Can Foam Board Be Used On Interior? - Insulation - DIY Chatroom Home Improvement Forum

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Old 11-09-2012, 02:24 PM   #1
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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?

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Old 11-10-2012, 07:03 AM   #2
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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.
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Old 11-10-2012, 09:00 AM   #3
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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.
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Old 11-10-2012, 09:37 AM   #4
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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.
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Old 11-10-2012, 03:44 PM   #5
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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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