If you are building this thing like a fortress with super insulation and foam, you better find someone who knows how to size the A/C or you will have water dripping from the ceiling.
Example: friend had a 1700 sq ft 2 story (850 a floor) plus full basement. House was foamed including roof deck. Lots of windows, probably lots more than a townhouse with people on the sides. And exposure on both sides which even an end townhouse won't have. We get similar temps and humidity as NYC.
She did fine with a 2 ton. The 92% furnace was 60K 2 stage with 36K input on low. Each level was a zone. Furnace couldn't go to high without all 3 zones calling. She never turned on the basement stat. So this house heated below zero on 33,000 BTU output.
Dealers just don't know how to size a tight house. My friend the foamer who did this house, showed me an email from another customer who listened to their HVAC sub on sizing and now has humidity problems.
Wit ha cool roof, sray foam in walls, even without touching my windows, I'd be easily under 3 Tons for my whole house and 60k for heating.