[dad911]

I believe texas has adopted the IECC Energy code, If it is like NJ, the architect has done a fairly thorough calculation of doors/windows/wall assemblies, submitted with building permit. We also submit Furnace & A/C specs and calculations. I'd ask your contractor for a copy.... and make sure he follows it.

As to A/C, not enough info here, but I agree with Builder, if you reduce size and it doesn't maintain, you will have no recourse. How many zones? We're doing a new 4800sf home now, 3 zone.

For a point of reference, 3" sprayfoam, closed cell, we were quoted as r-19, 2" r-13.6 .