One inch foam might be a little to much inside, but if your form fits, go for it. The foam will need to be foil covered, I would think, or it might melt. I am using the foil covered bubble insulation from Lowes inside mine, that everyone suggested. It is about 1/4" thick. You could put the one inch on the outside. You will need to insulate to get proper temp. I would at least put the one inch on the bottom to insulate from the concrete. I'm going to put wheels on mine to get it off the floor and be able to move it easy. Don