While still in the developmental stages, nanopaint is seen as an effective means of dealing with a number of different issues. As an example, the application of nanopaint on the exterior of a building could be used to block infrared rays and thus help to keep the interior of the space cooler, while also making it possible to absorb solar energy on days that are sunny but cool.
http://www.wisegeek.com/what-is-nanopaint.htm