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Air-Sealing a Balloon-Framed House

shrews01 | Posted in General Questions on

I have a wall that is balloon frame. I am air sealing right now. The opening to my baloon frame walls in the attic is only 2 inches. Do I need to cut foam plugs or can I just spray foam them shut? Will it matter if some of the loose fill in my wall comes into contact with the great stuff/ loctite?

thank you

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  1. charlie_sullivan | | #1

    I'm thinking that's a little big for it to work well, so if it's accessible, I'd put some solid material in and seal the edges. I'm not sure I'm visualizing your scenario accurately.

    Loose fill insulation touching the foam is fine, but be aware that the foam won't adhere to surfaces that are dusty.

  2. Expert Member
    BILL WICHERS | | #2

    Canned foam is probably going to fall through a gap that size before it cures. You'll need some kind of backer. You could use 1/2" XPS for this, or whatever is handy, but you can usually get "project size" 2 foot squares of XPS at the box stores that would work without wasting a lot of material.

    It's not a problem for canned foam to come in contact with loose fill insulation.

    Have you installed proper (wood) fire blocking within those balloon framed walls? If you haven't, you really should.


  3. Expert Member
    Michael Maines | | #3

    Where vertical cavities meet horizontal cavities (or other open spaces) you need to install approved fireblocking. Neither spray foam or rigid foam meet code requirements for fireblocking. Options are listed here:

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