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Community and Q&A

Low VOC sealant/caulk for use around windows?

Robert Dickinson | Posted in Green Building Techniques on

I am looking for for a high-quality, very durable caulk or sealant to use around the interior side of the perimeter of my newly installed windows.

I will be sealing the gap around the perimeter of the windows, which varies from less than 1/4 inch to about 5/8 inch in spots. The bulk of the depth of the gap is already filled with canned low-expansion window/door spray foam, and we would be applying the sealant either to the cured canned foam or to a backer-rod (i.e. foam rod) installed in the gap.

We used backer rods and Vulkem 116 on the exterior perimeter of the windows, but I am concerned that the Vulkem 116 might have too high a VOC content for the interior, especially considering that we are working to achieve very high air-tightness levels.

Because we are doing extremely air-tight construction, we want a sealant with a low VOC content. I like the Vulkem product for the outside, but am concerned that the VOCs are too high for my interior applications.

Obviously we want a product that will remain flexible over a long time period to accomodate framing settling and building movement.

I probably would have gone with EPDM gaskets if I had thought of it earlier. But we’re already too far along with filling these gaps with foam and backer rods, etc.

Rob

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Rob,
    Check out the GBA Product Guide.

    One recommended product is Quick Shield VOC-Free Sealant.

  2. Thorsten Chlupp | | #2

    If your goal is air tightness over a long period of time what you want is a high quality sealant tape. Any caulk, epically on a window sealing application is a temporary measure. Best for the interior seal I found is SIGA Corvum 12/48 which is especially made for this use and the only VOC free tape I have found. Not cheap, but worth its money in my book at least. On the exterior I assume that you already used a high quality flashing tape?
    Depending on climate keep dangers of a double seal in mind. A permeable tape on the exterior which has a moisture diffusing ability but is impermeable to water is ideal.

  3. Robert Dickinson | | #3

    Martin,

    Thanks for the reference to the Quick Shield VOC-Free Sealant. I had checked the product guide before posting and had seen the Quick Shield item, but I wasn't sure if items appearing there are really "recommended" after having been used or reviewed thoroughly or just happen to satisfy a "green" criteria like having low VOC. Clearly it meets my low-VOC criteria, but I didn't know how good it was as a sealant, i.e. durability and long-term flexibility.

    Rob

  4. Robert Dickinson | | #4

    Thorsten,

    Thanks for the suggestion for a high-quality sealant tape. I agree completely, and in fact have a few rolls of the SIGA Corvum 12/48 already on order.

    I would have used the Corvum 12/48 exclusively on the interior, but the size doesn't work perfectly for me. Many of the gaps I have are 1/2" or 5/8" and the 12cm shallow width of the Corvum 12/48 wouldn't have anything to adhere to. I plan to use the Corvum on the gaps that I have that are around 1/4" or so, given that will leave a reasonable amount of window frame for the tape to stick to.

    I wish there had been a Corvum 19/48 (ie. 3/4" / 2"), as that would have been perfect for my larger gaps. ;-) The other Corvum 30/30 (mm) is too wide at 1 1/8" inch width.

    Rob

    p.s. -- As an aside, I've been really impressed so far by the SIGA products (which I purchased from Small Planet Workshop in Portland). I used the Primur Roll for a difficult application and it worked wonderfully. And we've used the Wigluv tape and it's good stuff as well.

    p.p.s. -- Small Planet Workshop just announced availability of a product by Tremco Illbruck called illmod Trio, which is an expanding foam tape for sealing and insulating window perimeters. It looks pretty awesome and I would have tried it out if it had been available about two weeks earlier. :-(

  5. Albert Rooks | | #5

    Hi Rob,

    Thanks for the kind comments. :)

    Perhaps I can help with the installation of the Corvum 12/48. Siga's idea behind the 12mm x 48 mm legs is that the 12mm (or 1/2" leg) gets applied to the last 1/2" of the window frame face. That outer 1/2" of the window frame face eventually gets covered by the window casing. From that point, the 48mm (or 2") leg gets stuck to the RO Framing.

    The 90 degree fold in the Corvum 12/48 does not go in the corner of the RO to window. If it did, you would have the problem that you are having now with variable gaps. The gaps will always vary since the RO's are never plumb and that's why the windows are ordered undersized.

    The fold goes at the edge of the window. That does mean that when the tape meets the RO framing, it doesn't do it with a nicely folded 90 bend, but that doesn't matter because your window casing will be shimmed out from the RO following the same gaps. You've got 2" of tape to span the gap and stick to the RO Framing. That is typically plenty. If you fell that you need more, just add another piece. All of the tapes stick to all of the tapes, so "build ups" are fine.

    So... If the fold goes at the edge of the window frame, the outside of the window casing will follow the fold exactly. Since there is 1/2" of tape on the window frame face, if you case the window with 11/16" or 3/4" material, the 1/2" tape will will be covered by the first 1/2" of the thickness of the 3/4" (or so) casing. Now the tape is concealed.

    Make sense?

    Amazingly I don't have a good picture of the application. I'll see if we can put one together and post it this morning.

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