Barn retrofit, multi-use space (farm work space, workshops, office, wash room, seasonal housing), simple 25’x32′ rectangle, 10′ first floor ceiling, second floor 5′ knee walls cathedral ceiling 12′ at peak. Cont. insulation, R-19 below slab, R-30 walls, R-65 ceiling, vented metal roof.

The space will be used for many different things at different times of the year. I did a CoolCalc calculation with a indoor winter temp at 72 (the most we would have, if we rented out the space for client work like massage or therapy) and it came up:
Cooling: 12,432
Heating: 22,843 (at indoor temp of 65, we got 20,681. We will likely keep it closer to 55-60 in the winter with 2-5 day rises depending on the week/day of the week)

So I was thinking we’d do an 18k downstairs and a 12k upstairs. The upstairs unit would be the sole cooling in the summer. The downstairs would be the one mostly on in winter with help from the upstairs one during really cool snaps. It occurred to me another version is a 12k on both floors, and plan on running both units during the winter instead of trying to rely solely on the first floor unit. Thoughts?