Do heated shop buildings have the same moisture considerations as a house?
I’m in the planning stages of building a 1200 sf heated woodshop building at the northern edge of climate zone 6. I have more or less decided on 2×8″ framing on (19.2″ 0r 24″ oc spacing), taped exterior plywood sheathing, tyvek WRB, horizontal furring strips, and ribbed steel siding. On the interior of the stud wall I’m planning on dense pack cellulose with additional 1.5″ interior furring strips (“Mooney wall” to help reduce thermal bridging. The interior sheathing would be 3/8″ plywood untaped. Alternatively, I could omit the Mooney wall idea and use 1″ or 2″ of rigid foam with taped seams for an interior vapor barrier and then plywood.
Heat will be provided by a 95% efficient direct vent ceiling hung space heater and will be kept at 40 degrees unless I’m working in the shop in which case I usually turn it up to 60. Air conditioning will not be installed.
My question is, with only intermittent occupancy and intermittent use (nights/weekends), no cooking, no showering, single occupant, which insulation route would you go? I’m guessing that moisture drive is less of a concern than a house, but is this still something to recognize? Is it still a good idea to have the interior vapor barrier? If so, what would you recommend for the interior vapor barrier using the Mooney wall?
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