So I'm rebuilding a bathroom and I want to not have problems in the future. I live in Edmonton, Alberta, where the winters are long and cold. Two of the four walls of this bathroom are outside walls. They are currently insulated with fiberglass, 6mm poly over acoustic sealant on the studs, seams taped with tuck tape, and drywalled with greenboard. I've read a few things that suggest that greenboard is not to be used on outside walls that have a poly vapour barrier.
Is this so? Does the greenboard have to come down, and if so, what should I put up? Furthermore, what kind of wall material should I have behind the acrylic shower stall I'm going to install?
Personally, I would have installed cement board but since the green board is already up, consider installing a Kerdi membrane over the drywall. It's not that expensive ($140 for 54 sq.ft.) and seal the edges with Kerdi band. It is attahced with thinset and pretty easy to do. This will prevent moisture and vapour from ruining the green board.