HVAC in a very tall room?

[MushCreek]

I recently put a 12K BTU mini-split in a very tall (22') great room in my barn. Needless to say, the heat rises, so I run a ceiling fan on low to push it back down. Here's the question- When people talk HVAC, they always talk square feet of area, not cubic feet. My shop is just about twice the square footage of the great room, but about half the ceiling height. As a result, it's about the same cubic feet. Can I expect similar performance from a 12K mini in the shop? Insulation will be the same- R-19 walls and R-30 ceiling. I don't need living room comfortable; just take the chill off in the winter, and cool-ish in the summer. I could go to an 18K unit for not much more money.

 

[PoorUB]

Cubic feet is a concern, but most talk square feet. When I size an area I got to square feet and add some consideration for ceiling height

 

[MushCreek]

The ceilings in our house are 10', worthy of some consideration when calculating HVAC. 22' is another situation altogether. I guess I could download a program to see what the actual load for the shop will be. That's how I figured what I needed for the house, and it worked out very well.