How to keep cool without costing the Earth

A new material can cool buildings without drawing power or using refrigerant. It costs 50¢/square meter and 20 square meters is enough to keep a house at 20°C when it's 37°C outside...
http://www.economist.com/news/science-and-technology/21716599-film-worth-watching-how-keep-cool-without-costing-earth