Hi Bthree,
Not sure whether you are still on this board, but thanks so much for the idea using the foilboard. My husband and son did the garage door today in a couple of hours. The only difference is that we used small offcuts glued onto the metal, and then glued the larger sheets onto those. The idea was to create an air space between the door and the foilboard panels. This was suggested by Foilboard's super helpful and friendly Qld rep, Stephen. We used the 15mm thick panels, and roof/gutter sealant (for the heat resistance). My son has a garage bedroom, and tonight we could tell straight away that it wasn't as cold as usual, and we hope that it will also help modify summer heat. When I touched the foilboard tonight, and then the metal struts of the door, the temperature difference was dramatic. I think that foilboard or any of the similar products could work really well for other retro-fitting projects such as shed walls/ ceilings and patio ceilings, as it was easy and quick to use. The whole project cost $128 for foilboard, and another $6 for sealant.