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DebKM 01-31-2010 12:18 PM

Insulating exterior basement walls
Our house is about 15 years old. We are finishing the basement. All of the exterior walls are framed to the floor and have vapour barrior and fiber glass insulation. I was doing research and saw plenty of posts on vapour and mold problems in basements. So I checked our construction and this is what we have. There is vapour barrier directly up against the exterior concrete. All of the 2X4 studs are set about one inch out from the exterior walls. They are attached to the floor and ceiling not the exterior walls. The walls are all well insulated between the studs with dense fibre glass insulation and then there is a thick vapour barrier on the room side of the studs.

I did a visual check and checked randomly along the walls and they all appear dry. So, is the practice I described above good.

GBR 01-31-2010 04:18 PM

Not according to the latest science: BSD-103: Understanding Basements —

Notice the lack of an air gap at the foam/stud wall, your climate may need the interior v.b.: BSD-012: Moisture Control for New Residential Buildings —

Be safe, Gary

Hube 02-01-2010 08:30 AM

You say there is a vapor barrier on the face of the concrete wall AND also on the face of the studs.? Are you SURE it is a vapor barrier and not a MOISTURE barrier on the concrete?
A moisture barrier will BREATHE, while a vapor barrier will not. If this material on the concrete truly is a vapor barrier, then that is not proper and could cause mold/ condensation problems.
But since you claim the walls are dry then perhaps this material against the concrete is a breathable type of moisture barrier. Have you heated this basement at all in the past couple of years? If you have and there is still no mold or condensation showing on the walls then this must be a Moisture barrier material and NOT a Vapor barrier.

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