First, there were "smart windows" that modulate light. Now, it's smart walls and roofs. Suntek Inc. in Albuquerque has rolled out a prefabricated building component for roofs and walls that automatically controls the amount of solar light and heat that enters a building.
The panels encase a layer of a clear plastic film composed of water-soluble hydrocarbon copolymers, which transmit solar heat and light, then turn white to reflect both. The fibers of the copolymers are elongated when cool, making them thinner than the wavelengths of solar radiation, so 90% of the sun's rays enter. When the polymers warm up, they form microscopic globs that keep out sunlight. By varying the proportion of the polymers, it's possible to set the film's transition temperature anywhere from 60F to 150F. Suntek President Roy Chahroudi says the panels can handle most space heating needs and slash air-conditioning costs.