Florida bathroom reno – tub/shower against concrete wall and vapor barrier questions – GreenBuildingAdvisor

Hi. I’m renovating a bathroom in Florida and I’m trying to make sure I’m not building a mold trap which is a common case down here.

One wall of the tub area is an exterior concrete wall. The old alcove tub sat right up against it. Above the tub, the wall is furred out, and has fiberglass insulation in between, with poly sheeting on the interior side (right behind the drywall)

I was planning on using green/purple, Kerdi membrane over the drywall, then tile. Still not sure how to address the cavity.

1. In hot/humid Florida, does that poly make sense at all? If I’m using Kerdi on the surface, should I remove the poly so the wall can dry, or put it again the concrete blocks, or over furring strips and insulation?

2. Since the tub is basically against the exterior wall, is there any reason to try to add anything between the tub and the wall?

Thank you