How Low Can a Dehumidifier Go?

Note: This article covers how low a dehumidifier can reduce relative humidity. If instead you’re looking for information about the best low temperature dehumidifiers, check out the separate article linked here.

High humidity can cause many different problems in your home. If left for long, it can lead to the growth of mold, mildew, and dust mites, which can trigger allergic reactions and other health issues. To prevent these problems, dehumidifiers maintain indoor humidity within the ideal range. 

Usually, the best setting for a dehumidifier is from 30% to 50% RH. If the room is extremely humid, you can let the unit run continuously, but in most cases, this is unnecessary and can dry up the air. When setting your dehumidifier, it’s also important to note the ambient temperature to maximize your comfort. If it’s your first time using a dehumidifier, we’ll guide you through finding the best dehumidifier settings for you.

What is Humidity?


Before using a dehumidifier, it’s essential that you understand what humidity is. There is always water vapor in the air, and the amount of it is what we call humidity. We measure the relative humidity or RH (in percentage) as the amount of moisture actually present in the air compared to the maximum amount the air could hold at a given temperature.  

The temperature does not necessarily affect the relative humidity (and vice versa), but it can have some effect on how we perceive the other. In particular, as the temperature increases, the air can hold more water molecules. So if the temperature drops suddenly, the relative humidity rises. Furthermore, when the air temperature reaches the dew point, achieving 100% relative humidity, condensation occurs.

Conversely, if the relative humidity is high, the hot temperature feels even hotter to you because your perspiration cannot evaporate into the already saturated air. Meanwhile, during winter, the cold air can hold fewer water molecules and the lower humidity will make it feel even colder.

Optimal Relative Humidity

How Does a Hygrometer Work featured photo

The recommended relative humidity for your home is from 30% to 50% RH. When humidity is below 30%, you may suffer dry, scratchy throat, nasal congestion, and other respiratory conditions. On the other hand, when humidity is above 50%, it creates an environment suitable for mold growth and can attract pests to your home. So if your dehumidifier has a humidistat, choose a setting between 30% and 50% RH. Most people would be comfortable at a 45% setting, but it depends on the ambient temperature.

Your dehumidifier humidistat senses the room humidity level and automatically adjusts to your preferred settings  When you set the humidity, the unit will work until the ambient humidity is lower than this setting. The dehumidifier will run on fan mode and then measure the room’s humidity after a certain period. If the humidity reading is higher than your setting, then the unit will resume dehumidifying the room. 

Why You Need to Control Humidity 

Too little and too much humidity can both pose risks to your health. Dry air absorbs water from any moist surface, including your skin, eyes, and nasal passages, making them dry and irritated. Low humidity can also trigger allergy and flu-like symptoms including nasal congestion due to the inflammation of the airways.

Low humidity can also be harmful to building materials. Since wood is a porous surface, it releases loses moisture to the dry air, causing wooden beams and furniture to shrink and crack. On the other hand, wood also absorbs moisture when exposed to high relative humidity. This causes the wood to expand and warp.

Excess moisture makes a suitable environment for common allergens such as mold and dust mites. When airborne, mold spores and dust mite wastes can cause allergic reactions like sneezing, runny nose, and eye irritations. It can also trigger asthma attacks.

A common sign of humidity is musty or moldy odors. Mold and mildew can grow on any moist surface like your walls, ceilings, and furniture, and they feed off the organic material, damaging your furniture and house structure.  Excess moisture in the home can also cause rusting metals, rotting wood, and termite infestation.

Water Restoration Dehumidifier

Benefits of Using a Dehumidifier 

Here are a few benefits you can get from controlling humidity in your home using a dehumidifier.

Reduce allergies

Dehumidifiers reduce humidity levels and prevent mold growth. Maintaining proper humidity inside your home reduces the chances of these organisms surviving and reduces the risks of allergic reactions, allergy-induced asthma attacks, and other respiratory conditions. 

Improve indoor air quality

High humidity can increase the risk of dehydration due to the high amounts of water vapor and lower oxygen molecules in the air you breathe. Excess moisture makes the air feel sticky on your skin. Using a dehumidifier eliminates excess moisture along with unpleasant odors, improving the overall indoor air quality for your health and comfort.

