i pull heat into the booth from the shop. i have a big torpedo heater that i use farm deisel in. my shop is well insulated and even in the 30's i can keep my booth at 75 or better. i put the car in the booth the day before so i can put the small heater at the door to heat up the booth and warm the car.next morning the car will still be good to go. temp in the booth is not the critical part. temp of the metal is.