Wall Assembly and condensation with Zip vs Zip R – GreenBuildingAdvisor

Deciding final wall assembly.

Climate zone 5A.

Aiming for an R35-38 wall.

2 x 6 studs with Rockwool Comfortbatts – R22/23

Option for exterior continuous insulation:

A. 1″7/16 Zip R6 + 2″ Comfortboard 80.

– R value would be 6.6 + 8.4 = 15. 

– Total thickness would be 1″7/16 + 2″ + 1″ (furring strip) = 4″7/16. It would require a 6 inch nail/screws.

B. 7/16 Zip R + 3″ Comfortboard 80

– R Value would be 12.6

– Total thickness would be same as above, with same nailing

– Cost maybe higher due to higher cost of Comfortboard.

There is controversy that the polyiso of Zip R is on the wrong side. If I have a Zip R6, where I have R value of 6.6, plus additional R 8.4 Rockwool comfortboard 80, is there still a risk of condensation on the inside surface of the polyiso?  I am getting conflicting info. It seems that if you use Zip R9, then the risk of condensation on the inside is minimal. In my assembly where there’s R15 outside of the innermost side of polyiso, should there be any risks? 

I’m preferring Comfortboard 80 outside due to fire resistant properties. Could use a 2 inch Halo Exterra GPS board which provides R10 but it’s less fire resistant, and vapor permeability is low for drying outside.

Hoping to get some insight here.

Thanks in advance!!