International Construction Specialty Conference of the Canadian Society for Civil Engineering (ICSC) (5th : 2015)

3D finite element modeling of recycled glass cullets in asphalt shingles Asadi, Somayeh; Hassan, Marwa; Beheshti, Ali Jun 30, 2015

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5th International/11th Construction Specialty Conference 5e International/11e Conférence spécialisée sur la construction   Vancouver, British Columbia June 8 to June 10, 2015 / 8 juin au 10 juin 2015   006-1 3D FINITE ELEMENT MODELING OF RECYCLED GLASS CULLETS IN ASPHALT SHINGLES Somayeh Asadi1, Marwa Hassan2 and Ali Beheshti3 1Department of Architectural Engineering, Pennsylvania State University, University Park, PA, USA  2Department of Construction Management, Louisiana State University, Baton Rouge, LA, USA 3Department of Mechanical Engineering, Texas A&M University, College Station, TX, USA Abstract: Recycled glass cullets in asphalt shingles may be utilized as a cool roof strategy to reduce the harmful effects of Urban Heat Island (UHI).  A Three-Dimensional (3D) transient Finite Element (FE) model was developed and validated to quantify energy savings provided by the proposed recycling process under various climatic conditions.  Simulations were carried out for three cities located in three climate regions in the United States representing different climatic conditions. The three cities representing each region were Kansas City (Missouri) for Zone 3, Charlotte (North Carolina) for Zone 4, and Miami (Florida) for Zone 5.  Results for each of the climatic zones were quantified.  Results showed that the annual energy savings ranged from $35.37 in cold climatic regions to $ 92.58 in hot climates.   1 INTRODUCTION Building sector in most countries represent about one third of the total energy consumption. It is projected that the building’s energy demand will be increased 110–150% by 2050 and 160–220% until 2095 from its 2005 level. Several factors including design and building characteristics, occupants, and people who work and live in buildings can significantly contribute to the success of energy efficiency measures. HVAC systems account for the largest amount of energy consumption in both commercial and residential buildings. As a consequence, the thermal barrier (or building envelope) that controls the heat flow of building is responsible for up to 40% of residential energy use and 55% of commercial energy use. In addition, cooling load in residential building shows an increasing trend worldwide and is one of the main concerns not only for countries that are characterized by hot climatic conditions but also for cities suffering from the heat island effect. The lower albedo of urban surfaces and the replacement of vegetation by building structures are considered as contributing factors to the heat island effect. Due to this effect, the ambient temperature in urban areas is usually several degrees higher (e.g. 1°–6°C) than that of their surrounding suburban and rural areas. Increased ambient temperatures result in thermal discomfort and increase cooling energy consumption, energy demand, and energy prices (Hassid 2000; Santamouris 2007). In recent years several experimental studies have been conducted to investigate the energy saving effects of urban heat island mitigation measures such as high albedo coatings and urban greening (Akbari 2005; Akbari 2001; Sailor 2007; Taha 1988). In parallel, important simulation studies have been carried out to identify the heat island mitigation potential of cool roofs (M. Jacobson 2012; S. Menon 2010; Savio 2006).These studies found that the precise energy benefits depend on the local climate and more significantly on the specific building characteristics.  006-2 Intensive research has been carried out on the heat island effect and cool roofs, the impact and the significance, as well as its qualitative and quantitative characteristics. Recent studies found that there is a relationship between building energy consumption and heat island effect (Hassan 2013; Hassid 2000; Yukihiro 2006). Noteworthy among these publications are the works of Akbari et al. (Akbari 2001) who found that changing the roof albedo of a residence in Sacramento, California from 0.18 to 0.73 results in energy savings of approximately 2.2 kWh/day. It was also found that increasing the urban albedo by about 20% reduces cooling load between 2.9% and 21% for Toronto and 62% for Sacramento (Akbari 1992; Taha 1994) which indicates that energy benefits differ largely as a function of the climatic conditions and the characteristics of the building. In another study conducted by Synnefa et al., several types of cool materials have been identified and tested to assess their performance in reducing heat island effect in Athens, Greece. They studied the optical and thermal properties of the selected materials and results revealed that these materials can be classified as “cool” with the ability to maintain lower surface temperatures. They defined and studied two scenarios of modified albedo including a moderate and an extreme increase in albedo scenario. The results indicated that large-scale increases in albedo could reduce ambient air temperatures by 2°C (Synnefa 2008). Within this context, Akbari and Konopacki (Akbari 2004) carried out a field study to predict the energy-saving potential of several UHI mitigation measures in Toronto. Their results indicated that the level of savings in energy varies depending on the mitigation measures and building types. However, that study did not consider the temperature distribution in the urban area.  This study investigates the application of recycling of broken and waste glass cullet in the production of asphalt shingles in order to reduce energy consumption in residential buildings and to mitigate heat island effects by increasing the solar reflectance index (SRI) of the roof asphalt shingles. To achieve this objective, laboratory characterization of glass cullet was conducted and asphalt shingles prepared with and without glass cullet were tested in the laboratory. In addition, Three-Dimensional (3D) transient Finite Element (FE) model was developed and validated to quantify energy savings provided by the proposed recycling process under various climatic conditions.  