What It Means
Indoor humidity level is the amount of water vapor in a home's air, usually shown as a relative humidity percentage on a humidity meter. The U.S. Environmental Protection Agency advises keeping it below 60%, and ideally between 30% and 50%. Keeping moisture in check is EPA's main way to stop moldMoldA fungus that grows indoors wherever moisture lingers. EPA says fix the water problem, then scrub it off hard surfaces with detergent and water. See more growing indoors, since mold needs moisture to grow.
Try It: Check a Humidity Reading Against EPA's Range
Slide to the reading on your humidity meter. The bands follow EPA's advice: below 60%, ideally 30% to 50%.
%
Inside EPA's ideal range of 30% to 50%.
Under EPA's 60% limit but above its ideal range. Watch for condensation.
At or above 60%, over EPA's limit. Find and cut the moisture source.
Below the 30% end of EPA's ideal range.
How It Sounds at Home
- "The basement's at 65 percent again, turn on the dehumidifier."
- "Our windows are dripping every morning."
- "I got one of those little humidity meters for the bedroom."
The Breakdown
Bring it into range
- Buy a humidity meter. EPA describes it as a small, inexpensive instrument sold at many hardware stores.
- Read it in more than one room. That's Buhata's own suggestion, since a basement or bathroom can run damper than the rest.
- If it's at 60% or higher, start with the sources: vent the clothes dryer, the stove and any kerosene heater to the outside where you can.
- Run the bathroom fan or open the window while showering.
- Use an air conditioner or a dehumidifier when the reading stays high.
- Dry any condensation on windowsWindow condensationWater droplets that form on the inside of window glass when moist indoor air meets the cold pane, which EPA treats as a sign of high humidity. See more, walls or pipes quickly, and keep working on the source.
The ranges
| Reading | What EPA says |
|---|---|
| 30% to 50% | The ideal range |
| Above 50%, under 60% | Still below the limit |
| 60% or higher | Above the limit EPA gives |
Try it today. Put a meter in the room that feels dampest and read it morning and evening for a few days before changing anything.
Good to Know
EPA's mold guidance is built on moisture: mold spores can't grow without it, so controlling humidity is how you prevent or control mold indoors. EPA treats condensation collecting on windows, walls or pipes as a sign that humidity is high and says to act quickly, drying the wet surface and cutting the moisture source. Where mold is already growing, follow EPA's mold cleanup guidance on the mold page.
FAQ
What is a good indoor humidity level?
EPA advises keeping indoor relative humidity below 60%, ideally between 30% and 50%.
How do I measure humidity in my house?
Use a humidity meter. EPA says these are small, inexpensive and sold at many hardware stores.
How can I lower the humidity in my home?
EPA suggests venting moisture-producing appliances like dryers and stoves outside, running the bathroom fan while showering, and using air conditioners or dehumidifiers when needed.
Do It in Buhata
Tasks
Add "Check the humidity meter" to Tasks with a weekly repeat, so a reading creeping toward 60% gets noticed.
Open BuhataRelated Terms and Categories
- Mold
A fungus that grows indoors wherever moisture lingers. EPA says fix the water problem, then scrub it off hard surfaces with detergent and water.
- Mildew
A flat, usually gray or white mold that grows on damp surfaces such as shower grout, curtains and fabric left wet.
- Window condensation
Water droplets that form on the inside of window glass when moist indoor air meets the cold pane, which EPA treats as a sign of high humidity.
- Attic ventilation
The flow of outside air through an attic, in at vents under the eaves and out near the peak, that carries moisture out and keeps the attic cold in winter.
- Dryer vent cleaning
Clearing built-up lint out of the duct that carries a clothes dryer's hot, damp air outdoors. NFPA advises cleaning the vent pipe at least once a year.
- Seasonal home maintenance
Home upkeep sorted by time of year, so each job lands when the weather suits it and before the system it protects is needed most.
Sources
EPA, "A Brief Guide to Mold, Moisture and Your Home"; EPA, "Mold Course Chapter 2"; EPA, "Mold Information Slideshow"
- www.epa.gov/mold/brief-guide-mold-moisture-and-your-home
- www.epa.gov/mold/mold-course-chapter-2
- www.epa.gov/mold/mold-information-slideshow
Last updated .