Vapor Control for Exterior Insulation Retrofit
My question is about my planned wall assembly & vapor control.
I’m planning to add exterior wall insulation on a 1974 coastal home in Maine (6A). The house has 2×4 construction. Wall insulation appears to be R13 fiberglass batts. Sheathing is 5/8 ply. Over this are two layers of asphalt paper. Over that is T11 siding. With the exception of a few areas that we’re repairing, the siding is in good shape. Having broken into walls in a number of places, the inside of the sheathing is clean and dry.
We plan to wrap the exterior with WRB (Henry’s VP100 blueskin). To keep air from entering through the grooves of the T11, the bottom section of the WRB will attach to butyl flashing that will be adhered to the concrete foundation wall and up over the first 4-6″ of the existing siding. We are removing the eves and wrapping up the walls and on to the roof deck (new membrane & metal roof to be installed).
We plan to add 3″ of Rockwool comfortboard80 to the exterior walls (2 layers of overlapping 1.5″ panels), secured by 1×4″ strapping. Strapping will be drilled to 2×4 studs, 16″ on center, with new cypress shiplap siding finishing the exterior. All new double pane windows are also being installed.
A new ERV will exhaust air from bathrooms, kitchen & laundry. New heat pump system will heat & cool the house (combination ducted/ductless. We have generator power & Rinnai propane heaters for backup.)
My question is about the wall assembly and vapor control. Is this assembly and adding 12R to the exterior going to keep me warm and dry or give me potential problems with moisture and mold inside the walls?
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