Hello,

Apologies for the long post. I have browsed a lot of materials on this and other websites. We currently live in Northern NJ (zone 5) in a 150-year old house with little insulation. We plan on remodeling the entire home over the next 2 years. Phase 1 is to remove the plaster, insulate from inside and finish with drywall. Phase 2 is to remove the siding in 2 years time and replace all windows.

The current breakdown of exterior walls is: vinyl siding, original wood shiplap siding, studs (actual 4″), spotty blown-in fiberglass insulation, plaster.

Based on my research, we would do: new siding, rigid foam, WRB, original shiplap siding, 7.5″ rockwool, drywall. I have not researched the exterior in detail, so i might be missing some details like drains.

We are currently focused on Phase 1 (interior insulation). My main concerns / questions are around (1) moisture and (2) air sealing.

(1) both rockwool and drywall are permeable. However, the exterior wall should be warm enough once we add the exterior rigid foam insulation. For this reason, I would not install a vapor retarder behind the drywall.

(2) currently, the biggest air leaks are coming from the old shiplap siding. I was thinking of placing OSB sheets between the studs and covering the edges with canned spray foam. 1st line of defense which should stop a lot of the leaks. 2nd line of defense is to apply an airtight drywall technique. Once we do the exterior siding, I’m hoping the continues WRB and rigid foam will help with air sealing (breaking the thermal bridge is a bonus).

Going into more detail of the stud bays, my plan is to install 3.5″ rockwool into the current stud bays. The o.c. distance between studs is all over the place. Then build a 2×4″ frame against the existing wall, 16″ o.c. and non-overlapping with the current studs. In other words, in order to save room space, I would not leave a gap between both walls (unlike a traditional double stud wall), however, I would not align the studs to be on top of each other, which should break the thermal bridge. In the new wall I would place another layer of 3.5″ rockwool.

I’ll admit there’s a lot of information here and let me know if I missed something. We would be grateful if some of the experts can share their thoughts on our plan.

Many thanks in advance!
Thomas