This was one of the coolest things at the show: the KSD window from Eco-Logical Innovations. The window consists of three panes of glass. The key feature, though, is the green pane of glass on the outside. It reflects heat. When the green side it turned outside, toward the sun, it reflects heat from the sun back to the outside, keeping the house cool. In winter, you can pivot the window to bring the green side in. In that case, it keeps the heat from escaping. They have been on sale for a few years in Germany and are just coming to the U.S.