i o n s h i p of Landscape to B u i l d i n g . " P r o g r e s s i v e A r c h i t e c t u r e (June, 1974), pp. 72-81. Geiger, Rudolf. The Climate near the Ground. Massachusetts, Cambridge: Harvard U n i v e r s i t y Press, 1950. G i v o n i , B. Man Climate and A r c h i t e c t u r e (Second E d i t i o n ) . New York: Van Nostrand Reinhold Company, 1981 . . "Desert Housing and Energy C o n s e r v a t i o n . " In C l a r k and Paylor ( e d i t o r s ) , Desert Housing - Ba l a n c i n g Experience and Technology f o r Dwellings i n Hot A r i d Zones. A r i z o n a : O f f i c e of A r i d Land S t u d i e s , The U n i v e r s i t y of A r i z o n a , 1980, pp. 52- 64. . "Cooling of b u i l d i n g s by Passive Systems." Passive C o o l i n g . AS/ISES, 1981, pp.588-596. . "S o l a r Heating and Night R a d i a t i o n C o o l i n g by Roof R a d i a t i o n Trap." Energy and B u i l d i n g s , (Vol.1, 1977), pp. 141-145. . "Conservation and the Use of I n t e g r a t e d Passive Energy Systems i n a r c h i t e c t u r e . " Energy and B u i l d i n g s , (Vol.2,1981), pp. 228-243. Gokhale, R.G. "Appropriate Technology f o r Urban Housing in I n d i a . " In D a k h i l , U r a l and Tewfik ( e d i t o r s ) , Housing Problems i n Developing C o u n t r i e s : Proceedings of IAHS I n t e r n a t i o n a l Conference, Volume 1. New York: John Wiley and Sons, 1978, pp. 30-38. 171 Golneshan, A.A. and Yaghonbi, M.A. "Natural C o o l i n g of a R e s i d e n t i a l Room with V e n t i l a t i o n i n Hot A r i d Regions." In Fanger, P.O. ( e d i t o r ) , Clima 2000 Vol.4. Denmark: WS Kongres-WSMesse, 1985, pp.309- 313. Golany, Gideon. "Planning Urban S i t e s i n A r i d Zones: The Basi c C o n s i d e r a t i o n s . " In Golany, Gideon ( e d i t o r ) , Urban Planning f o r A r i d Zones: American Experiences and D i r e c t i o n s . New York: John Wiley and Sons, 1978, pp. 4-20. "Subterranean Settlements f o r A r i d Zones." in Golany, Gideon ( e d i t o r ) , Housing in A r i d Lands: Design and P l a n n i n g . London: The A r c h i t e c t u r a l P r ess, 1980, pp. 109-119. Greene, Guy S. "Landscape and C i t y s c a p e Design i n A r i d Regions." In Golany, Gideon ( e d i t o r ) . Urban Planning f o r A r i d Zones: American Experiences and D i r e c t i o n s . New York: John Wiley and Sons, 1978, pp. 199-203. Grover, S a t i s h . A r c h i t e c t u r e of In d i a (Hindu P e r i o d ) . I n d i a : Vikas P u b l i s h i n g Company L i m i t e d , 1980. Gupta, M.C. and Hariharan, D. "Solar Housing in I n d i a . " In Sayigh, A.A.M ( e d i t o r ) , S o l a r Energy A p p l i c a t i o n i n B u i l d i n g s . New York: Academic Press, 1979, pp. 377- 385. Gupta, Vinod. "Natural C o o l i n g Systems of J a i s a l m e r . " A r c h i t e c t u r a l Science Review, No.28.3 (Sept. 1985), pp. 58 - 64. "Case Study - Climate Conscious B u i l d i n g Design." In Gupta, Vinod ( e d i t o r ) , Energy and H a b i t a t . New D e l h i : Wiley Eastern L t d . , 1984, pp. 80-87. "Energy Conservation B u i l d i n g Design: Case Study of Research F a c i l i t y i n Hyderabad, I n d i a . " In Gupta, Vinod ( e d i t o r ) , Energy and H a b i t a t . New D e l h i : Wiley E a s t e r n L t d . , 1984, pp. 66-73. — . "Indigenous A r c h i t e c t u r e and N a t u r a l C o o l i n g . " In Gupta, Vinod ( e d i t o r ) , Energy and H a b i t a t . New D e l h i : Wiley Eastern L t d . , 1984, pp. 41-48. Personal Communication, Feburary, 13th, 1987. 