I'm looking to build a free-standing sauna building in a cold, damp area of the Catskill Mountains in NY State. The heated portion will be a 6' x 8' space, fired by a wood-burning stove. Much of the literature about sauna building on the internet suggests using foil-faced fiberglass batts covered by an air barrier. I have a few questions about this approach:

-Will this be sufficient to prevent moisture infiltration into the wall cavities?
-Can fiberglass withstand temps up to 160F?
-What air barrier can withstand temps up to 160F?

As an alternative one friend suggested using SIPs for the wall panels, but I have similar concern about moisture and heat with that approach.

Any advice is much appreciated.