Garage Heat

I have a non-insulated metal building for a garage. I heat it in the winter (as low as zero degrees F) when I am out there with a non-vented propane heater that hangs on the wall, the heater is off when I am not out there. I have been doing this for 7 years now.

I have never had an issue with condensation as a result of using the heater. My biggest issue is the tools stay cold to the touch, ie the garage will warm up to a comfortable working temp but it takes much longer for my tools to warm up. I solved that by wearing mechanics gloves.

Propane heaters are >99% efficient so there is very little in the way of emissions from them. The poisonous stuff is CO and they give off levels so far below safe levels they are approved for home heating. In a very well sealed space CO2 could become an issue but any reputable heater will have an O2 depletion sensor that will shut the unit down will before the CO2 levels get un-safe levels but any garage with an overhead door will not be sealed well enough for it to become an issue.

You always have to be careful of open flames or red hot heating elements where there is the potential for explosive fumes. Building codes in my area require all heaters to be at least two feet off the floor (gasoline fumes are heavier than air) in garages.

If you purchase a UL listed non-vented propane heater from a reputable company you won't have any issues.

PS: I only try to get it warm enough to work comfortably in my coveralls (40-50 degrees).