Crawl space dehumidifiers
A sealed crawl space still needs its humidity managed. In a Kentucky summer, a dedicated dehumidifier is usually what does it.
A crawl space dehumidifier is a compact, low-profile unit built to run in a sealed crawl space and drain on its own. For Lexington homeowners who have encapsulated or plan to, it's the most common way to keep relative humidity under control through the humid months. Contractors also replace failed units and set up drains, controls and filters on existing ones.
Why not use a regular household dehumidifier?
Portable units are made for living spaces. They usually need someone to empty a bucket, they aren't built for the cooler temperatures under a house, and they often aren't sized for the job. Crawl space units are made to sit on the liner or hang from the framing, run with a condensate line to the outside or a pump, and handle the space's full volume.
How is one sized?
Newer editions of the International Residential Code list dehumidification as one way to handle the air in a sealed crawl space, sized at 70 pints of moisture removal per day for every 1,000 square feet of floor. Kentucky's code is built on the 2015 edition, so ask the contractor how the proposed setup meets the local requirement. Contractors also look at how tight the space is, how much water the soil gives off, and whether the house has a basement section or ductwork that changes the load.
Signs your dehumidifier isn't keeping up
- The hygrometer reads high or the unit runs constantly
- A musty smell has returned after an encapsulation
- Condensation is back on ducts or pipes
- The unit is short-cycling, icing up or showing error codes
- The drain line is clogged or the condensate pump has failed
Why humidity control matters here
Lexington's summers are hot and humid, and a sealed crawl space keeps outside air out, but some moisture still comes up from the ground and in through small leaks. Without something removing it, the humidity drifts back up. The Department of Energy's Building America research on sealed, conditioned crawl spaces is a good primer on why the air side matters as much as the liner.
Repair or replace?
A clogged filter, a kinked drain or a failed condensate pump are cheap fixes. A unit with a failed compressor, refrigerant problem or a lot of years on it is often worth replacing, especially if it was undersized to begin with. The contractor can tell you which you're dealing with.
What affects the cost?
- Unit capacity and features such as remote monitoring
- Where the condensate goes: gravity drain, pump or existing line
- Whether a dedicated electrical circuit is needed
- Access to the crawl space and where the unit can sit
Pricing comes from the contractor you're connected with, after a look at the space.
Common questions
Can a dehumidifier go in a vented crawl space?
It can run, but it ends up trying to dry the outdoors. Dehumidifiers work best in a crawl space that's been sealed.
How often does a crawl space dehumidifier need service?
Filters need regular cleaning or replacement, and the drain should be checked. Follow the manufacturer's schedule or ask the installer.
What humidity should a sealed crawl space stay at?
Many contractors aim to keep relative humidity well below the levels where mold grows, often under 60 percent. Ask what target the installer sets.
Towns this covers
Related services
For the Kentucky code, karst and radon background, see the Lexington crawl space guide.
Damp smell, cold floors or a sag you can feel underfoot?
One call puts you in touch with a crawl space contractor who works in Lexington and the surrounding Bluegrass counties.