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Why a Crawl Space Needs a Dehumidifier

Humidity is the main driver of crawl space mold and wood rot. When relative humidity stays high, wood absorbs moisture, mold spores find enough water to grow and ducts sweat. Most guidance aims to keep a crawl space below 60 percent relative humidity, and many homeowners aim for 45 to 55 percent.

North Carolina summers push outdoor humidity well above that. Even a sealed crawl space can pick up moisture from the ground, plumbing and the air that leaks in. A dehumidifier removes that moisture continuously.

A Dehumidifier Works Best in a Sealed Space

A crawl space with open vents is constantly refilled with humid outside air. A dehumidifier in that space has to work around the clock and still loses the fight. The most effective setup is a sealed crawl space, with a vapor barrier on the ground and walls and closed vents, plus a dehumidifier to handle what remains. See vapor barrier installation and crawl space encapsulation.

Sizing a Crawl Space Dehumidifier

A household dehumidifier sized for a basement is usually the wrong choice for a crawl space. Crawl space units are built for low clearance, cool temperatures and long run times. The right capacity depends on the square footage, how well the space is sealed and how wet it is to start with.

An oversized unit cycles on and off too often, and an undersized unit never catches up. We size the unit for your space and explain why we chose it.

Drainage: Where the Water Goes

A dehumidifier collects water, and that water has to go somewhere. Options are a gravity drain line that carries it outside or to a low point, or a small condensate pump that lifts it to a drain. The drain route is a part of the install that matters, because a unit that fills and shuts off does nothing.

We plan the drain before we place the unit. If there is standing groundwater, we deal with that separately; see crawl space moisture control.

What Installation Includes

  • Inspect and measure. We check the space, the sealing and the moisture load.
  • Choose the unit. We size the dehumidifier for your crawl space.
  • Place and power. We place the unit where it can drain and be reached for service, with proper power.
  • Drain. We run the drain line or pump so the water leaves the space.
  • Set and test. We set the humidity target and confirm the unit runs and drains.
  • Explain maintenance. We show you how to check the filter and drain.

Signs Your Crawl Space Dehumidifier Is Not Doing Its Job

  • The house still smells musty on humid days
  • The unit runs constantly and the humidity never drops
  • The unit never runs, or shuts off with a full tank
  • Condensation on ducts and pipes is still there
  • The unit sits in a space with open vents or standing water
  • The drain line is kinked, clogged or lower than the unit outlet

Maintenance

A crawl space dehumidifier needs a little attention. Check the filter on the schedule the maker gives and clean or replace it as needed. Look at the drain line a couple of times a year to be sure it is clear. If the unit runs constantly, or never runs, the space may have a moisture source or an air leak that needs a look.

Dehumidifier Cost

The price of a dehumidifier installation depends on the unit, the drain route and the electrical work. We quote it as part of crawl space work, or on its own for a crawl space that is already sealed. You get a free estimate before work starts. We offer flexible financing options for qualifying homeowners; terms depend on the lender and your approval.

For the cost of a full sealed system, see crawl space encapsulation, which typically costs $3,500 to $7,500 for Triangle homeowners.

Crawl Space Dehumidifier by City

Pick your city for local information and a free estimate.

Crawl Space Encapsulation Apex, NC
Crawl Space Encapsulation Cary, NC
Crawl Space Encapsulation Charlotte, NC
Crawl Space Encapsulation Clayton, NC
Crawl Space Encapsulation Concord, NC
Crawl Space Encapsulation Fuquay-Varina, NC
Crawl Space Encapsulation Garner, NC
Crawl Space Encapsulation Holly Springs, NC
Crawl Space Encapsulation Knightdale, NC
Crawl Space Encapsulation Raleigh, NC
Crawl Space Encapsulation Wake Forest, NC
Crawl Space Encapsulation Zebulon, NC

Also see: Vapor barrier installation, Crawl space moisture control , sump pump services and mold removal.

Crawl Space Dehumidifier: Frequently Asked Questions

Most sealed crawl spaces in North Carolina benefit from one, because summer humidity is high. A dehumidifier keeps the humidity in a safe range once the space is sealed. We tell you honestly if your space does not need one.

Most guidance aims for below 60 percent relative humidity, and many homeowners aim for 45 to 55 percent.

It is not a good fit. Crawl space dehumidifiers are built for low clearance, cool temperatures and long run times, and they need a way to drain.

Through a gravity drain line to the outside or a low point, or a condensate pump that lifts it to a drain. We plan the drain route before placing the unit.

Not well. Open vents keep letting in humid outside air. A sealed crawl space with a dehumidifier works much better.

It depends on the unit and how often it runs. A well-sealed space needs less run time. We explain the running cost of the unit we recommend.

We serve Raleigh, Cary, Apex, Garner, Wake Forest, Knightdale, Zebulon, Clayton, Holly Springs, Fuquay-Varina and the Charlotte area. Send your address with your request.

Yes, we offer flexible financing options for qualifying homeowners. Ask when you request your free estimate. Terms depend on the lender and your approval.

Get a Free Crawl Space Dehumidifier Estimate

Request an estimate or call (704) 727-4344.

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