I’m not familiar with your part of the country, other than it is north of the M/D line and I assume is quite cold in the winter and possibly warm and humid in the non-winter months.
That being said, I noticed you didn’t ask/comment about A/C, dehumidification loads, nor about the utility cost to operate BB over say a Heat Pump or fossil fuel piggyback (either split or packaged) designed system. The space is small, but even at 500+/- s/f and 3 diff. areas to service, it may be worth looking at. Much more comfortable, reliable, flexible environmental control. Certainly more up front cost, but comfort and utility savings may out way the basic design you’ve chosen. I’d check out the local Utility Co. for a probable cost-free energy analysis. Depending on planned use., the investment maybe superior to your first choice.
Just a thought, one you’ve probably already considered. Good Luck