[68c10airstream]

I live up north, winters are cold but not a lot of days below zero. As a past auto mechanic sick of dealing with rotted out heat exchangers from solvents, carb cleaners, paint fumes being sucked up into the inside in 3 different repair shops. The heating industry calls it "halogenated hydrocarbons" and warranty null and void (quoted from grainger catalog under unit heaters}.

My option for safe (no explosion potential and no carbon monoxide poisoning potential) is a sealed combustion counterflow house furnace. 96 percent efficient, and it pumps the heat on the floor.

I make a stand so it sits about 2 feet above floor level(code is minimum18") and box it in and put 2 6" 90 degrees elbows on the underside pointing out horizontally. I make a box on top for the return air filters . My current shop is 40x40 with 12' ceiling, metal pole building, metal on ceiling with cellulose insulation above and spray foam on walls (this way when purchased used a year ago).

Just took a temp gun and shot the floor, objects, and ceiling. Floor 57 degrees, objects 60 degrees and ceiling 58 degrees, thermostat at 61 degrees. Ceiling is at r-38, 15" of cellulose.

This is the 5th garage i've been involved with installing a counterflow furnace and ony positive comments. i tell the owners to pump safe warm air on the floor and it will take care of the rest.

Goodman brand furnace is about $1,000 plus extras. I find a steel bed frame for the angle iron and make the stand out of that. The furnace sets down inside the angle iron so it can't shift and slide off. The flange where the headboard mounts become the feet, etc. Some may say this is overkill, but if you are killed from carbon monoxide or an explosion i bet your parents are too old to make another one just like you after the funeral These paragraphs should at least get you to think twice. Good luck!!

I should add that sealed combustion has one pipe that allows outside air to come into the furnace for combustion, and another pipe dumps the furnace exhaust outside! A gas tank leak in a sealed garage will be affected more from a spark from a light switch when you come in the door more than the sealed furnace!!