1 72 Halahyja, M. "Outdoor Climate C o n d i t i o n s as A Fa c t o r I n f l u e n c i n g Energy Balancing i n B u i l d i n g s . " In Johnsen, K j e l d ( e d i t o r ) , Energy Conservation i n the B u i l t Environment, Session4: Design f o r Low Energy Consumption. Copenhagen: Danish B u i l d i n g Research I n s t i t u t e , 1979, pp. 253-262. H a l l , E.T. The Hidden Dimension. New York: Doubleday and Co., 1966. Hardenberg, Von J.G. "C o n s i d e r a t i o n s of Houses Adopted to L o c a l Climate - A Case Study of I r a n i a n Houses in Yazd and Esfahan." In B i t a n , A ( e d i t o r ) , The Impact of Climate on Planning and B u i l d i n g . Lansanne, S w i t z e r l a n d : E l s e v i e r Sequoia, S.A., 1980, pp. 155- 160. Harkness, E.L. and Mehta, M.L. S o l a r R a d i a t i o n C o n t r o l i n B u i l d i n g s . London: A p p l i e d Science P u b l i s h e r s L t d . , 1978. Henshaw, P. "Envelope Homes, A Climate Study." A l t e r n a t i v e Sources of Energy (July/August, 1980), pp. 18-21. Hoffman, M.E. "Design of So l a r R a d i a t i o n and Thermal C a p a c i t y I n f l u e n c e on the Indoor Climate of B u i l d i n g s . " In B i t a n , A ( e d i t o r ) , The Impact of Climate on Planning and B u i l d i n g . Lansanne, S w i t z e r l a n d : E l s e v i e r Sequoia, S.A., 1980, pp. 221- 230. Holm, D i e t e r . Energy Conservation i n Hot Cl i m a t e s . London: The A r c h i t e c t u r a l Press, 1983. Jacobson, L. "Improvement of Window I n s u l a t i o n by Venetian ans R o l l e r B l i n d s . " In Johnsen, K j e l d ( e d i t o r ) , Energy Conservation in the B u i l t Environment, Session 2: Methods to Improve B u i l d i n g Envelope.. Copenhagen: Danish B u i l d i n g Research I n s t i t u t e , 1979, pp. 223-226. Johnson, F r i t z . ' Current Issues in Urban Housing - A Passive S o l a r Townhouse Development. Unpublished Master's T h e s i s , U n i v e r s i t y of Washington, School of A r c h i t e c t u r e , S e a t t l e , 1983. Kamon, E l i e z e r . " P h y s i o l o g i c a l and B e h a v i o r a l Responses to the S t r e s s of Desert C l i m a t e . " In Golany, Gideon ( e d i t o r ) , Urban Planning f o r A r i d Zones: American Experiences and D i r e c t i o n s . New York: John Wiley and Sons, 1978, pp. 41-60. 1 73 K e s s l e r , Jacob. "Town Design i n the Negev Region of I s r a e l . " In Golany Gideon ( e d i t o r ) , A r i d Zone Settlement P l a n n i n g : The I s r a e l i Experience. New York: Pergamon Press, 1979, pp. 110-127. King, A.D., The Bunglow. London: Routledge and Kegan Paul, 1984. Knowles, R.L. Energy and Form: An E c o l o g i c a l Approach to Urban Growth. Cambridge, Massachusetts: The MIT Press, 1974. Koenigsberger, O.H. Manual of T r o p i c a l Housing and B u i l d i n g , Part I: Climate Design. London: Longman Group L i m i t e d , 1973. Koenigsberger, O.H. and Lynn, Robert. Roofs i n Warm Humid T r o p i c s . London: Lund Humphries, 1965. Koenigsberger, O.H. " A r c h i t e c t u r a l Science f o r p r a c t i t i o n e r s . " A r c h i t e c t u r a l s c i e n c e Review (March-June, 19787^ Vol.21, pp. 6-7. Konya, A l l a n . Design Primer for Hot C l i m a t e s . London: The A r c h i t e c t u r a l Press, 1980. K r a l l , L . , L i t t l e r , J . G . F . and Thomas, R.B. Ambient Energy Design (House 