Any place where the warm air and cold air come together is prone to condensation. Heat "travels" in moisture. Cold air has less moisture and draws the moisture/heat from the warm air. The purpose of insulation/moist barriers is to keep the two air masses separate. If you insulate and seal the roof, you separate the warm/cold air masses and prevent/reduce the condensation. Also, since warm air is less dense it wants to rise, taking the moisture with it. Probably the most likely place for condensation would be the inner ceiling/roof.
In Montana, it's already cold enough to require some heat late night/early AM. When on shore power/gen. I have the
Coleman Mach III, it has a heatstrip and really is pretty effective since it moves a lot air at the roof/ceiling. I also found a catalytic type LP wall heater, but haven't installed or tested it. My plan would be to mount wall heater as per install instructions, and provide for a "fresh" vent below heater, and to vent exhaust out ceiling vent. Hopefully the heater will consume air from fresh vent, rather than cabin air, and exhaust hottest air (spent exhaust fumes) and thus allow radiant heat to warm cabin air without exchanging much cabin air. We'll see.
I don't have a lot of cubic feet to heat, 6'x6'x12'=432 cu ft, minus cabinets etc. and am well insulated and sealed so it shouldn't be that hard to heat and maintain, until it gets really cold.
McDave
This is the type of LP wall heater I have.
http://www.ebay.com/itm/Camco-57331-Oly ... 36013297a9