Insulation between two sheets of plywood?
I have an existing garage that I am hoping to both earthquake retrofit and insulate. The current state of the building is non-structural plywood sheathing over tar paper mounted on 2×4 studs on slab-on-grade. The sheathing is also the siding … previous owner just painted the sheathing and called it good. The inside is unfinished with exposed studs.
I am in Seattle area— climate zone 4C
An engineer has drawn up plans that put shear walls on all 4 walls. It seems to me that the best path for retrofit is to nail (via schedule) structural/rated plywood to the inside of the studs without disturbing the outside plywood… or maybe that’s not a decision to be made without checking with the engineer?
The garage will be unconditioned, at least for now, and I plan to drywall the ceiling and blow in R30+ above that / in the attic
Can I stick some batting in between those two layers of plywood? Anything weird there in terms of moisture/vapor/mold or considerations I should make in terms of long-term maintenance?
Does anyone have any better ideas?
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