Why Is My House So Humid?
Usually because moisture is being added inside faster than it leaves, or because water is getting in from outside. The EPA's line for "too humid" is 60 percent relative humidity; it suggests keeping a home below that, ideally between 30 and 50. So the first step is a number, not a guess: put a hygrometer in the room for a few days, then come back to the list below.
What too much moisture looks like
- Condensation on windows, walls or cold-water pipes. The EPA calls it a sign of high humidity. Window condensation has more on the glass.
- A musty smell you can't trace. The EPA lists it as a reason to suspect hidden mold, for example behind drywall or wallpaper, on top of ceiling tiles or under carpet pads.
- Rust on pipes, which the EPA points to as evidence that condensation keeps forming there.
- Mold that keeps coming back in a bathroom even after cleaning.
Where the moisture comes from
Moisture made inside the house:
- Showers and baths without a running fan or an open window.
- Cooking, the dishwasher and dishwashing without an exhaust fan.
- A clothes dryer that isn't vented outside.
- Unvented combustion appliances. The EPA notes that stoves and kerosene heaters produce water vapor and raise humidity unless vented outside.
Water getting in from outside or from the house itself:
- Blocked or broken gutters, and ground that slopes toward the foundation instead of away from it.
- Leaks in the roof, plumbing or around windows.
- An air conditioner whose drip pan is dirty or whose drain line is blocked.
- A damp basement or crawlspace feeding the rest of the house: see basement humidity levels and crawlspace moisture.
How to lower the humidity, in order
- Measure for a few days, in the room that feels worst and in one that doesn't.
- Vent what you can to the outside. Run the bathroom fan or open the window when showering; use exhaust fans when cooking or running the dishwasher; vent the clothes dryer outside.
- Stop water at the source. Clean and repair gutters, make sure the ground slopes away from the foundation, fix leaks, keep the AC drip pan clean and its drain flowing.
- Insulate cold pipes so moisture stops condensing on them, as the EPA recommends.
- Use air conditioning or a dehumidifier if it's still above 60 percent. The EPA lists both. Size a dehumidifier with ENERGY STAR's chart.
Not sure a dehumidifier is the right tool? Air purifier vs dehumidifier and dehumidifier or moisture absorber cover the two most common mix-ups.
Why is my apartment so humid?
The causes are the same, but your options are narrower. You can still measure, run the bathroom and kitchen fans, and avoid drying laundry indoors where you can: ENERGY STAR counts it among the heaviest moisture loads. Leaks, gutters and a broken exhaust fan are the landlord's to fix, and a hygrometer log of readings over 60 percent makes that conversation easier. A portable dehumidifier is the one fix that leaves with you.
Where this comes from
U.S. EPA, A Brief Guide to Mold, Moisture, and Your Home (updated February 18, 2026), read October 5, 2026. ENERGY STAR, Dehumidifiers, for sizing.