Roof Insulation Assemblies
GBA blogs are filled with discussions of wall assemblies (insulation/vapor & air barriers), but I haven’t found much on roof assemblies, particularly cathedral types. Assuming rafter construction, Is it best to build them like walls (rigid insulation outside, breathe to inside) or is it best to seal the rafters on the inside with taped rigid foam and let the assembly breath to the outside? Do we need to avoid rigid on inside and outside as with walls? With timber frames and SIP roofs, can shingles or metal roofing be placed right on the SIP without creating a cold roof via an air space? Zone 5A.
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