Double paned windows are energy efficient, certainly more so than single pane windows. However, there are still many factors to consider when choosing double paned windows. One is their UV coating or glazings. The application of a coating greatly decreases the amount of UV rays that get through the glass. The amount of UV coating should increase if you live in hot climates, and decrease if you live in colder climates. Framing is another consideration. In colder climates, wood, vinyl or fiberglass framing materials should be used and panes should be gas-filled. In hotter climates, aluminum framings and air-filled windows will work.