Poly Vs Smart Vapor Retarder: Need Barrier Help

[muskyhunter92]

Good Morning,
After endless reading on vapor barriers/retarders Im extremely torn between Poly and a smart vapor barrier system. Located in CNY (Zone 5b) Garage is attached and will be kept 40ish, rising up when work is to be done. Some cooling in the summer but infrequent. Can anyone weigh on what the current best practice is specifically for garages? I am fully convinced fully sealed drywall with little to no more vapor barrier is correct for the interior of the home (no VB) but in the garage I am very much second guessing my choice. It seems a garage is most akin to a bathroom where zone 2 VB is certainly not correct choice but it doesnt see the temp swings of the garage. Articles clearly state a majority of vapor is from air leak, not vapor drive so air sealing is my highest priority with this choice. Like most garage doors, mine doesnt seal 100% so there will likely be some air exchange there evening humidity indoors and out.

Build Details:
Insulating 30x30x12 with 2 8x10 garage doors. 2x4 studs, plywood sheathing, no house wrap or external insulation. Rockwool R15, Vapor barrier on walls and ceiling, drywall walls, liner panel ceiling, blown in above. Concrete block to 36” ontop of footer, framed wall ontop of that.

Thanks!

 

[jollygreengiant]

What are building code requirements for your area? That will likely tell you what you need to be at in terms of a vapour barrier.

I know for my build, in my area of SW Ontario, building code requires a class 1 vapour retarder (6 mil poly) on any shared walls and the ceiling that is attached to the house for gas proofing. In the house itself codes also require 6 mil poly, I'm assuming that's also the case for a heated garage here but I'm not entirely sure on that point. Though in my house I'm using a smart VB since I put exterior insulation on the house.

 

[muskyhunter92]

The requirement is class 2 however I’m not using Kraft faced insulation which is the typical class 2 option