I've had every heater you could think of. I now run a wall mounted 36,000 btu gas wall Heater, I'm 20x 20 ,I figured it out and I would need like 28,000 btu ,but for the extra $40 bucks they had a 36,000 btu ,(Heater was $150,from home depot,but I think NorthernTool has them too) Heater works...