Window film brochures are full of abbreviations. Four of them are enough to compare two products fairly.
VLT: how dark the film is
VLT (visible light transmission) is the percentage of visible light the film lets through. VLT 70% is almost clear, VLT 20% is dark, VLT 5% is very dark. This number is about looks and privacy, not heat. A darker film is not necessarily a cooler one.
UVR: protection from ultraviolet
UVR (UV rejection) shows how much ultraviolet light the film blocks. UV fades interiors and affects skin. Most quality films block nearly all of it, so this number rarely separates one product from another.
IRR: infrared rejection
IRR (infrared rejection) measures how much infrared light is turned away. Infrared carries much of the heat you feel from the sun. Compare with care: IRR can be measured over different wavelength ranges, so figures from two brands are not always like for like. Ask which range was measured.
TSER: the fullest picture
TSER (total solar energy rejected) counts all the solar energy turned away: visible light, infrared and ultraviolet together. If you can look at only one number to judge how cool the cabin will feel, look at TSER.
How to use them
- Choose VLT for the look and the visibility you are comfortable with, especially at night
- Compare TSER at the same VLT
- Ask the dealer for the spec sheet, not only the number on the banner