Okay, there are vinyl windows. There are some thermally broken aluminum windows. The aluminum actually has the polyurethane spaces between the inside and the outside. There are wood windows. There are fiberglass windows. There are composite windows, which are a relatively new product. Glass and the window are different parts of energy efficient windows. They are both important. The technology is improving for both of them. I mean the glass has improved, and the window frames have improved. Most vinyl windows today are actually fusion-welded together, meaning the frame parts are all welded together making them very strong. There are mechanical windows which are all screwed together, which over a period of time expand and contract. So there are a lot of different types of energy efficient windows out there. Even the weather stripping on the windows is a consideration. There are different weather stripping treatments for different windows. There are different characteristics of how windows are assembled.
