Why Is My House So Humid Even With the AC Running?

New England summers don't just bring heat — they bring moisture. If your thermostat reads 72° but the air feels heavy, your AC is likely cooling without properly dehumidifying. Indoor humidity above 55% leads to musty smells, sticky skin, and even mold growth on cool surfaces.

The four most common culprits we see in Marlborough homes: an oversized AC unit that short-cycles before it can pull water out of the air, a clogged or dirty evaporator coil, blocked condensate drainage, and unsealed air leaks pulling humid outdoor air into the envelope.

Quick wins you can try today: replace your air filter, confirm supply vents aren't blocked, and run the system on a longer cycle by raising the fan setting to AUTO. If humidity stays above 55% after 24 hours, it's time for a professional diagnosis.

Our technicians can measure static pressure, check refrigerant charge, and recommend a whole-home dehumidifier or right-sized variable-speed system if the equipment itself is the problem. Comfort is more than temperature — it's how the air feels.