I used two steel man doors and frames when I built my garage last year. The original plan was to fill the void in the frames with concrete for security purposes, but the builder left a 1/2" gap between the stud and the edge of the frame so I can slide drywall behind the frame which I do plan to do. The problem is that I don't see a good way to get concrete through that small of a gap and I'm beginning to think that may be overkill anyway. For insulation purposes, I'm now leaning toward using spray foam to fill the void unless my fellow GJ'ers have a better idea. The other options I can think of are to stuff fiberglass or cellulose through the gap. Thoughts??
