- Look for Low-E coatings on the glass. These coatings reflect heat inside your house and reflect UV rays from the sun outside your home. They have a slight tint that may or may not be visible depending on how dark you want the tint to be. In colder climates, the coating is applied to the inside panes of glass, while in warmer climates, the coating is applied to the outside of the glass.
- Casement and awning windows are the most energy efficient because they clamp more tightly against the weather stripping on the frame than double-hung windows.
- Look for windows with multiple panes of glass separated by low-conductive argon or krypton gas filling and warm edge spacers with tightly constructed frames.
- The best weather stripping on any kind of operative window is a compressible gasket type much like you would find on your car doors. The weather stripping combined with a quality latch will effectively keep out cold air and rain, plus keep warm air in in winter.
- Look for windows with low U-values or U-factors. These windows have the best insulating properties.