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IllDizzy 04-11-2010 08:45 AM

Vapor barrier question
 
Hi,

I live in Cananda and I had a question about vapor barrier. When doing a basement renovation, is it required to cover the concrete walls with vapor barrier up to the frost line before framing up the outside walls? I'm using bat insullation and have a space of 1.5 inches between the studs and concrete.

Thank you

Bob Mariani 04-11-2010 08:54 AM

you do not want a barrier like poly against the concrete wall at all. Warm air in the winter will hit the cold wall and condense. The moisture will be trapped against the poly and destroy your batt insulation. (which is also an bad choice) You need at least 2" rigid foam against the concrete wall to act as a thermal break and to keep this wall warm enough to prevent condensation. It must be completely sealed.. seams and edges with caulking or spray foam and tuck tape.

IllDizzy 04-11-2010 09:20 AM

Thanks Bob! I apprecaite your helpful information. It seems to be a very difficult question to answer. Some say to poly the concrete wall up to the grade line outside but some don't.

Bob Mariani 04-11-2010 09:47 AM

the reason for the confusion is vapor barriers need to be addressed differently depending on your climate. In your case you stated where you are located which makes it possible to give you the correct answer. Be sure you seal your rim joists with spray foam also. This is the most critical detail in basements.

ctkeebler 04-11-2010 01:30 PM

Quote:

Originally Posted by Bob Mariani (Post 427038)
you do not want a barrier like poly against the concrete wall at all. Warm air in the winter will hit the cold wall and condense. The moisture will be trapped against the poly and destroy your batt insulation. (which is also an bad choice) You need at least 2" rigid foam against the concrete wall to act as a thermal break and to keep this wall warm enough to prevent condensation. It must be completely sealed.. seams and edges with caulking or spray foam and tuck tape.

Bob, Im also in Connecticut and would this be your recommendation for the floor as well?

Rigid Foam board insulation then plywood as a sub floor without poly under the foam?

Thanks
Tom


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