There are many forms of vapor barriers that are normally available as coatings or membranes.  The membranes are flexible and thin materials, but vary and also come in thicker sheet materials.  


A vapor barrier is also known as “vapor diffusion retarder” is a material used to reduce the rate at which water vapor is transported from one location to another by vapor diffusion.  By having a professional install a vapor diffusion retarder, consisting of a layer of 6 to 20 mil. polyethylene (poly. layer varies depending on the crawl space type), you can help maintain humidity levels to minimize moisture-related problems and help reduce energy consumption.


A vapor barrier or vapor diffusion retarder is generally installed by placing on the ground, protecting the wood structure of the home from moisture rising up from the ground and adhering to the wood thereby causing condensation and mold, fungi, and decay to form.  


Crawlspace encapsulation utilizes a specific type of vapor barrier that is heavier in weight and is mold-repellant.  The process of installing a crawlspace encapsulation is performed by covering the ground and sealing all ventilated areas within the crawlspace and taping the vapor barrier on to support columns and side walls. 




Why use a Vapor Barrier?


The main purpose of a vapor barrier is to prevent the passage of the water vapor that is contained in the air from traveling or rising from the ground and latching onto the wood structures within.  Vapor barriers and insulation complement one another and are very effective when installed at the same time.  Whenever possible, they should be installed at the same time so that they interact beneficially and protect the home from issues arising from moisture damage.  


The specific functions of vapor barriers are: 


  • Protecting the envelope structure (crawlspace) and insulation from condensation and/or moisture damage.  

  • Prevents air leakage through the envelope.  A well-installed vapor barrier prevents or greatly reduces air leakage through the envelope surfaces, although it does not reduce air currents inside the envelope structure itself.  The vapor barrier reduces airflow through insulation thereby preserving the R-value.

  • Maintains interior humidification.  If humidification is used, a vapor barrier reduces the amount of energy and water required to maintain the desired level of humidity.

The Benefits of Installing Vapor Diffusion Retarder:

  • Improves indoor air quality

  • Prevents moisture from rising

  • Reduces Energy Costs

  • Fewer pest problems

  • Protects against wood dry rot

  • Protect against mold and mildew