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Window films provide year-round comfort

Question: The sun's heat and glare are uncomfortable coming through the windows, and my furniture and carpeting are starting to fade. Will applying clear, inexpensive insulating window film minimize these problems?

Answer: New insulating window films can reduce heat and glare by more than 50 percent and block nearly all the sun's ultraviolet rays through your windows. True insulating window films also reduce heat loss during winter and make sitting by a window more comfortable year-round.

Insulating window films are not completely clear, but the tint in some is so slight that when they are applied to the window glass, the tint is barely noticeable. All window film makes glass more shatter-resistant and safer for children. Some heavier films can also enhance security against window break-ins.

Window film is available in rolls or single window boxes for do-it-yourself application or from professional installers. Installing it yourself can save up to 75 percent of the cost of professionally installed film.

Residential window films are considered permanent because, with proper cleaning, they can last 10 years or longer. If you decide to remove the film at a later date, the manufacturers offer removal solutions that quickly dissolve the adhesive. The window glass surface is not harmed.

The primary difference between do-it-yourself and professional films from companies is the type of adhesive used. On all but the largest windows, which require more installation skills, DIY application looks as good. An advantage of professional installation, however, is a warranty.

True insulating window films derive their energy-saving/comfort properties from a low-emissivity (low-e) coating in the film. This is the same low-e technology used on new super-efficient replacement window glass.

This low-e coating is a microscopically thin layer of metal on the film's inner layer. Visible light passes through it, making it invisible. Heat energy from the sun and reflected from walkways, patios, etc., is a different wavelength than visible light and is blocked by the low-e film. During winter, it also keeps heat indoors.

Energy-saving qualities vary widely for different window films, so don't buy the cheapest film. Compare the film properties. The emissivity is a key property to determine year-round insulating/comfort value. Shading co-efficient indicates how much heat/glare are blocked.

If you can wash a window, you can install insulating window film. You purchase the film, in pieces from a roll or in boxes, and an installation kit. Most films have a water-activated adhesive on one side.

Write for or download at Update Bulletin No. 617, a buyer's guide of seven do-it-yourself (plus a small sample) and professional film manufacturers (34 films) listing savings/comfort properties and installation instructions. Include $3 and a business-sized, stamped (37 cents), self-addressed envelope. Send to: James Dulley, St. Petersburg Times, 6906 Royalgreen Drive, Cincinnati, OH 45244

James Dulley is a mechanical engineer and do-it-yourselfer. Send questions to James Dulley, The Sensible Home, St. Petersburg Times, 6906 Royalgreen Drive, Cincinnati, OH 45244. Visit his Web site at to download bulletins, tour his energy-efficient home, post questions for other readers and find other information.