Most homes do not need a dehumidifier in winter, but some do

Winter air is naturally dry because cold air holds less moisture than warm air. When you heat your home, that dry air becomes even drier — often dropping to 20 to 30 percent relative humidity, well below the 30 to 50 percent range most people find comfortable. A dehumidifier removes moisture, which makes the air even drier. Running one in winter usually makes the problem worse, not better.

The exception is a basement or crawlspace that stays damp year-round because of groundwater seepage or poor drainage. These spaces can stay humid even in winter, and a dehumidifier may prevent mold and musty smells. But for most bedrooms, living rooms, and kitchens, winter humidity is not the problem — dryness is.

Key Takeaways

  • Winter air is naturally dry, and heating makes it drier still, so running a dehumidifier in most rooms will make your air uncomfortably dry.
  • Basements and crawlspaces can stay humid in winter if they have water intrusion or poor drainage, and a dehumidifier may help prevent mold in those spaces.
  • If your home feels dry in winter, a humidifier adds moisture back; a dehumidifier removes it.
  • Humidity below 30 percent can damage wood furniture and flooring and irritate your skin and respiratory system.
  • Check your actual humidity with an inexpensive hygrometer before buying or running a dehumidifier in winter.

Why winter humidity is usually low

Cold air outside contains less water vapor than warm air. When the temperature drops to freezing, the air can hold only a fraction of the moisture it held at 70 degrees. That is why winter feels dry — the outdoor air is literally drier.

When you bring that cold, dry air into your home and heat it to 68 or 72 degrees, the relative humidity drops even further. A room at 50 percent humidity when it is 70 degrees outside will drop to 20 percent humidity when you heat it to 72 degrees indoors, even though no moisture has left the room. This is why your skin cracks, your lips chap, and static electricity becomes annoying in winter.

A dehumidifier removes moisture from the air. Running one in winter makes this natural dryness worse. If your home already feels dry, a dehumidifier is the wrong tool.

When basements and crawlspaces are different

Basements and crawlspaces often stay humid in winter because they are in contact with the ground, which holds moisture year-round. If your basement has water seepage, a sump pump, or damp walls, the air down there can stay at 60 to 80 percent humidity even when it is freezing outside. Mold grows in that environment, and the smell spreads upstairs.

A dehumidifier in a basement or crawlspace can reduce that moisture and slow mold growth. It works because the problem is real moisture in the space, not just dry winter air. However, a dehumidifier is a temporary fix. The real solution is to stop water from entering — by grading soil away from the foundation, installing gutters and downspouts, sealing cracks, or installing a sump pump if you do not have one.

If your basement is damp, run the dehumidifier in that space only, not in your living areas upstairs. Close the basement door to keep the dry air from spreading and making your main floor even drier.

How to measure humidity before you decide

Do not guess whether your home is too humid or too dry. Buy an inexpensive hygrometer — a small device that displays temperature and relative humidity. They cost between $10 and $30 and are sold at hardware stores and online. Place it in the room where you spend the most time and check it over a few days.

Comfortable humidity for most people is between 30 and 50 percent. If your reading is above 50 percent in winter, your home is unusually humid, and a dehumidifier may help. If it is below 30 percent, your air is too dry, and you need a humidifier instead. If it is between 30 and 50 percent, you are in the normal range, and you do not need either.

Many people buy a dehumidifier because they assume their home is humid, then run it without checking. A hygrometer takes the guesswork out and can save you money on electricity and equipment you do not need.

What happens if your home gets too dry

Air below 30 percent humidity damages wood and irritates people. Hardwood floors and furniture can shrink and crack. Wooden door frames can warp, and doors may stick or not close properly. The low humidity also dries out your skin, lips, and the mucous membranes in your nose and throat, making you more vulnerable to colds and respiratory infections.

If your hygrometer shows humidity below 30 percent, a humidifier is the solution. Whole-house humidifiers attach to your furnace and add moisture to the air as it circulates. Portable humidifiers work in a single room. Both are cheaper to run than a dehumidifier and actually solve the problem instead of making it worse.

Dehumidifier running costs in winter

A dehumidifier uses between 300 and 700 watts of electricity, depending on the size and model. Running one continuously for a month costs roughly $20 to $50 in electricity, depending on your local rates. That is money spent making your air drier when it is already too dry.

If you have a basement dehumidifier that actually needs to run, you can reduce the cost by running it only when humidity is high — many models have a built-in humidistat that turns the unit on and off automatically. Set it to run only when humidity rises above 60 percent, so it does not run constantly.

The difference between winter and summer dehumidifier use

In summer, outdoor air is warm and humid. When you cool your home with air conditioning, the AC removes some moisture, but the air inside can still stay above 50 percent humidity, especially in basements and bathrooms. Running a dehumidifier in summer makes sense if your home stays damp.

In winter, the outdoor air is dry, and your heating system makes it drier. The only reason to run a dehumidifier is if a specific space — usually a basement — has a moisture problem caused by water intrusion, not by seasonal humidity. For the rest of your home, a dehumidifier in winter is unnecessary and will make your air uncomfortably dry.

Frequently Asked Questions

Can running a dehumidifier in winter damage my furnace?

No. A dehumidifier removes moisture from the air, which does not affect how your furnace works. However, very dry air can make your furnace less efficient because dry air does not conduct heat as well as humid air. This is another reason to avoid dehumidifiers in winter — they make the problem worse.

Should I turn off my dehumidifier in winter if I have one running in my basement?

Check your basement humidity with a hygrometer. If it stays above 60 percent in winter, keep the dehumidifier running in that space only. If it drops below 50 percent, turn it off. Close the basement door so dry air does not spread upstairs.

What if my home feels dry but the hygrometer says humidity is normal?

Humidity between 30 and 50 percent is normal and healthy. If you feel dry, the problem may be air circulation, drafts, or your skin adjusting to winter. Try a humidifier in your bedroom at night, or use lotion and lip balm. A hygrometer reading is more reliable than how the air feels.

Is it bad to run a dehumidifier and a humidifier at the same time?

Yes. They work against each other and waste electricity. If your home humidity is below 30 percent, run a humidifier. If it is above 50 percent, run a dehumidifier. If it is between 30 and 50 percent, run neither.