What are Vapor Barriers?

One of the more confusing, and fairly important, aspects of home construction, and thus remodeling, is the matter of vapor barriers. A vast majority of homeowners don't know what these are, and it is also a sad fact that many in the construction field don't either. However, by simply forgetting to install some of these when you are doing a major remodel, you are creating an environment that could lead to some potentially dangerous situations later on in life, like mold or structural damage. But what are vapor barriers? The answer is really rather simple, as you will soon see.

Vapor barriers exist for one reason and one reason only, which is to help retard, resist, or even prevent the spread of moisture through the different enclosures of your home. By having these barriers installed properly, you help prevent moisture from getting into the dark spaces of your home, which can go a very, very long way to preventing mold from getting a foothold in your home and thus becoming a health hazard. These have become so important that the United States government has mandated that they be included in the building codes of most municipalities within its borders.

When they are installed properly, vapor barriers can (and should) be found between the walls, ceilings, and floors of your home. Simply put, anywhere that there could be a risk of exposure of moisture to the inside of your walls, ceilings, and floors, these are supposed to be.

Strictly speaking, vapor barriers are actually more of a vapor retarder than an actual barrier. The reason for this is that the ones that are typically used within the building are supposed to be somewhat permeable so that once water vapor has gotten in, it can get back out and allow the area to dry. Here are the technical classifications of the various vapor barriers, and some of the materials used for that type, according to the United States building codes.

• Permeable vapor barriers. These are anything that has a rating of more than 10 US perm, and can include things like unprotected fiberglass insulation, cellulose insulation, unpainted stucco, and so on.
• Semi-permeable vapor barriers. These have a rating of between 1 and 10 US perms, and are usually such materials as some latex based paints, heavy asphalt-impregnated building papers, and unfaced expanded polystyrene.
• Impermeable vapor barriers. For a vapor barrier to be considered impermeable it needs to have a rating of less than 1 US perm, and can be things like vinyl wall coverings, OSB, vapor retarding paint, and extruded polystyrene.