What does a VLT number tell you?
It tells you how much daylight reaches your eyes through the glass, and nothing about heat. A 35% window passes about a third of the visible light falling on it; a 5% window passes a twentieth.
3M’s Color Stable brochure puts it plainly in its “Terms to Know”: VLT is the visible light “that passes directly through filmed glass: the higher the number, the lighter the film.” Glare reduction is closely tied to it: LLumar’s performance data sheet lists ATC 05 at 5% VLT and 94% glare reduction.
Heat sits in separate columns. Clear AIR 80 lets 77% of visible light through and still rejects 60% of infrared energy, while dyed ATC 50 lets 60% through and rejects only 22%. For the overall heat figure, see TSER.
How is VLT measured, and why don’t film names match?
Film makers measure it in a lab on a standard pane, so every shade is compared on equal terms. LLumar captures its numbers to NFRC guidelines on a single 6 mm sheet of clear glass, and the code on the box is a product name, not the result:
| LLumar film | Measured VLT |
|---|---|
| ATC 05 | 5% |
| ATC 50 | 60% |
| IRX 05 | 6% |
| IRX 50 | 54% |
| AIR 80 | 77% |
| AIR 90 | 84% |
The angle you look through matters too. In a 1995 Federal Register notice, NHTSA explained that the US glazing test shines light square to the glass, while a driver looks through it at its installed slope, where less gets through: windshields that passed at 70% or more measured as low as 63% along the line of sight.
On a car, a tint meter reads glass and film as one, and the two transmissions multiply. Film rated 50% over glass that passes 80% leaves about 40%. The tint stacking calculator runs that sum, and the meters themselves are covered in how tint percentage is measured.
Does VLT decide whether tint is legal in BC?
No. BC writes no VLT percentage into its tint rule. MVAR s. 7.05(8) sorts glass by position instead. Behind the driver, side windows may take film of any VLT; so may the back window, provided mirrors are fitted left and right; and the windshield may carry a strip that ends within 75 mm of its top edge. The two front side windows get none, AIR 90 at 84% included.
A percentage only enters for glass tinted at the factory, which s. 7.05(9) holds to the federal safety standard; its visibility figure is commonly cited as 70%. Washington, by contrast, sets 24% in RCW 46.37.430.
When a driver still asks for front-door film, the shop fits it only after explaining that no VLT makes it road-legal here. Mission RCMP lists $109 as the typical fine for a tint ticket, and a Notice & Order can require removal plus an inspection at a designated facility. Each window’s rule is set out in BC’s darkness limits.
Choosing a VLT for the windows behind you
Choose by how much privacy you want and how much you rely on the rear glass at night. Dyed ATC and ceramic IRX are stocked at 5, 15, 35 and 50%, with clear AIR listed at 70, 80 and 90%.
Rear-glass prices for each body style sit on the shop’s price list. Which tint percentage to get walks through the choice shade by shade, and the tint shade visualizer previews each one.