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Best performing double-pane window from an energy standpoint?

joenorm | Posted in General Questions on

There are so many considerations in buying windows. I am probably not going to shell out for triple pane. So who are the best double panes from an energy standpoint?


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  1. Expert Member
    Dana Dorsett | | #1

    Double low-E double pane glass with argon fill works well in locations where it doesn't get down to negative double digits Farenheight very often. The second low-E coating on surface #4 (the surface of the glass in contact with the indoor air) reflects heat back to the room in winter, and emits less heat into the room when the glass is warm in summer. The internal low-E coating on surface #2 ( the indoor-facing surface of the exterior pane) can be selected to be either heat rejecting (for cooling dominated climates) or for high solar gain (cold climates). The U-factor of that glass is usually about U-0.20, comparable to many triple-panes, independent of the solar heat gain coefficient (SHGC.)

    Cardinal Glass has a range of options with SHGC from sub 0.2 to over 0.5 with their i89 coating on surface #4 (but there are others.) Several window vendors use that glass, including Pella & Andersen, but also regional players like Harvey. See pages 13 &14 (16 & 17 in PDF) in this bit o' marketing fluff:

    From the middle of US climate zone 6 or colder the surface #4 coating creates condensation issues when it's well below 0F outside. By reflecting the heat back into the room less heat is absorbed by the glass, and it's temperature runs a few degrees cooler than a single low-E double pane. When there is condensation forming on the surface it reduces the effectiveness of that coating, and puddles of condensation can form on the window sills during extended negative double-digit F cold snaps.

    1. RussMill | | #2

      What brand suggestions do you have that offers those options?

      1. Expert Member
        Dana Dorsett | | #4

        What, Harvey, Pella, and Andersen aren't a sufficient number of brand suggestions?

        With any manufacturer find out if they have double pane glazing options that include low-E coatings on both surfaces #4 & #2, with argon fill.

        1. RussMill | | #5

          I apologize Dana i read right past it. I see it now. THANKS

  2. harrison55 | | #3

    I bought a set of OKNA windows, and have been very happy so far.OKNAs are "premium vinyl" windows with good thermal performance and truly excellent performance on air infiltration.

    OKNAs cost far, far less than a Marvin fiberglass window, and perform better. They make affordable triple pane windows, too. See info attached.

  3. Expert Member
    Peter Yost | | #6

    Try the Efficient Windows Collaborative selection tool:


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