Window Film Can Reduce Energy Costs

Tuesday March 8, 2011
Posted at 08:14

High-reflectivity window film, also called solar window film, can be an affordable way to start saving energy and saving money on your monthly electric bills without spending a lot to upgrade your home’s windows, like you would with solar-control glazed, or low e2 coated, glass.

How Window Film Helps Cut Energy Costs

After-market solar window films work by blocking the sun’s ultraviolet (UV) light - and, with some film types, the sun’s infrared light - while allowing visible light to pass through. As light enters your home, less heat enters along with it, allowing you to use less energy to cool your home.

How effective window films can be at saving energy are usually determined by three main factors:

- the size of the window — the greater the window surface area, the more window film will help when it comes to saving energy
- whether the window is on the north, south, east, or west side of the house — east and west sides of homes get the most sunlight and, therefore, stand to benefit the most from window film
- climate — because window films also help prevent the sun from heating your home when it’s cold outside, and might cause you to spend more on heating bills, window films work best in warm climates

The Benefits of Window Film

Using window film to decrease the amount of UV and infrared light that enters your home offers several benefits:

  • reduce your monthly electricity bill by lowering the amount of energy your air conditioner uses to cool your home
  • increase your comfort by getting rid of hot spots and reducing glare inside your home
  • protect your health by lowering your exposure to harmful UV radiation
  • protect your home by reducing the amount of light that can cause fading in furniture, carpets, draperies, wood, and fabrics
  • increase the shatter resistance of windows, which decreases the danger from accidents while increasing the ease with which accidents can be cleaned up

How Window Films are Rated

There are several different types of high-reflectivity and solar window films, from those that look clear and only block UV light, to those that look almost like mirrors and block all sorts of solar heat gain.

All window films are essentially laminates of polyester and metalized coatings that are adhered together. Some window films have little or no metal in them, while others have several different types of metal in order to block different types of invisible light energy, such as UV and infrared light, that contribute to solar heat gain.

Window films are rated for Visible Transmittance (VT) and Solar Heat Gain Coefficient (SHGC) by the National Fenestration Rating Council.

Visible Transmittance measures the amount of visible light that passes through a particular type of window film. A particular film’s VT rating is expressed as a number from 0 to 1. The higher the number, the more visible light passes through the film. Tinted films will have a lower VT rating, while more translucent films will have a higher VT rating.

Although many homeowners look for a low VT rating to maintain the appearance of their windows and the amount of natural light in their homes, window film with a high VT rating could be preferable for homeowners looking to use window film to increase privacy as well as save energy.

Solar Heat Gain Coefficient measures the amount of heat admitted through a particular type of window film. Like VT, SHGC is also expressed as a number from 0 to 1. The lower the number, the less heat passes through the film.

The Cost of Window Films and Installation

Window film costs range from about $3 to $12 per square foot for the film and about $1 to $5 per square foot for professional installation. Warranties on window film vary by manufacturer. Some manufacturers only offer warranties if their window films are professionally installed, while others encourage do-it-yourselfers. Be sure to check out warranty information carefully.

Sources

- Energy Savers website, “High-Reflectivity Window Films.”
- House-Energy website, “Window Films.”
- International Window Film Association website, “Benefits of Dealer Installed Window Film Products for Residential and Commercial Buildings.”

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