I have a 30x40 metal building with 1 16x8 door, 1 8x8 door, and 1 man door, 10 ft. walls. r19 in walls and r19 wfoil insulation on roof. I have a 3.5t heat pump that works wonders in the Houston area. It runs all summer and all winter for about 1/2 what my house runs and its a little smaller.