Solar reflectivity of common building materials and its influence on the roof heat gain of typical southwestern U.S.A. residences

The fraction of incident solar energy reflected by the exterior elements of a structure significantly effects the overall heat gain or loss of the structure. This is particularly true for regions that receive an abundance of solar insolation as occurs in the southwestern part of the United States. However, the available data on the solar reflectivity of common building materials are apparently rather sparse. In order to augment these data, the authors developed a probe for measuring hemispheric solar flux and employed it to measure the solar reflectance of a wide variety of building materials. Results of these measurements are presented and reviewed. The measured reflectivity values have also been used in heat gain/loss computations for typical southwestern residences. Results of some of these computations are presented to demonstrate the change in structure heat gain/loss that can realistically be achieved by altering roof reflectivity.