What Size Dehumidifier For A Crawl Space?

Crawl spaces are narrow, unused, and unoccupied spaces between the ground and ground floors. It's a common component of many homes, and while it can be used for a variety of purposes, it usually faces a common problem: excessive moisture. 

A damp crawlspace can cause several serious problems, such as mold growth, odors, insect invasion, and wood rot. Fortunately, dehumidifiers can be an effective solution to this problem. However, different-sized crawl spaces need to be matched with the appropriate-sized dehumidifier. It's crucial to know the size of the dehumidifier you need before rushing to buy one.

In this article, we will discuss how to choose the right size dehumidifier for a crawl space and explore options such as dehumidifiers with pumps and crawl space ventilation fans. 

Why Do Crawl Spaces Need Dehumidifiers?

As mentioned earlier, crawl spaces are narrow spaces that are usually unoccupied and unused. They are either located at the bottom of the house or at the top of the house.

Mold grows in damp environments. These spores are usually toxic and can cause severe allergies. Mold isn't the only problem that comes with high humidity. Moisture can also cause structural damage, especially to wooden beams and seams. If left unchecked, this can lead to very expensive repairs and possibly ruin other parts of the home.

Poor air quality is another factor. Your air needs to be clean and pure. If one area of the house is affected by poor air quality, it can spread to other areas and adversely affect your quality of life.

Factors to Consider While Choosing the Right Dehumidifier for Your Crawl Space

Size is the most critical factor when choosing a dehumidifier for a crawl space. The larger the space, the larger the dehumidifier will need to be to effectively remove moisture. Since dehumidifiers work by extracting moisture from the air, the larger the area, the greater the amount of air that needs to be treated. Using a dehumidifier that is too small will not remove enough moisture, while one that is too large will result in wasted energy.

Calculating the Size of a Crawl Space

First measure the length and width of the crawl space, then multiply them to arrive at the total area. Many dehumidifiers specify the area (in square feet) that can be covered. For irregular spaces, calculate the square footage of each section separately and then sum. To determine the total volume, multiply the length, width, and height of the space to arrive at cubic feet.

Related reading: Can I Use a Regular Dehumidifier in a Crawl Space?

Humidity Levels

After measuring the space, the next factor to consider is the local relative humidity (RH). This will affect the capacity of the dehumidifier. A medium-sized dehumidifier will work well in moderate humidity levels, while higher humidity levels will require a larger capacity unit. We recommend using a hygrometer to get an accurate reading of humidity levels rather than relying on subjective assessments.

Dehumidifier performance is rated in pints per day (PPD), which is a measure of how much moisture a dehumidifier can remove from the air. For example, a 50-pint unit is suitable for a moderately humid space with humidity levels around 50 percent. However, a dehumidifier with a capacity of 70 pints or more may be needed for an underground space or basement with high humidity. Remember that humidity levels fluctuate throughout the day, so regular monitoring is required to match the right dehumidifier to your needs.

Humidity 50-60 per cent

• 300 square feet: 20 pints
• 500 square feet: 30 pints
• 800 square feet: 40 pints
• 1,200 square feet: 50 pints
• 1,500 sq ft: 60 pints

Humidity 60%-70%

• 300 sq ft: 30 pints
• 500 sq ft: 45 pints
• 800 square feet: 60 pints
• 1,200 sq ft: 70 pints
• 1,500 sq ft: 80 pints

Humidity 70%-80%

• 300 sq ft: 45 pints
• 500 sq ft: 50 pints
• 800 sq ft: 65 pints
• 1,200 sq ft: 80 pints
• 1,500 sq ft: 90 pints

Humidity 80-90 per cent

• 300 square feet: 45 pints
• 500 sq ft: 60 pints
• 800 sq ft: 70 pints
• 1,200 sq ft: 90 pints
• 1,500 square feet: 100 pints

Underground Space Temperature

The temperature of an underground space has a significant impact on the performance of a dehumidifier because temperature affects the humidity in the air. The higher the temperature, the higher the humidity and the more difficult it is to dehumidify. Studies have shown that dehumidifiers work best in the 65-80°F temperature range. At lower temperatures, moisture may freeze on the dehumidifier's coils, reducing the dehumidifier's efficiency and potentially damaging the dehumidifier. For very cold or hot underground spaces, a dehumidifier with a higher pint capacity may be required.

Some dehumidifiers, such as those from AlorAir, can operate efficiently in temperatures as low as 1°C (33.8°F), making them suitable for colder environments.

Underground Space Conditions (Sealing and Ventilation)

Underground spaces tend to be humid due to moisture seeping in from the ground and lack of direct sunlight. When selecting a dehumidifier, consider whether your crawlspace is sealed or ventilated. During humid summer months, the relative humidity in crawlspaces can be as high as 75%, leading to moisture absorption in wooden structures and potentially leading to mold or wood rot. While encapsulation (sealing the crawlspace) helps, it does not eliminate moisture. Proper ventilation is still necessary to speed up the evaporation of humid air, thus reducing the burden on the dehumidifier.

Dehumidifier Size Based on Crawl Space Sealing

When considering ventilation, make sure to maximize airflow by opening windows or doors, avoid blocking air conditioning vents, and place the dehumidifier in an unobstructed area. This will ensure that the dehumidifier can work efficiently and maintain ideal humidity levels in your crawl space.

Final Thoughts

Underground spaces are special places that are unoccupied and unused. Due to high humidity levels, the chances of mold growth in crawl spaces are high. To prevent moisture and mold from causing structural damage, you need to install a crawl space dehumidifier. Make sure you choose the right size for the size of your crawl space.

FAQs

Do I Need A Dehumidifier? Can't Encapsulation Control Humidity?

Many homeowners assume that encapsulating the crawlspace will control humidity, but this is not the case. Think of a dehumidifier as a thermostat for your crawlspace, while encapsulation is more like insulation for your home. Just as insulation by itself does not heat or cool a home, plastic sheeting in a crawl space does not by itself reduce humidity. Dehumidifiers and encapsulation work in tandem to ensure that your crawlspace stays dry at all times.

Dehumidifiers for Crawl Spaces Under 2,000 Square Feet

For a crawl space of around 1,000 square feet, a dehumidifier with a capacity of 70 to 80 pints is typically recommended. One of the best options for spaces under 2,000 square feet is the AlorAir Sentinel HDi90. If you're looking for more efficiency and quieter operation, the AlorAir Sentinel HD55 is also a great choice. The HD55 processes slightly less moisture but operates more quietly and has a more compact design, making it easier to fit into tight crawl spaces.

The Sentinel HDi90 is ideal for high or larger crawl spaces or basements under 2,000 square feet, providing powerful moisture removal while maintaining a moderate noise level. If noise is a concern, the Sentinel HD55 is a quieter option, making it perfect for homeowners seeking a less intrusive solution.