They're probably thinking that eventually, the wood chocks will catch fire and burn, letting the doors swing shut.

:)

You need to show the type of door. You mention sheets, so I suspect it could be a sectional door. If it's a corrugated roll up, you won't be using the sheets and keeping the door operational.

That being said, a large door that opens slowly with an endless chain loop could hardly be considered a fire egress door.

There are 2 types of insulation that pertain to your situation. Conduction and convection. Sealing the edges against air movement is the latter. I assume you are interested in the former.

Two ways to do that as I see it. Your way with the foam sheets, or you could hang a soft barrier outside of the door to reflect the heat away from the exterior surface. The 2nd method will allow the door to be used if needed w/o any difficulty.

One of those silver faced tarps would be perfect for the job. Just make sure some air can circulate behind the tarp between it and the door surface.