What is a Vapor Barrier?

If you are remodeling or building a new home, then you must consider putting up a vapor barrier in your home. But what exactly is a vapor barrier? According to the United States Department of Energy, the term "vapor barrier" is actually a misnomer as it implies it stops moisture from seeping in or leeching in from the soil that surrounds the building. Further, all material allows moisture to defuse to a certain degree; thus, the proper term is vapor diffusion barrier (VDR) as it only reduces the rate of moisture that comes through a building.

There are different types of materials that can be used from an asphalt coated paper attached to insulation to just drywall painted with latex paint. Further, they are graded with anything under a one is classified as a vapor barrier. The measurement is called "perms" or permeability, which is the number of grains of water passes through the material in an hour at a differential vapor pressure equal to one inch of mercy. Based on this perm test, asphalt coated paper rates a .02 while drywall is rated somewhere between a two and three - therefore, asphalt is better than drywall. The new barrier materials include a soft flexible membrane that can be placed over existing insulation and a rigid foam board that has both insulation and the barrier adhered together. There is also a paint coating that at one time was thought not to be much of a barrier; however, it is being discovered that is milder climates it works just as well as strong material.

No matter which material you use, it is important to keep in mind where it is placed within the wall. If you reside in colder climates, it is best to put the barrier on the interior; in Southern dry climates a vapor barrier is not necessary needed; and in hot and humid climates, the barrier is placed on the outside. Keep in mind that it can also be used in reverse, that is keep moist and humidity in a room such as a wine cellar or humidor.

Vapor barrier materials can be purchased at your local home improvement center such as Home Depot or Lowes. You can also explore the United States Department of Energy's Website to discover more interesting facts about vapor barriers and their website is www.energysavers.org/your_home/insulation_airsealing/index.cfm/mytopic=11810. You can also visit Ask the Builder at www.askthebuilder.com/VaporBarrier.shtml to learn more about the different varieties of materials use and find someone who can help install your barriers.