Re: Insulating a Basement
Mark ... you are correct in that if warm moisture laden air was to meet the cold surface of the foundation wall .... condensation could occur.
Originally Posted by Mark B
However .... the method you propose of leaving a 1 inch air gap between the inner wall and the foundation wall would create this condition .... even though you have insulation between the studs..... because the wall is not air tight.
In the cold winter months you might even find frost forming.
Also because the wall is not air tight ..... having this air gap would create a "chimney" effect of air movement inside the wall cavity which will reduce the insulation performance ... it's the law of nature.
Yes mold is always a concern ... but ... mold feeds on organic materials and wouldn't feed on rigid foam insulation and the metal studs.
How do I insulate? I don't want to glue rigid foam insulation board to the block wall because I'm afraid that if moisture gets between the wall and the insulation board mold will grow.
Ultimately the choice is yours..... as a recommendation ....
I don't want to use fiberglass because I believe it will sag over time and end up resting against the block wall anyways. So, I'm thinking about using rigid foam board in the metal track between the studs, 1" away from the block wall, no vapor barrier. Does this make sense? Am I getting any R value by doing this or should I just not bother with insulation?
I'm sure many of folks are tired of this method that I preach.... here goes...
Attach rigid foam insulation to the foundation walls first completetly covering the walls..... if you use 2 inch you are getting approx. R9.
Use a house wrap tape to cover the seams where they meet at the corners and at the butt joints.
The closed cell rigid foam insulation has a low air and miosture perm. value which means it doesn't pass air and miosture very easily and is an acceptable vapor barrier.
Then put up the wall framing in front of the foam and apply your wall finish to the studs.
What you end up with is a continious thermo break behind the wall framing which is far superior to the interupted method of insulating each stud cavity.
This will be especially advantageous since metal studs have about zero R value .... actually will transfer the cold all too well.
There is no need to apply any additional vapor barrier with this method.
If you decide not to do it this way and leave a 1 inch air gap then don't apply plastic to the wall ... you'll end up with moisture and possibly frost build up in the winter.
Hope this helps.
"" an ounce of perception -- a pound of obscure "