Over 80% of the window area is glass. That’s why the quality of glass is crucial to its energy efficiency and overall window performance. Most homeowners, while well aware of importance of energy savings resulting from high-performance windows, don’t understand what makes a window a highly energy efficient one.
No double pane window would currently meet these new more stringent Energy Star criteria. However, most triple glazed windows with argon or krypton gas fills already meet or exceed these new criteria planned for 2013. Some manufacturers experiment with other technologies such as heat mirror films in between two panes of glass.