How Do Dehumidifiers Work?

High humidity and moisture inside a home can result in uncomfortable conditions, musty smells, damage to fixtures and furniture, dangerous mold, and aggravated allergies. Thankfully, dehumidifiers are an effective moisture removal tool that can help protect your belongings and improve indoor air quality.

How do dehumidifiers work? What type is best for you? In this guide, we'll explore the common dehumidifiers, and the ways they operate. Whether you need a closet dehumidifier or a dehumidifier for your basement, you can find the right type for your home.

What Dehumidifiers Do

The main purpose of a dehumidifier is to remove extra moisture from the air around it. They are typically used in rooms and locations that have higher humidity, such as damp basements and parts of the country with a more humid climate. Dehumidifiers make the air more comfortable, inhibit the presence of dust mites and slow the growth of bacteria and mold — making the air healthier to breathe.

As a dehumidifier collects excess moisture from the air, it condenses the moisture into water, which is stored in a reservoir inside the unit. The reservoir should be emptied at regular intervals and cleaned occasionally to prevent any mold from growing inside the unit. Some units use a hose to drain out the water directly.

There are several types and sizes of dehumidifiers, and they are generally measured by the amount of water they can remove from the air. For a home dehumidifier model, the capacity is usually between 10 and 50 pints of water per day in conditions with 60% relative humidity at 80 degrees Fahrenheit. These numbers can vary with different temperature and humidity levels.

Why Indoor Humidity Matters

The humidity level inside your home matters for many reasons. The indoor humidity level can affect the comfort and health of the home occupants, as well as the air quality and conditions of furniture and fixtures in the home.

Whether indoors or outdoors, humidity is the measure of water vapor in the air. Because warm air has the ability to hold more moisture than cold air, we often use the term relative humidity. Relative humidity measures the amount of moisture relative to the air temperature. This measure is most important when discussing air quality and comfort levels.

Humidity can be a problem in climates that are generally warm and moist, as well as in many areas during the summer months. However, humidity can also be an issue in the winter in some areas. Inside a home, high humidity levels can lead to mold, mildew, bacteria and fungi growth. It can also warp wooden flooring, furniture, and musical instruments.

Why Indoor Humidity Matters

Benefits of Dehumidifiers

If humidity is a problem in your home, you can use dehumidifiers to help reduce moisture. There are a number of important dehumidifier benefits:

  • Dehumidifiers increase home comfort levels: High temperatures and high humidity can make everyday activities uncomfortable. High humidity makes moisture stick to the body, and sweat has a harder time evaporating. Evaporation is the body's way of cooling off, but it's more difficult in humid conditions. Dehumidifiers take some of this extra moisture out of the air, making it feel more comfortable for everyone.
  • Dehumidifiers protects fixtures, furniture, and more: When there's too much moisture in the air, it can wreak havoc on hardwood floors, wood furniture, musical instruments, electronic equipment and more. Wood can warp and age more quickly in moist conditions. Certain instruments like pianos do best in specific humidity conditions, and too much moisture can cause damage. Electronics and other equipment can also be damaged by humidity. Dehumidifiers will help regulate in-home humidity to protect wood floors, furniture and other belongings.
  • Dehumidifiers prevent mold growth: Mold and mildew grow quickly in moist environments. These conditions also encourage the growth of bacteria and fungi. All of these can be serious health dangers. Keeping moisture out of the air helps to prevent dangerous mold from spreading.
  • Dehumidifiers reduce allergens: Moist air is more hospitable to germs and dust mites that can be problematic for allergy sufferers. Using a dehumidifier can provide relief from allergies by keeping the air cleaner. Dehumidifiers can reduce airborne irritants for both breathing and the skin.
  • Dehumidifiers prevent odors in the home: Damp basements often create an unpleasant musty smell. These odors can be reduced or eliminated with the use of a quality home dehumidifier.
Type of Dehumidifiers

Types of Dehumidifiers

All dehumidifiers work to take water from the air, but there are several types that operate in different ways. Here are the three main types of dehumidifiers:

  • Refrigerant dehumidifiers: This type of dehumidifier works very similarly to the way a refrigerator operates and uses metal plates or coils along with fans to move air through the unit. A refrigerant dehumidifier draws moisture out of the air through the process of condensation and cooling, and the water drips into a reservoir or container that should be emptied regularly. Refrigerant dehumidifiers are some of the most common types used as basic room dehumidifiers.
  • Desiccant dehumidifiers: Instead of using cooling and condensing, desiccant dehumidifiers use absorption to reduce humidity levels. Desiccants are materials known to absorb moisture, and you may have seen the word on the little packets that often come with new shoes and electronics. This type of dehumidifier can operate in rooms with lower temperatures than other types. They are often used in garages and workshops, however, they are not the most energy-efficient dehumidifiers.
  • Ventilation dehumidifiers: Whole-house dehumidifiers, also known as ventilation-style dehumidifiers, are generally considered the most effective and economical choice for reducing moisture in a home. This type of unit can be installed in an attic space with a vent into a hallway below. They bring fresh, dehumidified air to the whole home.