1). Cambridge: P r i v a t e l y P u b l i s h e d , 1 979. K r e i d e r , Jan F. and K r e i t h , F. S o l a r Energy Handbook. New York: McGraw-Hill Book Company, 1981. Kuhn, M i c h a e l . "An A r c h i t e c t ' s Experience at the Dead Sea." In Golany Gideon ( e d i t o r ) , A r i d Zone Settlement P l a n n i n g : The I s r a e l i Experience. New York: Pergamon Press, 1979, pp. 87-109. Laquerbe, M., Amoros, D. and C a s t e l J . "Thermal Measurement fo r B u i l d i n g M a t e r i a l s . " In D a k h i l , U r a l and Tewfik ( e d i t o r s ) , Housing Problems i n Developing C o u n t r i e s : Proceedings of IAHS I n t e r n a t i o n a l Conference, Volume 1. New York: John Wiley and Sons, 1978, pp. 353-361. Lentz, C l a r k . A Pattern Language f o r an Energy responsive A r c h i t e c t u r e . Unpublished Master's T h e s i s , V i r g i n i a P o l y t e c h n i c I n s t i t u t e and State U n i v e r s i t y , school of A r c h i t e c t u r e , 1981. Leu, Max Hans. Energy Conservation in O f f i c e B u i l d i n g s . Unpublished Master's T h e s i s , U n i v e r s i t y of B r i t i s h Columbia, School of A r c h i t e c t u r e , Vancouver, 1980. 174 L i t t e r , John and Thomas, R a n d a l l . Design with Energy: The Conservation and Use of Energy i n B u i l d i n g s . London (England): Cambridge U n i v e r s i t y Press, 1984. Lynch, Kevin. S i t e P l a nning. London, (England): The M.I.T. Press" 1971 (Second E d i t i o n ) . Manchanda, S u n i l . "Future S t r a t e g i e s for Urban Housinge." J o u r n a l of Indian I n s t i t u t e of A r c h i t e c t s . ( A p r i l - June 1986), Vol.51, pp.16-18. Mani A. Handbook of Solar R a d i a t i o n Data for I n d i a . New D e l h i : A l l i e d P u b l i s h e r s P r i v a t e L t d . , 1980. Mani, A. and Rangarajan, S. S o l a r R a d i a t i o n Over I n d i a . New D e l h i : A l l i e d P u b l i s h e r s P r i v a t e L t d . , 1982. Markus and M o r r i s . B u i l d i n g s Climate and Energy. London: Pitman P u b l i s h i n g L t d . , 1980. Markus, T.A. "The Window as an Element in the B u i l d i n g envelope, Techniques f o r o p t i m i z a t i o n . " In Johnsen, K j e l d ( e d i t o r ) , Energy Conservation i n the B u i l t Environment, Session 2: Methods to Improve B u i l d i n g Envelope. Copenhagen: Danish B u i l d i n g Research I n s t i t u t e , 1979, pp.255-268. Ma r t i n , Ted. "Community Energy C o n s e r v a t i o n : Lessons from Tumbler Ridge." H a b i t a t . Vol.27, No.3, 1984, pp. 20-28. Melaragno, M.G. Wind in A r c h i t e c t u r a l and Environmental Design. New York: Van Nostrand Reinhold Company, 1982. Metz, Don. "Underground Homes: E a r t h S h e l t e r s . " In Ralph, Gary and Przybylowski, G. ( E d i t o r s ) , B u i l d i n g Towards 2001 Proceedings. O n t a r i o : M i n i s t r y of M u n i c i p a l A f f a i r s and Housing, Nov.1-4, 1981. pp. 144-149. Milbank, N e i l 0. "Energy Savings and Peak Power r e d u c t i o n Through the U t i l i z a t i o n of n a t u r a l V e n t i l a t i o n . " Energy and B u i l d i n g s . (Vol.1, 1977), pp.85-88. M i l l e r , J.D. "Landscape A r c h i t e c t u r e f o r A r i d Zones." In C l a r k and Paylor ( e d i t o r s ) , Desert Housing - Balancing Experience and Technology f o r Dwellings in Hot A r i d Zones. A r i z o n a : O f f i c e of A r i d Land S t u d i e s , The U n i v e r s i t y of A r i z o n a , 1980, pp. 17- 35. 