Window films can reduce your cooling bills

Posted7/12/2019 7:00 AM

Q. My single-pane windows are still good, but much heat comes in during summer and it's chilly near them during winter. Would installing one of the newer year-round or heat-control window films help much?

A. Installing window film can be an effective method to improve the efficiency of your window glass. The newer window films are neither highly reflective nor darkly tinted, so your house will not look like an office building with mirrors for windows. Some of the films are barely perceptible.


The newer energy-control window films use a technology similar to super-efficient glass in new replacement windows. A low-emissivity coating, which is a several-atom thickness of metal, is applied to the film. Easily visible light passes through the coating, but it blocks heat energy.

The amount of tint applied to the window film also changes the amount of the sun's heat that passes through the glass. With the low-emissivity coating on a dark film, a high percentage of heat and glare is blocked. This type of sun-control film is typically used in hot climates.

For homeowners who wish to save energy year round, a very lightly tinted window film is best. This type of film barely alters the view outdoors, but it blocks some summer heat in addition to heat loss during winter. Also, during winter, it still allows some free passive solar heat in through the window and it reduces that chilly feeling when you are near a window.

A secondary benefit of installing window film is it blocks the majority of the sun's UV (ultraviolet) rays that fade curtains, furniture fabrics and carpeting. Many homeowners install the nearly clear window film solely for this purpose. Another benefit of film is it reduces the possibility of glass shattering from an impact. This is a safety plus around children.

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If you have double-pane windows, check with your window manufacturer before installing window film. Dark films can warm the glass, which may affect the airtight seal between the panes. The nearly-clear films do not cause much heat buildup, but still check to make sure about the glass warranty.

Do-it-yourself window film kits, including a squeegee and application tools, for various-size windows are available at most home center stores. The film is also available on large rolls so you can buy as much as you need. For summer heat control, the west- and south-facing windows are most important to do. Awnings are also effective over windows on the south side.

Installing the film yourself is not difficult. There is a water-activated adhesive on the window film. Make sure the glass is very clean and the film is thoroughly wet. Apply the film and carefully run the squeegee over it to force out all the bubbles to the edges.

The following companies offer energy-saving window films: 3M,, (866) 499-8857; Gila Films, (800) 528-4481,; Madico, (800) 456-4331,; Plastic-View International, (800) 468-6301,; and Solar Gard, (877) 273-4364,


Q. When I build an addition on to my home, I plan to use rigid foam insulated sheathing on the outside of the wall studs. Will it harm the efficiency to use more nails and fasteners for a stronger wall?

A. Adding more nails and metal fasteners than recommended by the manufacturer does not produce a better wall. It is usually best to follow the foam manufacturer's instructions or building code requirements.

Any metal fasteners decrease the effectiveness of rigid foam insulation. Using just the recommended number of nails and fasteners (on 8-inch centers) can reduce the overall insulation value by 5% or more.

• Write to James Dulley at 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit

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