I am in the planning stages of renovating a home that has cathedral ceilings with 2 x 8 rafters and R-19 kraft-faced insulation. Ventilation is poor at best. There is frost on the underside of the roof sheathing.
I would like to turn it into a hot roof by sealing up any vents and either replacing the the insulation with closed-cell foam or adding 2 two-inch layers of polyiso on top of the roof deck (leaving the existing insulation in place). If I choose the latter, will I be trapping moisture with the kraft facing?