Kneewall SPF Insulation for Cape Cod 1937 - GreenBuildingAdvisor
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I have a gable vented attic and just got a new roof. My house is a cape cod from 1937. I understand the proper method would have been […]
Kneewall SPF Insulation for Cape Cod 1937 Luca174 | Posted in Energy Efficiency and Durability on April 5, 2026 08:55am I have a gable vented attic and just got a new roof. My house is a cape cod from 1937. I understand the proper method would have been to have a soffit and ridge vent. Im in climate zone 4a. Question #1: (OFFICE) I got a new OFFICE shed dormer that is venting into the main roof line. On the outside we added 3/4″ insulation and new siding. However my contractor failed to adhere Z-tape sheathing seams externally. I want to insulate these walls as much as possible. R15 or even better R21 without SPF. But also understand the wall still has to breathe. For the 2×4 framing for walls: If I apply Z-tape to the INTERIOR sheathing’s seams/ gaps SPF interior cavity picture perimeter frame SPF top plate and bottom plate then Rockwool (or Cellulose dense pack wall cavities) then can I add a continuous layer of 1-2″of rigid foam board over the entire wall to prevent thermal bridging? (ie so studs are not visual anymore) Please see enclosed Pic 1 and then add 1/2″ drywall over the “unfaced (should it be unfaced?)“ foam board? Would this be too much rigid insulation in addition to the 3/4″ insulation under the new siding? Does this still allow for the walls to breathe? Also do I need to apply some furring strips to the rigid foam board so that the drywall can be adhered? Question #2: I added 2 unvented smaller gable dormers (2×8) in the Bathroom and M...