2 EXPERIMENTAL PROGRAM Conventional and recycled-glass modified asphalt roofing shingles were prepared in the laboratory by varying the amount of glass cullet and conventional materials used in asphalt roof shingles, and acceptability was based upon the standard specifications described in ASTM D 3462.  A full description of the laboratory experimental study has been presented elsewhere (Kiletico 2014).  Three different colors of recycled glass cullet including green and two sources of clear glass were collected from Construction and Demolition (C&D) processing plant to prepare the asphalt shingles.  Since the size of the collected glass cullet was large, a high performance mixer was used to reduce particle sizes.  The ground glass cullet was then used in lieu of conventional mineral aggregates as surface granules, filler material, and backdust.   The preparation of asphalt shingles in the laboratory consisted of three steps including preparation of the formwork, preparation of the asphalt blends, and aggregate preparation. The dimensions of the prepared asphalt shingles were 76mm x 76mm x 3mm. In the first step, the metal forms containing a fiberglass mat substrate were prepared. In the next step, asphalt binder was poured in the prepared forms. A white pigment powder was used in the fabrication of the asphalt shingles. The powder consisted of 98% pure titanium dioxide (TiO2) and was added at 8% by weight of the top surface granules. To add the TiO2 pigment powder to the surface granules, two grams of powder were mixed with 23 grams of surface granules, saturated with water, and then oven-dried. The filler material was then homogeneously mixed with liquefied asphalt binder for each sample, which was heated to 204°C. After mixing the filler material, 36 grams of asphalt coating mixture was reheated to become liquefied at 230°C. The asphalt coating mixture was then poured in the metal formwork of each shingle and then placed into the oven at 204°C for impregnation of the fiberglass for 1 hour. Then, the samples were removed from the oven and firm pressure was applied on the top surface granules in order to achieve 100% surface coverage.  A forced heat gun was used to separate the shingles from working surface.  Finally, the backdust particles were applied to the back surface while keeping the underside heated. The new shingles are patented under Provisional Patent 61/952515 “Method for the Manufacturing of Energy Efficient Shingles using TiO2 006-3 Coated Recycled Glass Cullets.”  The color appearance of all the prepared asphalt shingles is shown in Figure 1.   Figure 1. Asphalt shingle with/without  glass cullet 2.1 Solar Reflectance Index (SRI) SRI incorporates both solar reflectance and emittance into a single value and is a measure of the constructed surface’s ability to stay cool in the sun by reflecting solar radiation and emitting thermal radiation. It is defined such that a standard black surface (initial solar reflectance 0.05, initial thermal emittance 0.90) has an initial SRI of 0, and a standard white surface (initial solar reflectance 0.80, initial thermal emittance 0.90) has an initial SRI of 100.  Materials with the highest SRI values are the coolest choices for roofing. To calculate the SRI of the prepared asphalt shingles with and without glass cullet, their solar reflectance and thermal emittance were measured in the laboratory. The SRI of the asphalt shingle with and without glass cullet was calculated according to ASTM E 1980. The following formulas were used to calculate the SRI:   [1] SRI=123.97-141.35X+9.655X 2   [2] X= ((α-0.02ϵ1)(8.797+hc))/((9.5205ϵ+hc)) Where α  is the solar absorptance and ε represent for the thermal emissivity of the prepared asphalt shingle samples. The calculation was conducted for three convective coefficients (hc) that correspond to low, medium, and high wind conditions (5, 12, and 30 W·m–2·K–1, respectively). Table 1 shows the SRI of some of the available asphalt shingles in the market (EETD 2014).  006-4 Table 1. Solar Reflectance Index of Asphalt Shingles Type of the asphalt shingle  SRI Type of the asphalt shingle  SRI White 21 Black  1 Gray   4 Weathered Wood 4 Green 18 Dark Brown 4 Antique Silver 19 Beachwood Sand   19 Table 2 shows the description of the shingle specimens and their SRI based on laboratory measurements.  As shown in this table, the control samples had the lowest SRI (i.e., 0), which was expected.  On the other hand, the sample G1, which contains clear glass and TiO2 pigment, had the highest SRI (i.e., 30). Table 2. SRI of the prepared samples ID Material Composition SRI Top Surface Filler X1 Control 1: Ceramic Coated Granules Limestone 0 X2 Control 2: Ceramic Coated Granules Clear Glass 1 0 A Green Glass Limestone 3 B Clear Glass 1 Limestone 5 C Green Glass Green Glass 3 D Clear Glass 1 Clear Glass 1 5 C1 Green Glass & Pigments Green Glass 28 D1 Clear Glass 1 & Pigments Clear Glass 1 27 G1 Clear Glass 2 & Pigments Clear Glass 2 30 3 CLIMATE REGIONS IN THE UNITED STATES  In order to estimate the effect of the application of glass cullet asphalt shingle on the residential building energy load, simulations were carried out for three cities located in three climatic regions including Zones 3, 4, and 5 in the United States. US Energy Information Administration (EIA) categorized the climate regions in the United states into 5 main categories based on the last 30-year average heating degree-days (HDD) and cooling degree days (CDD) (EIA 2011; NOAA 2012). A HDD is a measure of how cold a location was over a period of time, relative to a base temperature of 65 °F (18.3 °C). On the other hand, a CDD is a measure of how hot a location was over a period of time, relative to the same base temperature of 65 °F (18.3 °C). Zone 3 is defined as the region with less than 2000 CDD and less than 4000-5499 HDD; Zone 4 is defined as the region with less than 2000 CDD and less than 4000 HDD; Zone 5 is defined as the region with 2000 CDD or more and less than 4000 HDD. Figure 2 shows the 3 main studied climate zones in the United States. Table 3 also provides the latitude and the longitude of the selected cities for this study. 