I have an aircraft hangar here in Northern Wisconsin that I'm in the process of adding some partition space to. I'm going to have the ceiling done in closed-cell foam, and one of the insulation contractors suggested spraying a skim coat of the same product on the inside of the walls' tin sheathing before I install the fiberglass batting.
The building construction is steel truss, with 2-by wood gerts and purlins, and a tin exterior. My construction project entailed building partition space inside the structure leaving about a 6" air gap between the original outside wall, and the load bearing walls of the new shop space/storage.
What I'm wondering is, is it a good idea to put a vapor barrier on the inside of the outside sheathing, then have 6" of fiberglass, 6" of dead airspace, another 4" - 6" of fiberglass, and interior vapor barrier, before my drywall? Seems like a moisture trap to me.