The Efficient Windows Collaborative (EWC) operates this informative site about the benefits and energy saving characteristics of efficient windows. A good overview of the various types is given in the How Windows Work section. This explains many different glazings, frames, and operating designs of the windows. The three main technologies used to improve insulating performance are covered, and another section highlights some advantages of efficient windows. The Web site also offers fact sheets with statistics for various cities around the US. If users are interested in switching to efficient windows for their homes, there is plenty of information about how to make the best selection.