Studies: Lighten Up on Roof and Pavement Color

August 4, 2010

Two recent studies have helped quantify the heat-reduction benefits of using light-colored roofs and pavements. The concept has been touted for many years, but the recent reports help fill in some previously missing facts.

Researchers at the Lawrence Berkeley National Laboratory and NASA have calculated that converting roofs and pavements in tropical and temperate cities of one million or more people to light-colored materials would provide the equivalent one-time benefit of eliminating two years' worth of global CO2 emissions, or eliminating the emissions of 300 million vehicles for 20 years.

Such efforts are easy to immediately implement on a local basis. However, they are not a stand-alone climate change-fighting measure, since doing this on a global scale cuts the temperature by only 0.01 degrees. Nonetheless, it can make a small contribution to slowing temperature increases, the authors conclude.

"Radiative Forcing and Temperature Response to Changes in Urban Albedos and Associated CO2 Offsets," by Surabi Menon et al., Environmental Research Letters, Jan. 21, 2010 (includes some analysis for CA, FL, TX, and the US as a whole, and some mapping for all of the US and the globe); Berkeley Lab press release, July 19, 2010.

Convinced of the importance of this issue, the Dept. of Energy announced July 19, 2010, that it is pushing forward with an initiative to substantially increase the use of light-colored roofs on all federal buildings. The move is designed to reduce the federal government's direct impact on rising temperatures, and to serve as a role model for others.

"Secretary Chu Announces Steps to Implement Cool Roofs at DOE and Across the Federal Government" (includes link to guidelines for selecting cool roofs).

Researchers from the National Center for Atmospheric Research and the Univ. of Kansas came to a generally similar conclusion after evaluating the effects of making all roofs white (not just light-colored). Both studies noted that the benefits of white or light-colored roofs become marginal in certain cold-weather settings, but that the benefits generally apply to areas where the great majority of the global population lives.