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Skinny triple pane IGU window availability

alankchan | Posted in Green Products and Materials on

I’m renovating a my first house and about a quarter of the windows have had the seals fail and are all fogged up on the inside. Since they’re double-pane windows, I was wondering if there’s anyone in the US that’s making triple-pane drop-in IGU’s:

There was a government study published in 2018 but I haven’t been able to Google any glass company that actually makes these “Skinny-Triples” that could be drop-in replacements to the 7/8″ thickness IGU’s I have. Is Skinny-Triple pane IGU’s vaporware? I’m in Southern California so maybe a glass dealer local to the area would be great but if there isn’t a glass dealer in the US that makes them yet, then the point is moot.

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  1. Expert Member
    BILL WICHERS | | #1

    Skinny triples don’t gain much relative to their cost — the air gaps are just too narrow for good efficiency. The best triple panes commonly available are 1-3/8” thick. There is also a compromise 1-1/8” thick triple pane. You gain in insulating performance as the thickness increases, to a point. The 7/8” would perform better with a krypton fill, which gives better performance than argon in thin spaces, but cost goes up significantly.

    I’d look into a double pane option with i89 and an argon fill, which I think is more cost effective than a skinny triple pane option. They both have similar performance in terms of U value, and the other window parameters are more dependent on the lowE coatings you choose than they are on the number of panes in the IGU.


  2. alankchan | | #2

    Thank you. They're saying 100% improvement over double pane glass. Is the cost difference close to or more than 100%?

  3. Expert Member
    BILL WICHERS | | #3

    I would read “100% performance improvement” to mean it should perform twice as well. I think that is overly optimistic unless you’re going from a clear glass (no lowE at all) air-filled double pane to a skinny triple with aggressive lowE and at least argon (maybe even krypton) fill. Basically I don’t think “100% improvement” is realistic going from a double pane to a skinny triple.

    There is a lot of good comparison info between different IGU assemblies in Cardinal’s technical glass guide here:

    I personally do not think the skinny triple pane IGU upgrade options are worth the cost premium over a good double pane. The purpose of “skinny” triple pane windows is to allow the window manufacturers to offer an easy “triple pane” upgrade option in the SAME FRAME window. This is NOT optimal for a triple pane IGU.

    Window manufacturers offering windows with triple pane IGU options intended for PERFORMANCE will generally use frames designed for 1-3/8” thick triple pane IGUs, which are where triple panes really start to show noticeable improvement over double panes in regards to insulating performance.


  4. christopherw | | #4

    Personally, I'm worried about the risk of increased condensation with i89 on the interior. That's for myself though where we like to keep the humidity a bit higher than might be typical and we're in northern NJ. That's a lot different from Southern California. I'm not sure that type of cold weather performance important there?

    In my mind, triple pane has been more of a cold climate kind of thing, but then I've really only been paying attention to how things would affect me in the Northeast.

    Alpen would be the one to look into if you're interested in availability of thin triples (and not the thin film stuff they're known for) See:

    You might notice that that article is written by Peter Yost. His posts and articles have been the source of anything I know about it.

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