Understanding Visible Light Transmission (VLT)

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Updated November 2017

As you decide about window tint for your home or office you’re probably wondering, “How dark should I go?” There are a couple of tricks to understanding the darkness or light-blocking power of window tinting, and your Homeowner’s Association may actually have regulations regarding the level of tint you use on your home. Technically called “visible light transmission”, the less light that passes through tinted glass, the darker it appears. This also dictates how many UV rays can pass through the glass.

The VLT (also called “visual light transmission”) is a crucial part in figuring out how much heat protection, UV protection, and security protection you get. Creators of films and tinting services came up with a method for measuring “how dark” a tint is. This is how the VLT was born, and there are a few things you should know about it.

Calculating visible light transmission

Visible light transmission is calculated on the percentage of light that’s visible through a tinted glass. The lower the VLT, the darker the tint, and ultimately the more light that will get blocked. For example, if a window has a VLT tint of five percent, that window only lets in five percent of exterior light. If you have a window with a VLT of 50 percent, it lets in 50 percent of exterior light.

However, there’s another factor to consider: Color. You may think of window tints as black or brown, but those are just the most popular hues—you can get a window tinted in virtually any color. The method for calculating VLT doesn’t change, but you may notice a color value attached to the calculation. For example, a green tinted window might be “green 45”. Do your research beforehand when determining the color and tint level you’d like for your home or business. Or speak with one of our technicians for their expert opinion on visible light transmission and its effect on tint levels.

How visible light transmission affects window tint

There’s more to the final VLT figure than color and calculating how much light gets through. For example, your window glass actually has a VLT factor of its own, and that needs to be calculated into the final number. Let’s say the owner of your office building allows no less than 30 percent VLT, but the existing windows are already at 15 percent VLT on their own. That means you can only “add” another 15 percent via tinting in order to comply.

Commercial window film calculated with visible light transmission levelsWhy does this matter for you as a potential tinted window owner? It helps explain why your local tinting professional might steer you away from that super dark tint you see in their display. That really dark tint is for glass that doesn’t have a naturally high VLT already. Remember that their goal is to keep you as comfortable as possible while remaining legal—no amount of tinting is worth a constant hassle with your HOA.

Need a quote for window tinting installation? Still curious about visible light transmission? Contact Pacific Window Tinting today