What Size Dehumidifier For A Crawl Space?

A dehumidifier is an efficient moisture remover for mold-prone areas. But before you install one, you should be particular about what size dehumidifier is appropriate for your crawl space. Otherwise, the appliance won't be as effective. We've done the research to provide you with a comprehensive guide.

The right size dehumidifier for your crawl space will depend on its square footage and relative humidity levels. For a crawl space of 300 square feet, you may need a 20–30 pint-size dehumidifier, 25–40 pints for 500 square feet, 35–50 pints for 800 square feet, and 50–60 pints for 1,200 square feet.

Continue reading to learn how humidity levels will affect a dehumidifier's pint capacity. We'll also discuss what dehumidifier type is appropriate for a crawl space and the factors to consider before installing a unit, as well as its draining location.

A dehumidifier in a crawlspace, What Size Dehumidifier For A Crawl Space?

The Appropriate Size Dehumidifier For Your Crawl Space

As homeowners tend to ask what is the ideal humidity level for a crawl space, they would usually get different answers. But according to a crawl space expert, in most cases, humidity levels should be between 45 and 55 percent.

Bacteria, germs, and indoor pollution can develop in extremely low humidity levels as well as an area with over 60 percent of humidity levels. Therefore, a dehumidifier is a perfect solution for maintaining healthy humidity.

The proper size dehumidifier is a crucial thing to consider in dehumidifying your crawl space. If the unit is too small, it doesn't have the capacity to extract the moisture from the entire crawl space, while a quite large unit may lead to an increase in your electric bill.

When sizing the unit for your crawl space, you should consider the area's square footage and humidity. Here's a dehumidifier sizing chart that can serve as your reference:

Humidity Levels 300 square feet 500 square feet 800 square feet 1,200 square feet
Slightly Damp 50-60% Humidity 20 pint 25-30 pint 35-40 pint 50 pint
Moderately Damp 60-70% Humidity 20 pint 25-30 pint 35-40 pint 50 pint
Very Damp 70-80% Humidity 25 pint 30 pint 45 pint 55 pint
Wet 80-100% 25-30 pint 35-40 pint 45-50 pint 60 pint

The Rule Of Thumb

If your crawl space's square footage is not included in the chart, the technique is to add 5 or 10 pints for every 200 square feet. If you have doubts that the unit will fully work in your crawl space, then always stick for a bigger pint capacity. Just make sure that the size will not increase your electricity too much.

A dehumidifier should also extract so much moisture within 24 hours, for the reason that a crawl space is an extremely humid place. For example, a 1,500 square feet crawl space requires a unit that removes 90 pints of moisture per day.

In addition, many manufacturers describe the pint capacity of their dehumidifiers in saturated conditions. This value is usually higher, but it's the same level of standardized testing as the PPD (pints per day) set by the Association of Home Appliance Manufacturers.

For example, the Alorair basement/crawl space dehumidifier can remove 55 pints of moisture per day and 120 pints in saturated conditions.

Since choosing the right size dehumidifier for a crawl space may be quite complicated compared to choosing the right size for basements or the upper floors, you might want to let professionals do the square footage calculations. They can also help find the appropriate size dehumidifier for your crawl space.

Can I Use A Regular Dehumidifier For A Crawl Space?

Most experts don't recommend the use of a regular dehumidifier for a crawl space. The regular dehumidifier is rarely capable of drying out your crawl space. Though it may extract some moisture, a crawl space dehumidifier is more powerful and specifically designed to withstand such environment.

Click here to see this basement/crawl space dehumidifier on Amazon.

How Do You Dehumidify A Crawl Space?

Crawl space with upper floor insulation and wooden support

The right type and size dehumidifier will help you to effectively dehumidify your crawl space. But proper and convenient dehumidifying does not only require an efficient unit, you will also need to consider other factors.