006-5  Figure 2. Climate Zones in the US adapted from (EIA 2011) and (NOAA 2012) Table 3. The latitude and longitude of the selected cities for the simulations City, State Latitude (°) Longitude (°) Cooling Degree Days (ºC) Miami, FL 25.82 80.28 2645 Charlotte, NC 35.22 80.93 1105 Kansas City, MO 39.32 94.72 1110 4 FINITE ELEMENT MODEL  ABAQUS 6.13 software was used in this study to develop a three dimensional transient finite (FE) element model. Two FE models were developed to simulate the heat transfer mechanisms and evaluate energy consumption in the house with conventional asphalt shingle and house with glass cullet asphalt shingle in different climate regions in the United States. The developed FE model considered all the heat transfer mechanisms that may occur within the space. It is worth mentioning that many factors affect the calculated temperature distributions and the heat flux in the roof. The inputs to the FE model include the emissivity of asphalt shingle with and without glass cullet, emissivity of insulation, attic flow rate, longitude, latitude, and time zone of the locations. Although the physical model was symmetric, the amount of solar radiation differed from one side of the roof to the other depending on the surface orientation and inclination. Thus, in order to conduct an accurate analysis, the entire configuration of the roof was simulated in the FE model. It is worth mentioning that in order to attain reliable and accurate results; a mesh convergence technique was conducted using different mesh sizes. Final mesh size was selected after considering both computational efficiency and accuracy. To model the conduction heat transfer mechanism in the roof and the ceiling, approximately 49,000 DC3D8 elements were used. Featuring a hexahedron shape with eight nodes, these linear heat transfer elements were used for all the materials except the air. To model the advection, that is, bulk motion of the air in the attic, the convection/ diffusion option in ABAQUS was utilized by means of eight-node DCC3D8 elements with forced convection/diffusion capabilities. The total number of aforementioned elements was approximately 73,000. In addition, forced convection inside the roof was simulated by means of the mass heat transfer option in ABAQUS. A full description of the model has been presented elsewhere (Asadi 2012). In addition, hourly climatic data, including ambient air temperature, solar radiation, wind speed, wind Zone 5: Miami Zone 4: Charlotte Zone 3: Kansas City 006-6 direction, and relative humidity were used in the simulation. The metrological data was obtained from the Typical Meteorological Year 2 (TMY2)(NREL 2014). Figure 3 shows the finite element mesh of the model.     Figure 3. Finite Element Mesh Figure 4 shows the operation of the conventional and reflective roofs. During daylight hours, a roof is constantly subjected to solar energy striking its surface. A reflective roof with high SRI would have a lower surface temperature as compared to a conventional roof. In the case of a reflective roof, a lower surface temperature translates into less heat gain into the attic space or living space below the roof, which result in a cooler living space and lower cooling/heating energy consumption. The building used in the simulation is a single story residential building with a tilted roof with area of 148.6 m2.  The attic had two pitched roof sections, two vertical gable-end sections, and one horizontal ceiling frame. The thermostat set point temperature for cooling and heating was set to 26 and 21°C, respectively.              4.a. Conventional roof           4.b. Reflective roof  Figure 4. Operation of conventional and reflective roofs   XYZ 006-7 5 RESULTS AND DISCUSSIONS  Model validation was necessary to demonstrate the precision and the viability of the FE model.  Therefore, the developed models were validated based on experimental data collected in Zackary, LA. To validate the FE model, a site-located weather station was placed on the roof to measure the actual weather parameters and collected data was used in the model. Figure 5 compares the results based on FE model and experimental data for a typical day in the summer.  The results showed that there is a good agreement between experimental data and FE model and error was less than 5%. The obtained results demonstrate that the finite element model could be applied with success even for more detailed situations and with better precision on the results.  Time (hour)1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Temperature (ºC)0102030405060FMExperiment    Figure 5. Model validation In order to investigate the performance of the glass cullet asphalt shingle to reduce building energy consumption, the heat flux were calculated for the control house and the house with asphalt shingle containing glass cullet in different climate regions in the United States. It should be noted that the values mentioned in this part of the study depend on the building characteristics. As expected, increasing the roof SRI resulted in reduced summer cooling loads particularly in hot climate regions. Figure 6 shows the required cooling and heating loads in the house with and without asphalt shingle containing glass cullet. For the building chosen and the climates examined in this study, it was found that the potential savings are greater in hot climate regions such as Miami, FL. It was found that the application of asphalt shingle containing glass cullet in the roof can reduce energy consumption from 7.8 kwh/m2 to 6.9 kwh/m2 in June in Miami-FL and save approximately $16 in this month.  Results showed that increasing the SRI of a roof is clearly more advantageous in hot climate regions where cooling load dominates most of the year. This study provides further evidence that roof asphalt shingles containing glass cullet are effective strategies for urban heat island mitigation. The increased SRI of these roofs effectively reduces their surface temperature and decreases sensible heat flux into the urban atmospheric system. 006-8 Miami, Florida Charlotte, NC  Kansas City, MO Fig. 6. Required heating and cooling load in 3 climate regions in the US 6 CONCLUSIONS   The present study evaluated the application of waste glass cullet in the production of asphalt shingles in order to reduce energy consumption in residential buildings and to mitigate heat island effects by increasing the SRI of the roof asphalt shingles.  Laboratory tests were conducted to determine the solar reflectance and thermal emittance of the prepared asphalt shingle samples with and without glass cullet.  Based on the laboratory results, it is concluded that glass cullet can be successfully blended with conventional materials to produce a sustainable asphalt shingle that has a solar reflectance of that is significantly greater than conventional asphalt shingles.  