Re: Polyfilm Needed? Mold Growth?
Having the air space between the exterior wall and the insulation is a bad idea also considering it would also be open to the ceiling above.
The last thing you want is this air space since you will end up with warm moist air from the interior reaching and contacting the cold block walls and condensing.
Also you will be creating a stack effect of moving air which will carry cooler air ---- fiberglass is terrible within moving air and it's performance is greatly reduced.
I have to agree with your assesment regarding the vapour barrier placement suggested by the owner.
Besides faced batts aren't really all that effective in controlling vapour transmission.
To offer a suggestion ------
Using an adhesive formulated for foam ----- glue 1-2 inch rigid foam insulation to the exterior block walls making sure to seal all joints with house wrap tape and seal along edges and along the tops and bottoms with spray foam.
The foam will provide a continious layer of insulation thaat is far superior than the interuppted method. The foam will also be the vapour barrier.
It's required here that the insulation be continious from floor to the underside of the roof for commerical spaces --- it's also a good idea to do this anyway.
You will have to cover the foam with drywall as a fire rating.
This way you there isn't a need to move the walls so far out if you don't want to.
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