Unvented attic and cathedral insulation – new addition: standing seam roof, Zone 4A – GreenBuildingAdvisor

I am expanding my cabin – this refers to the new build portion.

We have two primary roof scenarios in a complex roof.  

(1) Bedroom has cathedral ceiling.  Will be T&G pine, 2×10 rafters, Zip Board with Synthetic Underlayment.  24 GA standing seam roof.

(2) Other areas have attic.  My plan is conditioned attic but I can still revert.  Same system but of course the T&G is the flat ceiling, but otherwise 2×10 rafters, Zip Board, synthetic underlayment except where near transitions to adjacent slopes in which case Snow & Ice shield.

Most areas 10 on 12 slope.  

The designer was not a registered architect and did not specify the insulation system.  Contractor has quoted open cell foam under the zip board.  I am concerned about this system from a moisture management standpoint, even though I do have a whole house dehumidifier coming.

What is the best system for each scenario?