Window films (applied to the glazing surface) help block against solar heat gain and protect against glare and ultraviolet exposure. They are best used in climates with long cooling seasons, because they also block the sun's heat in the winter.
They can be useful for homeowners who don’t want to block views with other window treatments, but who have issues with glare and solar heat gain. They can also be a good choice on windows that are difficult to fit with other window treatments, or in places where artwork, furniture, or carpeting could be faded by UV exposure.
Films typically have three layers: an adhesive layer that sits against the glass, a polyester film layer, and a scratch-resistant coating. You may also choose options such as tints, UV blockers, or thicker films that offer security. Low-e films are also emerging as an energy-saving option.
Window films are rated by the National Fenestration Rating Council (NFRC), which also created window labeling and ratings for consumers. The NFRC’s Window Film Energy Performance Label looks like this: