Crawl Space Dehumidifier

Keeping your home dry is important, and this is true from the peaks of the attic to the lowest level of the basement or crawl space.

If your home has a crawl space, you need to consider using a crawl-space dehumidifier. These appliances not only protect your home from structural damage like wood rot and warping, they can also improve the overall air quality by reducing the chances of mold and pests.


crawl space entrance

What is a Crawl Space?

Before we dive into the dehumidifiers, it helps to explain exactly what a crawl space is and what it is not. A crawl space is the hollow area underneath some homes between the floorboards and the ground itself. Usually about one to three feet high, the crawl space is just large enough for someone to scuttle underneath, hence the name crawl space.

This area serves a few different purposes. For one, it lifts the house above the ground, which can help with reducing moisture and other issues. The crawl space is also a good location for various appliances and parts, such as A/C, heaters, ductwork, and plumbing.

Generally, crawl spaces are more affordable than digging a basement, and are usually preferred in areas with humid air, high moisture or in coastal areas that have sandy soil. In these places, excessive moisture can seep into the basement, so crawl spaces are a better alternative.


Why is Moisture in the Crawl Space Such a Problem?

While a crawl space can be a good alternative in some areas, it does have a few issues that need a homeowner’s attention. One of those issues is moisture. Moisture in a crawl space creates a wide range of issues for the home, including both structural problems and potential risks to people living in the house.

When you have excess moisture in the crawl space, it can cause premature wear and tear to the home. Wood rot is more likely to occur to the lumber, including support beams, floorboards, and wood panels. This rot can severely harm your home and can lead to massive repair bills if left alone. If you have moisture underneath, it can also cause noticeable problems in the flooring above. Cupping, warping, and damage to floorboards is common when there is a lot of moisture in the crawl space. Even if you don’t have hardwood floors, the plywood that makes the base of the floor can become disfigured, leading to an uneven floor.

While structural issues are certainly a concern, excessive moisture in the crawl space can also cause health issues. Mold, for example, is more likely to occur if there is a high amount of moisture in your home. Even a high relative humidity without standing water can cause mold to grow.

This common fungus is able to survive off some of the most sparse resources, and it while it certainly appreciates standing water, moisture in the air is enough for mold to thrive. When they grow, mold and mildew release spores, which is how the fungi reproduce. These spores float on the air and can enter the home, creating musty odors as well as respiratory issues for virtually anyone. If you are allergic to mold or suffer from preexisting respiratory issues, you are at higher risk from mold problems.

As unpleasant as it might be to think about, dust mites, which are microscopic insect-like pests, can also be increased if there is excessive moisture. Like mold, dust mites absorb moisture from the air, so if you have high levels of humidity in your crawls space, you could have higher rates of growth for these pests. When dust mites are present, allergy sufferers can have symptoms triggered by the mites’ leavings as well as their body parts, which can flake off and float in the air.

As you can see, high relative humidity in the crawl space can be a significant problem. With a crawl space dehumidifier, however, you can tackle the issue and reduce your chances of rot, mold, dust mites, and other problems created by moisture.


What is a Crawl-Space Dehumidifier?

A crawl space dehumidifier is just that: a dehumidifier specifically designed for your crawl space. Household and basement dehumidifiers are commonly used inside the home, that is, inside the living space, especially the basement. By taking moisture from the air, they reduce humidity levels and maintain a well-balanced humidity percentage, which is usually about 30 to 50%. Most dehumidifiers are a few feet tall and made to stand on a level, solid surface. For many reasons, sitting on the ground will not do for a crawl-space dehumidifier, so a special unit is required.

Crawl-space dehumidifiers are built to perform the same task as any other unit, only they are properly shaped and designed for use in the narrow spaces under a home. They also tend to be more powerful, as crawl space moisture can be much higher than the moisture in, say, your bedroom. Because of the higher capacity and unique design, they also tend to be more expensive than typical dehumidifiers.



Where Installed

Many crawl-space dehumidifiers are not set on the ground of the crawl space but are mounted to the beams that support the floor. Essentially, they are mounted to the ceiling of the crawlspace. This keeps them above the ground, where water is more likely to pool. They often have a thin pipe that runs from the unit to the house’s main drain pipes. This allows the moisture collected by the dehumidifier to be sent away from the home, causing no more trouble.


Common Features

One of the common features for a crawl-space dehumidifier is an auto-defrost function. This feature allows the unit to avoid excessive frost that can build up on the compressor coil. Dehumidifiers in cooler areas can easily freeze, as the crawl space is not heated and rarely insulated. In low-temp environments, having an automatic defrost can be extremely useful to the longevity of the dehumidifier.

A large capacity for moisture collection is also required from crawl-space dehumidifiers. Most household units won’t have the capacity to keep up with the higher amounts of moisture that are found in crawl spaces, so units under the home need to be specifically built to handle more moisture at any given time.

Proper water removal is another unique feature for crawl-space dehumidifiers. Household units generally have a holding tank that stores the water collected from the air; homeowners are then required to empty the tank on a regular basis. (Some have hoses that can run to drains.) Accessing a crawl-space dehumidifier is obviously more difficult, so, as we described above, they are usually equipped with a hose that is connected to the nearest drain pipe. This allows the collected moisture to flow outward without a continual need to empty the tank.

Because you can always access a household unit, most dehumidifiers have basic controls like “on” and “off” or even “high,” “medium,” and “low.” These can usually be controlled manually from the outside of the unit, but with a crawl-space dehumidifier, you can’t access it to operate the dials, at least not easily. Therefore, a built-in humidistat, which measures the humidity levels, is often included in the unit. The humidistat is then attached to an on/off function that controls the unit automatically.

Other features can include an internal pump, which moves water if downhill drainage is not an option, or an air-purification system, which can be useful since air underneath the home is often pulled upward.


Tip: Ground Liners Can Assist Dehumidifier

If you have a crawl-space dehumidifier installed in your home, there are many features and additions that can be added to enhance the overall performance and reduction in moisture.

For example, a ground liner may be added to the bottom of the crawl space to act as a vapor barrier. This ground liner becomes an air-tight, water-tight barrier, blocking ground moisture and preventing it from entering the lower area. To see how liners look when installed, this video from American Crawlspace Solutions provides a great demonstration of crawl-space liners.


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