Understanding the long-term effects of environmental exposure on roof reflectance in California

Contaminants from cool-pigmented roof samples exposed at seven California sites were analyzed for elements and carbons to identify those that degrade or enhance solar reflectance. The losses in solar reflectance varied by site and the color of the sample. The least reflectance drop was observed in the alpine climate, while the largest drop occurred in sites near urban development. The change of reflectance appears cyclical with the onset of seasons having more rainfall. A deposition model suggests that chromium ranks first, iron second, and elemental carbon third in importance to soil light absorption.

► Change of roof reflectance is cyclic with smaller dust amounts during wet seasons. ► Metals and carbons of roof particles yielded contamination profiles for a site. ► Loss of solar reflectance was mostly by dusts and particles from man-made sources. ► Chromium, iron compounds and soot contributed to the change in solar reflectance.