Window film is only for single pane glass.

False! Window film is for any single or double pane window unit that needs greater efficiency and where thermal stress is not an issue.

Generically speaking, double pane units are more energy efficient than their single pane counterparts. However, the difference in efficiency is greater during the winter than it is in the summer.

As you can see, there is a much greater drop in U-Value, a measure of wintertime efficiency, than there is SHGC, a measure of summertime efficiency.

The addition of window film can help reduce a single pane window’s U-Value and SHGC to approximately that of a double pane unit. And the addition of window film can help reduce a double pane window’s U-Value and SHGC to approximately that of a triple pane unit — all without the significant cost, burden, and disruption of window replacement.

However, a window’s performance characteristics don’t necessarily determine whether occupants inside will be comfortable against unwanted heat gain or loss. It is quite feasible that an energy-efficient window is not efficient enough to mitigate against the effects of unwanted heat gain or loss for a particular building. And that is where window film presents itself as a great retrofit solution. Because no matter how efficient a window, window film will lower its SHGC and U-Value.

Important to note is that installing the wrong film on the wrong window can cause thermal stress breakage. For example, installing an interior applied window film on triple pane glass is most likely going to cause thermal stress breakage. Your 3M Authorized Window Film Dealer is trained to identify situations where thermal stress may be an issue. As such, 3M Company requires its dealers to perform a 3M Glass Checklist in certain situations, whereby information specific to a given building or home is entered into 3M’s Glass Checklist system to see if there is a possibility of glass breakage due to thermal stress. Assuming the 3M Glass Checklist system provides approval and the film is installed, 3M offers a glass breakage warranty against thermal stress. Please be sure to check warranty terms and conditions.