Conflicting advice on moisture barrier – GreenBuildingAdvisor

I would like to use Rockwool insulation to retrofit my 1-storey home in Quebec (zone 5b: cold winters, hot/humid summers) while changing the envelope. The problem is that the house is unlikely to have a vapour barrier/retardant in place, and it seems necessary in this climate. (The Rockwool with retardant is unavailable in Canada. Another product that looked promising, Zip R-12, also seems to be unavailable here.)

My contractor is suggesting that I need to go, instead, with fibreglass insulation up against the drywall and Durospan 250 under the cladding. However, everything I’m reading suggests that a vapour barrier must be against the drywall (the warmer side) to be effective.

I would very much like to use green products if possible, but it seems that the most realistic solution is foam boards with vapour barrier backing. Is there a better option?

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