Scientists are reporting development of a “smart” roof coating, made from waste cooking oil from fast food restaurants, that can “read” a thermometer and help save energy. 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. Scientists described the sustainable material at the 239th National Meeting of the American Chemical Society in San Francisco. Intro theme and music by Kevin MacLeod. Creative Commons licensed audio from freesound.iua.upf.edu.