These two terms get used interchangeably by contractors, and that creates a lot of confusion for homeowners trying to understand what they actually need.
They are not the same thing. A vapor barrier is a component. Encapsulation is a complete system. Understanding the difference helps you evaluate quotes accurately and make the right decision for your home.
What a Vapor Barrier Is
A vapor barrier is a sheet of polyethylene plastic, typically 6-mil to 12-mil thick, that is laid across the dirt floor of a crawl space. Its job is to slow the movement of soil vapor (moisture evaporating from the soil) into the crawl space air.
A basic vapor barrier covers the floor only (not the walls), does not seal the crawl space, does not control humidity inside the space, and does not stop moist outside air from entering through foundation vents. A vapor barrier is better than bare dirt, but in Georgia’s climate, it is usually not enough on its own.
What Crawl Space Encapsulation Is
Encapsulation is the complete treatment. A properly encapsulated crawl space has several components working together.
Heavy-duty liner. Commercial-grade 20-mil polyethylene covers the floor AND wraps up the foundation walls, creating a continuous barrier. The liner is mechanically fastened to the walls and sealed at all seams and penetrations.
Vent closure. Foundation vents that allow outside air to enter are sealed. In high-humidity climates like Georgia, venting pulls warm, moist air in rather than drying the space out. Sealed vents are a core component of any complete encapsulation.
Active humidity control. A properly sized commercial dehumidifier maintains the sealed space at a target humidity level year-round, regardless of exterior conditions.
Together, these three elements create a controlled environment under your home. Moisture from the soil cannot get through the liner. Moisture from outside air cannot enter through sealed vents. Any residual moisture in the air is removed by the dehumidifier.
The Key Differences
A vapor barrier uses a 6-12 mil liner, covers the floor only, leaves vents open, and has no dehumidifier. It provides partial humidity control (soil vapor only) with limited effectiveness in high humidity climates. Lifespan is roughly 5-10 years at a cost of $1,500-$3,500.
Full encapsulation uses a 20-mil liner, covers floor and walls, seals all vents, and includes a properly sized dehumidifier. It provides complete humidity control regardless of outside conditions. Lifespan is 20-25+ years at a cost of $4,000-$10,000+.
When a Vapor Barrier Is Enough
A vapor barrier alone may be appropriate if you are in a dry climate with naturally low ambient humidity (not Georgia), your crawl space has excellent drainage and no history of moisture issues, or budget constraints mean something is better than nothing for now, with a plan to complete the encapsulation later.
When Full Encapsulation Is the Right Choice
Full encapsulation is appropriate for most Georgia homes with visible mold or mold odors, moisture readings above 60 percent relative humidity inside the crawl space, condensation on pipes or joists, wood softening or early wood rot, higher-than-expected energy bills, or an existing vapor barrier that has not solved the problem.
What to Watch Out For
Some contractors sell vapor barrier installation as “encapsulation.” If a quote includes only floor coverage with no wall liner, no vent closure, and no dehumidifier, it is a vapor barrier installation regardless of what they call it. Before accepting any quote, confirm the liner thickness, whether walls are covered, whether vents are sealed, and whether a dehumidifier is included and properly sized.
FAQ: Encapsulation vs. Vapor Barrier
My current vapor barrier is only a few years old. Do I need to replace it?
That depends on whether your moisture problem has been resolved. If you still have humidity issues or musty smells, the vapor barrier is not addressing the full problem. A free inspection will tell you exactly what is happening.
Can a vapor barrier be upgraded to full encapsulation later?
Yes. A properly installed liner can be supplemented with wall coverage, vent closure, and a dehumidifier at a later date.
Do I need to remove an existing vapor barrier before encapsulation?
In most cases, the existing liner is cleaned up and the new 20-mil liner goes over or beside it. If the old liner is severely deteriorated, we remove it first.
Why are foundation vents closed? Are they not required by code?
Building codes in many areas have been updated to allow or require sealed crawl spaces, recognizing that venting in high-humidity climates is counterproductive. We confirm local requirements before closing vents.
Not sure which option is right for your home?
A free inspection will tell you. We come out, measure the moisture levels, assess the current condition, and give you an honest recommendation. No obligation, no sales pressure. Call Crawl Space Doctors at (678) 512-9201 or request your inspection online.
