# House feels humid even with the AC on: what to do Updated: 2026-10-24 ยท https://pros411.com/en/guides/hvac/house-too-humid ## Short answer Set the thermostat fan to "Auto", not "On", so the water on the coil drains away instead of blowing back into the house. Replace a dirty filter, make sure the drain line runs and use the bathroom and kitchen exhaust fans. A dehumidifier helps in damp rooms. Keep indoor humidity between 30 and 50%. If the AC runs in short bursts and the house stays sticky, call a technician. ## How to dry out a humid house ![Cartoon indoor AC unit worried in a sticky room: foggy window and a humidity meter reading 65 percent](https://pros411.com/img/guias/house-too-humid.webp) 1. **Cool but sticky: 65% on the meter.** The AC cools, but the air feels damp and the windows fog up. A cheap humidity meter tells you how bad it is. 2. **Fan on Auto, not On.** On "On", the fan keeps blowing over the wet coil between cycles and puts the water back in the air. "Auto" lets it drip and drain. 3. **Replace a dirty filter.** A clogged filter slows the air, and the coil pulls out less moisture. Put in a new one of the same size. 4. **A dehumidifier for damp rooms.** In a basement or a damp bedroom, run a dehumidifier set to about 45 to 50%. Empty its tank or run its hose to a drain. 5. **Aim for 30 to 50%.** Give it a day or two. Drier air feels cooler at the same setting. Still above 60%? Call a technician. ## Why the AC is not drying the air - The fan is set to "On" and blows the moisture back off the coil. - The system is too big for the house: it cools fast, shuts off and never runs long enough to dry the air (short cycling). - A dirty filter or coil, or low refrigerant from a leak. - A clogged drain line or a full drain pan. - Damp air getting in: open windows, leaky ducts in the attic or crawl space, or showers and cooking without exhaust fans. ## What not to do - Do not crank the thermostat way down. A colder house with the same moisture feels clammy and can sweat on the vents and walls. - Do not leave windows open on humid days with the AC running. - Do not ignore mold on the vents, walls or closets. Clean small spots and find where the moisture comes from. ## When to call an HVAC technician - The humidity stays above 60% for days with the AC running. - The AC runs in short bursts of a few minutes and shuts off. - You see mold on the vents, ceilings or walls, or water drips from the vents. - You want a whole-house dehumidifier or a system with a variable-speed fan. Find AC & heating in your city: https://pros411.com/en/hvac ## Frequently asked questions ### What should indoor humidity be with the AC on? Between 30 and 50% is ideal, and below 60% to keep mold away, according to the EPA. A humidity meter from a hardware store tells you where you are. ### Why is my house humid even with the AC running? The fan may be set to "On", the system may be too big and short cycling, or the filter, coil or drain needs attention. Leaky ducts and open windows also let damp air in. ### Should my AC fan be on Auto or On for humidity? "Auto". With "On", the fan keeps blowing over the wet coil after the cooling stops and puts moisture back in the air. ### Does an AC remove humidity? Yes. Moisture condenses on the cold indoor coil and drains away. It works best with long, steady cycles and a clean filter. ### Will a dehumidifier help if my AC is running? Yes, especially in basements and damp rooms. Set it to about 45 to 50% and keep the doors of that room closed while it runs. ### Can high humidity cause mold? Yes. Humidity above about 60% for long periods lets mold grow on walls, closets and vents. Bring the humidity down and fix any leaks. ## Sources - [U.S. EPA: A brief guide to mold, moisture and your home](https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home)