Proposed wall layers
I am planning a 1100 square foot single story house in climate zone 4C (coastal Oregon 1/4 mile from the ocean) and I am considering the following exterior wall layers (outside to inside):
1. Hardie plank siding
2. Air gap with 1×4 furring or Cora-Vent system
3. Water resisting barrier/air barrier with Delta-vent SA
4. 5/8in plywood sheathing
5. 6in studs (with rock wool batts)
6. 1/2in plywood with taped seams
7. 4″in stud wall (or 2×4 turned sideways for 1 1/2in “wall”) for utility chase
8. 1/2in sheetrock
The taped 1/2″ plywood layer is intended to provide a second air barrier so that electrical and plumbing does not interfere with the air barrier and insulation. It would also add some additional shear strength. I should also mention that there will be a conditioned crawl space, whole house ventilation (HRV), and ventilated attic.
1. Are the two plywood layers permeable enough to dry (inward and outward) if moisture got into the 6in space?
2. Would insulating the 4in utility chase be worthwhile?
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