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Title
The effects of roof albedo modification on cooling load of scale model residences in Tuscon, Arizona
The effects of roof albedo modification on cooling load of scale model residences in Tuscon, Arizona
Date
0/1997
0/1997
Author(s)
J R Simpson; E G McPherson
J R Simpson; E G McPherson
Page(s)
127-137
127-137
Source
2001 Company
2001 Company
Keyword(s)
roof albedo; scale model resistance; roof color; Arizona; cooling load
roof albedo; scale model resistance; roof color; Arizona; cooling load
Abstract
Data supporting reductions in cooling load and related demand for electric power possible from increasing building surface albedo are limited. Electrical use of wall-mounted air conditiners, roof temerpatres and related environmental factors were monitored during the summer of 1990 of three initially identical 1/4-scale model buildings situated in rock mulch landscapes in Tucson, Arizona. Model thermodynamic properties were scaled to approximate thermodynamic similarity with full-size buildings. With ceiling insulation of R value 5.28 meter squared installed, increasing roof albedo of the gray composition shingles by painting one roof silver and another white reduced daily total and hourly peak electrical use for air conditioning approximately 5% for the house with white-colored roof compared to either gray or silver-coloredroofs. Larger differences were found without ceiling insulation, with daily total and peak hourly demand for houses with white compared to dark brown roofing reduced 28 and 18% respectively. Computer simulations of daily total energy use confirmed comparable savings for similar full-sized buildings. White roofs were 20-30C cooler than either silver or dark-colored roofs on hot, sunny days, indicating that expected cooling due to an increase in albedo may not be realized if it is accompanied by a decrease in emissivity. Light-colored roofs, by maintaining cooler attic temperatures, may provide savings in addition to those presented here by reducing heat gain to air distribution systems located in the attic space.
Data supporting reductions in cooling load and related demand for electric power possible from increasing building surface albedo are limited. Electrical use of wall-mounted air conditiners, roof temerpatres and related environmental factors were monitored during the summer of 1990 of three initially identical 1/4-scale model buildings situated in rock mulch landscapes in Tucson, Arizona. Model thermodynamic properties were scaled to approximate thermodynamic similarity with full-size buildings. With ceiling insulation of R value 5.28 meter squared installed, increasing roof albedo of the gray composition shingles by painting one roof silver and another white reduced daily total and hourly peak electrical use for air conditioning approximately 5% for the house with white-colored roof compared to either gray or silver-coloredroofs. Larger differences were found without ceiling insulation, with daily total and peak hourly demand for houses with white compared to dark brown roofing reduced 28 and 18% respectively. Computer simulations of daily total energy use confirmed comparable savings for similar full-sized buildings. White roofs were 20-30C cooler than either silver or dark-colored roofs on hot, sunny days, indicating that expected cooling due to an increase in albedo may not be realized if it is accompanied by a decrease in emissivity. Light-colored roofs, by maintaining cooler attic temperatures, may provide savings in addition to those presented here by reducing heat gain to air distribution systems located in the attic space.