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Vapor Barrier
Energy Efficiency, Comfort, and Health | Function and Optimal Operation | Components and Options | Plastic Liners | Spray FoamQuick Facts
- Sometimes called “Vapor Diffusion Retarder”
- In humid climates, a vapor barrier can be effective in reducing moisture and subsequent mold problems
- A vapor barrier is an impermeable surface most commonly installed in the crawlspace as a retrofit to enhance the health, comfort and durability of a home (when installed correctly)
- During new construction or renovation, a vapor barrier can also be can also be installed on the inside or outside of exterior walls, depending on the climate
- Can complement a well sealed and insulated house as a finishing touch for the home’s building envelope.
Energy Efficiency, Comfort, and Health
The building envelope is what separates your home from the outside world. A vapor barrier as part of a properly engineered building envelope can reduce the load on your heating and cooling systems impeding the infiltration of outside moisture and humidity into your home. Not only does this reduce energy needs in the house, it significantly reduces problems from mold problems spreading rampantly in the damp crawlspace environment, making the home a much healthier place to live.
Function and Optimal Operation
The vapor barrier is a non water permeable surface which protects the integrity of the building structure (wood studs, insulation) from moisture which causes mold infiltration. Some prefer to call it a vapor diffusion retarder since it greatly impedes movement of vapor instead of blocking it entirely.
Components and Options
There are two main materials which can be used to create a vapor barrier. They may be used independently or together, but it is vital that their placement is coordinated with the functionality of the rest of the building envelope such as the insulation system. Proper placement of the vapor barrier, especially in walls varies depending on the strongest potential direction for moisture infiltration (from interior to exterior or vice versa, as determined by climate). Improper placement of the vapor barrier can lead to durability issues with the home, since it will trap moisture where it can cause damage, instead of protect from moisture.
Plastic liners
Particularly in crawlspace or exterior wall applications, plastic sheets are generally very effective vapor barriers. The sheet must be thick enough to resist tears or punctures which would jeopardize the integrity of the barrier system. This may be installed in the walls during construction of the home or installed along the crawlspace floor after the home as a retrofit. In a proper crawlspace vapor barrier installation, the liner must be very durable and should be firmly attached to the foundation walls and piers.
Examples include: Stego Wrap
Closed cell spray foam
Unlike open cell spray foam, closed cell spray foam (a denser, stiffer variety) is a quite effective vapor barrier. It is impermeable to air, as well as to any water it may contain. Closed cell spray foam may be sprayed onto the crawlspace ceiling and along foundation walls to create a vapor barrier in an existing home.[+] MORE