How to Prevent High Humidity Levels at Home

Clever ways to lower the moisture in your home to stay comfortable—and prevent damage

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Illustration of sweaty person sitting in front of a fan. Illustration: iStock

There’s a reason most people hate hot and humid weather. It’s uncomfortable, and it’s harder for your body to cool down because your sweat doesn’t evaporate as quickly.

But high humidity isn’t just bad for you, it’s also bad for your house. Humidity levels above 50 percent can breed dust mites, mildew, and mold, triggering allergies or other health problems.

Dust mites love to burrow into your mattress. And mold can damage the surfaces that it grows on, which can be almost anything from ceilings, walls, and floors to even clothing. Mildew prefers places where moisture is high, like bathroom walls and windowsills.

Dehumidifiers and air conditioners can wring moisture out of the air, but there are other things you can do without running them 24/7. Here are some tips from the experts at Consumer Reports and the U.S. Department of Energy.

Simple Things to Do to Lower Moisture

Test the air. Even if it’s not screaming hot, you may have a moisture problem in your home. For less than $20 you can buy a combination thermometer/humidistat that tells you whether your humidity levels are high. There are also visual clues. “If you are seeing condensation anywhere unexpected, that’s a sure sign that your humidity is too high,” says Misha Kollontai, the project leader who oversees our dehumidifier tests. “If the humidity in your living spaces exceeds 70 percent, then it’s worth identifying if there is an underlying problem.”

Check the vents. Make sure your dryer is venting properly to the outside by checking that the system is sealed from the back of the dryer all the way to the outside. If it’s not, moisture from your wet clothes can escape into the inside air. And remember to clean the vent regularly following the manufacturer’s instructions.

Same goes for all your exhaust fans, like the ones in your kitchen and bathroom. If possible, it’s best for them to vent to the outdoors instead of redistributing the humid air inside your home. Run the fan on your over-the-range microwave or range hood every time you’re using the stovetop, especially if you’re cooking something steamy like pasta. Run your bathroom fan when you take a shower and for at least 20 minutes afterward. And don’t forget to clean the filters on your range hood or over-the-range microwave often to keep your fans in top-notch working condition. To remove dust from the outside of your bathroom fan, you can vacuum it with a soft brush attachment.

More on Controlling Humidity

Seal air leaks. Moist outside air can creep in around your window AC or around doors and windows. To check for leaks, Consumer Reports has found that a simple incense stick can do the trick. If smoke from the stick blows sideways when you hold it up to windows, doors, and walls, air is seeping in and out from those areas. You can seal them with caulk or weatherstripping.

Insulate your pipes. The DOE says that condensation can occur when there’s a difference between the temperature of your water pipes and the humid air in your home. Wrapping your pipes with insulation keeps condensation from occurring on the cold water pipes and adding to the moisture in your home. The insulation is cheap and quick, and you can buy it at any home improvement store.

Be proactive. Dehumidifiers are notoriously noisy, so while they’re fine for basements, you may not want one in your living space. For example, if your bedroom seems damp on hot summer nights, Kollontai recommends “running a dehumidifier there during the day to keep the relative humidity down, and then turn the dehumidifier down or off during the night so it doesn’t keep you up.”

Deal with potential exterior issues. Make sure that rainwater and runoff from your gutters and downspouts is flowing away from your foundation and not toward it. “Investigate if moisture is entering your home from an outside source through cracks,” Kollontai says. You may need the help of a professional to redirect it and to seal any foundation cracks, but it’s worth the expense to reduce the moisture in your house and the harm it may cause.

Best Dehumidifiers From CR's Tests

Consumer Reports tests dehumidifiers in three sizes, based on the amount of moisture they remove from the air. If your space is particularly damp, buy the larger size—you won’t have to empty it as often.

Best Room Air Conditioners From CR's Tests

Room ACs like window and portable units also remove humidity from the air—and, of course, so does central air. For the best cooling, match the window AC size (in Btu) to the size of your room.

Mary H.J. Farrell

Knowing that I wanted to be a journalist from a young age, I decided to spiff up my byline by adding the middle initials "H.J." A veteran of online and print journalism, I've worked at People, MSNBC, Ladies’ Home Journal, Good Housekeeping, and an online Consumer Reports wannabe. But the real thing is so much better. Follow me on Twitter.