I was planning on putting rigid foam between the drywall and studs for a bit of a thermal break. I was going to use 1/2″ foil faced polyisocyanurate. Has anyone done this before? I’m haning the sheetrock directly over the foam (no strapping). The polyiso seems soft. Would xps be better in this application?
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You may need something more breathable, like EPS (it looks like white pressed together balls). If you insulate the inside wall with something as vapor blocking as Polyiso or XPS, you will get condensation forming inside your walls on the inside face of that insulation. This will eventually rot wood, grow mold, attract bugs, cause cats and dogs to sleep together, and all sorts of bad things.
Tu stultus es
Rebuilding my home in Cypress, CA
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Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
I'm thinking that Doobz would be safe with a vapor retarder on the inside, seeing that he is in Upper Michigan.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Maybe in Florida or Georgia, but not in a heating climate.
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I prefer 1", but half-inch can work.
Use aluminum tape on the seams to get a complete vapor barrier.
Careful when hanging the drywall, hold the drywall/foam tight on the studs when you drive the screws. You also don't want to over compress the foam by snugging the screw too tight. If you do, then the foam can "bounce back" later, causing the screw head to pull through the drywall core.
I do this a lot, generally prefer to use strapping over it.There is some inconvenience and technique in finding the stud with the screw and in how snug to drive them. rock hangers dislike going directly on the foam, but a patient person can do the job just fine.
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I did similar on my house. Applied 1" thick styrofoam to the inside of the studs then 1/2" sheetrock over that. This changed our house from a rather drafty cold walled place to very comfortable. Of course the new windows, caulk, foam, new heating system, etc also helped.
As another said... press the sheetrock well while screwing it. I nailed the foam in place using plastic washer headed nails. I also used spray foam around every electrical box and in all the corners.