Ideas for insulating cinder block wall interior
Hi. We are renovating a bathroom on a 1950’s brick house in Connecticut, which has one westward facing cinder block and brick wall. It is brick facade, a 3/4″ air gap, then a layer of 4″ cinder block. Understood that the ideal situation is to insulate from exterior but this is not an option for us, so we are looking to do it properly from the inside.
The old interior wall was 1/2 gypsum board on 3/4″ furring strips which were nailed directly into the wall, creating an air gap between the board and cinder block. The type board was plastered with an additional brown and finish coat of 3/4″ total. The wall was in good shape and I can see no evidence of moisture issues on the inside or brick damage on the outside.
I see a lot of conflicting information online about how to deal with this. My original plan was to attach 2×3’s on the flat to the block, then put rigid foam (EPS or Polyiso) between them. On the other hand I have seen info to say the foam should cover the entire block wall and THEN build a wall in front. We do not want to make the wall too thick because it will interfere toilet placement.
Is it possible to attach the foam to the block without studs, then attach furring strips through the foam into the block wall (even glueing them on might work). I can have a total wall thickness of about 1.5″ max excluding drywall before I run into problems. Would I need any additional vapor barrier with less than 2″ of rigid foam? I’m open to and appreciate any other suggestions.
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