The problem with overhead doors is that regardless of how much insulation you put on the panels, there will still be energy loss, as the main leakage isn't through the face of the metal panels, it's BETWEEN the panels themselves and along the sides... It may help for the issue of the sun beating on the outside of the doors, but I've found its pretty much impossible to completely seal the outside edges, top and bottom , and areas between the door sections... if they were completely air tight the door would be so stiff it wouldn't open. Mine seal up pretty well, and I have insulated panels, but there is still some leakage along all edges. I'd have to say generally speaking, the overhead doors are the biggest source of energy loss in a garage, regardless of how well insulated the panels are.