I am wondering if my unit is doing all that it can do. After we added on to the house, it seems like its more difficult for the house to cool off. The unit is a Armstrong 3-ton about 12 years old. Today, I done a little checking. It was 84 degrees outside. The humidity was probably about 60%. I measured the temp at the register that was the most distance from the unit and it was 64 degrees with 90% humidity. The air at the closest register was the same. The air at the return was 73 degrees at 60% humidity. That's only a 9 degree difference. Also, is there a simple way to check to see if my air flow is sufficient. Any ideas would certainly be appreciated.