Once you chose the right size dehumidifier, you will need to install it in the most ideal location in your crawl space. It should be placed where there is no airflow blockage, and where it can be easily drained. Its location should also be accessible for future maintenance and cleaning.

Other things to consider in installing a dehumidifier include the area's shape, setting up the gravity drain, etc. Thus, installing a dehumidifier may be quite complicated, especially if you're not a handy person. So if you don't have prior knowledge and skills, you might as well hire a professional to do all the work.


To have a convenient dehumidifying experience, you will need to encapsulate your crawl space. Crawl space encapsulation serves as protection from moisture that uses a vapor barrier (plastic) to cover its floor and walls, keeping the moisture sealed outside the plastic.

Keep in mind that you should encapsulate your crawl space first before installing a dehumidifier. A dehumidifier can remove some moisture in the air, but the environment is also the main factor in maintaining healthy humidity levels.

Here's a video for you that further explains why crawl space encapsulation is necessary:

Take note that before putting up a vapor barrier and installing your unit, you should ensure that your crawl space is well-sealed.

You also need to make sure that your crawl space is free from debris and unwanted clutter. Watch out for the steps that will explain how you should clean up and fix issues in your crawl space.

Will A Dehumidifier Dry Out Crawl Space?

Yes, a dehumidifier can dry out crawl space. You can usually dry out your crawl space for 8 to 10 hours with a setting between 30 and 45 percent. The specific time of drying depends on the unit's size, the area's square footage, and its humidity levels.

How To Dry Out Your Crawl Space

Wooden framing and floor joist under a crawlspace of a small house, Should Crawl Space Vents Be Open Or Sealed?

Before you effectively dry out your crawl space with a dehumidifier, you will need to follow these few steps:

1. Clean wet debris and remove damp materials

Regardless of whether your crawl space is damp or in a flat-out wet condition, you should check if the area has any accumulation of wet debris. Before running your unit to dry out the area, you will need to clean all of the wet debris and inspect its insulation.

Damp insulation should be replaced to completely dry your crawl space. Make sure that you clean and remove all the wet debris and junk in your crawl space, not doing so will only leave excess moisture that would worsen over time.

2. Use a sump pump to remove standing water

After removing wet debris and insulation from your crawl space, you will need to remove the standing water. If your area is only damp, draining won't be necessary, meaning you can move forward to the last step.

It's convenient to use a sump pump to drain the crawlspace, especially if the area is flooded. Here's a video that shows how to pump out your flooded crawl space:

3. Use a dehumidifier to dry out your crawl space

Finally, after doing the previous steps, you can already use a dehumidifier to completely dry your crawl space. There is no golden rule on how long a dehumidifier takes to dry out the area.

Aside from the unit's size, the area's square footage and humidity levels, the crawl space's ventilation linked to the whole house will also affect the drying time.

Using a dehumidifier alone to dry out your crawl space will take an estimated time of 8 to 10 hours. Set your unit between 30 and 45 percent and operate until the area is sufficiently dry.

Where Do Crawl Space Dehumidifiers Drain?

A crawl space dehumidifier could be drained under the plastic or out of the flower bed. You can use a sump pump or condensate pump in pushing the water wherever it needs to go.

Watch the video below for some helpful tips:

The discharge line's location will depend on how cold your place is. If you're in a colder climate, you can just drain directly under the plastic, you won't need the condensate water going out of the crawl space.

In Closing

In choosing the right size dehumidifier, you will need to consider your crawl space's square footage and humidity levels. Its pint capacity in saturated conditions is also an important factor insofar as choosing a crawl space dehumidifier to dry out the area.

Cleaning up, sealing, encapsulation, and the installation of the dehumidifier will help to efficiently dehumidify your crawl space. Yet to fully dry out this humid area, you should also check out for other underlying issues.

To learn more about basements and dehumidifiers, check out these posts:

What Size Dehumidifier For A Basement?

How Long For A Dehumidifier To Dry Basement?

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