Visible Transmittance Windows
Our guide to visible transmittance windows explores how window glass transmits and/or reflects light and its effect on window ratings. Visible transmittance or VT is a measure for how much visible-spectrum light enters through a window. The higher the VT value, the more light enters through the window. The lower the VT value, the less light is trasmitted. VT is a lesser explored window rating than others such as U-factor, air infiltration and SHGC. However, visible transmittance can make a huge difference in how well light enters the home and how this affects the brightness inside.
Review By John M. - Site Editor Publish Date: October 29, 2021
Last Update: November 12, 2025
The ideal Visible Transmittance rating is the highest visible transmittance number you can achieve, while synonymously achieving the best U-factor and SHGC numbers. So, how does this work? Typically, the best solution is a simple low-e glass, which allows a VT around 50 to 55, while still achieving good energy efficiency ratings. Generally, ere are some generic numbers consumers can expect with with various types of window glass. Clear glass will allow 78% to 84% visible-spectrum light through the window (high VT, not very efficient). Low-e II glass allows in 72% visible-spectrum light. Laminate glass allows in 79% visible-spectrum light. Lastly, a triple pane low-e 3 with a tint will allow in 48% to 54% visible-spectrum light (low VT, very efficient).
Visible Transmittance Rating
Here are the associated costs with upgrading from clear glass to other glass options. As the cost goes up, the visible transmittance goes down. However, the energy efficiency of the windows improves.
Glass Window Costs
Clear Glass - Included
Low-e Glass Upgrade - $75 per window
Glass Low-e II Upgrade - $100 per window
Low-e III Glass Upgrade - $125 per window
Here are some real world examples of visible transmittance windows ratings. Of course, VT numbers change just as soon as you change up your glass package. A good rule of thumb for consumers is to ask the sames person for a list of their different glass packages and options and the accompanying VT numbers.
Visible Transmittance Windows Ratings
Amsco Vista Series » .26 VT ::: Loewen Cyprium Series » .31 VT
Alpen Zenith Series » .43 VT ::: ProVia Aeris Series » .47 VT
Soft-Lite Starmark Series » .50 VT ::: Sunrise Essentials Series » .56 VT
Below, you'll find homeowner questions related to visible transmittance. Additionally, if you have a question this subject (or anything else), please get in touch with us using the email link found above.
Hi John, I have some pricing and performance numbers for you to take a look at and please give me your opinion. In particular we are interested in getting windows that have a good visible transmittance as our current windows are really hard to see thru. Thank you. I picked a 28"x38" window for apples to apples comparison.
Wow, amazing price. The ProVia Endure by a mile. It's a great window. I'm still scratching my head how the Endure is the lowest price of the bunch. It's the best series on the board for the lowest price. You're making my job easy today :) Aha, smaller window, it's all starting to make sense now - still a very good price! The difference in those visible transmittance windows numbers are so small you wouldn't be able to tell the difference.
Visible Transmittance Windows Q And A
ProVia vs Viwinco VT Numbers
Provia endure. $314. U .27, shgc 19. vt .45
Viwinko Cambridge $487 U .28, shgc .17, vt .40
Viwinko Cambridge Northern glass package $487 U .30, shgc .38, vt .48
Harvey Classic U .28, shgc .28, vt .49
Harvey Tribute U .29, shgc .25, vt .45
Evelyn - Homeowner - November, 2025
Website Editor's Answer
Editor John M. - November, 2025