Solar reflective, thermally emissive (cool) roofs decrease demand for building air conditioning power, lower the ambient air temperature, and, by promoting lower ambient air temperatures, retard the formation of smog. For example, raising the solar reflectance of a roof from 0.10 (typical of a conventional dark roof) to 0.35 (typical of a cool dark roof) can reduce building cooling energy use by more than 10 percent. In 2002, suitable cool white materials were available for most products, with the notable exception of asphalt shingles, the most widely used roofing material. However, cooler colored (nonwhite) materials were needed for all types of roofing, especially in the residential market. The California Energy Commission engaged Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory to work with the roofing industry to develop cool-colored roofing products, with the goal of bringing to market within three to five years roofs that meet the ENERGY STAR qualifying solar reflectance of 0.25. This project led to the development of prototype colored asphalt shingles with solar reflectances of up to 0.35. One manufacturer currently markets colored asphalt shingles with solar reflectance of 0.25. Colored metal, clay tile, and concrete tile roofing materials with solar reflectances of 0.30 to 0.60 are currently sold in California.
Hashem Akbari, Paul Berdahl, Ronnen Levinson, Steve Wiel, William Miller, and Andre Desjarlais 2006. Cool-Color Roofing Material. California Energy Commission, PIER Building End-Use Energy Efficiency Program. CEC-500-2006-067.
Paul Berdahl (Lawrence Berkeley National Lab (LBNL))
Ronnen Levinson (Lawrence Berkeley National Lab (LBNL))
Steve Wiel (Lawrence Berkeley National Lab (LBNL))
William Miller (Lawrence Berkeley National Lab (LBNL))
Andre Desjarlais (Oak Ridge National Lab (ORNL))
Source: California Energy Commission PIER Program, February 2006
Publication Date: January 2006