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.

Shingles with a "smart" coating could save energy and lower bills by adjusting to temperature changes. (Credit: Ben Wen, Ph.D.)

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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