How Dehumidifiers Work

Different dehumidifiers work in different ways to draw moisture out of the air. Let's take a look at how the two most common types of dehumidifiers: refrigerant and desiccant.

How Refrigerant Dehumidifiers Work

In this most common type of home dehumidifier, moist air from the room is drawn into the unit, and the processes of cooling and condensation draws the moisture out of the air.

To do this, refrigerant dehumidifiers use the following process:

  1. First, moist air from the room is drawn into the dehumidifier through a grille or vent on the front of the machine. Usually, an electric fan is used to draw the air into the unit.
  2. The air passes over a cooled metal plate or coils of tubing that have coolant constantly circulating through them. These freezing elements cool the air as it passes through. They force the moisture in the air to condense, changing into a liquid and dripping down through the coils into a container below.
  3. Next, the air passes over the compressor or condenser, which is warm. This warms the air back up to a similar temperature as the surrounding room.
  4. The warm and dry air blows out of the machine into the room again through a separate vent or grille.
  5. Meanwhile, inside the dehumidifier, the water that has been condensed out of the air drips down into the reservoir.
  6. As the water collects, a plastic floater or other type of sensor keeps track of the volume of water in the container.
  7. When the reservoir is full, the sensor trips a switch to shut off the machine and turn on an indicator light to let you know it's time to empty the tray. The container must be emptied for the machine to continue working again.

How Desiccant Dehumidifiers Work

Instead of using cooling and condensing, desiccant dehumidifiers work mainly through absorption. Essentially, they mop up moisture from the atmosphere. These types of dehumidifiers contain some sort of absorbent material to sop up the moisture, which they then squeeze out into a collection reservoir.

To do this, desiccant dehumidifiers use the following process:

  1. The desiccant dehumidifier draws air from the room into the machine through a duct.
  2. Inside the unit, a wheel made from a water-absorbing material rotates constantly. As the air is drawn through the machine, it passes by the wheel, and the absorbent material sucks the moisture from the air.
  3. A fan inside of the unit blows the drier air back into the room.
  4. Meanwhile, an electric heating element keeps a hot air duct warm underneath the system.
  5. As the moisture-absorbent wheel rotates, it cycles through this area of hot air, which serves to dry it out so it can keep absorbing more moisture.
  6. Air is blown at the wheel to dry it out quickly. A fan blows the hot, moist air out of the unit through an exhaust duct.
Choosing the Right Dehumidifier

Choosing the Right Dehumidifier

You may know your home could use a dehumidifier, but how do you know what type of dehumidifier is right for you? And what size dehumidifier do you need? With all the choices available, it can be confusing to know what's best for your home. Keep these important considerations in mind when you are choosing a dehumidifier for your home:

Energy Used

If energy efficiency is a priority for you, you'll want a dehumidifier that aligns with your goals. Desiccant or absorption style dehumidifiers are the least energy-efficient choice, so you may want to avoid them when optimizing energy use. Refrigerant style dehumidifiers are more energy efficient, and whole-house or ventilation-style dehumidifiers are often the most energy-efficient models. Look for Energy Star-certified models for the most efficient options.


Dehumidifier wattage can vary greatly with the different types and models. Tabletop and small dehumidifier models use a very small amount of wattage, and larger units use much more wattage. Though larger units use more wattage, they also remove more water from the air and may have better overall efficiency. For this reason, wattage alone isn't always the best indicator of the right unit for your home, but it is valuable to consider when making your decision.

Water Removed per Day

Each dehumidifier will have a different rate of water removed per day. This amount can depend on the size, type and power of the unit, as well as the conditions of the room it is used in. Consider the room or rooms you need to dehumidify, and how humid these rooms are. You should also consider how often the reservoir may fill up based on the specifics of your dehumidifier and the conditions of your room. Make sure you'll be able to empty the dehumidifier when it is full to keep it going.

Room Size and Humidity Conditions

When you're choosing what type of dehumidifier you need, one of the most important things to consider is the size of your room and the humidity levels. You can easily measure the room and use a humidity meter to measure the room's humidity.

Other factors that can affect the humidity of a room that you may want to consider include:

  • The general climate you live in
  • The number of people who live in your house and use the room that needs a dehumidifier
  • The number of windows and doors in the area
  • Whether the room contains appliances like a clothes washer or dryer
Buy Quality Dehumidifiers

Find Quality Dehumidifiers at Ingrams Water & Air

If your home needs a dehumidifier, shop at Ingrams Water & Air. For more than 30 years, we've provided quality HVAC equipment online. We are family-owned and operated, and have a long history in the business. You get fast and free shipping, price matching, and personalized customer service.

We will help you find the right dehumidifier for your home and ship it to you right away. You'll benefit from our lifetime tech support and exceptional customer service, which gives you access to a real customer service representative any time you have a question.

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