Sail boats and boats in general have many of the same problems.. some of their solutions are great. ONE of them I liked was a large breathable mesh that goes under mattresses so that moisture and mold don't start under mattresses. Stuff isn't cheap however IF one is using camper a lot I'd wager it's worth the investment...
Propane create water when it burns so the ventless burners add lots of moisture to the air also.
The truck camper crowd also does a lot of cold WX camping and have many great ideas.