Dehumidifier Purpose: Benefits and High Moisture Signs

The ideal humidity for your health and home needs

White dehumidifier machine next to house plant on green plant stand

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Humans need some humidity to function optimally, but excessive humidity is a problem. While too little humidity can cause some discomfort issues such as chapped lips and cracks in wooden furniture, the reverse—too much moisture—can make your home a breeding ground for mold and mildew. A dehumidifier can help you remedy excess moisture problems.

Read on to learn more about the signs that you have too much humidity in your home, the benefits of using a dehumidifier, and the ideal moisture level for most people.

Benefits of Using a Dehumidifier

  • Reducing the incidence of allergies for people sensitive to mold, mildew, and dust mites
  • Mitigating pests problems; spiders, roaches, silverfish, centipedes gravitate to humid environments
  • Improving comfort by eliminating sticky, moist air in a room
  • Potentially lowers an energy bill if you use an air conditioner since it helps an air conditioner work more efficiently
  • Cleaning your home becomes easier with a dehumidifier, too. Humidity makes surfaces moist, which causes dust to cling to objects, like ceiling fans. Reducing humidity will keep dust from clinging and building up.

Ideal Humidity Levels

According to the Environmental Protection Agency, indoor relative humidity should remain below 60 percent—ideally between 30 percent and 50 percent. You can accurately measure your home's humidity level with a hygrometer or humidity gauge and then take appropriate action to add humidity with a humidifier or remove moisture with a dehumidifier.

A hygrometer is a handy instrument for detecting home moisture, but people tend only to measure certain living areas, forgetting to check room corners where moisture problems can occur. And in some cases, the issue may only be localized to one room or area of the home (like basements, for example). Other homes may have moisture problems that only occur at certain times of the year, such as in spring when there is a lot of groundwater runoff, while other residences need help to control moisture levels year-round.

If you detect excessive moisture, discontinue the use of humidifiers if you have them or try to remove the cause of the humidity. You should take further action to find the reason and remedy the situation.

Humidifier vs. Dehumidifier

A humidifier is a device that is used to add moisture to the air. A dehumidifier does the exact opposite; it is a device that removes water suspended in the air.

  • 01 of 05

    Surface Condensation

    Condensation on interior window glass closeup

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    Condensation on the interior glass, water beading on a window, or the presence of what looks like a fog or vapor on the glass are typical signs that there is too much moisture in the room. 

    Condensation often happens when a humidifier is too large for the room and puts out too much humidity. A build-up of moisture on a window sill can eventually rot wooden casings, and that wetness will allow mold to grow. Mold will look like a black or dark grunge on the bottom window trim or in the track of a patio door.

    Immediately turn off any humidifier that is operating, and in the future, downgrade the unit to reduce the amount of moisture output. When too much humidifier output is the cause, the moisture level may correct itself simply by stopping humidifier use and opening a window to add air circulation to the room.

    Another thing that can cause moisture buildup on windows is humidity present in the home's construction materials, such as improper sealing of sheetrock walls or moisture present in cement.

    The outdoor climate can also cause indoor moisture problems, such as when it rains for several days or the area where you live has a high humidity factor. A dehumidifier will effectively remove the moisture from the home and restore proper indoor levels. Remember to rotate the dehumidifier through all the areas affected by excess humidity.

  • 02 of 05

    Mold Spots

    Mold on ceiling
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    Since steam rises, bathroom moisture problems are often found on ceilings or up in the corners of the walls. Bathrooms that do not have efficient fans to divert steam and humidity to the outdoors usually have some mold problems. 

    Mold can grow on the wall, ceiling, under or around the toilet, or behind the bath or shower surround. A leaky toilet or plumbing can also cause moisture problems.


    Excess moisture can cause black mold to grow. You do not have to see the mold for it to affect you; it just has to be present somewhere.

    Running a dehumidifier in these areas can help, but remember that while this is necessary, you have to get at the root of the problem to find a long-term solution. A dehumidifier will lessen the amount of moisture damage but do not ignore the cause.

    For those finding a repair solution for excess moisture, such as removing mold and repairing walls, you must use a specially formulated paint to resist mildew and seal those areas that have been repaired. Otherwise, mold will find its way back through layers of regular paint and be noticeable once again.

    Other areas of the home often affected by trapped moisture are closets, garages or basement rooms, and storage areas. You might also see dripping or mold spots below the windows. Faulty window seals or rotting casings can cause damp spots. In this case, you should replace windows with frames, sheetrock, and insulation to remove all wet areas.

