Hi all, I'm new to this forum. I'm very impressed so far with the Q & A. Here are my questions and forgive me if the questions may sound silly because I'm not familiar with how it works. Background info. The AC unit was from original build back in 10/1996 and I'm the orginal owner. We never open the windows, so the house is always conditioned with either cold or hot air. The system consists of gas pump with the unit in atic and compressor outside the house. The system was never has any problems and I do change filters every 2 months. Over the years, I noticed several things: 1. The house seems to always have excessive amount of dust. We didn't do much about it because we attributed to cat's (we have 2) hair for the most part. Recently, we changed from carpet to wood floor, now the dust really shows up. If we don't dust or vaccum for 2 weeks or so, it will show up on all surfaces. Does this mean we need to clean the air ducts? 2. During summer time, we set the AC to 80 degrees, and like the pass few days where temp reach 100+ during the day, the unit doesn't seem to be able to bring the temp to 80. It would after maybe 6 or 7 pm, therefore the unit is always running. There's cool air coming fom the ducts but not freezing COLD. What seems to be the problem here? Thanks in advance for any suggestions.