Color-changing roof tiles

Color-changing roof tiles are just what environmentalists want – after all, having roof tiles that will change color (e.g. white when it is hot and black when it is cold) could potentially eliminate a whole lot of greenhouse gas emissions, where white would reflect the sun’s heat during the summer while turning black during the winter to absorb as much heat as possible. Initial tests of these smart roof tiles show that they are able to reflect around 80% of the sunlight falling on them when white, and reflecting around 30% when black – translating to a savings of up to 20% of present cooling costs. Where do we sign up?