Improve your air conditioning 

When the air is both too hot and humid, your air conditioning may not be enough to control both the temperature and humidity levels. As the air conditioner cools down the warm air, it also helps reduce humidity as a result. However, when there is more moisture in the air the job becomes too difficult for your AC alone, giving you higher cooling bills and less effective air conditioning. A dehumidifier’s main purpose is to reduce humidity, lessening the load on your air conditioner so you can maintain both the temperature and humidity.

Protect furniture and structures

High humidity can cause many damaging effects on different materials in your home, including wood, fabrics, and even metal. Maintaining your indoor humidity within the recommended levels can help prevent damages caused by mold, rust, corrosion, or pest infestation. It also helps preserve the structural integrity of your house.

What is the Lowest Setting For Your Dehumidifier?

Turning on a Dehumidifier Constantly

When choosing the best dehumidifier setting for your home, there are some factors that can affect your decision. Particularly, some types of dehumidifiers may limit your options. 

Dehumidifier Type

There are different types of dehumidifiers you can use to control humidity in the house. Most dehumidifiers allow you to set your preferred humidity level on the digital display and then the unit will automatically maintain your humidity settings. You can usually set the humidity from 30% to 80% or 90% RH on the humidistat of portable refrigerant dehumidifiers. In most situations, 45% is the most comfortable setting.

This type of dehumidifier usually also features a Continuous mode. The unit will operate continuously for 24 hours (if you’re using the continuous drainage option) or until the tank is full. This can be useful in large spaces with extreme humidity like a basement with a floor drain for automatic draining. Although, note that continuous operation of your dehumidifier can also be inefficient or wasteful of energy when it keeps running unnecessarily. It will keep working even when humidity is already below 30%, resulting in excessively dry air.

Another type of dehumidifier commonly used at home, particularly in small rooms, is called a Peltier or thermoelectric dehumidifier. It doesn’t give you as much control over the humidity as the larger refrigerant dehumidifier does. A Peltier dehumidifier typically only features a single button so you can turn it on or off. However, there are a few larger models that have an additional built-in humidistat so you can set the humidity level you want. 

The other main dehumidifier type is called a desiccant. This type is usually smaller and can be disposable or renewable. The full-sized desiccant models are similar to the smallest refrigerant dehumidifiers in appearance and features. They also include a humidistat so you can set the humidity level you want from 30% to 80% RH.

Lastly, whole-house dehumidifiers can be ducted to multiple rooms to dehumidify them all at once. They either have an onboard or remote humidistat so you can set your desired humidity level for the entire house. Getting a whole-house dehumidifier is usually more cost-efficient than buying multiple portable units.

Ambient Temperature

The ambient temperature also impacts the right humidity level for your house. Remember that cooler air can hold less moisture. If the outdoor temperature is from 20°F to 40°F, the humidity must be set not higher than 40%. If the temperature is from 10°F to 20°F, the humidity must be set not higher than 35%. And if the temperature is below 10°F, the humidity must be not higher than 30%. In any case, most dehumidifiers will only work in temperatures down to 41°F, or 33°F for desiccant units.


What is the best setting for a dehumidifier?

The best setting for a dehumidifier varies in every situation. The optimal relative humidity is between 30% and 50% but you can adjust the dehumidifier setting depending on tour preference.

Where should you place a dehumidifier?

Ideally, a dehumidifier must be placed near the humidity source. Close all windows and doors when operating the dehumidifier but make sure there is adequate airflow to cover the entire room evenly.

Should you run a dehumidifier constantly? 

No, you don’t need to run a dehumidifier constantly. Ideally, you should only operate the unit when the relative humidity reaches above 50%. Continuous operation may be unnecessary and inefficient.

How long does it take for a dehumidifier to work?

You can usually notice a change in humidity within a few hours depending on the size and dampness of the space. When dehumidifying a room for the first time, it can take up to 12 hours. For whole-house units, it can even take a couple of days to achieve your preferred humidity.

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