Ok, so based on the advice of several people from this board I decided to check my house for needed load. Bought the software from bullseye above. I will try to make it short.
House in Raleigh-NC built in 1925. Down Stairs is 1400 sq ft normal amount of original windows. Uninsulated wall and floors. We are finishing the attic upstairs. Will be adding 6 double paned windows. R-13 insulation in walls walls, and hopefully will get R-22 out of the roof (putting composite system with reflective barrier). Upstairs will add approx 700 sq ft. Existing unit on downstairs is 3 ton unit. Does fine in normal summer (90 F) but works all day when it is 100 F outside. The load calc came back at 66,000 btu heat gain for entire house (5.5 ton).
Does this pass the smell test? Do you think I did the calc wrong? I am very worried about the contractor putting an oversized unit upstairs. 5.5 tons for a 2,100 sq ft? Any comments appreciated?