Gap Between Rigid Foam and Stud Wall
MikeCell
| Posted in General Questions on
Hi – I am in the process of finishing my basement. I am in zone 4 and it is a poured concrete foundation. I am planning to spray foam with closed cell foam the rim joists (with the DAP home 2 canister kit) then put 2 inches of foamboard adhered to the walls then frame in front of that. Due to various plumbing and other obstructions the back of the studs may be several inches away from the foamboard in various locations. Will this airspace be a problem? If so how can I address it. Having spray foam installed everywhere is not an option due to cost. Thanks, Mike
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Replies
I'd put the foamboard up prior to spray foaming. This way you can use the spray foam to tie the top of the foamboard into the rimjoist insulation for a good seal.
You won't have an issue with an air gap here as long as you're planning on the rigid foam performing 100% of the insulating work in the wall. That would mean you have all of your required R value in the rigid foam and won't be adding any batts to get your wall up to your target R value. The air gap would only be a problem if you had insulation on either side, in which case convection currents would reduce your overall R value from what you would otherwise be able to achieve with the assembly.
Personally I would try to put all the R value in the rigid foam anyway, since rigid foam is always safer than batts in basement applications.
Bill