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Another basement insulation question

1241 Views 8 Replies 4 Participants Last post by  HomeSealed
I have the stud walls up with electric, plumbing etc...
Don't want to tear it down. Was about to put paper backed insulation in until I started reading here. What about 2" xps and using spray foam around the edges? I have been in the house 15 years and the walls and floors stay dry
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You want to put 2" XPS between the studs or against the wall, behind the studs? If between the studs, you would be putting your plumbing on the cold side...

Also, add your location.
In between the studs against the block. I live in Columbus Ohio. Thanks for the reply
No, it wouldn't work well because the foamboard should air-seal (continuous) the concrete wall from moisture condensing there;

Gary is absolutely correct. My recommendation is to always complete your project using the best practices that we have available... It will be a major blow to have to move/redo your framing etc at this point, however it would be a far worse feeling in the pit of your stomach if you walk downstairs 5 yrs from now and see staining on the wall and carpet from moisture mold and mildew.
On the other side of the coin, these are best practices, but not fool-proof. Basements were not meant to be finished living space so there is always the possibility of problems, and the procedures that you use offer different degrees of mitigating the potential for those issues. Ultimately, you will need to decide how far you want to take that, but at minimum, you'll need to meet the standards of your local building code.
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For Ohio, you are under the 2009 IBC:

Which does not require a Class 1, 2 vapor barrier/retarder below grade:

I would not recommend it;

Many times, basements appear dry due to the air currents wicking away the moisture before it condenses on the wall, after you insulate/drywall, there will be different scientific conditions present...

I decided to do it right, pull the stud walls put 1" xps foam, stud walls back then unfaced fiberglass and I am very glad I did it.
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All right! I think you will be much happier. Using Jan., Feb., Dec. low temps average your location, below grade to the "frost line" (3') and above grade; 1" f.b. will give a dew-point on the cavity side (of f.b.) at 27% RH, use 2" board = 37% RH, or just control the relative humidity down there when outside temps are at/below 21*F.
Reminders; sill-sealer under p.t. bottom plate, f.b. the rims w. canned foam, fire-stop frame wall top/every 10' horizontally, no gaps from fibrous insulation to f.b., and air-seal the drywall;

Good choice :)
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