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bpchiil

Question Regarding Visual Transmittance

bpchiil
10 years ago

Last year I replaced a patio door (sliding - double pane) that has a VT of .44.

I will be replacing windows (triple pane) that have a VT of .42 - will the exterior visual difference between the two be negligible?

Thank you.

Comments (5)

  • PRO
    Windows on Washington Ltd
    10 years ago

    Yes.

    A 0.02 VT difference is not perceptible to the naked eye in my opinion.

    Keep in mind, VT is of the unit in total and not the darkness of the glass if you are comparing NFRC numbers.

    If you want the most accurate comparison, you need to know the VT on the glass packages themselves.

  • bpchiil
    Original Author
    10 years ago

    WoW thanks.

    Darkness of the glass - how is that measured?

  • PRO
    Windows on Washington Ltd
    10 years ago

    You need to get the glass specifics, i.e. what glass package is specified.

  • TheWindowDog.com
    10 years ago

    The company providing the windows should be able to tell you the VT rating of the glass alone. For example a typical 1" IG with 2 surfaces of SolarBan 60 low-e will have a VT rating of .57.

    Windows on Washington is exactly right that the VT rating for the whole window or door doesn't really tell you about the look of the glass. The rating for the whole unit takes into account the thickness of the frame and any grids in the glass.

    A VT rating of .44 for a double pane patio door seems a little low, but without knowing more about the door it's hard to say. If it has grids in the glass or if it's a French door instead of a sliding door the .44 starts to make more sense.

    Some companies do use darker coatings in order to achieve better ratings so there certainly is a possibility that the glass in the windows will look different than the glass in the door.

    It sounds like you're already ahead of the game, but for anyone just starting to sort through VT ratings we've recently posed some basic info.

    If you can't get the rating of the glass alone in the door you already have another easy way to be sure you'll like the look is to get a sample of the window so you can see for yourself how similar the glass is. If you open the door and set the window sample in the opening your question will be answered immediately!

    Here is a link that might be useful: VT Ratings Explained

  • bpchiil
    Original Author
    10 years ago

    Yes grids in patio door - Sunrise

    The windows will be Okna (Enviro Star) triple pane