Understanding the performance figures

Window film performance is described with a handful of standard measures. Here is what each one means, so you can compare films with confidence.

VLT — Visible Light Transmission

The percentage of visible light that passes through the filmed glass. A higher VLT means a brighter room; a lower VLT means a darker, more private look. Your eyes adapt, so a room feels brighter than the raw number suggests.

TSER — Total Solar Energy Rejected

The combined measure of solar energy the film rejects — the single best guide to heat control. The test basis (glass type and build) must always be stated, because the same film performs differently on different glazing.

Glare reduction

The reduction in visible solar glare, given as a product-specific percentage. Useful where screens or bright surfaces are a problem.

UV transmission / rejection

The share of ultraviolet light blocked. UV is the biggest single driver of fading, but not the only one — visible light and heat also contribute.

g-value

The solar energy transmittance of the glazing system — the lower the g-value, the less solar heat gets through.

U-value

The rate of heat transfer through the glazing. We avoid claiming a major insulation improvement from film alone without system-level evidence.

Reflectance (internal & external)

The visible light reflected from each face. It drives the appearance and the one-way privacy effect — a mirrored exterior comes from high external reflectance.

Absorption

The solar energy absorbed by the film and glass. High absorption raises thermal stress, which is why dark absorptive films need care on certain glazing — see our glass compatibility guide.

Micron thickness

Useful for classifying safety and security films, but thickness alone is not a certification. A film's safety performance depends on the film, the glazing and correct installation.

Still comparing? Use the Compare tool to line films up side by side, or the Film Finder to work from your goal and glazing.