how to insulate under the wall


Old 01-04-10, 10:24 AM
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Join Date: Dec 2009
Location: IL
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how to insulate under the wall

My daughter's bedroom has one corner which juts into the attic over the garage. It's insulated but cold air comes in through the gap between the floor trim and the subfloor. Is there any reason that I shouldn't spray some foam insulation along the floor, under the trim, to seal this air leak?

And brand recommended would be appreciated.
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Old 01-04-10, 12:31 PM
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Spray foam in that area will be ugly and will only likely move the leak down the wall. Any way to get to the area in the garage and spray it from there? The best solution is to remove the trim and sheetrock in the room and reach back and spray foam at the crack itself.
Old 01-05-10, 11:47 AM
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Thanks Chandler

I can totally access the site from the garage attic, but have never noticed this problem until this winter, so we haven't ventured into the garage attic (sub zero here). I am planning to pull up the carpet and replace it in her room, so thought the spray foam could just shoot under the floor trim in the crack above the sub floor. Sounds like this is a no go, huh? right now we are using a rolled up towel!
Old 01-05-10, 12:15 PM
Join Date: Jan 2010
Location: West Virginia
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Depending on the size of the gap, you could use masonry backer rod and force it into the crack. I've used it with success before. You could even caulk the front to hide the gap if you are good with a caulk gun. They sell the backer rod with the weatherstripping at Lowe's and HD.
Old 01-05-10, 01:16 PM
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Sealing the air leak you can feel may only be the tip of the iceberg, appropriate image. As Chandler stated, the leak may just move to another location. What you want to check is how the framing extends out over the garage and how well that framing is air sealed. The insulation you speak of is most likely fiberglass and it is notorious for allowing cold air to pass right through. If the cold air is getting in under the floor framing, that is just as bad as the leak you are after. Some pictures would help.

The other end of a draft is the air that is leaking out of your home, creating a pulling effect that is bringing in the cold air. Attic doors or hatches, recessed lights, electrical and plumbing penetrations all allow warm inside air to find a way out, which then requires cold air to leak in to replace it. Here is another link on whole house air sealing:


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