Can I Put A Dehumidifier In Crawl Space Without Encapsulation?

The short answer is – yes. You can have a dehumidifier in a crawl space without encapsulation. Several people do it.

However, the biggest question is – is it practical? Is it beneficial? Unfortunately, the answer here is – NO. Having a dehumidifier in a crawl space that’s not encapsulated is a waste of time. Why? Because the moisture issues in a non encapsulated, crawl space are beyond the capabilities of a dehumidifier.

During the summer season, the moisture levels in the crawl space are so high that you usually have water dripping from the roof of the area like it is raining. In pretty much all cases, you’ll have large pools of water condensed on the floor. If you don’t have proper drainage to lead the water out, the entire crawl space floor will be a pool of water.

So, no, it doesn’t make much sense to install a regular dehumidifier in crawl spaces. It’s zero work. You need a lot more.

Read on to find out the benefits of encapsulation, how it impacts humidification, and more reasons why you don’t need dehumidification without encapsulation. We also discuss alternative solutions if you have significant moisture problems in the non-encapsulated crawl space.

What’s Crawl Space Encapsulation?

Encapsulation is the process of sealing the crawl space to reduce humidity and prevent leaks. It also prevents unpleasant odors, pest infestation, and mold growth.

The process involves sealing the vents and conditioning and lining the floor and foundation walls with overlapping sheets of polythene plastic. You may also go the extra mile and install a moisture barrier on the exposed walls and surfaces of the crawl space.

Benefits of Crawl Space encapsulation

Crawl space encapsulation comes with several key benefits. However, most homeowners encapsulate for three main reasons;

1. Make the Area Less Hospitable to Pests

Pests such as termites thrive in dark, warm, moist areas such as the crawl space. They can form large colonies within a few days of settling, creating a significant issue as ridding the home of large colonies of termites, for instance, is very difficult. Moreover, pets tend to spread very fast. It takes only a week or two to start seeing a few on the upper floors.

Encapsulating the crawl space significantly reduces moisture, thus eliminating the damp conditions that attract pests.

2. Prevent Mold and Mildew

Fungi such as mold and mildew also thrive in warm, moist conditions such as the crawl space. The darkness proves another advantage allowing mold colonies to expand fast and without notice.

Within weeks, you may begin to see spores in your living areas, not knowing that they’re flying in from the crawl space. Failure to address the issue promptly can result in allergies and respiratory system infections.

Encapsulation dries out the moisture in the crawl space, making it very difficult for mold to survive. It also improves air circulation.

3. Enhance Energy Efficiency 

An unlined crawl space typically forces your HVAC systems to work harder to achieve the desired comfort levels. For instance, the air conditioner will need to work extra hard to pull out the hot, moist air in the crawl space. The fact crawl spaces worsen the situation let in a lot of heat and moisture through the exterior walls. It can result in sky-high energy costs.

Keeping the crawl space dry through encapsulation reduces the amount of energy needed to keep the home cool and comfortable.

4. Preserve the Home’s Structural Integrity 

Excess humidity in the crawl space isn’t just bad for your health and comfort. It’s can also impact the home’s structure negatively. For one, damp conditions are associated with wet rotting. When the wooden structures below the home rot, it makes the home weaker. Additionally, excessive dampness can cause water pooling in the crawl space. Some water may seep through the foundation wall into the soil surrounding the foundation, making the foundation weaker. 

Encapsulation keeps the crawl area dry, thus preventing rotting. It also prevents water from seeping into the surrounding soil. 

What Happens in the Absence of Encapsulation?

This is the biggest question you should ask before you even consider purchasing a dehumidifier for your non-encapsulated crawl space.

And the answer is – a lot can go wrong. For one, the crawl space typically has a bare dirt or gravel floor. This means that water seeping from the surrounding ground is a certainty. In addition, there is nothing to prevent water from rising into the floor due to hydrostatic pressure in the underlying soil. Water may also enter the crawl area through cracks in the foundation wall and over the top of the foundation.

This is worsened if the ground slopes towards the house. All the moisture and water in the surrounding ground would flow into the crawl space via the wall.

Other ways moisture and water can enter the crawl space include;

Foundation Vents 

Most crawl spaces have vents to help with air movement. These vents are critical to maintaining comfortable indoor air conditions. They help pull fresh air from outside, which then flows to the rest of the home. However, the vents also serve as exit points for stale, dense air.

However, foundation vents can also worsen relative humidity in the crawl space by bringing in too much moisture during the summer. The moisture often condenses on the foundation roof and dripping on the floor to create water pooling.


There’s a chance your crawl space has soil. Not all do. However, many ill-maintained crawl spaces have soil. Soil accumulates a lot of moisture, especially when the surrounding air is warm and moist. A meter of soil can hold as much as 400 to 600 milliliters of moisture at saturation. That’s about half a liter on average.

During the summer, soil in your crawl space will absorb and release moisture at the same time. As it loses warm air to the surrounding crawl space air, the area is automatically refilled underground.

Plumbing leaks 

Finally, don’t forget that most plumbing pipes, both supply and return, run through the crawl space. These pipes can occasionally leak. However, no one would know if there are leaks in the dark, abandoned crawl space unless it’s a significant issue that forces you to check beneath the house.

Over time, the small leaks can accumulate to create pools of water on the crawl space floor. Imagine a leak going on for an entire year, for example! Unfortunately, the dirt or gravel floor usually absorbs the water, so you may not notice until it’s too late.  

The Dehumidifier would be Overwhelmed

You can already tell that the extreme moisture and water conditions in a non-encapsulated crawl space would be too much for the dehumidifier.

For one, the moisture is just too much and gets replaced all the time. Second, the open vents mean that as you pull out moisture from the air inside the crawl space, new moist, warm air automatically enters the area through diffusion to create a natural balance. So, you’d be doing zero work. Third, moisture will keep seeping from the underlying ground in large amounts because of the incomplete floor.

Worse still, dehumidifiers only remove water vapor – not water. You can’t place the dehumidifier in an area with pooling water and expect it to dry up the area. It may do eventually – but only after the water evaporates to moisture.

Above all, the conditions inside an encapsulated crawl space mean the dehumidification process would be highly inefficient. Since moisture constantly enters the area through the vents and from the ground, you’d waste most dehumidifying energy.

So, What’s the Solution?

Ideally, you need to dehumidify the crawl space. Otherwise, the high moisture levels would eventually reach the upper floors through the stack effect, capillary, and other means. In addition, mold and odors from the rotting wood in the crawl space would eventually end up in the living areas.

However, since having a dehumidifier in a non-encapsulated crawl space amounts to zero work, you need first to find a way to minimize the moisture issue. We recommend the following options;

  1. Consider encapsulating: HVAC professionals are unanimous that encapsulation is the best medicine to humidity issues in the crawl space. It involves covering every inch of the crawl space floor, walls, and roof.
  2. Consider sealing: If you feel that encapsulation is expensive, a more affordable option is sealing. Sealing involves covering only the floor and wall (up to eight inches) of the crawl area. The rest of the surfaces remain exposed.
  3. Install a vapor barrier: A basement vapor barrier is quite adequate, too, though not as much as an encapsulation. It involves laying down a 6mm black polythene throughout the crawl space floor. The other surfaces remain exposed.
  4. Provide a drainage system: Whether you choose encapsulation, sealing, or vapor barrier installation, a drainage system is vital to lead condensed water out. A sump pump located at the lowest section of the crawl space will do the trick.

Once you’ve set up the above, you can bring in the dehumidifier to dry and moisture-free the crawl space. Don’t forget to cover the vents. As we’ve seen, open vents allow outside air to enter the crawl space, usually worsening the humidity issues in the house. You can purchase airtight vent covers easily from an HVAC store.