Basement Wall Frost

Old 01-16-17, 04:00 PM
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Basement Wall Frost

I happen to pull a section of the insulation back from the foundation.
Noticed toward top of the wall, there was frost that formed on wall.
Its also wrapped with plastic. Not sure how many other spots there are.
I live in Central Illinois Temp at present time was in the low 20s.
What is the cause? Normal? Appreciate, Your comments.
Old 01-16-17, 04:36 PM
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Pictures would help.

How tall is the foundation? Is there a sill? Is there a sill gasket in place? Is there insulation in the floor joist/rim bays?
Old 01-16-17, 05:12 PM
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The frost is from warm moist air getting through the insulation. If the kraft paper or vapor barrier is not 100% air sealed, that means warm moist air can get to the cold block. When it does, it frosts up. So basically the frost is proof that the area wasn't sealed up very well. Also, normally insulation gets covered with drywall, which is also an air barrier once it gets taped. So no drywall makes it that much more likely that it's going to frost up.

Maybe pictures will tell us more. Like maybe the basement walls have no fire blocking / air sealing behind the top plate where the plate meets the floor joists.

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