Great Idea,
That may be better than the one I'm thinking of.
I was going to fab a plane shaped frame at the rafters and drop a curtain from it slinky fashion. it goes up when the door is going up and uses the same electric motor.
Just brainstorming but I think your idea is a better use of heat source. I'm just trying to save floor space.
I'll keep you posted with pix when done.