Insulation in a non-vented roof assembly
I am building a flat roof home that we are using TPO roof on that the roofer will need a minimum of 1″ polyiso for an underlayment. I plan to spray the underside of the roof sheathing and up the vertical side of the raised heel truss with closed cell foam for air seal. So my question is, to protect the roof sheathing from condensation is it better to use the 1″ of Polyiso and 2″ of closed cell or 2 of poly and 1 of closed cell?
I am in climate zone 5.