Durable wall assembly? – GreenBuildingAdvisor

I am in discussions with a modular factory home builder in my area. Climate zone 7a. I would like to achieve a net zero ready envelope following the Pretty Good House method. For my climate R40 walls looks like a good target.

Their preferred wall assembly for achieving R40 is using 2×6 and 2×4 offset studs with 10” thick walls and fibreglass batts. This alone wouldn’t get to R40, but they mention adding to this assembly outside insulation at 1.5” foam board (R5) or 2.5” foam board (R10) to get to R40 range. 

From the articles I’ve read on GBA this assembly sounds risky in my climate zone with the low permeable ESP outside foam insulation ratio to the permeable cavity insulation at 24%. I look forward to reading some informed thoughts on this wall’s durability.