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By James Dulley, Published August 07 2009

Removable window film helps keep out the heat

Dear Jim: A lot of heat and glare comes in my windows. It makes the air conditioner run more and us uncomfortable. I don’t want permanent window film because I want winter solar heating. What are my options? – Katie J.

Dear Katie: Everybody knows the summer sun’s heat comes indoors through windows, but they often do not realize how much.

Not only do many windows have an insulating R-value, which is only about one-tenth that of a wall, but they also allow the sun’s radiant heat in. This heating is significant and does make your air conditioner run much longer using more electricity.

This also impacts your electric rates. Utility companies have to invest millions of dollars extra to provide enough electric-generating capacity just for the peak afternoon demand. The rest of the time, it is not needed. By decreasing your afternoon air-conditioning load, this will help delay the need for new generating plants. This can minimize or delay rate increases.

Installing permanent window film on the windows is very effective, but being permanent, it cannot be removed for free passive solar winter heating. Some of the newer nearly clear low-emissivity permanent window films reduce summer heat gain and also reduce winter heat loss back outdoors. Even though they block some solar winter heat gain, they save overall.

Removable window film is another option. You can install it on your south- and west-facing windows in early spring and remove it in the fall. If you take care of it, it can be reused for many years and it will not lose its effectiveness.

Most removable window film adheres to the window glass by means of a static cling. The natural properties of the tinted film, often vinyl, create a static charge to make it stick to the glass. This is similar to the film labels you see on new television or cell phone screens.

This film is often available in a bronze or smoke tint. It is best to install it on the indoor surface of the window glass. Clean the window thoroughly and squeegee the window while it is still wet. Since the film is tinted, do not use it on double-pane windows. In the direct sun, the absorbed heat may make the glass panes too hot and the seal between them may fail.

Another static-cling film option is film imprinted with stained or etched glass or floral patterns. These are very attractive. Although the nearly clear etched-glass patterns do not block as much heat as tinted film, they do block some heat. They also reduce the sun’s fading ultraviolet rays coming through the glass.

Another option is a roll-up sun-control shade. The most effective ones slide in vertical side tracks in the window opening. These can use special sun-control fabrics, screening or window film material.

The following companies offer removable window film and shades: Artscape, (877) 729-0708, www.artscape-inc.com; Etch Art, (800) 320-8439, www.wallpaperforwindows.

com; Gila Film Products, (800) 528-4481, www.gilafilms.com; Halcyon Shades, (800) 234-2280, www.halcyonshades.com; and North Solar Screen, (866) 230-4700, www.northsolarscreen.com.


Dear Jim: Our house is built into a hill for energy efficiency. This provides us with a daylight basement. We want to add air conditioning to the basement, but do not want window units. What are our options? – Patty F.

Dear Patty: Building a house into a hill, called earth-bermed, is energy efficient. I am surprised your basement does not stay cool, but perhaps the sun warms it through the glass during the afternoon.

A mini-split ductless system is probably your best cooling option if you do not want a window unit. These systems have the cooling coils and blower mounted up on the wall. The outdoor compressor is connected to it with a small refrigerant tube and wiring.


Send inquiries to James Dulley, The Forum of Fargo-Moorhead, 6906 Royalgreen Drive, Cincinnati, OH 45244, or visit www.dulley.com