175 M i l n e , Murry and G i v o n i , B. " A r c h i t e c t u r a l Design Based on Climate." In Watson, Donald ( e d i t o r ) , . Energy Conservation Through B u i l d i n g Design. New York: McGraw H i l l Book Company, 1979. Monaghan, M.M. L i m i t e d . C l i m a t i c Information f o r Energy Conscious Planning (Report). Toronto, O n t a r i o : M i n i s t r y of Energy, October, 1981. Moreland, F.L. "Earth S h e l t e r e d Housing." In Cl a r k and Paylor ( e d i t o r s ) , Desert Housing - Balancing Experience and Technology f o r Dwellings i n Hot A r i d Zones. A r i z o n a : O f f i c e of A r i d Land S t u d i e s , The U n i v e r s i t y of A r i z o n a , 1980, pp. 257-265. Moughtin, J.C. "Settlements and Housing i n an A r i d Zone Developing Country: Case Study i n Hansaland, Northern N i g e r i a . " In Golany Gideon ( e d i t o r ) , Desert Planning: I n t e r n a t i o n a l Lessons. New York: N i c h o l s P u b l i s h i n g Co., 1982, pp. 145-157. Murphy, M.E. "The Inf l u e n c e of the Thermal Cap a c i t y of a B u i l d i n g on i t s Energy consumption." In Johnsen, K j e l d ( e d i t o r ) , Energy Conservation i n the B u i l t Environment, Session 2: Methods to Improve B u i l d i n g Envelope. Copenhagen: Danish B u i l d i n g Research I n s t i t u t e , 1979, pp. 17-32. Northeastern I l l i n o i s Planning Commisson. G u i d e l i n e s f o r Energy E f f i c i e n t Community Development. Unpublished Report, Chicago, I l l i n o i s , 1981. N o v e l l , Bruce. "A Simple Design Method f o r Shading Devices and Passive C o o l i n g S t r a t e g i e s Based on Monthly Average Temperatues." Passive C o o l i n g . AS/ISES, 1981, pp.392- 396. Ngoka, N.I. "Design f o r Energy Conservation i n B u i l d i n g s . " In Johnsen, K j e l d ( e d i t o r ) , Energy Conservation i n the B u i l t Environment, Session 4: Design f o r Low Energy Consumption. Copenhagen: Danish B u i l d i n g Research I n s t i t u t e , 1979, pp. 323-338. Olgyay and Olgyay. S o l a r C o n t r o l and Shading Devices. P r i n c e t o n , New J e r s e y : P r i n c e t o n U n i v e r s i t y Press, 1 957. Olgyay, V i c t o r . Design With C l i m a t e . New J e r s e y : P r i n c e t o n U n i v e r s i t y Press, 1963. Owens, S.E. "Energy and Settlement P a t t e r n s . " B u i l t environment (May/June, 1979), pp. 282-286. P a r i k h , K i r i t . Energy: Second India S t u d i e s . I n d i a : Macmillan Company, 1976. 1 76 Rapoport, Amos. House Form and C u l t u r e . New J e r s e y : P r e n t i c e - H a l l , Inc., 1969. Raychudhuri, B.C., A l i , S. and Garg, D.P. "Indoor Climate of R e s i d e n t i a l B u i l d i n g s i n Hot A r i d R e g i o n s - E f f e c t of O r i e n t a t i o n . " B u i l d i n g S c i e n c e. Vol.1, 1965. Robinette, G.O. Energy e f f i c i e n t s i t e Design. New York: Van Nostrand Reinhold Company, 1983. Rowig, F. and O ' S u l l i v a n , P. " B u i l d i n g s and the Energy Future." RIBA J o u r n a l . (October, 1979), pp.441- 443 . Rudofsky, Bernard. A r c h i t e c t u r e Without A r c h i t e c t s : A Short I n t r o d u c t i o n to Non-Pedigreed A r c h i t e c t u r e . Garden C i t y , N.Y.: Doubleday, 1964. Rudoy, W. and Dougal, R.S. " E f f e c t s of the Thermal Mass on Heating and C o o l i n g i n Residences." ASHRAE T r a n s a c t i o n s , (Ph-79-11, No.3,), Vol.85, Part I, pp. 