Results show that a typical black ceramic coated asphalt shingle has SRI of 0. In order to achieve cool roof attributes, the addition of a white pigment mixed together with the top surface granules increased the SRI to 30 for clear glass.   A FE model was developed to calculate and quantify the energy consumption reduction in the house with and without glass cullet.  The developed model was successfully validated with measured experimental data collected in Zachary, LA.  Annual models were run for three cities in five climate regions in the United States.  For the building studied and the climates considered in the simulation, it was found that the potential savings are greater in hot climate regions such as Miami, FL. Results indicated that the application of asphalt shingle containing glass cullet in the roof can reduce energy consumption from 7.8 kwh/m2 to 6.9 kwh/m2 in June in Miami-FL and save approximately $16. Results showed that increasing the SRI of a roof is characteristically more advantageous in hot climate regions where cooling load dominates most of the year. This study provides evidence that roofs covered with asphalt shingles containing glass cullet are effective strategies for urban heat island mitigation.  The increased SRI of these roofs effectively reduces their surface temperature and decreases sensible flux into the urban atmospheric system. 006-9 References Akbari, H., and H. Taha (1992). "The impact of trees and white surfaces on residential heating and cooling energy use in four Canadian cities." Energy, 17(2), 141-149. Akbari, H., Konopacki, S (2004). "Energy effects of heat-island reduction strategies in Toronto, Canada." Energy, 29, 191-210. Akbari, H., Konopacki, S. (2005). "Calculating energy-saving potentials of heat-island reduction strategies." Energy Policy, 33, 721-756. Akbari, H., Pomerantz, M, Taha, H (2001). "Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas." Solar Energy, 70(3), 295-310. Asadi, S., Hassan, M., Beheshti, A. (2012). "Performance analysis of an attic radiant barrier system using three dimensional transient finite element method." Building Physics. EETD, E. E. T. D. (2014). "Solar Reflectance Index of Asphalt shingles." <http://energy.lbl.gov/coolroof/asshingl.htm>. EIA (2011). "Annual Energy Outlook." DOE/EIA –0383. Hassan, R., Stephen ,Sharples (2013). "Quantifying the domestic electricity consumption for air-conditioning due to urban heat islands in hot arid regions." Applied Energy, 112, 371-380. Hassid, S., Santamouris, M, Papanikolaou, N, Linardi, A, Klitsikas, N, Georgakis, C, Assimakopoulos, D.N (2000). "The effect of the Athens heat island on air conditioning load." Energy and Buildings, 32, 131-141. Kiletico, M., Hassan, M., Mohammad, L.,  Alvergue, A. (2014). "A New Approach to Recycle Glass Cullet in Asphalt Shingles to Alleviate Thermal Loads and Reduce Heat Island Effects " Journal of Materials in Civil Engineering In Press. M. Jacobson, J. E. T. H. (2012). "Effects of urban surfaces and white roofs on global and regional climate." Journal of Climate, 25, 1028. NOAA (2012). National Oceanic and Atmospheric Administration National Weather Service. NREL (2014). "1991- 2005 Update: Typical Meteorological Year 3." <http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/>. S. Menon, H. A., Sarith Mahanama, Igor Sednev, Ronnen Levinson (2010). "Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets." Environmental Research Letters, 5, 014005. Sailor, D., Dietsch, N. (2007). "The urban heat island mitigation impact screening tool (MIST)." Environ Model Software, 22, 1529-1541. Santamouris, M., Paraponiaris, K., Mihalakakou, G. (2007). "Estimatingthe ecological footprint of the heat island effect over Athens, Greece." Climate Change, 80, 265-276. Savio, P., Cynthia Rosenzweig, Solecki, William D., Slosberg, Ronald B. (2006). "Mitigating New York City’s Heat Island with Urban Forestry, Living Roofs, and Light Surfaces. New York City Regional Heat Island Initiative.", The New York State Energy Research and Development Authority, Albany, NY. Synnefa, A., Dandou, A., Santamouris, M.,  And Tombrou,M. (2008). "On the Use of Cool Materials as a Heat Island Mitigation Strategy." Journal Of Applied Meteorology And Climatology, 47, 2846. Taha, H. (1994). "Meteorological and photochemical simulations of the South Coast Air Basin,Analysis of Energy Efficiency of Air Quality in the South Coast Air Basin, Phase II." 35728, ed., Lawrence Berkeley Laboratory, 161-218. Taha, H., Akbari., H., Rosenfeld., A., Huang, J. (1988). "Residential cooling loads and the urban heat island -the effects of albedo." Building and Environment 23(4), 271-283. Yukihiro, K., Yutaka, G., Hiroaki, K., Keisuke, H. (2006). "Impacts of city-block-scale countermeasures against urban heat-island phenomena upon a building’s energy-consumption for air-conditioning." Applied Energy, 83(6), 649-668.   5th International/11th Construction Specialty Conference 5e International/11e Conférence spécialisée sur la construction   Vancouver, British Columbia June 8 to June 10, 2015 / 8 juin au 10 juin 2015   006-1 3D FINITE ELEMENT MODELING OF RECYCLED GLASS CULLETS IN ASPHALT SHINGLES Somayeh Asadi1, Marwa Hassan2 and Ali Beheshti3 1Department of Architectural Engineering, Pennsylvania State University, University Park, PA, USA  2Department of Construction Management, Louisiana State University, Baton Rouge, LA, USA 3Department of Mechanical Engineering, Texas A&M University, College Station, TX, USA Abstract: Recycled glass cullets in asphalt shingles may be utilized as a cool roof strategy to reduce the harmful effects of Urban Heat Island (UHI).  A Three-Dimensional (3D) transient Finite Element (FE) model was developed and validated to quantify energy savings provided by the proposed recycling process under various climatic conditions.  Simulations were carried out for three cities located in three climate regions in the United States representing different climatic conditions. The three cities representing each region were Kansas City (Missouri) for Zone 3, Charlotte (North Carolina) for Zone 4, and Miami (Florida) for Zone 5.  Results for each of the climatic zones were quantified.  Results showed that the annual energy savings ranged from $35.37 in cold climatic regions to $ 92.58 in hot climates.   