Airsealing and adding rigid foam over old clapboards with no sheathing but under vinyl siding
I’ve got an old (1871) balloon framed two-story house in Connecticut with blown-in fiberglass (probably done in the 80s) behind the old clapboards. The old siding has no sheathing, and the previous owner put vinyl siding on.
I’d like to add at least a WRB/air barrier to the outside and possibly some sort of rigid insulation–either foam or Roxul. I don’t have the money to do new siding, but I feel that it’s reasonable for me to pull the vinyl off without damaging too much of it, adding one or more layers of material to provide insulation and airsealing to the exterior, and then putting the vinyl back on. I’ll figure out the best way to deal with the flashing details around windows and doors, but I’m looking for feedback about cost effective exterior insulation assemblies. I’m mostly concerned with material costs and finding assemblies that are safe and effective from a air-sealing and water-management perspective. I’m not as concerned about labor/time since I’ll be doing the work myself, but I would consider choosing time-saving options if the cost difference isn’t huge.
Here are the ideas I’d considered, but I’m completely open to suggestions:
– some sort of house wrap (what kind?) over the old clapboards with 2-4inches of rigid foam and furring strips over the foam
– some sort of house wrap with 2-4 inches of rigid mineral wool and then furring strips
– Zip-R or other similar “one-step” process
– any other suggestion?
For the rigid foam option, I would consider buying recycled foam, even though I know that the condition and thickness of the foam could lead to a more challenging installation.
I’m open to suggestions, but I figure that I might pull or cut back the clapboards around the perimeter of each wall and add strips of wood or plywood there to make airsealing to the old wall easier and more reliable.
Please offer advice about what I have considered, plus point out any details I’ve missed. Thanks!
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