Is the Airtight Drywall Approach safe to use in a basement?
slugboy6000
| Posted in Energy Efficiency and Durability on
I’ve looked at several BSC basement insulation recommendations, and they all use foam next to the concrete wall…looks great, but I don’t like foam.
Would a wood stud wall, physically separated from the cement, insulated with fiberglass, rockwool, or even cellulose, detailed according to the ADA, and painted with something vapor permeable be scientifically sound?
My only concern is if the basement were left unheated (zone 5) for the winter, setting up a possible condensation problem on the backside of the drywall where relative humidity and warmth might be a little higher than the basement interior.
Thanks for your help,
-Rich
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Replies
Rich,
I don't recommend your approach. Many people have tried it and failed.
Here's one way to look at it: if you succeed at creating an absolutely airtight barrier at the drywall layer -- an almost impossible task, by the way -- will there be any moisture in the air behind the fiberglass batts? Of course there will. The warm, interior air from the basement has moisture, and the concrete is usually damp. If the fiberglass successfully insulates the wall, will the concrete be cold? Of course it will. So, will the concrete be wet? You bet it will. It will be dripping with condensation, or allowing moisture from the soil to migrate inwards, or both.
Moreover, most basements are subject to periodic flooding events.
Use rigid foam or spray foam. You won't regret it.
Too, I think that if your studded wall is kept away from the concrete blocks, you'll have convective loops in there, stealing away btu's.
Richard,
More reading on this issue: The Air Gap Myth.
I figured an air gap would prevent capillary moisture from moving into the studs, I hadn't considered convective air loops. Interesting article, thank-you.