1 INTRODUCTION Building sector in most countries represent about one third of the total energy consumption. It is projected that the building’s energy demand will be increased 110–150% by 2050 and 160–220% until 2095 from its 2005 level. Several factors including design and building characteristics, occupants, and people who work and live in buildings can significantly contribute to the success of energy efficiency measures. HVAC systems account for the largest amount of energy consumption in both commercial and residential buildings. As a consequence, the thermal barrier (or building envelope) that controls the heat flow of building is responsible for up to 40% of residential energy use and 55% of commercial energy use. In addition, cooling load in residential building shows an increasing trend worldwide and is one of the main concerns not only for countries that are characterized by hot climatic conditions but also for cities suffering from the heat island effect. The lower albedo of urban surfaces and the replacement of vegetation by building structures are considered as contributing factors to the heat island effect. Due to this effect, the ambient temperature in urban areas is usually several degrees higher (e.g. 1°–6°C) than that of their surrounding suburban and rural areas. Increased ambient temperatures result in thermal discomfort and increase cooling energy consumption, energy demand, and energy prices (Hassid 2000; Santamouris 2007). In recent years several experimental studies have been conducted to investigate the energy saving effects of urban heat island mitigation measures such as high albedo coatings and urban greening (Akbari 2005; Akbari 2001; Sailor 2007; Taha 1988). In parallel, important simulation studies have been carried out to identify the heat island mitigation potential of cool roofs (M. Jacobson 2012; S. Menon 2010; Savio 2006).These studies found that the precise energy benefits depend on the local climate and more significantly on the specific building characteristics.  006-2 Intensive research has been carried out on the heat island effect and cool roofs, the impact and the significance, as well as its qualitative and quantitative characteristics. Recent studies found that there is a relationship between building energy consumption and heat island effect (Hassan 2013; Hassid 2000; Yukihiro 2006). Noteworthy among these publications are the works of Akbari et al. (Akbari 2001) who found that changing the roof albedo of a residence in Sacramento, California from 0.18 to 0.73 results in energy savings of approximately 2.2 kWh/day. It was also found that increasing the urban albedo by about 20% reduces cooling load between 2.9% and 21% for Toronto and 62% for Sacramento (Akbari 1992; Taha 1994) which indicates that energy benefits differ largely as a function of the climatic conditions and the characteristics of the building. In another study conducted by Synnefa et al., several types of cool materials have been identified and tested to assess their performance in reducing heat island effect in Athens, Greece. They studied the optical and thermal properties of the selected materials and results revealed that these materials can be classified as “cool” with the ability to maintain lower surface temperatures. They defined and studied two scenarios of modified albedo including a moderate and an extreme increase in albedo scenario. The results indicated that large-scale increases in albedo could reduce ambient air temperatures by 2°C (Synnefa 2008). Within this context, Akbari and Konopacki (Akbari 2004) carried out a field study to predict the energy-saving potential of several UHI mitigation measures in Toronto. Their results indicated that the level of savings in energy varies depending on the mitigation measures and building types. However, that study did not consider the temperature distribution in the urban area.  This study investigates the application of recycling of broken and waste glass cullet in the production of asphalt shingles in order to reduce energy consumption in residential buildings and to mitigate heat island effects by increasing the solar reflectance index (SRI) of the roof asphalt shingles. To achieve this objective, laboratory characterization of glass cullet was conducted and asphalt shingles prepared with and without glass cullet were tested in the laboratory. In addition, Three-Dimensional (3D) transient Finite Element (FE) model was developed and validated to quantify energy savings provided by the proposed recycling process under various climatic conditions.  2 EXPERIMENTAL PROGRAM Conventional and recycled-glass modified asphalt roofing shingles were prepared in the laboratory by varying the amount of glass cullet and conventional materials used in asphalt roof shingles, and acceptability was based upon the standard specifications described in ASTM D 3462.  A full description of the laboratory experimental study has been presented elsewhere (Kiletico 2014).  Three different colors of recycled glass cullet including green and two sources of clear glass were collected from Construction and Demolition (C&D) processing plant to prepare the asphalt shingles.  Since the size of the collected glass cullet was large, a high performance mixer was used to reduce particle sizes.  The ground glass cullet was then used in lieu of conventional mineral aggregates as surface granules, filler material, and backdust.   The preparation of asphalt shingles in the laboratory consisted of three steps including preparation of the formwork, preparation of the asphalt blends, and aggregate preparation. The dimensions of the prepared asphalt shingles were 76mm x 76mm x 3mm. In the first step, the metal forms containing a fiberglass mat substrate were prepared. In the next step, asphalt binder was poured in the prepared forms. A white pigment powder was used in the fabrication of the asphalt shingles. The powder consisted of 98% pure titanium dioxide (TiO2) and was added at 8% by weight of the top surface granules. To add the TiO2 pigment powder to the surface granules, two grams of powder were mixed with 23 grams of surface granules, saturated with water, and then oven-dried. The filler material was then homogeneously mixed with liquefied asphalt binder for each sample, which was heated to 204°C. After mixing the filler material, 36 grams of asphalt coating mixture was reheated to become liquefied at 230°C. The asphalt coating mixture was then poured in the metal formwork of each shingle and then placed into the oven at 204°C for impregnation of the fiberglass for 1 hour. Then, the samples were removed from the oven and firm pressure was applied on the top surface granules in order to achieve 100% surface coverage.  