I am renting a small metal building for my shop. The ceiling is open and the gable ends have no insulation. I have some fiberglass batts left over from insulating my house. Should I use a vapor barrier or can I just put the insulation on the bare metal. If I use a vapor barrier, does it go against the metal or on the inside of the insualation? I also have some spray foam that was extra from insulating my job trailer. Can I use that w/o a vapor barrier? This building is not tight. The gap under the 12 foot sliding door is 1 to 2 inches and the gap at the top is similar. At least, none of the gaps are large enough to throw a cat through.