One July afternoon a Cumming homeowner called me: "The thermostat says 74, exactly where I set it, but the house feels sticky." She was right. Her AC was doing half its job. It was cooling the air but not pulling enough moisture out of it.
Your AC has two jobs
An air conditioner cools the air and removes water from it as the air passes over the cold indoor coil. In Forsyth County, with long, humid summers, that second job is where the system works hardest.
Signs of a humidity problem
- The house feels muggy even though the thermostat reads a comfortable number.
- You keep turning the thermostat down and never feel cool.
- Condensation on windows or a damp feel on floors.
- A musty smell in basements or closets.
- The AC runs almost constantly, but the air never feels crisp.
Aim for 45 to 55% indoor humidity in summer. A simple hygrometer from a hardware store will tell you where you are.
Why it happens
Short cycling. This is the one I see most in Cumming, Alpharetta and Johns Creek. An oversized AC cools the air quickly and shuts off before it removes much moisture. The house ends up cold and clammy at the same time. Bigger is not better.
Fan set to ON. With the fan running all the time, water on the coil evaporates back into the house between cycles. Set the fan to AUTO.
A dirty filter or coil. Low airflow over the coil reduces how much moisture it can remove.
Single-stage equipment. It runs at full speed in short bursts. Two-stage and variable-speed systems run longer at low speed and remove far more moisture.
What you can do
- Set the fan to AUTO.
- Change the filter every month through the cooling season.
- Use bathroom and kitchen exhaust fans.
- Keep interior doors open so air can move.
Where we help
- Tune-up. A clean coil and clear drain let the system remove moisture properly. A tune-up is $135 for one system.
- Right-sizing at replacement. We size every system with a load calculation, not by matching the old label. See AC replacement.
- Two-stage or variable-speed equipment for the best humidity control.
- Whole-home dehumidifier. Installed with your HVAC system, it removes moisture on its own so you can often set the thermostat a degree or two higher and still feel cooler. We quote these in writing after seeing the home.