Insulating a climate controlled workshop storage loft. The entire building (walls/roof) is sheathed with Huber Zip (all seams taped).
The loft will have wood walls/ceiling (1/2” OSB). 2 x 6 walls with R23 mineral wool batts. Cathedral ceiling rafters R23 mineral wool batts and R7.5 rigid foam on top of the rafters for thermal break. Above the ceiling will be R49 blown in cellulose. R49 blown in for the floor/bottom of the loft attic. Baffles will be installed to maintain an air circulation from soffit to ridge vent.
Question is, do I need any additional vapor barrier? One of my potential insulation contractors suggested putting house wrap on the attic side of the loft wall on the backside of the R23 batts to “seal” that space and prevent moisture intrusion into the insulation. Doesn’t sound right to me.