The scary thing is that this builder is considered better than most of the others around here. I found all of the major problems before purchase, and these sorts of problems are why we purchased the house for wayyyy less than it originally sold for so I am OK with it. The bank couldn't sell the house because home inspectors caused previous buyers to back out due to very scary errors in their reports.
The original post on the thread concerned our other house which we are selling. That house was built for us, and I inspected it while it was being built so most of these problems don't exist there. This new house was originally a spec home so nobody cared enough to do the quality control. The house we are selling is a lot cheaper to cool and there are virtually no leaks in the system. Our neighbor, in fact, is rather envious of our cooling bill which is 2/3 or his on the same size house. Still, most of the ducts in the house we are selling exhaust with a temperature in the mid 60's on a 100 degree day, with the shortest run exhausting at 59 deg F and the longest supply duct run exhausting at 71 degrees F. This is with an air temp just downstream of the evaporator of 56 degrees F and a return temp of 78 degrees F. The buyer's home inspector stated that this is defective and caused by a low refrigerant charge which will destroy the HVAC equipment, so now I have to go through a bunch of hassle and expense to prove otherwise. Grrr. That is why I will never use a home inspector again, I have never benefited from using one, but they cost a lot of money and their mistakes always cost me even more. The frustrating part is that I consider this amount of energy loss to be thoroughly defective so it is rather hard to argue otherwise even though it is standard practice.
I am sure that sealing up all the attic leaks in the new house and getting someone to clean up the ductwork will cause the energy usage to be the same or less than the one we are selling, and that energy usage will be within the range considered acceptable. I think maybe the range of what is considered acceptable needs to be moved up a notch or two.