Crawl space dehumidifiers
In eastern North Carolina's summers, a closed crawl space needs a way to pull moisture out of the air. A dehumidifier is the most common one.
Once the vents are sealed and the ground is covered, moisture still gets into a crawl space through the foundation walls, small air leaks, plumbing and the house above. A crawl space dehumidifier runs on a humidistat and removes that moisture, draining the water out of the crawl space.
Is a dehumidifier required?
A closed crawl space in North Carolina needs some form of moisture control under Section R409.5 of the state Residential Code, and a dehumidifier is one of the listed methods. Others include supplying a small amount of conditioned air from the HVAC system, using house air, or an exhaust fan. According to the NC Office of State Fire Marshal's licensing interpretation, the dehumidifier and exhaust fan methods don't require an H-3 heating license, while supply air and fully conditioned crawl spaces do.
Why not just use a basement-style dehumidifier?
Crawl space units are built for the job: compact enough to fit under the floor, rated to run in cooler air, and set up to drain continuously so nobody has to empty a bucket. A portable unit sitting on the liner is easy to forget and can overflow.
Signs your dehumidifier needs attention
- The musty smell in the house has come back
- The unit runs constantly through summer but humidity stays high
- Water on the liner near the unit or its drain line
- Error lights, or the unit isn't running at all
Routine care
- Clean or replace the filter on the schedule the manufacturer recommends
- Check that the condensate line drains outside or to a pump and isn't clogged
- Glance at the humidity readout every few months, especially in July and August
- Make sure the vents stay sealed and the crawl space door closes tightly
What affects the price?
- Crawl space size and how much moisture gets in
- The unit's capacity and features
- Electrical work and drain routing
- Whether the crawl space is already sealed or needs encapsulation too
The crawl space company prices the job after getting under the house and measuring. We don't quote prices, and any number given over the phone before an inspection is only a rough starting point.
Where we connect you with help
Common questions
Can I put a dehumidifier in a vented crawl space?
It won't do much. With vents open, the unit is trying to dry the outdoors. Dehumidifiers are meant for closed or encapsulated crawl spaces.
Does a crawl space dehumidifier need an HVAC license in NC?
Per the NC Office of State Fire Marshal's interpretation, the dehumidifier method doesn't need an H-3 license, but a permit is still required to close the crawl space. Electrical work follows its own rules.
Related services
- Encapsulation and vapor barriers
- Damp and musty crawl spaces
- Sagging floor and joist support
- Crawl space drainage and sump pumps
More background: Greenville, NC crawl space guide.
Musty smell, damp insulation or a soft, bouncy floor?
Call now and a local crawl space company will help you figure out what's going on under the house.