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-   -   Cold air coming through joist holes in concrete block foundation. (

Ptron 01-27-2011 06:13 PM

Cold air coming through joist holes in concrete block foundation.
I felt cold air coming up through a hole in the floor that the cable cable comes through, so I went down to the basement and pulled down the sill insulation and see this:

That's a concrete block foundation/wall, the joists rest on 10" blocks and then it's 8" blocks up to the roof (yes, my house is made of concrete blocks). The joists go about an inch into holes knocked into the cavities of the 8" blocks. You can see the mortar that fell down down the cavity and out the hole during construction. I feel cold air coming in through thse holes. There may also be cold air coming down through the " inch gap between the finished wall and block (the gap goes all the way up to the attic but is covered by insulation up there) but it's difficult to tell for sure. Does this mean there is a leak to the outside somewhere? There's some cracks on the outside but no gaps or holes that I'm seeing. I've checked around several joists and so far it's the same. There is no insulation in the walls and it's January in Wisconsin so I'm sure the air in the cavities would be cold either way but you can see the cobwebs move so there is air movent. Could this just be caused by the difference in air temp?

Should I spray a bunch of expanding foam in those holes? Stuff in fiberglass insulation? Or do I have a bigger problem?

stadry 01-27-2011 07:35 PM

unless you've got some foam-in-a-can hanging around, grab some f/g insulation & stuff the holes for tonite,,, even newspaper will work temporarily.

your furnace creates a draft & probably uses inside air for fuel combustion,,, kitchen & bathroom exhaust fans suck air out & create a negative air pressure situation,,, lots of ways heat can escape a house.

remember the old times when people stacked haybales & leaves about the foundation walls at ground level ? it wasn't for curb appeal :no:

Van3 01-30-2011 04:29 PM

I had a similar problem and I just bought a can of foam insulation and sprayed it to fill the hole - worked just fine!

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