A Closer Look At Vapor Barrier Insulation

As their name suggests vapor barriers are manufactured to be barriers against vapor—mainly, the moisture present in the air in humid areas. When properly installed, vapor barrier insulation impedes moisture from coming into contact with your walls, thus protecting them from potential water damage, and mold and mildew growth. Installing vapor barrier insulation properly can be a tricky thing. When in doubt, your best bet is to enlist the help of a skilled professional who specializes in vapor barrier and attic insulation.

What Is Vapor Barrier Insulation

One of the most common types of insulation used in homes and buildings is fiberglass batt insulation—a cotton-like material of varying depth depending on its R-value that is available as pre-measured and cut sheets or as a packaged roll. In dry climates, this kind of insulation works well on its own. In areas where humidity levels are high, moisture retardant materials are absolutely necessary. Vapor barrier insulation is essentially standard batt insulation with a moisture-negating lining, customarily made of polyethylene, attached to one of its sides.

How Does Vapor Barrier Insulation Work


Vapor barriers are commonly used when exterior walls of buildings are framed. Indoors, vapor barrier insulation protects interior walls from excessive moisture. It is particularly useful in areas of the home where moisture levels are high such as bathrooms and basements. In renovation situations, vapor barrier insulation should never be installed over existing insulation because this could create an issue where moisture becomes trapped between the old and new layers.

When the temperature drops outside, the moisture contained in the air inside of your home will often try to escape and move outside. As it passes through your walls, though, it can condense and cause rot and/or mildew. In a worst-case scenario, it can even freeze in the walls and cause damage that you can see once it thaws later. A vapor barrier prevents moisture from entering the walls in the first place, thus preventing rot, mildew, or any other major damages.

Why Vapor Barrier Is Important

If you do not have a vapor barrier installed in your home and, more specifically, in your attic, then the moisture that is located there will be free to pass through the walls whenever it gets cold outside. Your attic insulation will keep it from entering the walls to some degree, but when the temperature drops below freezing, it will be no match for the moisture. A vapor barrier is the best way to block moisture and to keep it from causing serious issues. The moisture will be forced to exit through attic vents instead of through the walls.

How Vapor Barrier Is Installed

Some types of attic insulation, like batt and roll insulation, come with a vapor barrier included. Others do not. If you need to install a vapor barrier along with regular insulation, it is well worth it. It goes up easily and will serve as a great supplement to your insulation.

Homes with crawlspaces benefit from having something that can protect them from excessive moisture, which mainly results from water vapor evaporating from the ground below. The most effective thing to do is to install a crawlspace vapor barrier—a product that is made to prevent dampness from infiltrating the space. Overly moist crawlspaces can smell musty and be breeding grounds for mold and mildew. Most homeowners who aren’t claustrophobic, and who don’t mind doing the work, can install vapor barrier insulation by themselves, given that their spaces needing to be covered are manageable. For a larger home with significant square footage, enlist the help of a professional who specializes in crawlspace and attic insulation.

Focus on Controlling Moisture, Not Eradicating It

You can drive yourself crazy trying to eradicate moisture from your crawlspace, especially if you live in an area that receives a good deal of seasonal rain. Instead of trying to get rid of moisture completely, focus on keeping water vapor at a controllable level. Install a high quality vapor barrier to impede excessive moisture from negatively affecting your home’s foundation and promoting the decay of wooden structures.

How Crawlspace Vapor Barriers Are Installed

Crawlspace vapor barriers are made of polyethylene and usually come in large rolls, which can be purchased at your local hardware store or construction materials supplier. For the most part, strips of this barrier can be taped together with a durable adhesive, like duct tape, to create one large sheet that can be laid over the ground directly below the crawlspace. This sheet can be effectively held in place with sand, which does not puncture the polyethylene material. When laid properly, this sheet can keep ground moisture from evaporating up into your crawlspace.

Protect Your Foundation’s Walls

For added moisture control, a vapor barrier insulation can be run up your home’s foundation walls, provided you don’t run the sheet all the way up to your floor joists if you live in an area where termites can be a problem. If given the opportunity, termites can build their mud tunnels on foundation walls that are covered up by vapor barriers.

Vapor Barrier Insulation in Attics

Since warm air rises, attic spaces can potentially harbor stagnating vapor. If you’re planning an attic insulation installation, make sure that there is adequate ventilation in the space to allow for air movement. Use vapor barriers wisely, especially if you intend to finish the attic to create usable living space.

In the past decade, Atticare has provided topnotch commercial and residential services to our customers that include attic and crawlspace insulation, rodent control, air duct repair, and vapor barrier insulation.

Atticare specializes in installing a vapor barrier and can do it quickly. You can arrange to have a vapor barrier installed in your home by calling 1-866-692-5449.

Updated 7/23/20 at 11:00 am


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