903-916. S a i n i , B.S. B u i l d i n g in Hot Dry Cl i m a t e s . New York: John Wiley and Sons, 1980. . "Housing in the Hot A r i d T r o p i c s . " A r c h i t e c t u r a l Science Review. (March, 1982), Vol.5, pp.3-12. Saleh, Mohammed Abdullah Eben. The Development of Energy- E f f i c i e n t B u i l d i n g Systems and Techniques f o r Housing the Masses in Hot Dry Cl i m a t e s , With S p e c i a l Emphasis on Saudi A r a b i a . Unpublished Ph.d T h e s i s , U n i v e r s i t y of Michigan, School of A r c h i t e c t u r e , Ann Arbor, 1980. S a r i n , Madhu. Urban Planning i n the T h i r d World. London: Mansell P u b l i s h i n g L t d . , 1982. Sathaye, Jayant and Meyer, Stephen. "Energy Use i n C i t i e s of The Developing C o u n t r i e s . " Annual Review of Energy. Palo A l t o , C a l i f o r n i a , USA: Annual Reviews Inc., Vol.10, 1985, pp. 109-134. Sayigh, A.A.M. "Passive C o o l i n g of B u i l d i n g s . " In Sayigh, A.A.M.(Editor), S o l a r Energy a p p l i c a t i o n i n B u i l d i n q s . New York: Academic Press, 1979, pp. 147- 1 66. Schoenauer, Norbert. 6,000 Years of Housing, Volume2, The O r i e n t a l Urban House. New York: Garland STMP Press, 1981. 177 Sengupta, A.N. "High Density Housing and Q u a l i t y of L i f e . " J o u r n a l of Indian I n s t i t u t e of A r c h i t e c t s . ( A p r i l - June 1986). Vol.51, pp.25-28. Shaviv, E. "A Method fo r the Design of F i x e d E x t e r n a l Sunshades." B u i l d i n g I n t e r n a t i o n a l . (Sept., 1975), pp. 121-150. Sobin, H.J. "Window Design f o r Passive V e n t i l a t i v e C o o l i n g : An Experimental Model-Scale-Study." Passive C o o l i n g , 1981, AS/ISES, pp.191-195. Sodha, M.S. and Bansal, N.K. "Methods fo r the N a t u r a l C o o l i n g of B u i l d i n g s . " In Gupta, Vinod ( e d i t o r ) , Energy and H a b i t a t . New D e l h i : Wiley E a s t e r n L i m i t e d , 1984, pp. 49-56. Stead, Peter. "Lessons in T r a d i t i o n a l and Vernacular A r c h i t e c t u r e in A r i d Zones." i n Golany, Gideon ( e d i t o r ) , Housing in A r i d Lands: Design and P l a n n i n g . London: The A r c h i t e c t u r a l Press, 1980, pp. 33-44. S t e i n , R ichard G. A r c h i t e c t u r e and Energy. New York: Anchor Press, 1978. S t r a a t e n , J.F.Van. Thermal Performance of B u i l d i n g s . New York: E l s e v i e r P u b l i s h i n g Company, 1967. Uppal, K.R., Khawza, Z i a . "Solar Energy and A i r - C o n d i t i o n i n g in Low Cost Housing i n Developing C o u n t r i e s . " In D a k h i l , U r a l and Tewfik ( e d i t o r s ) , Housing Problems i n Developing C o u n t r i e s : Proceedings of IAHS I n t e r n a t i o n a l Conference, Volume 1. New York: John Wiley and Sons, 1978, pp. 270-278. Wallace, Robert Alan. The E v o l u t i o n of Modern Courtyard Housing. Unpublished Master's T h e s i s , U n i v e r s i t y of Washington, School of A r c h i t e c t u r e , S e a t t l e , 1983. Watson, Donald. Energy Conservation Through B u i l d i n g Design. New York: Mc Graw H i l l Book Company, 1979. " B i o c l i m a t i c A n a l y s i s and Design Methods". In P a s s i v e C o o l i n g . AS/ISES, 1981, pp.597-611 Watson and l a b s . C l i m a t i c Design: Energy e f f i c i e n t B u i l d i n g P r i n c i p l e s and P r a c t i c e s . New York: McGraw-Hill Book Company, 1983. 178

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