Seal then flash and Rockwool or just seal and Rockwool.
I already have the r10 XPS on the outside, would it be overkill to install 1″ of Closed cell on the inside? No matter what I do, I do not want to use open cell since it’s more like a sponge and would take for ever to release the moisture it absorbs.
Also I usedhttp://www.ekotrope.com/r-value-calculator, from my understanding it wouldn’t make sense to do all spray foam in a 2×4 wall with no exterior insulation because the cavity would have r21ish but the studs would only be r4 max. But r10 on the exterior plus r15 Rockwool in the cavity equates to r25 in the cavity and r13 at every stud. Much better overall r value, plus the Rockwool is fireproof when compared to closed cell, also Rockwool is vapor permeable but moisture resistant as it is made from either rock or steel. For my roof since it was a new shingled roof by previous contractor, I will be using 4″ of closed cell plus r23 rockwool in the attic, I will be sealing off the soffits with the same r10xps as blocking and then the spray foam will be applied 4″ on roof deck. Total r51 roughly between cavity, 2×10 SL rafters with no exterior insulation on the roof unfortunately. Next time I do the roof over I’ll install exterior foam there as well. I will have a return and supply in the conditioned attic as well to control humidity at the ridge. Does this sound like a well thought out plan?
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