In climate zone 5b. I’m remodeling a shower that is against an exterior wall. I’m wondering what type of insulation is best for this assembly. I haven’t yet taken the old out so I’m not sure of exterior material. I’m gonna assume at this point it is house wrap over OSB, with metal siding that looks a lot like the cheap vinyl siding. Also, not yet sure on materials for the shower itself so if I could get some info on whether I do fiberglass surround walls or if I go with cement board with tile finish it would be much appreciated.