A forced heat gun was used to separate the shingles from working surface.  Finally, the backdust particles were applied to the back surface while keeping the underside heated. The new shingles are patented under Provisional Patent 61/952515 “Method for the Manufacturing of Energy Efficient Shingles using TiO2 006-3 Coated Recycled Glass Cullets.”  The color appearance of all the prepared asphalt shingles is shown in Figure 1.   Figure 1. Asphalt shingle with/without  glass cullet 2.1 Solar Reflectance Index (SRI) SRI incorporates both solar reflectance and emittance into a single value and is a measure of the constructed surface’s ability to stay cool in the sun by reflecting solar radiation and emitting thermal radiation. It is defined such that a standard black surface (initial solar reflectance 0.05, initial thermal emittance 0.90) has an initial SRI of 0, and a standard white surface (initial solar reflectance 0.80, initial thermal emittance 0.90) has an initial SRI of 100.  Materials with the highest SRI values are the coolest choices for roofing. To calculate the SRI of the prepared asphalt shingles with and without glass cullet, their solar reflectance and thermal emittance were measured in the laboratory. The SRI of the asphalt shingle with and without glass cullet was calculated according to ASTM E 1980. The following formulas were used to calculate the SRI:   [1] SRI=123.97-141.35X+9.655X 2   [2] X= ((α-0.02ϵ1)(8.797+hc))/((9.5205ϵ+hc)) Where α  is the solar absorptance and ε represent for the thermal emissivity of the prepared asphalt shingle samples. The calculation was conducted for three convective coefficients (hc) that correspond to low, medium, and high wind conditions (5, 12, and 30 W·m–2·K–1, respectively). Table 1 shows the SRI of some of the available asphalt shingles in the market (EETD 2014).  006-4 Table 1. Solar Reflectance Index of Asphalt Shingles Type of the asphalt shingle  SRI Type of the asphalt shingle  SRI White 21 Black  1 Gray   4 Weathered Wood 4 Green 18 Dark Brown 4 Antique Silver 19 Beachwood Sand   19 Table 2 shows the description of the shingle specimens and their SRI based on laboratory measurements.  As shown in this table, the control samples had the lowest SRI (i.e., 0), which was expected.  On the other hand, the sample G1, which contains clear glass and TiO2 pigment, had the highest SRI (i.e., 30). Table 2. SRI of the prepared samples ID Material Composition SRI Top Surface Filler X1 Control 1: Ceramic Coated Granules Limestone 0 X2 Control 2: Ceramic Coated Granules Clear Glass 1 0 A Green Glass Limestone 3 B Clear Glass 1 Limestone 5 C Green Glass Green Glass 3 D Clear Glass 1 Clear Glass 1 5 C1 Green Glass & Pigments Green Glass 28 D1 Clear Glass 1 & Pigments Clear Glass 1 27 G1 Clear Glass 2 & Pigments Clear Glass 2 30 3 CLIMATE REGIONS IN THE UNITED STATES  In order to estimate the effect of the application of glass cullet asphalt shingle on the residential building energy load, simulations were carried out for three cities located in three climatic regions including Zones 3, 4, and 5 in the United States. US Energy Information Administration (EIA) categorized the climate regions in the United states into 5 main categories based on the last 30-year average heating degree-days (HDD) and cooling degree days (CDD) (EIA 2011; NOAA 2012). A HDD is a measure of how cold a location was over a period of time, relative to a base temperature of 65 °F (18.3 °C). On the other hand, a CDD is a measure of how hot a location was over a period of time, relative to the same base temperature of 65 °F (18.3 °C). Zone 3 is defined as the region with less than 2000 CDD and less than 4000-5499 HDD; Zone 4 is defined as the region with less than 2000 CDD and less than 4000 HDD; Zone 5 is defined as the region with 2000 CDD or more and less than 4000 HDD. Figure 2 shows the 3 main studied climate zones in the United States. Table 3 also provides the latitude and the longitude of the selected cities for this study. 006-5  Figure 2. Climate Zones in the US adapted from (EIA 2011) and (NOAA 2012) Table 3. The latitude and longitude of the selected cities for the simulations City, State Latitude (°) Longitude (°) Cooling Degree Days (ºC) Miami, FL 25.82 80.28 2645 Charlotte, NC 35.22 80.93 1105 Kansas City, MO 39.32 94.72 1110 4 FINITE ELEMENT MODEL  ABAQUS 6.13 software was used in this study to develop a three dimensional transient finite (FE) element model. Two FE models were developed to simulate the heat transfer mechanisms and evaluate energy consumption in the house with conventional asphalt shingle and house with glass cullet asphalt shingle in different climate regions in the United States. The developed FE model considered all the heat transfer mechanisms that may occur within the space. It is worth mentioning that many factors affect the calculated temperature distributions and the heat flux in the roof. The inputs to the FE model include the emissivity of asphalt shingle with and without glass cullet, emissivity of insulation, attic flow rate, longitude, latitude, and time zone of the locations. Although the physical model was symmetric, the amount of solar radiation differed from one side of the roof to the other depending on the surface orientation and inclination. Thus, in order to conduct an accurate analysis, the entire configuration of the roof was simulated in the FE model. It is worth mentioning that in order to attain reliable and accurate results; a mesh convergence technique was conducted using different mesh sizes. Final mesh size was selected after considering both computational efficiency and accuracy. To model the conduction heat transfer mechanism in the roof and the ceiling, approximately 49,000 DC3D8 elements were used. Featuring a hexahedron shape with eight nodes, these linear heat transfer elements were used for all the materials except the air. To model the advection, that is, bulk motion of the air in the attic, the convection/ diffusion option in ABAQUS was utilized by means of eight-node DCC3D8 elements with forced convection/diffusion capabilities. The total number of aforementioned elements was approximately 73,000. In addition, forced convection inside the roof was simulated by means of the mass heat transfer option in ABAQUS. A full description of the model has been presented elsewhere (Asadi 2012). In addition, hourly climatic data, including ambient air temperature, solar radiation, wind speed, wind Zone 5: Miami Zone 4: Charlotte Zone 3: Kansas City 006-6 direction, and relative humidity were used in the simulation. The metrological data was obtained from the Typical Meteorological Year 2 (TMY2)(NREL 2014). Figure 3 shows the finite element mesh of the model.     