Tackling Crawl Space Moisture: A Comprehensive Guide to Crawl Space Dehumidifiers

By: Evan Scoboria, Last updated: June 26, 2023

Crawl spaces are often overlooked areas of a home, but they can significantly impact the overall indoor air quality and the structural integrity of your home. Excessive moisture in crawl spaces can lead to mold growth, wood rot, and pest infestations, among other issues. This article will discuss the importance of crawl space dehumidifiers, how they work, and how to choose the right one for your home.

 Crawl Space Dehumidifier

The Dangers of Moisture in Crawl Spaces:

Due to their often-neglected nature and relative obscurity in the house, crawl spaces can become breeding grounds for several issues when excess moisture is present. The following complications can arise:

  1. Mold and Mildew Growth: One of the most common problems associated with high moisture levels in crawl spaces is the growth of mold and mildew. These fungi thrive in damp, dark conditions, and a moist crawl space provides an ideal environment. Mold and mildew can cause a musty odor that permeates the house, but more importantly, they can lead to significant health problems. Exposure to mold spores can trigger allergies, cause respiratory problems, and in severe cases, lead to chronic health conditions.

  2. Wood Rot and Structural Damage: Crawl spaces often house essential structural elements of the home, such as beams and joists, typically wood. Over time, excessive moisture can lead to wood rot, where the wood becomes soft, crumbly, and loses its structural integrity. This can compromise the overall stability of the house, leading to costly repairs and potential safety risks.

  3. Pest Infestations: Damp environments attract various pests, including termites, carpenter ants, and rodents. These pests can cause additional damage to the house's structure, and some, like termites, can cause severe damage if left unchecked.

  4. Increased Energy Usage: When a crawl space is damp, the excess moisture can seep into the living areas of your home, making your heating and air conditioning systems work harder to maintain a comfortable temperature. This can lead to increased energy consumption and higher utility bills.

  5. Damage to Insulation: Many homes have insulation in the crawl space to prevent heat transfer from the outside. When moisture levels are high, it can saturate this insulation, rendering it ineffective. Wet insulation can also become a breeding ground for mold.

  6. Unpleasant Odors: As mentioned earlier, the growth of mold and mildew can cause a musty smell. Additionally, if pests are attracted to the moisture in the crawl space, their waste or even deceased bodies can create unpleasant odors that can seep into the house's main living areas.

By understanding the dangers associated with moisture in crawl spaces, homeowners can take proactive steps to address any issues before they escalate into significant problems.

The Role of Crawl Space Dehumidifiers:

Crawl space dehumidifiers are designed to maintain a consistent, low humidity level within the crawl space, reducing the risk of moisture-related issues. They draw in damp air, remove moisture through condensation, and then redistribute dry air back into the space. This helps to prevent mold growth, wood rot, and pest infestations.

Choosing the Right Crawl Space Dehumidifier:

When selecting a crawl space dehumidifier, consider the following factors:

  1. Size and capacity: Choose a dehumidifier with the appropriate capacity (measured in pints of moisture removed daily) for your crawl space's size and humidity levels. As a general rule, larger rooms and higher humidity levels will require a dehumidifier with a higher capacity.
  2. Energy efficiency: Look for a dehumidifier with an Energy Star rating or a high energy factor (EF) to ensure you get an energy-efficient model that won't significantly increase your utility bills.
  3. Durability and build quality: Crawl space dehumidifiers are often exposed to harsh conditions, so opt for a model with high-quality, durable materials that can withstand the environment.
  4. Automatic features: Consider a dehumidifier with an auto-humidistat that can automatically maintain the desired humidity level and shut off when the desired level is reached. This can help save energy and reduce wear on the unit.
  5. Ease of installation and maintenance: Look for an easy dehumidifier to install with a user-friendly design for simple filter cleaning and maintenance.

Installing a Crawl Space Dehumidifier

Step 1: Prepare for Installation

Before installing a crawl space dehumidifier, assessing and preparing the area to ensure optimal performance is essential. Start by inspecting the crawl space for any signs of water damage, mold growth, or other issues that must be addressed before installation. Ensure the crawl space is adequately sealed, with proper vapor barriers in place, to prevent excess moisture from entering the area. Additionally, check for proper ventilation and make necessary improvements to promote adequate airflow. Finally, clear the space of any debris, dirt, or other obstacles to provide easy access for the installation process.

Step 2: Select the Right Location

Choosing the right location for your crawl space dehumidifier is crucial for maximizing efficiency and effectiveness. Ideally, the dehumidifier should be placed in a central location within the crawl space to ensure an even distribution of dry air. Position the unit on a level surface, ensuring it is elevated slightly off the ground, either on a pedestal or using specially designed mounting brackets. This elevation will help prevent the dehumidifier from drawing in cool air from the ground, which can reduce its efficiency. Ensure sufficient clearance around the dehumidifier for proper airflow, and keep the unit away from sources of excess moisture, such as water pipes or sump pumps.

