What is the best to insulate metal structures for all seasons?
I have been researching methods and best practices for insulating metal structures for four season use, esp. the likes of vehicles & campers, realizing that the methods would likely apply to metal sheds, garages, and barns. I suspect that the biggest concerns are heat gain / loss via conduction, condensation due to the highly conductive surfaces (and corrosion risks), plus radiant heat gain / loss.
I hypothesize that, with condensation being so likely due to the highly conductive surface, that any vapour barrier would be a bad idea. Instead, one would want to rely on a very good air barrier, preventing air flow, but allowing moisture to dry. I understand that any number of air barrier is acceptable, but would inner, outer, or both be preferable?
Continuing my hypothesis, it seems that any insulation that limits moisture retention and encourages breathability would be best. My current research leads me to lean towards "wool" insulations such as sheep's wool or rockwool. Is that accurate?
Lastly, continuing down the path of favoring allowing moisture to travel through any barriers, I'd guess that perforated radiant barriers should be used. Naturally, that still assumes that appropriate air gaps are provided to prevent conductive heat transfer. Presumably, good radiant barrier use could really help limit temperatures differences that would cause condensation, correct?