I'm about to discuss wall construction details with my GC and would like input on the following stack-ups regarding performance and ease-of-install. My GC is open to 'green methods' but has a tendency to say 'it's different so it costs more'. We're located in zone 6 (St. Paul, MN) and are aiming towards ~R35 whole wall (in conjunction with good triple pane windows - U 0.20ish) and ~R60 roof. Stack-ups under consideration (very much open to other viable alternatives as well): Option 1 -Latex Paint -Drywall -2x3 service wall -Insulated with split/compressed rock wool batts (

Oddly truncated post above...apologies.

I'm about to discuss wall construction details with my GC and would like input on the follow stack-ups regarding performance and ease-of-install. My GC is open to 'green methods' but has a tendency to say 'it's different so it costs more'.

We're located in zone 6 (St. Paul, MN) and are aiming towards R35 whole wall, in conjunction with good triple pane windows @ u 0.20ish, and an R60 roof.

Stack-ups under consideration below, though we're open to other viable alternatives or modifications as well.

Option 1
Latex Paint
Drywall
2x3 service wall
insulated with split/compressed rock wool, less than R15
1/2" OSB with taped seams
2x6 structural wall
insulated with rock wool batts, R23
3" type 2 EPS, R12
Caulked to framing at every stud bay and with taped seams
Tyvek WRB
Furring Strips (airgap)
Cementitious siding

Option 2
Latex Paint
Drywall
2x4 service wall
Insulated with rock wool batts, R15
2x6 structural wall
Insulated with rock wool batts, R23
1.5" ZIP R Sheathing, R6
Caulked to framing at every stud bay
Furring strips (airgap)
Cementitious siding

My gut says Option 2 is 'easier' for my GC but I'm unsure of just how comparably it will perform against Option 1. Just how effective is the ZIP R at protecting against thermal bridging?

The air space between the stud walls will do more for creating a thermal break than the insulated ZIP. Using ZIP you need to tape the seams and caulk around the wall edges, but there is no need to caulk every stud, since the tape will air seal the main part of the wall. Option #2 without the insulated sheathing will dry to both sides, but the added insulation would help also. And yes, installing foam takes longer than building another stud wall. If it is an airtight wall, the results will be comparable to the difference in R value.