Crawl Space Dehumidifier

Crawl space dehumidifier is a “go-to” product for humidity control, especially in certain parts of the country. Dehumidifiers have many advantages and are an amazing tool to reduce moisture in a crawl space. However, as a homeowner, there are several things to consider when selecting products for your crawl space. Dehumidifiers also have some disadvantages to consider in your decision making process.

Key Advantages:

  • Reasonably quick to install
  • Drying can happen quickly
  • Generally automatic once installed
  • Operates efficiently in warm temeperatures
  • Allows for filtration of air

Key Considerations:

  • Use a lot of energy when running leading to a higher electric bill
  • Circulates same air throughout the space – no fresh air introduced
  • Humidity is measured at the location of the unit. May not recognize differences across the crawl space. May cause unit to cut on and off frequently.
  • Potential for over drying near dehumidifier and under drying in far corners of the crawl space
  • Inefficient in cooler temperatures

Best Performance in Moisture Reduction

A crawl space dehumidifier with the ATMOX controller and other crawl space products create the best performance in moisture reduction. Furthermore, the crawl space ATMOXsphere brings together the goals of the ATMOX products: Moisture Reduction, Energy Efficiency and Air Quality. Let’s evaluate each of those goals.

Moisture Reduction

There are two main ways to dry out a crawl space: a dehumidifier or outside air.

Which is better? It depends on the conditions – particularly the temperature and often the season. Dehumidifiers begin to lose effectiveness below 80 degrees, but most will still operate well until you start getting to temperatures below 60 degrees. At this temperature level, it starts becoming harder and harder for the dehumidifier to cool the air further to get out the moisture. It has to work very hard just to remove small amounts of moisture. On the other hand, colder outside air is generally very dry. Throughout most of the year and most of the geographic areas in the US, the outside air dries more effectively, more quickly and more energy efficiently. However, there are days, especially in the summer and in the southeast, when the outside air is hot and humid. At those moments, the outside air will not improve the crawl space.

Why not use both? An ATMOX crawl space controller does that. If both a dehumidifier and crawl space fans are installed, it will direct the operation to use the best tool for moisture reduction at any given time. Most of the time that will be using outside fresh air pushed and pulled in with fans. The dehumidifier operates when outside air is not available allowing the crawl space to reach a target humidity level. Additionally, crawl space circulation fans inside the crawl space improve the air movement to the dehumidifier to better dry all corners and areas more evenly.

Energy Efficiency

A dehumidifier uses a lot of energy. The manufacturers are always making improvements to improve energy efficiency, but the long and short of it is that “dehumidifiers can be real energy hogs!” Let’s put some numbers to this. A typical crawl space dehumidifier uses between 580 and 850 watts of power when running. As a comparison, six ATMOX crawl space fans will use between 60 and 90 watts of power when running. When you look at your electricity bill, which one do you think you would rather have running? Fans are going to win on energy usage every time. When fans are used with an ATMOX controller, there is also a temperature limitation to make sure that air that is either too hot or too cold is not being drawn into the crawl space.

Air Quality

Air quality improves with fresh air.  Some people use the term air quality to refer to better temperature or better humidity. However, that isn’t what we are talking about here. We are talking about air that isn’t stale and musty. The only way to improve air quality and to remove toxins and odors is to exchange it.  A dehumidifier will dry the air and filter it, but it doesn’t exchange it. Filtration is effective in reducing some particles in the air. However, outside dry air using fans brings in fresh air and actually improves the air quality.

Industry Leading Crawl Space Dehumidifiers

There are numerous dehumidifier brands on the market and almost all of them can be used with an ATMOX controller.

ATMOX manufactures a 24VAC relay for use of dehumidifiers with terminal blocks. For other setup options, please contact ATMOX for assistance.

Frequently Asked Questions about a Crawl Space Dehumidifier

How to use a dehumidifier in a crawl space?

A dehumidifier is a great moisture reduction tool. For the best results, use the dehumidifier with an ATMOX controller, crawl space vent fans, and circulation fans. It is important to solve any water issues first. Dehumidifiers and fans reduce moisture – they cannot move water. The second important step is to install a vapor barrier on the ground. After those two steps, you are ready for the final moisture removal with dehumidifiers and fans.

What size dehumidifier do I need for my crawl space?

Dehumidifiers are typically rated by “pints per day” as a measure of how much water they can pull out of the air. Dehumidifiers for a crawl space are mostly either 70 pints per day or 90 pints per day. Therefore, the size and type needed depends on the size of the crawl space. As a rough rule of thumb, crawl spaces up to about 2600 square feet use a 70 pint per day dehumidifier. Larger crawl spaces use a 90 pint per day dehumidifier or if crawl space is very large may use two or more dehumidifiers.

Can I use a regular dehumidifier in a crawl space?

Dehumidifiers fundamentally all work in the same manner. However, there are some differences in the design of a crawl space dehumidifier compared to a residential home dehumidifier.

One main difference is the range of the operating temperatures as most crawl spaces will be colder at times than the typical indoor environment of 70 to 80 degrees. Other differences are easily seen. As an example, a crawl space dehumidifier is often smaller to be able to fit into tight spaces and through doors. It is also built with heavier duty materials for the harsher environment of a crawl space. Often, the crawl space dehumidifiers also have air flow movement directed to the side to match the low height of the crawl space.

While a regular dehumidifier may work in certain crawl spaces, there are definite advantages to using one specifically designed for a crawl space.

How do crawl space dehumidifiers work?

A dehumidifier works almost like a mini air conditioner. An internal fan pulls the warm moist air into the dehumidifier. Then, that air is cooled down. (If you think back to middle school science, you may remember that cold air can hold less moisture than warm air.) That cold air can no longer “hold” the moisture. Therefore, the moisture condenses out of the air and becomes water that is pumped out of the unit. The drier air blows back out of the dehumidifier into the crawl space. The dehumidifier will continue to run and cycle air through it until it receives a signal to stop. In most cases, the operation stops when the measured air drops below its target humidity.

Dehumidifier Ratings

Dehumidifier ratings are based on how many pints of water can be removed from the air in a day. This means that a 70 pint per day dehumidifier can pull 70 pints of water out of the air if it runs for 24 hours. However, this is only true if the temperature is 80 degrees. As the temperature gets colder and colder, the ability for the dehumidifier to get water out of the air gets lower and lower. It will continue to run but it won’t be nearly as effective.

Learn more about how ATMOX Crawl Space Products all work together.