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Best Crawl Space Dehumidifier

Best Crawl Space Dehumidifier

Any homeowner whose house has a crawl space understands its importance. A crawl space greatly decreases the chance of the house flooding and provide additional storage space. The crawl space, however, requires to be insulated and proper ventilation to ensure it remains in good condition.

Why Does Crawl Space Humidity Matter?

As air rises in a home, it carries with it the air that was previously in the crawl space. That includes moisture and mold spores, as well as anything else that may be airborne down there. As this air rises in the home, replacement air is drawn through the vents. This replacement air is made up of unconditioned outside air that enters through vents and other leaks. This natural upward air movement is called the "stack effect" - similar to how a chimney works.

Because of that, whatever is in the air at the lowest point of your home eventually flows up into the living areas. Almost half of the air we breathe on the first floor of our home comes from the crawl space. A dirt crawl space with open crawl space vents is a never-ending source of moisture. Even if the dirt's surface seems dry, digging down a few inches reveals moist earth. This moisture is constantly released into the crawl space.

Why Do You Need a Dehumidifier in Your Crawl Space?

  • Getting rid of excess moisture: You might be living in a wooden house. If so, humid air is your archenemy. It can significantly weaken the framework of your house. Besides, even if you live in a concrete-made home, the damp odor from your crawl space can be unpleasant. Hence a crawl space dehumidifier is your solution.
  • Keeping the crawl space mold-free: The humid environment of a crawl space is the ideal home for mold and pathogens. Therefore investing in a dehumidifier will also ensure your family’s health.
  • Increasing the comfort level: Humid air makes us feel damp and sticky all the time. It even makes breathing a bit more strenuous. Hence the installation of a dehumidifier might improve the comfort level of your indoor life.

Encapsulation Alone is Not Enough

The term crawl space encapsulation means applying vapor barrier to all walls, pillars, and floor of the crawl space. The crawl space plastic is designed to slow the evaporation of moisture in the space but is not designed to stop the moisture.

Crawl space encapsulation does not address dew point. Even if the crawl space plastic was a barrier to ground moisture, dew point could still be a problem and the dehumidifier is needed to control dew point. When cold objects come in contact with a warm air or vice-versa, condensation can occur.

Humidity Basics

Humidity is a measure of water content in the air. When you hear about humidity on weather reports, it is referring to “relative humidity.” This is a percentage of the maximum amount of water the air can hold at the same temperature.

The water particles in humid air hold heat, which means humid environments trap heat better than dryer ones. This creates the feeling that the climate is warmer than a dry one at the same temperature.

But some humidity is good. If an environment is too dry, then dust and other particles disperse through the air and cause other problems. A little bit of humidity also is good for your skin and respiratory system.

So, what should the humidity be in a sealed crawl space? A good ballpark range is 30 to 65 percent. Above 65 percent, you will begin to see problems, and anything above 75 percent is cause for concern.


Moisture in your crawl space can get the attention of a variety of pests, including dust mites, rodents, and a variety of insects. These include termites that cause billions of dollars in property damage every year, more than natural disasters.

If you have noticed an abrupt insect infestation, it could be the result of high humidity. Addressing the source of the issue could be the first step to eliminating it.

What should the humidity and moisture levels be in my crawl space?

It can be hard to determine this without the right tools or level of expertise, but luckily with our free inspection offer, we can check all of these levels for you.

Relative humidity, or RH, measures moisture in the air within the environment it’s being measured in. Ideally, keeping the crawl space between 50-60% RH creates a dry and sustainable environment, with wood moisture levels at or around 8-12%. RH levels above 60% increase the likelihood that the wood moisture begins to rise, creating a hospitable environment for fungal growth. If RH is too low, and being mechanically controlled to operate at a lower level, then an overly dried crawl space can have the inverse effect by reducing levels so much that the wood begins to crack and shrink.

Again, crawl space or basement with healthy moisture and humidity levels will help keep mold, pests, and wood rot farther away from your home.

How many pints capacity should your dehumidifier have?

If your space has 50-75% humidity levels that you want to remove, go for a dehumidifier that has at least 20-30 pints per day capacity. It should be able to last the day without much of an issue.

For spaces slightly more humid, 75-90% humidity, you'll need a commercial dehumidifier 25-40 pints per day. Aim for 40, but you can get away with a slightly lower number too.

In rooms that are "wet" (there's a leakage or standing water is present in the room) with humidity levels at 90-100%, you'll need something more powerful so look in the capacity range of 30-50 pints, as close to 50 pints as possible and the crawl space dehumidifier will be able to get rid of most of the humidity from the room!

To pick the best basement dehumidifier, you must understand:

  1. The size of your basement –Most basement dehumidifier’s capacity is measured in per square footage. Just measure the size of your basement(in square feet) before choosing a dehumidifier.
  2. The capacity of the dehumidifier – The Capacity of any dehumidifier is the number of pints of water the basement dehumidifier is able to extract from the basement in a period of 24 hours.

Here is a list of the best basement dehumidifiers in 2023: