New 'Smart' Roof Reads the Thermometer, Saves Energy in Hot and Cold Climates

http://www.sciencedaily.com/releases/2010/03/100321203506.htm

ScienceDaily (Mar. 31, 2010) — Top a building with a light-colored "cool roof," and it reflects sunlight, cutting air conditioning bills in summer, but increasing winter heating costs. Choose black shingles, and the roof soaks up sunlight to cut winter heating costs but makes the roof bake in the summer sun. One or the other. You can't have it both ways.

Until now.

Scientists reported the development of a "smart" roof coating, made from waste cooking oil from fast food restaurants, that can "read" a thermometer. The coating automatically switches roles, reflecting or transmitting solar heat, when the outdoor temperature crosses a preset point that can be tuned to the local climate.

They described the coating at the 239th National Meeting of the American Chemical Society (ACS) in San Francisco.

Roofs coated with the material would reflect scorching summer sunlight and reduce sticker-shock air-conditioning bills. When chilly weather sets in, the coating would change roles and transmit heat to help warm the interior.

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Wen cautions against pouring ordinary cooking oil on a roof in an attempt to achieve a similar energy-saving effect. That's because ordinary cooking oil won't turn into a polymer, doesn't contain the key ingredient for controlling infrared light levels, and could well pose a fire hazard for the building.

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