By Dr. Ronnen Levinson, Staff Scientist and Leader, Heat Island Group at Lawrence Berkeley National Lab (bit.ly/RonnenLevinson)

Solar-reflective building envelope surfaces, such as cool roofs and walls, can be especially helpful in disadvantaged communities that have poorly insulated older homes, aging or absent air conditioning units, steep utility bills, polluted air, and high vulnerability and exposure to extreme heat. With support from the U.S. Department of Energy (DOE), the U.S. Cool Surfaces Deployment Project (bit.ly/CoolSurfacesDeployment) seeks to dramatically increase the climate-appropriate deployment of cool surfaces across the United States with an emphasis on their application to disadvantaged communities.

Just as wearing light-colored clothing can help keep a person cool on a sunny day, “cool” roofs and walls reflect sunlight to help lower building temperatures. Traditional dark roofs and walls can reach 150 °F (66 °C) or higher in the summer sun. Reflective roofs and walls under the same conditions can stay more than 50 °F (28 °C) cooler. They reduce energy costs in air-conditioned buildings, control indoor air temperature in buildings without air conditioning, mitigate the urban heat island effect, improve outdoor air quality, protect public health, improve grid stability and slow climate change.

Homes in the Mediterranean and the Middle East often have white roofs and walls. These cool surfaces have been a common architectural element for thousands of years. Although cool roofs and walls are some of the most cost-effective ways to reduce the temperature inside buildings during the hot summer, Western architecture has yet to adopt them to their full potential.

In the 1980s, the Department of Energy and the Heat Island Group at the Lawrence Berkeley National Lab (heatisland.lbl.gov) initiated research on the benefits of cool roofs for energy savings and reducing summertime urban temperatures. Today the influence of this research is felt globally as cool roofs now dominate the commercial roofing marketplace in some warm and hot climates. Many national and international building energy standards now prescribe cool surfaces for low-slope roofs, steep-slope roofs and exterior walls in certain climates.

Cool products exist for virtually every kind of building roof and wall. They come in a variety of colors and materials. While lighter-colored materials tend to be better at lowering temperatures, cool surfaces do not have to be white. There are “cool-color” versions of dark-colored roof and wall products engineered with pigments that efficiently reflect near-infrared radiation, such as “cool” asphalt shingles and metal panels.

Consider converting to a cool roof and/or walls if your roof is due for replacement, your exterior walls are in need of an upgrade, you’re experiencing high cooling costs or you’re experiencing discomfort due to excessive heat indoors. It is generally not cost-effective to replace a structurally sound roof solely to enhance solar reflectance, but property owners can consider applying a reflective roof coating to achieve cool-roof benefits. (Asphalt shingle roofing manufacturers do not recommend coating these products.)

The project team, including Lawrence Berkeley National Lab (lbl.gov), Oak Ridge National Lab and Arizona State University (ornl.gov), the Smart Surfaces Coalition (smartsurfacescoalition.org) and the Cool Roof Rating Council (coolroofs.org), recently launched an educational campaign explaining the science and benefits of cool roofs and walls, how to find cool products, and ways to promote a cooler future through urban policies and programs. •

To learn more about how cool roofs and walls can help you and your community, visit keepyourcool.lbl.gov