PRELIMINARY SURVEY OF THE SOLAR REFLECTANCE OF COOL ROOFING MATERIALS

Air-conditioning energy savings and improved comfort in hot climates c an be obtained with the use of roofing materials that reflect solar ra diation. Available quantitative information on the solar reflectance o f most roofing materials is insufficient, so it is difficult for build ing designers to choose cool materials. Here we report quantitative va lues of solar reflectance for a few types of materials and discuss whi ch material properties, such as composition, roughness, purity, etc., affect the solar reflectance. Outdoor temperature measurements on mate rials in sunlight are used to illustrate the strong correlation of roo f temperature with solar absorptance, and further, to demonstrate the effects of infrared emittance and convection.