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What have I done 11-09-2012 02:24 PM

can foam board be used on interior?
i have an old 2 story farmhouse. the bathroom was gutted. the exterior walls are only 2x4 so r-13 insulation is being used.

On the face of the 2x4's can I use 1" foam board to give another r-5? then drywall over it.

What would the drawbacks of this be?


Windows on Wash 11-10-2012 07:03 AM

Drawback of this is that it will keep the framing even more cold and therefore increase the chance of condensation on them.

Foam to the inside is not a great idea when you are talking about covering the studs.

If you want additional R-Value in that wall, cut foam board to fit inside the wall and do a layer of foam first, then the batts.

Fix'n it 11-10-2012 09:00 AM

1 Attachment(s)
this is what i was told to do, here. seems to be working very well. i am also going to do 1" xps under new siding.

user1007 11-10-2012 09:37 AM

Check your local building/fire code. Most foam board is not fire rated and code may call for you to cover it with a certain thickness drywall. I am fairly certain you could not meet code unless the foam was inside the framing and then covered. And as mentioned, you do not want to create a moisture barrier.

If you really want the r value, you would better off finding someone to come out and spray foam into the cavities if you can find someone willing to do a small job.

Gary in WA 11-10-2012 03:44 PM

If you do "cut-n-cobble" to the cavities, use EPS rather than more expensive XPS, and it's a lot "greener" because of the blowing agent used.

1. Any OSB in the wall make-up?

2. Where are you located?


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