科學60秒:用屋頂保暖

Buildings consume about a third of the energy and two-thirds of the electricity in the U.S.. Roofs are a good place to try to cut those figures. Because traditional black asphalt roofs heat up in summer and strain the air conditioners. White roofs are better. But they don’t retain heat in winter, so furnaces work harder. Now scientists from the United Environment and Energy Company think they have a roof fix, which they presented at a recent meeting of the American Chemical Society. Via a proprietary technique, the researchers turn waste cooking oil into a liquid polymer, which hardens after application. As a roof coating, the polymer can reflect or absorb depending on conditions: it changes reflectivity at a particular temperature and so goes from reflecting light and emitting heat in the dog days to absorbing light and retaining heat in the cold. The company claims that the coating cools traditional roofs by 50 to 80 percent in summer, and holds on to about 80 percent more warmth than a white roof in the winter. If it pans out, the cooking oil roof coating could be a productive use for our national obsession with French fries.