[Bicycle Bob]

I'm moving the mini-camper interior to its new home in the Chevy Sprint Coupe, and this time, I want it well insulated. However, I see the amateurs on YouTube having struggles with vapor barriers, and it certainly seems like a steel body would produce a lot of condensate if warm, moist air has access. It could also freeze, creating a whole new range of problems.
Does anyone here have experience with this? I'm currently thinking of having the steel completely covered with closed-cell spray foam, behind thick styrofoam, but wonder if moisture would still infiltrate. I'm also considering coating the steel with epoxy, and then using epoxy to bond the foam on, but not with a close fit everywhere.