Twenty odd years ago when I lived in New Jersey, I heated my Concrete block Garage (20'x36'), but then again at the time I also derived around a third of my income from the sale of cured firewood, Suprisingly I was the only firewood seller in three counties that only sold split firewood that had been split and stacked more than a year earlier. I made the out of state contractor that cut down the dying shade trees in town a deal, where he did not have to transport felled trees 120miles out of state, I allowed him to dump logs locally on my private property, only requiring him to buck the trunks to 22" lengths, I employed a flock of teenagers to feed my two 30ton Log splitters and turn it into firewood and stack it in 1 cord stacks then I'd Date the stacks with laminated signs (plastic no trespassing signs mounted backwards, the plastic is made as a "Writeable surface" and can be stapled to the firewood) and all my wood was under cover! I did well enough at it I was able to PAY OFF a NEW 1989 F450 Dump truck in three years. unfortunately my business partner absconded with the assets when we were finally shut down by zoning officials.
I'm now 58 and don't have the energy for all that effort, and there aren't enough trees locally, so I burn coal.
And currently my coal bin is entirely full and has been since May, I still want to get another three tons in my uncle's dump trailer, sometime before the Snow flies!