I use a radiant propane heater that sits on top of a 20# bottle. I point that at my tool box as soon as I light it off. Overnight the garage stays about 45 regardless of how cold it gets outside, I suppose from the radiant heat of the ground and the adjacent heated rooms. But that's still too cold for my hands on the tools. By the end of the day the roll-away and tools are tolerably warm and the room is up to 55.
Before I insulated the ceiling it would freeze at about 31. The insulation has also stopped the ice dams on the roof. And there's about 30 inches of snow on the roof now and that helps with insulation too. Now, about replacing those roll up doors with some insulated ones and that one last big wall...
