ARTICLES
Window film
Some windows have a dark side: They can damage a home's interior by letting in too much unfiltered sunlight. "Over the years, sunlight completely destroyed my mother's living room carpet and couch," says Sunset's style editor, Yvonne Stender. She also recalls that heat buildup in summer and heat loss in winter made the room uncomfortable. To solve these interrelated problems, her mother had the original windows retrofitted with state-of-the-art solar window film.

Fading is caused mostly by the sun's radiant energy; ultraviolet light causes the most damage. The best window films block almost 100% of the UV light, while admitting most of the desirable light spectrum. They also reduce glare and solar-heat loss or buildup, add privacy, lower energy bills, and even add resistance to shattering.

Not all solar films perform the same way, and you can select certain types to solve problems related to your particular climate and exposure. For instance, people living in the Southwest need to keep the desert's heat and glare out of their homes, while homeowners in mountain states often need to brighten their interiors and keep heat inside during winter months.

What's in a film
Solar window film is a high-tech laminate of a thin coating bonded to a clear polyester backing with an adhesive on one side; it's usually applied to a window's interior surface. The coating can be made of a number of materials, such as metals or even ceramic, that give it different appearance and performance characteristics; it's protected by a scratch-resistant outer layer. Most films are tinted, but a variety of shades have been developed to please different tastes. Low-emissivity (low-e) film prevents heat loss in winter months and has a metallicized look.

Check with the manufacturer for warranties before purchasing, to ensure that the product will not bubble or warp. After cleaning the interior side of a window, an installer will remove the film protecting the adhesive then spray it and the window with water, slide the film into place, remove the water with a squeegee, and cut the film to fit. The adhesive dries clear.

An experienced professional can help you find the right film for your needs and may bring samples of different films applied to real glass so you can see differences in appearance. An installer also can bring meters that measure levels of UV and infrared radiation.Cost varies depending on the type. Figure $6-$12 per square foot, including installation.Treat and clean the film like any glass surface.Before adding film to double-glazed windows, ask the window manufacturer if it affects any guarantees.