Today's New York Times has a good piece on the advantages that come from painting roofs white, especially in hot climates at: http://www.nytimes.com/2009/07/30/science/earth/30degrees.html The principle, of course, is simple: white roofs would absorb less heat than those of any other color. Scientists argue about how much of a difference this would make in the colder parts of the USA, for example, in winter, when white roofed homes would have to be heated more. But there is a clear market for this in the part of the world that I come from: South Asia.
Much of India, Pakistan, Bangladesh and Sri Lanka is hot to extremely hot for most of the year. The region receives sunlight for several hours a day for most of the year. In the past, homes either had thatched roofs, or some like the one where I was born and spent the first twelve years of my life, had twenty foot ceilings in the pre-airconditioner era. Now, of course, with multi-storey apartment buildings all over the region and with booming populations forcing the construction of even more of these shoebox-stacks, one option that could help is white roofs. Hopefully, someone will take heed in that part of the world. This is as simple as an idea can get - and the savings when we consider that the region has one and a half billion residents - should be huge.
I'm keeping my fingers crossed!