I want to add to the insulation topic. Whenever you have an loose-fill (batt, blown-in, etc.) insulated cavity, you need a vapor barrier on the side that you have climate control over. The other side needs to be somewhat air permeable, so that any moisture that makes it's way in can eventually escape. The body makes a tight air impermeable barrier. If loosefill insulation is to be used, then there can't be an interior barrier, with high permeability being desired.
The best solution is to use a 2pound spray foam against the outer metal skin. It would be important to have a very dry surface to spray the foam to, as 2pound has an air permeablity rating to classify it as a vapor barrier. The thicker the insulation, the higher the impermeability. Foam has an insulation rating of R5/inch.