Window Films
(Window Tints)
Installing a reflective film - commonly named window films,
window tints or solar films - over non-efficient windows, skylights
or doors with clear glass can reduce cooling costs by 5% to 15%.
In fact, according to
US DOE EERE,
over 25% of the heating and cooling energy bills in a typical
home are due to inefficient windows, skylights and doors.
Clear single glass is highly inefficient and causes too much
energy to be lost and too much undesirable sunlight to enter in
homes (damaging carpets, furniture and so on).
By applying window/solar films to the inside of windows or
glazed doors and skylights, you can cut most of harmful ultraviolet radiation
and solar heat gain (up to 75 percent), without reducing
visibility.
Modern solar films: what are
they?
Solar films / window films / window tints 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.
Window films are a proven low-cost method for reducing cooling
bills. Many of the benefits of solar-control glazing (low-e
coating or lowe2 coating) can be obtained by applying
after-market films to common non-efficient windows.
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
The
North American NFRC label for
residential windows, skylights and glazed doors includes two measures on energy performance:
the SHGC (Solar Heat Gain Coefficient) and the VT (Visible
Transmittance) coefficients.
The Visible Transmittance (VT) is
a measure of
the amount of visible
light passing through a windows or door. VT is expressed as 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 solar radiation
admitted
through a window or door. The SHGC is expressed as a
number between 0 and 1. A lower Solar Heat Gain Coefficient
means less solar heat and more shading.
When looking for home window films,
choose those
with the higher VT and the lower SHGC.
Solar/window film
prices
The solar film prices range from $3 to around $12 per square foot.
Warranties
Warranties can vary a lot, depending on manufacturers. Warranties
of 5 years are common, but some manufacturers offer a lifetime
warranty.
Professional installation or
do-it-yourself?
Some window film manufacturers require professional installation
in order to offer warranties, while others promote
do-it-yourself installation.
Installed costs of window films range from $1 to $5 per square
foot.
Alternatives to window films
Solar screens -
made of
vinyl-coated polyester, typically mounted with screws on the
exterior side of the windows... -
are a common alternative to window films.
Exterior overhangs or sunscreens, interior blinds and devices as
shades and draperies can be to a certain extend other types of alternatives
(see: House
Awnings, blinds...).
Efficient windows and doors with double and triple pane Low-E
coating glass and Low E2 glass (also called solar low-E, or
spectrally selective glass) are other more radical alternative. See:
Glass and windows
Tax Credit for Solar Films
USA Energy Policy Act of 2005 provides to homeowners a 10
percent credit on window film costs, up to $500 (purchases done before Dec. 31).
See
also:
Windows, Doors and Skylights basics
Frames and sashes
Glass panes
Advanced Doors
Skylights
Weatherstripping
Caulking
Rebates and Tax Credits
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