But on the high-slope roofs of single-family homes, which can been seen from the street, the market is dominated by colorful shingles, tiles, metal products, and wood shakes.
Existing white and nonwhite cool coatings are fine for the low-slope roofs of commercial and industrial buildings and apartment structures, where white is acceptable. However, technical barriers to getting cool roofs on homes still remain. And the Environmental Protection Agency’s Energy Star program certifies cool roof products with its voluntary labeling EPA maintains a web-based guide to Energy Star roofing products. The building-materials industry has brought a number of products to the marketplace that help increase the reflectance of roofs, including elastomeric coatings, single-ply membranes, tiles, and metal roofing. Thanks to the work of Akbari’s team, the roofing industry in recent years has adopted voluntary industry standards for measuring the reflectance of roofing materials and has set up the Cool Roof Rating Council to develop labels that inform buyers about the relative coolness of various products used in roofing - that is, their ability to reflect solar energy and release heat through thermal radiation. Lower temperatures on the roofs may also increase the life of a roof, according to preliminary research by the group. Cool roofs can also reduce peak electrical demand in the summer, which helps reduce strain on the aging electricity grid when relief is most needed. The Heat Island Group’s research has shown that, regionally, widespread application of cool roofs can reduce ambient air temperatures and retard smog formation. achievable by applying white roofs to commercial buildings and cool-colored roofs to houses is more than $750 million per year,” says Hashem Akbari, an EETD researcher and head of the Heat Island Group. “Our research estimates that the potential net energy savings in the U.S. It is possible to create a nonwhite cool roof by using colorants or pigments that reflect the invisible, near-infrared radiation that accounts for over half of the energy in sunlight. Cool-colored, nonwhite roofs meet that need. homeowners typically demand nonwhite roofs. Berkeley Lab research has demonstrated that raising the solar reflectance of a roof from about 20 percent (dark gray) to about 55 percent (weathered white) can reduce cooling energy use by 20 percent.įlat-roofed commercial buildings are often fitted with white roofs, but U.S. Since dark surfaces are better heat absorbers, traditional cool roofs are white. Home owners whose houses have pitched roofs prefer darker colors for roofing.
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