I am just about finished insulating my pole barn. It is 30 by 48. I plan on walling off about half so that the back end of the barn will be my workshop with 30 by 26 dimensions. The ceiling is 12 ft at the bottom and slopes up to 15' in the center(trusses are about 11ft high). I have/am insulating with R-18 in the ceiling and the walls. The whole barn is also wrapped in a radiant barrier. The barrier supposedly adds a few in R-value. I have decided on a Mr. Slim ductless system but am not sure what size to get. I haven't been able to find a free manual J calculator online. I have read many of the AC posts but most don't mention tonnage of their unit and size of the shop just that it works well and most people seem to be in garages. I think I would prefer to undersize it a little. I don't need to get the shop to 70 degrees in the summer but 80 with low humidity would be nice. The 15k btu units seem to have the highest seer rating and it goes down considerably if I go up to 24k. I was also considering add a drop ceiling. I think I can put one of these in for less than 800 bucks and it would significantly reduce air volume, but it would be a lot of work and would limit ceiling height to around 10ft. The 15k unit is eligible for a small tax credit also but anything larger than that isn't efficient enough to get the credit. Also I am in middle Tennessee and it was humid and 96 today. Typical highs during the summer are high 90s and humid.
Anyone out there have one of these in a pole barn with relatively high ceiling? If so what is your insulation like? What size area are you heating/cooling? and whats the btu output of your unit? I greatly appreciate any input.