Cool Roofs
On this page you'll find information about the Building Technologies Program envelope materials R&D project on cool roofs.
A cool roof has a white or special cool color that absorbs less sunlight, staying cooler in the sun and transmitting less heat into a building. Traditional dark-colored roofing materials strongly absorb sunlight, making them warm in the sun, which in turn adds heat to a building.
R&D has been underway since the mid-1980s at the U.S. Department of Energy's (DOE) Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory to measure the energy-saving benefits of solar radiation control coatings on roofs and light-colored roofing products on summer urban heat islands (dry and impervious areas that strongly absorb light). The coolness of a roof is determined by two properties and their combined effects on temperature:
- Solar reflectance—the fraction of sunlight that is reflected
- Thermal emittance—the efficiency with which a surface cools itself by emitting thermal radiation
Benefits of Cool Roofs
Studies show that in warm or hot climates, substituting a cool roof for a conventional roof can:
- Reduce the annual air-conditioning energy use of a single-story building by up to 15%
- Cool interior spaces in buildings that do not have air conditioning, making occupants more comfortable
- Reduce carbon emissions by lowering the need for fossil-fuel generated electricity to run air conditioners
- Reduce peak demand for electricity, helping to lower costs and avoid power outages
- Potentially slow global warming.
Cool roofs are available for both low-slope and steep-slope roofs. Learn more by reading the Cool Roofs fact sheet (PDF 1.3 MB) and Q&A (PDF 272 KB). Download Adobe Reader.
Related Links
The following links provide additional resources about cool roofs, including ways to calculate efficiency and available products.
- DOE's Building Energy Software Tools Directory provides information on 370 building software tools for evaluating energy efficiency, renewable energy, and sustainability in buildings.
- DOE's online Cool Roof Calculator allows you to make a side-by-side comparison of potential savings for flat roofs on small- and medium-sized facilities.
- The U.S. Environmental Protection Agency (EPA) also offers a Roofing Comparison Calculator to estimate how much energy and money you can save by installing an ENERGY STAR® labeled roof product on your home or building.
- The EPA lists about 3,000 ENERGY STAR compliant reflective roof products.
- The Cool Roof Rating Council (CRRC) maintains a third-party rating system for radiative properties of roof surfacing materials. Find CRRC rated products by searching the Rated Products Directory.
- Energy Efficiency Journal Article: Potential Benefits of Cool Roofs on Commercial Buildings: Conserving Energy, Saving Money, and Reducing Emission of Greenhouse Gases and Air Pollutants