I run a business from my home and am having a problem keeping the upstairs and office cool. My office is on the 2nd floor in the furthest room from the upstairs AC (longest duct run). The other rooms upstairs stay comfortable with the thermostat set at 78 degrees. In the office, I keep three computers and a battery backup running 24x7, so quite a bit of heat is generated. The room itself is approx 15'x15' with a 10' vaulted ceiling and has both a supply and return duct. Also, every room in the house has a ceiling fan, and I have a 36" whole house fan in the upstairs hallway. To make matters worse (or better, depending how you look at it), I live in Atlanta and have no trees around the house, so cooling the upstairs in general is difficult. There are 6 fixed exhaust vents and two turbine vents on the roof, as a result the attic stays between 110-120 degrees. The attic also has 18"+ of blown-in insulation.
The problems I have are two-fold: First, my upstairs AC unit runs constantly, from around 9am until 11pm. The AC units are serviced twice a year and I change the filters monthly, and the upstairs unit just had a new compressor put in (it is 8 years old). I've checked the temperature of the air leaving the registers and it is between 58 to 62 degrees, depending on the time of day. Secondly, the office stays around 80 degrees during the hottest part of the day, and is uncomfortable to work in.
I'm lost as to what else I can do to help cool this room and the upstairs in general. Should I consider putting in a larger AC unit for the upstairs? Do I need to add a register booster for the office? Help!