Earl... I have a ventless propane in my garage. Works great....Except it puts a great deal of moisture in the air. Windows are steamed up all the time when it is cold out. AND if the compressor kicks on, or you start grinding, etc. the thing will start burning yellow instead of a clean blue. In my opinion, shop around for a regular furnace to heat with. A good source would be where they sell mobile homes. I had our furnace replaced this year and kept the older one (12 years old) for use in the garage. My recomendation would be to not put in a ventless. Also search down thru the threads in the Garage forum. One member put in the type that hangs from the ceiling.