  • 03 of 05

    Musty Smell or Odor

    Attic crawl space with boxes causing musty odor

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    The presence of a musty odor in basements, crawl spaces, entrances, and garages may signal the presence of mold and mildew. The cause may have been a one-time event or a recurring problem.

    Possible causes range from improper window or door seals to wet basement areas from high groundwater seepage.

    Anytime there is a musty smell, it may suggest mold and is worth investigating. A dehumidifier can help with immediate moisture removal, but you will have to investigate and remedy the situation to avoid recurring problems. In all likelihood, those areas will also require heat to help dry the affected space.

    In the laundry room, a musty odor in the air, or musty-smelling towels or bedding could signal a high-efficiency (HE) or front-load washer problems. Though more efficient in many ways than a traditional top-load washer, front-loading washers are more likely to have mold issues. 

    Manufacturers have made many advances to reduce mold risk in front load washers, but it can still happen. Mold issues are not specific to a particular brand, though some washers have been redesigned and are better than others. (Learn the differences between a top-load washer and a high-efficiency front-load washing machine.)

    A musty odor in the laundry room can also be caused by a plugged exterior vent or an interior dryer lint filter that has been neglected and impacted by lint. When drying clothes, a clogged filter can cause moist air inside the dryer to become trapped since there is no clear, unobstructed airflow, resulting in a musty smell. Plugged lint filters, in or outdoors, can also become ​a fire hazard. You should clear them of lint—you should empty the interior dryer lint filter after each dryer load; the exterior lint filter should be cleared as required.

  • 04 of 05

    Recurring Dampness

    Springwater dampness with grayish water marks on wall

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    If spring groundwater dampness has become a recurring problem or you have purchased a home that has white or grayish water level marks in the basement, a dehumidifier can help to remove the extra moisture should these events occur.​

    It would also be a good idea to investigate why your basement is prone to water, which may be from inadequate weeping tiles around the home, concrete that may need to be re-parsed and sealed, or it may simply be because the house was built on a historical river bed or low plain.

    Continue to 5 of 5 below.
  • 05 of 05

    Water Stain Marks

    Keys being handed over after buying a home

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    If you are buying a home or RV, you should always look for signs of excess moisture problems. Tell-tale signs that a home has had water problems are mold or mildew in corners of walls or ceilings in any rooms, including the bathroom, and water level marks in the basement.

    An overly fragranced home often may have something to hide regarding odors or mold. Look inside closets at the walls, behind furniture at baseboards, around and below windows for evidence of mold or water stain marks, and be on the lookout for musty smells. It is not uncommon for some people to give their home a fresh coat of paint to mask potential problems when it goes up for sale. A fresh coat of paint can make it harder to detect water problems but look inside closets and inspect the foundation and basement.

    If you encounter noticeable water problems, ask why and if the homeowners remediated the issue. You may want to bring in an expert to confirm or allay your fears and give you an estimate of possible costs to remedy the situation.

  • When should you use a dehumidifier?

    Depending on where you live, it may run all year round, particularly in states with higher relative humidity like Florida, Louisiana, Mississippi, and Hawaii. If you live in most other states and encounter moisture issues in your home, you will likely need a dehumidifier from late spring to early fall when outside temperatures are highest. 

  • What are the disadvantages of a dehumidifier?

    If you have a professionally installed whole-house dehumidifier, it may increase your energy costs annually—depending on if it's on year-round and covers your entire home. If you have portable units, they tend to be loud and some blow out warm air, affecting your room comfort levels. Also, if you have a dehumidifier that uses a water collection tank, you may have to empty the tank regularly. You may also have to perform maintenance like changing filters and cleaning the unit periodically.

  • Does a dehumidifier cool a room?

    A dehumidifier can make a room feel cooler but it technically does not cool the room or lower the temperature. Your body cools down by sweating; however, a humid environment does not allow your sweat to evaporate into the air readily, leaving you feeling hotter. A dry environment can absorb your body's moisture, enabling you to cool down more efficiently.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Mold. Centers for Disease Control and Prevention.

  2. Humidity's Role in Asthma and Allergy Management. Asthma and Allergy Foundation of America.

  3. Mold Course Chapter 2: Why and Where Mold Grows. Environmental Protection Agency.

  4. Mold. Centers for Disease Control and Prevention.

  5. Clothes Dryer Fire Safety Outreach Materials. U.S. Fire Administration.

  6. Why do we sweat more in high humidity? Massachusetts Institute of Technology School of Engineering.