window films

Window films are a proven low-cost method for reducing cooling bills. Many of the benefits of solar-control glazing (low e2 coating) can be obtained by applying after-market films to common non-efficient windows.

Modern window films

Modern window films are a laminate of polyester and metalized coatings, bound by adhesives. The films are able to isolate and reject invisible infrared and ultraviolet radiation and the correspondent heat.

Typically, window films are attached to the interior of existing windows, skylights or glass doors.

Just look for the latest technology in spectrally selective films. They allow daylight to enter in your home while blocking solar heat gains. Take into account their VT and SHGC coefficients in official labels.

NFRC labelling

When looking for home window films, choose the ones with a higher VT and the lower SHGC (NFRC rating).

Note: The Visible Transmittance (VT) is a measure of the amount of visible light passing through a windows or door. VT is expressed by a number between 0 and 1. An higher VT is a good indicator, since it means more transmitted light without undesirable heat gains. The SHGC (Solar Heat Gain Coefficient) is a measure of the heat admitted through a window or door. The SHGC is expressed by a number between 0 and 1. A lower Solar Heat Gain Coefficient means less solar heat and more shading.

Solar/window film prices and warranties

The solar film prices range from $3 to $12 per square foot. Warranties also vary a lot. Warranties of 5 years are common, but some manufacturers offer a lifetime warranty.

Professional installation or do-it-yourself?

Installation costs range from $1 to $5 per square foot. Some window film manufacturers require professional installation in order to offer warranties, while others promote do-it-yourself installation.

Alternatives to window films

Cooling bills can be reduced by other means. The advantage of window films is on their price. They are relatively efficient and cheap and easy to install. But efficient windows (or glass doors) with a good Low E2 glass (also called solar low-E, or spectrally selective glass) are a more long-lasting and efficient way of reducing air conditioning bills. Prefer that alternative, if your are going to install new windows. See: Glass and windows.

Solar screens - made of vinyl-coated polyester, typically mounted with screws on the exterior side of the windows... - are another common alternative to window films.

Exterior overhangs or sunscreens, interior blinds and devices as shades and draperies can also be - to a certain extend - other types of alternatives (See: Awnings, blinds...).