Key takeaways
- Humid outdoor air entering a vented crawl space can condense on cool surfaces.
- A ground liner is the first step, and sealed walls are the next.
- Insulate the walls or the floor, not both in the same way.
- Standing water must be fixed before encapsulation.
Why crawl spaces get damp
Soil gives off moisture, and Tennessee summers bring humid air through crawl space vents. When that air touches cooler joists, ducts and subfloors, it condenses. Over time that can lead to musty smells, sagging insulation, rot and mold.
The longer a crawl space stays damp, the more work it can take to fix.
Encapsulation
Encapsulation seals the crawl space from the ground and the outdoors. A heavy liner covers the floor and runs up the walls, seams are taped, vents are closed, walls are insulated and a dehumidifier keeps the humidity in range. The crawl space becomes part of the conditioned envelope.
Encapsulated crawl spaces stay cleaner and drier and make floors warmer.
Insulating the walls or the floor
In a closed crawl space, you insulate the walls and rim joist with foam or board. In a vented crawl space, you insulate the floor with batts or foam. Doing both in the same space can trap moisture.
Your installer will explain which approach fits your crawl space and your goals.
Fix water first
Standing water, leaking pipes, poor drainage and gutters that dump at the foundation must be fixed before encapsulating. A liner does not solve a flooding problem.
We tell you if a drainage or plumbing repair is needed first.
Quick answers
Should I close my crawl space vents?
In a properly encapsulated crawl space, yes. Without encapsulation, closing vents alone can trap moisture.
Can I put plastic on the ground myself?
You can, but thin plastic tears. A heavy liner with taped seams lasts much longer.
Will encapsulation stop musty smells?
Often, once moisture is controlled, but the cause must be fixed too.
