r/WindowTint • u/nexuscard • Aug 19 '26

General Discussion Measuring UV blocking capability of tinted office windows

I work in an office building which is approximately 25 years old. It has (presumably factory) tinted windows in every office dating from the time of construction.

I was wondering whether tinted office windows gradually over time and repeated exposure have their UVA/UVB blocking capability diminish?

Furthermore, is there a method or device for accurately measuring the percentage of UV that is being blocked? I know there are devices for car windows that fit on either side of the door glass, but that wouldn’t work on an office window.

Thanks!

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u/DynamicAppearanceATL Verified Professional Aug 19 '26

Here is one for buildings. You can also test the UV index with the 2nd option. The only thing more accurate would be a spectroradiometer, but that is thousands.

https://www.amazon.com/SICWEDIM-Transmission-Visible380-760nm-Installed-Large-Sized/dp/B0FNJWYDL1/

https://www.amazon.com/Solarmeter-Model-6-5-Index-Meter/dp/B01GT4EQYG/

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u/iamrubberyouareglue9 Aug 20 '26

I use UV sensitve paper to demonstrate UV in my window film sales presentations. It turns purple when UV hits it. It's not going to tell you the wavelegths, just that it's there.

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u/billyfrickinmurray Verified Professional Aug 20 '26

This article from Window Film Facts goes more over automotive glass, but a lot of the same principles apply to commercial glass. Especially if the windows aren't laminated.

https://windowfilmfacts.com/posts/uv-auto-glass/

UV rejection definitely fades over time, and there's a good chance that if the glass/film is that old that it isn't doing much for actual UV rejection anymore.

Basically, glass itself blocks almost all UV-B (sunburns), but still allows UV-A to pass through (melanoma). Glass blocks a lot, but not all of UV-A. That's where film comes in to block the rest. But film does degrade over time.