Going to be installing ac in my engine builders home shop, roughly 4-5" spray insul. on ceiling and front wall that faces West, 2" styrofoam insul. on side walls and he's looking more for humidity control to keep the iron heads & blocks from rusting while in storage and of course still be comfortable while working so I don't want to go over board to make it a cold damp environment with a 5 ton so Im installing a 4 ton air handler with a 3.5 ton ac outdoor unit to make a semi high eff. 3.5 ton system, I've tried 2 different load calc tools (both res ACCA) but cant really get anything above 2 ton, Jason if you see this I'd like your opinion, Im shooting for no higher than low 50's RH and on a 93-95 day no higher than 78°, rule of thumb says 3-3.5 ton but this is going to be pretty well insulated but with his equipment in use Im not sure what the heat load will be, it'll be his home machine shop for engine building, porting heads/intakes etc., here's a few pics