Hi Everyone,

I’m currently working on the design of an addition to my house.  The project involves adding a second story and an attic with vaulted ceiling to an existing 1950’s bungalow.  In the end the house will be 2.5 stories. I’m in climate zone 6.

Im working through my wall assembly design now and I’m looking for ideas on how I could improve it.

For starters, we’ve settled that the attic will be vented parallel chord trusses with dense pack cellulose.

The new walls wil be 2×6 24” OC with rock wool, and a smart vapor barrier (intello or siga).

I plan on removing the existing board sheathing, insulating (with rockwool) the old walls from the outside and installing new plywood.

This allows me to use taped plywood as the air barrier.

So the issue is that Im hoping I can make the assembly a little better than code but Im not sure what to do. We decided on cedar shingles as the cladding but they make continuous exterior insulation somewhat complicated.  Zip R is in my radar but I’d have to go with R12 for my climate zone and the cost would be stretching the budget pretty far.

So is it feasible to add foam to the inside of the studs? Should I consider a different assembly (we’re pretty set on cedar shingles)?

So if you have any suggestions or ideas I’d be grateful.
Thanks!