Thank you. I am not sure where you are located but, especially in the cathedral area, I think having a vapor barrier behind the drywall would help prevent moisture migration into the insulation.
Additionally, check with your metal roof manufacturer to see whether they suggest a layer of mechanically fastened underlayment on top of the ZIP System sheathing. I believe that most manufacturers do.
We are building a hybrid steel home and I have not decided how to insulate the roof and was hoping for some feedback. We are building a 40x60 residence that will be T'd to a 30x60 garage. The residence building will be half attic and half cathedral open ceiling. I have read a lot about Zip System sheathing, tape and flashing and want to use this as the sheathing for both buildings. I am thinking that the section of residence with attic, we will insulate like a standard home with blown in and vent the space with soffit and ridge vents. But I am unsure about the cathedral roof/ceiling section. My purlins will be 2x8's for residence and 2x6's for garage and not steel. I am thinking that I would insulate the 7.5" cavity with either mineral wool or fiberglass. The garage building I am again thinking complete zip sheathing and then blanket insulation.
Please let me know if this makes sense of if there are best practices for insulating a steel roof, steel sided home? Again, our home will be a hybrid steel structure, the girts and purlins will be wood. The only steel will be the trusses themselves. Thanks for the help!
