Understanding Residential Window Tint and How It Works


Understanding how heat enters your windows is important when it comes to deciding which window tint will work best for you.

Window tint can be an effective tool in combatting high energy costs, but before deciding on what film works best it is important to understand how residential window tint works, and more importantly how it reduces heat coming into your home. Basically heat enters through your windows in three ways; Infrared Light, Visible Light, and Ultraviolet Light.

Ultraviolet (UV), harmful to people and building interiors, makes up 3% of the solar energy. Although we can’t see UV rays, we feel them. UV radiation can cause skin damage and can fade and degrade some materials. There are three types of UV:

UV-A – About 99% of the ultraviolet radiation that reaches the Earth’s surface, UV-A contributes to 15-20% of a sunburn.

UV-B – Sun burn and skin cancer can be caused by UV-B.

UV-C – Although the highest-energy and most dangerous type of ultraviolet light, UV-C is absorbed by the atmosphere.

Visible Light (VIS) accounts for 47% of solar energy and determines the general look and color of the light you can see, including the glare. Each color has its own wave length within the electromagnetic spectrum, with violet as the shortest wavelength. Without VIS, we would be unable to see.

Finally we have Infrared, which we experience as heat. Infrared is invisible to the human eye and makes up 53% of the spectrum. This radiated energy from the sun represents a majority of the heat you feel in your car on a bright day or in a room that receives direct sunlight through an untreated window.

Taking into account all of these heat sources it is important to look at the Total Solar Energy Rejected or TSER.

When sunlight strikes glass, solar energy is either transmitted through the pane of glass, absorbed by the glass or reflected away from the glass. Solar Transmittance refers to the amount of solar energy (visible, infrared and ultraviolet) that passes through a glazing system, expressed as a percentage.

So when measuring the effectiveness of window film, the TSER is the number to closely examine. The TSER reflects the true performance of solar heat gain or rejection through a window into a building, and its calculation includes IR rejection.

The TSER value includes two elements of heat gain through a window. The first is the amount of radiation directly transmitted thru the glass and entering the home. The second element is the amount of radiation that is absorbed by the window, and subsequently re-radiated into a home. Some window films and coatings operate by absorption, which blocks radiation and converts it to heat energy in the window pane. The higher the absorption of a window or window film, the more blocked heat it re-radiates into the home as the window heats up.

So a high TSER and low ABSORPTANCE percentage are always the most desirable numbers you can aim for when selecting window film.

Some films, like Ceramic films can reject considerable heat without a high absorptance number. A film we like to install is a product called IRIS 70 made by GEOSHIELD.

It is a virtually clear film, and yet it reduces up to 52% of the sun's total solar energy! Clear films offer a very low absorptance percentage.

If you have more questions about what film is best for your home feel free to call us at 210-669-2940. Fletch Window Tint has been installing window tint since 1989 and we will be happy to assist you in making the right choice in residential window tint.


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