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Reposting question about continuous exterior insulation – GreenBuildingAdvisor
I’m reposting an updated question since my initial question got a bit buried while I was unable to reply due to the site issues.
Our home, in Zone 6A, update has uncovered significant carpenter ant damage. We had originally planned for new windows and siding.
This website has been a great resource, but I worry I might have read just enough to make a foolish mistake so hopefully someone can tell me my thinking is sound.
The current wall insulation is fiberglass batts. We need to replace the rimjoist, bottom plate, and studs on the backside of the house. For the rebuilt section we will fill the cavities with TimberHP batts most likely. All the the 1″ board sheathing has been removed from the rotten side of the house, but we plan on leaving it intact where it is sound elsewhere. Our local building supplier proposed the following wall assemblies:
Back half: Painted drywall > 2×6 studs w/ mineral wool or TimberBatts > 2″ EPS > Adventech sheathing > HydroGap as WRB & rainscreen > cedar shakes
Remainder of house: Painted drywall > 2×6 studs w/ mineral wool or TimberBatts > 1″ board sheathing > 2″ EPS > Adventech sheathing > HydroGap as WRB & rainscreen > cedar shakes
I wonder if we may want to air seal the 1″ board sheathing with HydroGal SA, but he suggested well-detailed 2″ of foam would be sufficient. I was also thinking for the section we are rebuilding we probably want to add sheathing to the studs for both shear strength and rigidity when installing the foam, but then I wonder if we need to also wrap that layer as well.
Initially I had planned on doing the following: sheathing > WRB (Hydrogap SA) > 2″ foam (type yet undetermined > furring strips/strapping for rainscreen matrix > cedar shakes.
My assembly is probably more labor-intensive given the strapping step.
Also, it sounds like HydroGap SA might not be a sufficient rainscreen for cedar shakes and we should be going with BenWrap WRB and Slicker rainscreen according to the Benjamin Obdyke website.