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Cool roof technology keeps buildings and people cooler; helps environment
Why, on a hot summer day, is it more comfortable to walk barefoot on a white concrete sidewalk than a black asphalt street? And why does it feel cooler when you get in a white car that's been parked in the sun than a black one? It's as simple as black and white. Black absorbs the sun's energy; white reflects it. The same principle applies to the roof over your head. Buildings with white roofs stay cooler than those with black ones. But there are a lot of black roofs in these United States!
Apartments, offices, hospitals, schools, libraries, warehouses and many urban homes throughout the country have flat or low-sloped roofs, and 80 percent of them are covered with either black asphalt or a black rubber sheet product known as EPDM. That's like having a hot blanket on your roof — it keeps everything underneath very warm.
Rohm and Haas research has shown that blacktop roofs can soar to 170 degrees on a 95-degree day and remain as high as 150 degrees after dark. On the same 95-degree day, a white roof will reach just 88 degrees. So how do you cool off a black roof? Coat it white! But not any coating will do. Regular white paint, for example, won't stick to roofing material.
Rohm and Haas scientists in the Spring House, Pa. Technical Center have developed technology and products to solve that problem. Research Fellow Willie Lau, Ph.D., and his associates developed a revolutionary new technology that enables white coating to adhere to black roofing material. Then Coatings Research Section Manager Dave Kelly, Ph.D., and his associates used that technology to develop Lipacryl®, a polymer designed for use with black asphalt roofing materials, now widely used on commercial buildings nationwide. Lipacryl® is manufactured at the company's plant in Croydon, Pa.
Another research initiative, led by Tom Ennis, research scientist, Coatings Technical Service, yielded Rinseable Primer®, which enables white roof coating to adhere to black rubber roof material. Currently, this primer product is being used to coat a new roof on Stapleton International Airport in Denver. It also has been used on the Superdome in New Orleans and the Federal Reserve Bank in Dallas, among many other buildings.
Two roof coating manufacturers in the metropolitan Philadelphia area — Henry Company of Kimberton, Pa. and Acrymax Technology of Media, Pa. — use these Rohm and Haas products to produce their roof coatings which are sold through home centers, roofing suppliers and contractors nationwide.
Solving a Public Health Issue
A number of large U.S. cities, including Philadelphia, have been increasingly concerned about the number of heat-related deaths each summer, especially among the elderly. Two years ago, a Philadelphia non-profit organization, Energy Coordinating Agency Inc., began putting white coating on the roofs of older residents in low-income city neighborhoods. They found that the coatings reduced the temperature inside these homes, making them safer for elderly residents. Now the City of Philadelphia is considering a new building code mandating that flat or low-slope roofs have high solar reflectance. In most cases, this means coating them white. Chicago recently adopted a similar building code.
Saving the Planet One Roof at a Time
In addition to assisting with public health issues, Rohm and Haas cool roof technology also helps to sustain the environment, according to William A. Kirn, technical service manager. "Nearly 17 percent of all electricity consumed in the U.S. is used to cool buildings," says Kirn. "Coating black roofs white can help to reduce that number by increasing energy efficiency." During a one-year study, Rohm and Haas scientists discovered that a building with a white acrylic roof coating consumed nearly 22 percent less energy for air conditioning in the summer than one with an uncoated black roof. Surprisingly, the white coating also reduced energy demand by almost four percent in the winter.
The U.S. Environmental Protection Agency now awards its Energy Star to white and reflective roofing materials, recognizing their value in promoting energy efficiency and conservation. In another vote of confidence for cool roof technology, some electrical utility companies are offering cash incentives to customers who coat their roofs white, thereby reducing peak energy demand.
White roof coatings also contribute to a healthy environment by extending the lifespan of black roofs. "Six percent of waste material dumped in landfills consists of old roofs," notes Kirn. "White coatings help roofs last longer by reducing the drastic changes in temperature that cause roof wear and tear, and that benefits the environment by reducing the size of our landfills.
"Rohm and Haas prides itself on 'quietly improving the quality of life,'" Kirn adds. "We're proud that our cool roof technology helps keep people safe and comfortable in the summer heat while helping to sustain our environment — a benefit to everyone."
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