I am in the process of installing a heater in my detached two car garage. The garage is a relatively new building and is constructed of concrete block walls with a roof of wooden trusses, asphalt shingles and no interior ceiling. The heater is gas fired and hangs from the ceiling and has a fan on the back to blow air through the heat exchanger. I've hung the heater from the ceiling, run the gas line and run the electric. I have two options for venting this thing. I can either go straight up through the roof, or I can go through the block wall and then up. Personally, I'm inclined to go through the block wall. That way I don't have to disturb the roof. Some people have suggested that going through the roof is the better option. What does everybody here think? And if I do vent through the roof, how do I do it?