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Retrofit: Best practice method to air seal the interior sill plate to the concrete wall and rim joists?

Andrew207 | Posted in Green Building Techniques on

As I continue insulating and air sealing my basement from the interior, I wonder what materials are best to create an air tight sill plate in a retrofit. I see that in new builds the best method is to use an exterior tape, but what about in an old 1940’s cape? Is canned spray foam or silicone caulk good enough? Tape seems tough sense the joists would be in the way every 16 inches.

I have the same question for the top and bottom of the rim joist area.

After I air seal it I’ll be covering it up with 2 inch rigid board insulation, but I know that this area can leak even after sprayed with closed cell spray foam. Thank you for the help.

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  1. GBA Editor
    Martin Holladay | | #1

    Caulk or canned spray foam are the usual options. While this approach may not make for a 100% seal, it will address almost all of the leakage, and will make a tremendous difference in comfort.

    For more information, see Insulating rim joists.

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