Heat retention? I live in North Dakota, so lets start there.
I have a 45KBTU NG heater and some nights it barely keeps up. I have a 3 car garage with 12' ceilings so in hindsight, I should have went with a 75KBTU model.
How I control this is by turning down the speed control and directing the smoke through the snorkel attachment (thx for the idea
@Jfire). This still allows the smoke to be evacuated plus the garage is naturally drafty, so I don't have to open a window to feed it with fresh air. I have a CO detector so I know that I am not bringing in the exhaust from the heater back in the garage either.
When I am not using the snorkel attachment, I crank up the cfms and open the window a titch on the opposite side of the garage to get a good cross breeze.
Hope this helps!
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