Then the decision was whether to do open cell or closed cell insulation. Closed cell is harder than open cell, so gives extra strength to the thin metal walls. It is also waterproof and seals off air leaks, so prevents air and water from coming through all those little openings. Because it is denser than open cell, it has a higher R value, but that also makes it more expensive than open cell.
We considered putting closed cell on just the living portion of the barn and doing the garage part later, but decided that would be a big hassle. We also considered putting an inch of hard cell and three inches of closed cell, but in the end, we decided to do two inches of closed cell over the whole thing. They did a non-expanding foam around the windows.
Since the highs have been hovering around 90 degrees lately, we could tell an immediate difference in both the inside temperature and the noise of the building itself.