Figure 3. Finite Element Mesh Figure 4 shows the operation of the conventional and reflective roofs. During daylight hours, a roof is constantly subjected to solar energy striking its surface. A reflective roof with high SRI would have a lower surface temperature as compared to a conventional roof. In the case of a reflective roof, a lower surface temperature translates into less heat gain into the attic space or living space below the roof, which result in a cooler living space and lower cooling/heating energy consumption. The building used in the simulation is a single story residential building with a tilted roof with area of 148.6 m2.  The attic had two pitched roof sections, two vertical gable-end sections, and one horizontal ceiling frame. The thermostat set point temperature for cooling and heating was set to 26 and 21°C, respectively.              4.a. Conventional roof           4.b. Reflective roof  Figure 4. Operation of conventional and reflective roofs   XYZ 006-7 5 RESULTS AND DISCUSSIONS  Model validation was necessary to demonstrate the precision and the viability of the FE model.  Therefore, the developed models were validated based on experimental data collected in Zackary, LA. To validate the FE model, a site-located weather station was placed on the roof to measure the actual weather parameters and collected data was used in the model. Figure 5 compares the results based on FE model and experimental data for a typical day in the summer.  The results showed that there is a good agreement between experimental data and FE model and error was less than 5%. The obtained results demonstrate that the finite element model could be applied with success even for more detailed situations and with better precision on the results.  Time (hour)1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Temperature (ºC)0102030405060FMExperiment    Figure 5. Model validation In order to investigate the performance of the glass cullet asphalt shingle to reduce building energy consumption, the heat flux were calculated for the control house and the house with asphalt shingle containing glass cullet in different climate regions in the United States. It should be noted that the values mentioned in this part of the study depend on the building characteristics. As expected, increasing the roof SRI resulted in reduced summer cooling loads particularly in hot climate regions. Figure 6 shows the required cooling and heating loads in the house with and without asphalt shingle containing glass cullet. For the building chosen and the climates examined in this study, it was found that the potential savings are greater in hot climate regions such as Miami, FL. It was found that the application of asphalt shingle containing glass cullet in the roof can reduce energy consumption from 7.8 kwh/m2 to 6.9 kwh/m2 in June in Miami-FL and save approximately $16 in this month.  Results showed that increasing the SRI of a roof is clearly more advantageous in hot climate regions where cooling load dominates most of the year. This study provides further evidence that roof asphalt shingles containing glass cullet are effective strategies for urban heat island mitigation. The increased SRI of these roofs effectively reduces their surface temperature and decreases sensible heat flux into the urban atmospheric system. 006-8 Miami, Florida Charlotte, NC  Kansas City, MO Fig. 6. Required heating and cooling load in 3 climate regions in the US 6 CONCLUSIONS   The present study evaluated the application of waste glass cullet in the production of asphalt shingles in order to reduce energy consumption in residential buildings and to mitigate heat island effects by increasing the SRI of the roof asphalt shingles.  Laboratory tests were conducted to determine the solar reflectance and thermal emittance of the prepared asphalt shingle samples with and without glass cullet.  Based on the laboratory results, it is concluded that glass cullet can be successfully blended with conventional materials to produce a sustainable asphalt shingle that has a solar reflectance of that is significantly greater than conventional asphalt shingles.  Results show that a typical black ceramic coated asphalt shingle has SRI of 0. In order to achieve cool roof attributes, the addition of a white pigment mixed together with the top surface granules increased the SRI to 30 for clear glass.   A FE model was developed to calculate and quantify the energy consumption reduction in the house with and without glass cullet.  The developed model was successfully validated with measured experimental data collected in Zachary, LA.  Annual models were run for three cities in five climate regions in the United States.  For the building studied and the climates considered in the simulation, it was found that the potential savings are greater in hot climate regions such as Miami, FL. Results indicated that the application of asphalt shingle containing glass cullet in the roof can reduce energy consumption from 7.8 kwh/m2 to 6.9 kwh/m2 in June in Miami-FL and save approximately $16. Results showed that increasing the SRI of a roof is characteristically more advantageous in hot climate regions where cooling load dominates most of the year. This study provides evidence that roofs covered with asphalt shingles containing glass cullet are effective strategies for urban heat island mitigation.  The increased SRI of these roofs effectively reduces their surface temperature and decreases sensible flux into the urban atmospheric system. 