Crawl space encapsulation
Encapsulation turns the crawl space from a damp, vented cavity into a sealed space that's kept dry on purpose. Here's what's involved.
Most older Florence-area homes were built with open foundation vents. The idea was that air moving through would carry moisture away. In a climate this humid, the summer air coming through those vents is often the main source of moisture. Encapsulation closes the space off from outdoor air and from the ground, then dries it.
What does the code require for a sealed crawl space?
The International Residential Code, which South Carolina enforces in its 2021 edition, lets you skip foundation vents if the crawl space meets section R408.3. In short, the exposed ground must be covered with a continuous vapor retarder, the seams lapped at least 6 inches and sealed or taped, and the edges carried at least 6 inches up the foundation wall and attached. The space then needs one way of handling the air:
- A continuously running exhaust fan sized at 1 cfm for every 50 square feet of floor
- A supply of conditioned air at the same rate, with a return path to the house
- A dehumidifier able to remove 70 pints of water per day for every 1,000 square feet
Your building department may also want to see the plan, so ask whether a permit is needed in the City of Florence, Florence County or your town.
What happens on a typical job?
- Inspection. Moisture readings in the wood, a look at the ductwork, plumbing and insulation, and a check for standing water, rot and termite damage.
- Prep. Removing debris and wet insulation, fixing leaks, and addressing any rotted wood or drainage problems first.
- Sealing. Closing the vents and sealing gaps in the rim and foundation.
- Lining. Laying a heavy liner over the ground and up the walls, with seams taped and edges fastened.
- Drying the air. Installing a dehumidifier or other code-approved method, and often insulating the walls.
Does it save energy?
It can. Building America research for the U.S. Department of Energy found that unvented, conditioned crawl spaces cut heating and cooling energy use by 15 to 18 percent and lowered humidity by more than 20 percent in the homes studied. Your results depend on the house, its ductwork and how it's sealed.
What affects the price?
- Square footage and how much clearance there is to work
- Liner thickness and whether walls and piers are covered
- Removing old insulation, debris or a failed plastic sheet
- Drainage, sump or dehumidifier needs
- Wood or framing repairs found during prep
Every crawl space is different, so the company prices the job after someone has been under your house and measured it. We don't quote prices, and a number given over the phone before an inspection is only a guess.
Where we connect you with help
Common questions
Can I encapsulate a crawl space that floods after big storms?
Not until the water problem is handled. Gutters, grading, a drain or a sump usually come first, because a liner over standing water just hides it.
Will encapsulation affect my CL-100 at resale?
A dry, well-sealed crawl space usually gives lower moisture readings, but the pest company still needs access to inspect. Ask the installer how inspection access is kept open.
Related services
More background: Florence crawl space guide.
Damp insulation, a musty hallway or a floor that dips by the tub?
Call and we'll put you in touch with a crawl space company that works around Florence.