Why is my AC not lowering indoor humidity?
An air conditioner that cools the house too quickly or is oversized will shut off before it has run long enough to pull moisture out of the air. This leaves indoor humidity stuck above 60 percent, which creates the conditions for mold to grow around the house within a few months.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1running dehumidifiers
- 2dropping the system setpoint to force longer cooling cycles
- 3Retaping the plenum box
- 4Using a humidifier (or dehumidifier) downstairs
- 5Bought multiple hygrometers to monitor humidity levels
- 6Set up a portable Midea dehumidifier
- 7Had an HVAC company inspect the units
- 8Consulted ChatGPT for advice on air quality specialists
- 9Opening the apartment window for 30 minutes a day
- 10Running an air conditioner or bathroom vent
- 11Using a countertop dehumidifier with a continuous drain into a sink or bathtub
In their words
Unedited, most upvoted first, each linked to the thread it came from.
“Now that we have been cooling for 4 months we started noticing mold around the house.”source ↗
“It’s been 4 days and humidity levels are still averaging in the mid 60%.”source ↗
“Apparently the humidity even when I don't cook is 66%. Is it worth buying one to remove these pests ?”source ↗
“there is just one big window in the whole apartment, the bathroom has a vent. I open that window 30 minutes a day. Maybe because I live at the 16th floor? no idea.”source ↗
“I want to get my home humidity levels down, my unit can’t keep it below 60%.”source ↗
“I am back. And it feels awful in my home right now.”source ↗
“Today I woke up and noticed the musty smell was back and it was humid/damp feeling both up and downstairs.”source ↗
“The whole house is between 71 and 80 % humidity depending on the thermostat vs the actual humidifier.”source ↗
“This thing is only a year old so I feel at my wits end”source ↗
“I also want to add that the doors have swelled so much they are not closing. (For atleast 2 rooms and the front door)”source ↗
“Recently we found several clothing items in our master bedroom closet with mold/mildew on them.”source ↗
“Reading up to 85% at time in the house (we live in the southeast U.S. and heat and humidity has been extremely high for weeks)”source ↗
“Got a midea de-humidifier set up and it’s keeping it around 65% RH.”source ↗
Where this came up
People with this problem also raised
- 2Why is there condensation and damp spots on walls only on laundry days?
- 4How to fix bad air quality in a rental apartment
- 7Why is my AC air handler wet and smelly?
- 3Why is just one upstairs room so hot in the summer?
- 4Why are my metal floor vents sweating and growing mold?
- 2Why is my bedroom hotter than the rest of the house at night?