Should You Run A Dehumidifier In Your Basement?

At Ensign, we regularly encounter homes with elevated relative humidity levels throughout North Georgia and the surrounding areas, largely due to the humid climate of the Southeastern United States. Relative Humidity (RH) is the measure of the amount of water vapor in the air with respect to the temperature of that air. Throughout most of the year, the state of Georgia and most of the southeastern United Staes has high levels of RH, particularly in the Summer months. High RH can create problems for the home that are costly to address, including water damage and mold growth. Controlling mold growth is also essential for maintaining good indoor air quality and avoiding health issues. Mold spreads by reproducing itself from tiny spores roaming in the air. These spores are not visible to the human eye, but mold begins to grow once these spores land on moist surfaces. Water is necessary for any mold to grow. Therefore, if you can remove the water source, you can stop the mold growth. 

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Using a dehumidifier is a great way to keep moisture levels under control in your home, creating a safer and healthier home environment. Key areas we commonly see with high levels of RH in a home are in basements, particularly ones which are unfinished and untreated with HVAC units. With unfinished basement homes, we recommend homeowners to keep a dehumidifier running in the basement at all times. Even after finishing your basement, it is still a good idea and highly recommended to keep a dehumidifier running due to the humid environment surrounding the home outdoors. In addition, basements are often used less frequently than other areas of the home, making it more likely for rising relative humidity levels to go unnoticed over extended periods of time.

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How a Dehumidifier works

A dehumidifier works by pulling moisture from the surrounding air, using condensation to convert water vapor from a gas into liquid for removal. The device pulls in warm air in and exposes it to refrigeration coils to cool the air down. As the temperature of the air decreases, it is no longer able to hold the moisture within that air. The water vapors turn to liquid where they can now be collected by the dehumidifier. The dryer and cooler air is then released back out of the device.

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Dehumidifiers typically collect water vapor in a detachable bucket. The device is usually equipped with a meter which can measure the relative relative humidity of a space. Dehumidifiers can also be equipped with a valve where a drain hose can be attached for convenient draining for long-term use.

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Why Moisture is a common problem in basements?

Understanding relative humidity (RH) is essential for managing moisture in your basement. Being below ground level, basements are typically cooler than other areas of the home. They also undergo daily temperature changes from day to night, with these fluctuations often intensified by seasonal shifts. Together, these factors create a unique environment that requires careful moisture management to prevent issues like dampness and mold growth.

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Because basements are built below grade, they are naturally more susceptible to moisture issues. The surrounding soil holds moisture, which can turn into water vapor beneath the home and migrate upward through the structure due to the natural stack effect. As this moisture enters the basement, it can cause relative humidity levels to rise. Every home experiences this phenomenon to some degree. The difference lies in how well the home was constructed and what moisture management measures were implemented during and after construction by the homeowner.

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The relationship between humidity and temperature

Relative humidity (RH) is the amount of water vapor in the air relative to the maximum amount it can hold at a given temperature. It’s expressed as a percentage, indicating how "full" the air is with moisture at that given temperature:

• 75º Fahrenheit at 50% relative humidity: 75º F air is holding half the capacity of water vapor it can at that temperature.
• 75º Fahrenheit at 100% relative humidity: 75º F air is fully saturated with water vapor, and any additional moisture will likely condense into liquid.

‍In the context of Relative Humidity, the relationship between humidity and temperature is an inverse relationship. As temperature increases, relative humidity decreases. As temperature decreases, relative humidity increases. 

Scenario: High Relative Humidity in Basements

Let’s say it’s late Summer going into fall and we have an unfinished basement in Georgia, which is a humid climate most of the year. During the transition from summer to fall, temperatures in Georgia can vary by as much as 20 degrees from day to night. This drop can make an already cool basement even colder during the nighttime hours. As basement temperatures drop, relative humidity rises because cooler air has a lower capacity to hold moisture than warmer air. At 65% relative humidity, there is enough moisture in the air for mold to begin growing. After about 48 hours of moist conditions in the basement, mold spores present on organic surfaces will begin to proliferate. 

Since Mold requires air, an organic surface, and moisture to grow, then the solution is to control what we can. The easiest of the 3 to control is the amount of moisture within the basement. This is where a dehumidifier comes in. Actively running a dehumidifier in your basement helps you avoid the headache of expensive remediation costs to address mold growing in your basement.

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Tips to running a dehumidifier in your basement

Placement

When setting up a portable dehumidifier in your basement, placement is key. If you’re using a single dehumidifier for the entire basement, it should be located in the largest open area and properly sized for the total square footage it’s intended to serve. To ensure effective moisture removal throughout the space, keep doors to other finished rooms open so air can circulate freely and reach the dehumidifier. If the basement includes multiple enclosed rooms or areas with limited airflow, additional smaller dehumidifiers may be needed to properly manage humidity in those spaces.

Basement Dehumidifier Settings

Set your basement dehumidifier to maintain a relative humidity between 40%–50% when the unit allows for a specific humidity setting. Ideally, indoor RH should stay around 50% or lower and should not exceed 65%, as higher levels increase the risk of moisture and mold issues. If your dehumidifier does not allow you to set a target humidity, monitor the space with a separate hygrometer and adjust run times as needed to stay within this range. It’s also important not to over-dry the space. Relative humidity below about 15% can lead to discomfort from overly dry air, such as dry throat, irritated sinuses, etc.

Dehumidifier Drain Line

Most dehumidifiers include a drain outlet that allows a garden hose or a dedicated dehumidifier hose to be attached. If your unit fills up frequently and emptying the reservoir becomes inconvenient, consider running a drain line from the back of the dehumidifier. This line can be routed to the exterior of the home, connected to an HVAC condensate pump, or directed to a nearby drain, such as one near a bathtub, if accessible. If you’re unsure of the best setup for your home, it’s a good idea to consult a professional for guidance.

Take advantage of moisture collected by your dehumidifier

You can also make good use of the water collected by your dehumidifier instead of simply pouring it down the drain. This reclaimed water can be used to water plants around your home, outdoor landscaping, or non-edible houseplants. It’s a simple way to put that captured moisture to practical use while keeping your indoor air healthier.

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If you need assistance with setting up a dehumidifier in your home or you have issues with mold due to moisture buildup, call the team at Ensign today. We service all of North Georgia and surrounding areas providing mold and water restoration services.

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