Step 3: Install and Connect the Dehumidifier

Install the dehumidifier once the crawl space is prepared and the ideal location has been identified. Follow the manufacturer's instructions for proper assembly and setup. Connect the dehumidifier to a dedicated power source, ensuring the electrical wiring is up to code and properly grounded. If your dehumidifier includes a built-in condensate pump, connect the pump to a suitable drainage system or route the drainage hose to a designated drainage area, such as a sump pump pit or a floor drain. For units without a built-in pump, you may need to purchase an external condensate pump or ensure the drainage hose is sloped downward to allow gravity-assisted drainage. Once the dehumidifier is installed and connected, you can set the desired humidity level on the unit's control panel. This will enable the dehumidifier to operate continuously to maintain a healthy, dry crawl space environment.

Crawl Space Dehumidifier Maintenance

Maintaining your crawl space dehumidifier is crucial to ensure its optimal performance and longevity. Here are some steps to keep your dehumidifier in top shape:

  1. Cleaning the Dehumidifier: Wipe down the exterior of the dehumidifier regularly with a damp cloth to prevent dust build-up. Refer to the manufacturer's instructions for the interior, as some parts may need specific cleaning procedures.

  2. Filter Maintenance: The filter in your dehumidifier traps dust and other particles. Depending on your usage and the manufacturer's recommendations, cleaning the filter every two weeks to a month is generally reasonable. Some dehumidifiers have a filter indicator light that lets you know when to change or clean.

  3. Checking the Coils: Dehumidifier coils can accumulate frost if the temperatures are too cold. If your dehumidifier isn't working as well as it used to, check the coils for frost build-up. If ice is present, turn off the unit and let it defrost.

  4. Checking the Drain Hose: If your dehumidifier has a continuous drainage feature, ensure the drain hose is clear of clogs.

  5. Annual Maintenance: It's a good idea to have a professional service for your dehumidifier once a year. They can check the refrigerant levels, clean hard-to-reach areas, and ensure the dehumidifier works correctly.

  6. Replacing Parts as Needed: Over time, parts like filters or even the dehumidifier itself may need to be replaced. Always use parts from the original manufacturer to ensure they fit and work correctly.

By carrying out regular maintenance, you'll keep your crawl space dehumidifier running efficiently, helping maintain a healthy home environment.

Frequently Asked Questions

Why do I need a dehumidifier in my crawl space? A dehumidifier in your crawl space helps control the moisture level, preventing the growth of mold and mildew. This not only preserves the structural integrity of your home but also improves air quality, reducing allergens and potential health risks.

How often should I check my crawl space dehumidifier? Ideally, you should check your crawl space dehumidifier once every two weeks to ensure it functions appropriately and empties its water reservoir. However, the frequency can depend on your unit and the humidity levels in your crawl space.

How do I choose the right dehumidifier for my crawl space? When choosing a dehumidifier, consider the size of your crawl space, the average humidity level, and the dehumidifier's capacity and energy efficiency. You may need a high-capacity dehumidifier for larger areas or areas with high moisture levels.

Can I install a crawl space dehumidifier, or should I hire a professional? If you're comfortable with DIY projects, install a crawl space dehumidifier yourself. However, it's best to hire a professional if you need clarification or if the unit needs to be integrated into your home's HVAC system.

What are the signs that I need a dehumidifier in my crawl space? Signs that you may need a dehumidifier include a damp or musty smell, visible mold or mildew, condensation on walls or windows, or wood rot in your crawl space.

How often should I replace the filters in my crawl space dehumidifier? It's usually recommended to replace the filters in your dehumidifier every 6-12 months, but this can vary depending on usage and air quality. Always refer to your unit's manual for specific guidance.

Can a crawl space dehumidifier help improve the air quality in my home? Yes, by reducing humidity and preventing the growth of mold and mildew, a crawl space dehumidifier can help improve the overall air quality in your home.

Are there any potential problems or issues I should know about with crawl space dehumidifiers? Crawl space dehumidifiers are generally safe and reliable, but they need regular maintenance to prevent issues like overflowing reservoirs or filter clogs. They also use electricity, so incorrect installation could pose a fire risk.

How much does it cost to run a dehumidifier in a crawl space? The cost to run a dehumidifier depends on the unit's size, how often it runs, and your local electricity rates. Energy-efficient models can help reduce these costs.

What's the difference between a regular dehumidifier and a crawl space dehumidifier? Crawl space dehumidifiers are typically designed to be more robust and are often more capable of handling higher humidity levels. They are also generally designed for continuous operation and may be more energy-efficient in the long run.


Investing in a quality crawl space dehumidifier is crucial for maintaining a healthy, structurally sound home.  It can effectively prevent mold growth, wood rot, and pest infestations, ultimately protecting your home and your family's well-being. This device works diligently to remove excess moisture, preventing dampness, musty odors, mold growth, and potential structural damage. Its operation can be discrete and unintrusive, especially with features like automatic humidity control and direct draining. However, regular maintenance, including cleaning, filter replacement, and annual servicing, is crucial to maximizing your crawl space dehumidifier. Doing so ensures your dehumidifier operates optimally, serving you efficiently for years.