I know there are a lot of DIY guys out there. I just built an 800sqft garage. It is insulated all around with R19 in the walls and R34 above. Insulated garage door and double paned windows. How well insulated...-1F last night and garage got down to 43....that is not bad. So here is the question. I do not want to use anything that requires venting, but I want to have a heater in there. Kerosene is out as is a wood stove. I want to spend $100 or less. Recommendations please that will not cost too much to run?