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Humidifier vs. dehumidifier: What’s the difference?

Humidifiers add moisture to the air, dehumidifiers remove it — read this to find out when to use each one
Updated on December 10, 2023
Written by
Danny Ashton
Danny is the founder of HouseFresh and has been writing about air purifiers and indoor air quality since 2010. He is our lead tester, conducting all the tests we use to evaluate air quality products. That is why you will always see his name attached to our reviews.

Even though the words sound similar and may seem to have similar meanings, their differences become obvious you learn more about the function of each one, the technologies behind them and the benefits associated.

Here is the TL;DR:

  • Humidifiers add moisture to the air, raising the humidity levels
  • Dehumidifiers to they opposite, they remove moisture from the air

If you are reading this, you probably have no idea how moist or dry the air in your home is. But that’s completely normal as most people don’t notice until they experience one extreme or another.

Have you noticed your skin bleeding and cracking for no discernible reason? Then, it could be the dry air. Do you sometimes get out of the shower and cannot get the moisture off of your body? If this is the case, chances are your home is too humid.

The amount of moisture in the air is measured using RH or relative humidity. Relative humidity refers to the amount of water vapor in the air concerning how cool or hot the temperature is. When it comes to a comfortable RH level, the range should be between 30 to 50%.

  • If your home has more than 50% relative humidity, you will need to get a dehumidifier to remove moisture from the air, and failure to do so could spur bacterial growth.
  • If your home has a relative humidity of less than 30%, the air is quite dry, and you need a humidifier to put some moisture into the air.

For the most part, the climate helps us control relative humidity. Nevertheless, there are extreme cases where the air is too dry or humid, resulting in fatigue, shortness of breath, and coughing. These extremes can even worsen respiratory conditions such as asthma or allergies by drying out your airways.

How do you find out how humid your house is?

Measuring the humidity levels in your home is actually relatively easy. There are a plethora of methods to do this. However, we are only going to focus on the less complicated procedures. You can measure humidity in your home by getting a hygrometer.

A hygrometer is a device that measures humidity in an environment. It works using the principle of evaporative cooling. When water evaporates from a surface, it becomes cool due to molecules taking heat from that surface.


The most effective way to get an accurate reading is by picking the right location. Make sure to find a room that doesn’t experience wide humidity or temperature fluctuations, take measurements over a week in various rooms to develop a baseline, and take readings at different times of the day.

What does humidity do to your house?

High humidity in your home can spur the growth of mildew and mold, while excessive moisture could result in rot, causing your belongings to become damaged. Apart from mildew and mold growth, high humidity could also cause your wallpaper to peel and any paintings or artwork to become damaged.

Excess moisture in your home can damage wood, either creating growths and stains or causing severe decay. Furniture placed closer to outside walls are at a higher risk of damp setting in.

The different types of humidifiers

There are two major types of humidifiers (warm-mist and cool-mist), but other popular technologies are worth knowing. They are all equally effective at adding moisture to the air, with minor differences.

The diagram below shows how humidifiers add moisture to the air:

The type of humidifier you choose is simply based on personal preference, as one doesn’t have an advantage over the other.

Cool-mist humidifiers blow cool air through a wet object to moisturize the air, pushing water through a filter to expel all impurities right before releasing a cool vapor mist into the air.This type of humidifier works best in warmer climates.
Warm-mist humidifiers use a disc in water that spins at high speeds, generating tiny water droplets that exit the humidifier in the form of steam. These are best suited for cold climates.
Evaporative humidifiers create a cool mist without heating the water (compared to warm-mist humidifiers). Instead, a fan pulls humid air through a moist wick filter at the bottom of the humidifier. This water evaporates into a vapor and is expelled as a spray or mist, creating humidity in the air. They are ideal for children and pets since they don’t involve hot water.
Vaporizer humidifiers use a boiling process to rid water of pollutants before releasing fresh moisture into the air, with the option of warm or cool mist. You can add inhalants to help ease cold and flu symptoms.
Ultrasonic humidifiers use a vibrating metallic diaphragm (usually made of metal or ceramic) to release moisture into the air. The diaphragm vibrates at high speeds, stirring up water into droplets when they exit the humidifier. They are extremely quiet, so they are perfect for bedrooms and children who are easily startled by noise.

The two main types of dehumidifiers

As stated earlier, dehumidifiers do the opposite of what humidifiers do. They take moisture out of the air, keeping the air indoors dry. A well-functioning dehumidifier should reduce the indoor RH to a 30 to 50% comfortable range.

There are two types of dehumidifiers: desiccant and refrigerating.

  • Refrigerative dehumidifiers are the most common types of dehumidifiers used in households. They don’t offer as much cooling power as a desiccant. However, they can seamlessly maintain a healthy humidity level in a home.

    The fan in the dehumidifier captures and contains warm air, cooling it using metal coils. As the warm air is cooled down by the refrigerant-filled metal coils, the air begins to shrink, producing warm water droplets, which are then stored as condensation in the dehumidifier’s tank. With the cold air now free of warm water droplets, another fan blows it back into the home. 
  • Desiccant dehumidifiers are extremely powerful dehumidifiers. For this reason, they are typically used in commercial storage for chemicals, food, and pharmaceuticals.

    A desiccant can reduce the humidity levels from 45% down to 1%. Compared to a refrigerative dehumidifier that uses electrical outlets, a desiccant dehumidifier uses thermal energy (steam or natural gas). It also differs from a refrigerative dehumidifier in how it gets rid of moisture. It uses chemical attraction rather than condensation to decrease humidity levels.

Final thoughts

They both deal with the humidity levels in your home; however, a humidifier adds moisture to the air while a dehumidifier removes moisture from the air. The device you use typically depends on the Relative Humidity level of your home.


About the author

Danny Ashton

Danny is the founder of HouseFresh and has been writing about air purifiers and indoor air quality since 2010. He is our lead tester, conducting all the tests we use to evaluate air quality products. That is why you will always see his name attached to our reviews.