Garage heat

Boy, it doesn't matter what kind of heat you have, radiant or heated air, with no insulation it's going to be a bugger to heat. 2 1/2 car garage? About 26' X 30' X 10' sidewalls? With no insulation and a cold climate, any of the on-line heating calculators come up with 700,000 to 800,000 BTU/hr heating demand for heated air. With good insulation this drops to about a tenth of that. You'll spend more money on heat than you would spend on insulation. If you are really limited on what you can do, IMHO the only reasonable way to go is radiant heat probably with one of the propane fired radiant heaters. Radiant heats objects, not the air, so as long as you are line of sight, it could be what you are looking for. Good luck, it's going to be a long winter!!