006-9 References Akbari, H., and H. Taha (1992). "The impact of trees and white surfaces on residential heating and cooling energy use in four Canadian cities." Energy, 17(2), 141-149. Akbari, H., Konopacki, S (2004). "Energy effects of heat-island reduction strategies in Toronto, Canada." Energy, 29, 191-210. Akbari, H., Konopacki, S. (2005). "Calculating energy-saving potentials of heat-island reduction strategies." Energy Policy, 33, 721-756. Akbari, H., Pomerantz, M, Taha, H (2001). "Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas." Solar Energy, 70(3), 295-310. Asadi, S., Hassan, M., Beheshti, A. (2012). "Performance analysis of an attic radiant barrier system using three dimensional transient finite element method." Building Physics. EETD, E. E. T. D. (2014). "Solar Reflectance Index of Asphalt shingles." <http://energy.lbl.gov/coolroof/asshingl.htm>. EIA (2011). "Annual Energy Outlook." DOE/EIA –0383. Hassan, R., Stephen ,Sharples (2013). "Quantifying the domestic electricity consumption for air-conditioning due to urban heat islands in hot arid regions." Applied Energy, 112, 371-380. Hassid, S., Santamouris, M, Papanikolaou, N, Linardi, A, Klitsikas, N, Georgakis, C, Assimakopoulos, D.N (2000). "The effect of the Athens heat island on air conditioning load." Energy and Buildings, 32, 131-141. Kiletico, M., Hassan, M., Mohammad, L.,  Alvergue, A. (2014). "A New Approach to Recycle Glass Cullet in Asphalt Shingles to Alleviate Thermal Loads and Reduce Heat Island Effects " Journal of Materials in Civil Engineering In Press. M. Jacobson, J. E. T. H. (2012). "Effects of urban surfaces and white roofs on global and regional climate." Journal of Climate, 25, 1028. NOAA (2012). National Oceanic and Atmospheric Administration National Weather Service. NREL (2014). "1991- 2005 Update: Typical Meteorological Year 3." <http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/>. S. Menon, H. A., Sarith Mahanama, Igor Sednev, Ronnen Levinson (2010). "Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets." Environmental Research Letters, 5, 014005. Sailor, D., Dietsch, N. (2007). "The urban heat island mitigation impact screening tool (MIST)." Environ Model Software, 22, 1529-1541. Santamouris, M., Paraponiaris, K., Mihalakakou, G. (2007). "Estimatingthe ecological footprint of the heat island effect over Athens, Greece." Climate Change, 80, 265-276. Savio, P., Cynthia Rosenzweig, Solecki, William D., Slosberg, Ronald B. (2006). "Mitigating New York City’s Heat Island with Urban Forestry, Living Roofs, and Light Surfaces. New York City Regional Heat Island Initiative.", The New York State Energy Research and Development Authority, Albany, NY. Synnefa, A., Dandou, A., Santamouris, M.,  And Tombrou,M. (2008). "On the Use of Cool Materials as a Heat Island Mitigation Strategy." Journal Of Applied Meteorology And Climatology, 47, 2846. Taha, H. (1994). "Meteorological and photochemical simulations of the South Coast Air Basin,Analysis of Energy Efficiency of Air Quality in the South Coast Air Basin, Phase II." 35728, ed., Lawrence Berkeley Laboratory, 161-218. Taha, H., Akbari., H., Rosenfeld., A., Huang, J. (1988). "Residential cooling loads and the urban heat island -the effects of albedo." Building and Environment 23(4), 271-283. Yukihiro, K., Yutaka, G., Hiroaki, K., Keisuke, H. (2006). "Impacts of city-block-scale countermeasures against urban heat-island phenomena upon a building’s energy-consumption for air-conditioning." Applied Energy, 83(6), 649-668.   3D FINITE ELEMENT MODELING OF RECYCLED GLASS CULLETS IN ASPHALT SHINGLESSomayeh Asadi, Marwa Hassan, Ali Beheshti Introduction  Building sector in most countries represent about one third of the total energy consumption. Many cities world-wide with populations that equal or exceed 1 million people experience an increase in annual mean air temperature of 1 to 3°C compared to their surroundings. Evening differences as high as 12°C. Introduction Heat Island Effect Background High albedo coatings and urban greening Cool roofs Objective Investigates the application of recycling of broken and waste glass cullet in the production of asphalt shingles to reduce energy consumption in residential buildings  Mitigate heat island effects by increasing the solar reflectance index (SRI) of the roof asphalt shingles. EXPERIMENTAL PROGRAMAsphalt shingle with/without  glass culletSolar Reflectance IndexSolar Reflectance Index of Common Asphalt ShinglesType of the asphaltshingleSRI Type of the asphaltshingleSRIWhite 21 Black 1Gray 4 Weathered Wood 4Green 18 Dark Brown 4Antique Silver 19 Beachwood Sand 19Solar Reflectance IndexSolar Reflectance Index of prepared Asphalt ShinglesIDMaterial Composition SRITop Surface FillerX1 Control 1: Ceramic Coated GranulesLimestone 0X2 Control 2: Ceramic Coated GranulesClear Glass 1 0A Green Glass Limestone 3B Clear Glass 1 Limestone 5C Green Glass Green Glass 3D Clear Glass 1 Clear Glass 1 5C1 Green Glass & Pigments Green Glass 28D1 Clear Glass 1 & Pigments Clear Glass 1 27G1 Clear Glass 2 & Pigments Clear Glass 2 30CLIMATE REGIONS IN THE UNITED STATES The latitude and longitude of the selected cities for the simulationsCity, State Latitude (°) Longitude (°) Cooling Degree Days (ºC)Miami, FL 25.82 80.28 2645Charlotte, NC 35.22 80.93 1105Kansas City, MO 39.32 94.72 1110Operation of conventional and reflective roofsConventional roof Reflective roofFinite Element Model Finite Element MeshResults and DiscussionsModel validationTime (hour)1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Temperature (ºC)0102030405060FMExperimentResults and DiscussionsRequired heating and cooling load in 3 climate regions in the USZone 5: MiamiZone 4: CharlotteZone 3: KansasConclusions A typical black ceramic coated asphalt shingle has a very low SRI.  The addition of a white pigment mixed together with the top surface granules increased the SRI to 30 for clear glass.   FE results indicated that the application of asphalt shingle containing glass cullet in the roof can reduce energy consumption from 7.8 kwh/m2 to 6.9 kwh/m2 in June in Miami-FL and save approximately $16. Conclusions Results showed that increasing the SRI of a roof is characteristically more advantageous in hot climate regions where cooling load dominates most of the year.  This study provides evidence that roofs covered with asphalt shingles containing glass cullet are effective strategies for urban heat island mitigation.  The increased SRI of these roofs effectively reduces their surface temperature and decreases sensible flux into the urban atmospheric system.Thank You for Your Attention

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