Conscious Choice: Window Films Can Reduce Summer Heat

August 2002 | Sensible Home

Window Films Can Reduce Summer Heat

by James Dulley

Dear Jim: The sun’s heat and glare are uncomfortable coming through the windows and are also fading my furniture and carpeting. Will applying clear inexpensive insulating window film minimize these problems? — Jack N.

Dear Jack: 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. They also reduce heat loss during winter and make sitting by a window more comfortable year-round. Insulating window films are not totally clear, but the tint in some is so slight as to be barely noticeable. All window film makes glass more shatter-resistant and safer around 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 (DIY) 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 ten years or more. 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 DIY and professional films from companies that offer both is the type of adhesive used. On all but the largest windows, which require more installation skills, DIY application looks just as good. Another advantage of professional installation is a long 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 superefficient replacement window glass. The 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 savings vary widely for different window films, so don’t just buy the cheapest film you find. Compare the film properties first. The emissivity is a key factor to determine year-round insulating/comfort value. The shading coefficient indicates how much heat/glare are blocked. If you can wash a window, you can easily install insulating window film yourself. You purchase the film, in a roll or in boxes, and a simple installation kit. Most films have a water-activated adhesive on one side.

Write for (or instantly download) Update Bulletin No. 617, buyer’s guide of seven DIY (plus a small sample) and professional film manufacturers (thirty-four films) listing savings/comfort properties and installation instructions. Please include $3.00 and a business-size SASE. James Dulley, Conscious Choice, 6906 Royalgreen Dr., Cincinnati, OH 45244.

Dear Jim: Several of our thermal-pane windows have developed leaks and there is a fog between the panes of glass. Is it possible to repair them or do I have to replace the entire window sash? — Andy N.

Dear Andy: It is very difficult to repair windowpanes to clear out the fog. You must get the panes apart, clean out the fog and the glass and reseal the panes with dry desiccant between them. It is also dangerous to work with the glass.

It would be much better to replace the glass assembly. Whether or not you have to replace the entire sash depends on the design you have. With the vinyl casement windows in my home, I can remove the panes from the sash.

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