I have a 16x24 board and batten sugarhouse, but about 1/4 of the batten are not on yet. Also, I'd need to seal up spaces at the top plate. On the gable ends there is a 1" space between each 1x8 purlin, then another space, on the other walls there is a 2" space, between the trusses (every 2'). In addition I have just steel on the purlins, no plywood so I get loads of heat loss. When boiling that is not an issue, it gets warm enough but not hot in there unless the outside temp climbs to 65F or higher. I only heat my RO storage closet.
That being said, if you get Infrared heaters, aimed down I think you will feel warm. I've been in large warehouses with such heating and it's surprising how warm it feels. Those heaters don't heat the air, just solid surfaces (and you).
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.