Vapor Barrier
Definition and meaning of Vapor Barrier in real estate.
A vapor barrier is any moisture-resistant material, such as plastic sheeting or treated paper, used in construction to prevent damp air from passing through walls, ceilings, or crawl spaces.
In more detail
In residential homes, vapor barriers are installed on the warm side of insulation to stop interior humidity from condensing inside the wall cavity where it can cause rot and mold. In crawl spaces, sheets of heavy plastic are laid over the bare earth to block ground moisture from rising into the wooden floor joists.
Proper installation is critical because gaps or tears in the barrier can compromise the moisture protection of the entire building envelope.
Key facts
| Category | Property Types & Construction |
|---|---|
| Common materials | Polyethylene plastic, foil, or kraft paper |
| Typical location | Crawl spaces, concrete slabs, and exterior walls |
| Primary purpose | Preventing moisture condensation and mold growth |
To pass a building inspection during a renovation, the contractor installs a thick six-mil plastic vapor barrier over the gravel floor of the home's crawl space to prevent damp earth odors from rising into the living area.
Frequently asked questions
Do all climates require a vapor barrier?
No, the requirement and placement of a vapor barrier depend on local climate conditions and building codes, which vary by geographic region.
What is the difference between a vapor barrier and a vapor retarder?
The terms are often used interchangeably, but a vapor barrier has a lower permeability rate, meaning it blocks almost all moisture, while a retarder allows a small amount to pass.