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Crawlspace 101: What is a Vapor Barrier?

Encapsulating a crawl space saves energy in the form of heating and cooling costs, keeps out pests and critters, and prevents moisture and water damage to the foundation and the building above it. Understanding what goes into encapsulating crawl space gives homeowners an idea of whether to do the jobs themselves or to hire a professional company.

What Is It?

A vapor barrier has two purposes – it prevents water from entering and allows moisture to safely evaporate. You may have noticed when new construction is going up that the houses are wrapped in a kind of white sheeting that is often branded as Tyvek. This material is called “house wrap,” and it prevents moisture from attacking wood and drywall from that direction.

Unfortunately, crawlspaces often do not receive this kind of treatment from builders and in older homes moisture may allow rot, mold, and kinds of a fungus to establish themselves.

Is It Safe?

Vapor barrier is made from high-density polyethylene film and varies in density from use to use. Typically, you would use a 20 mil crawl space vapor barrier when encapsulating your crawl space. It’s essential to use a branded vapor barrier because of off-gassing concerns. The material should meet or exceed federal VOC limits for building exteriors. To compare the thickness of 20 mil crawl space vapor barrier, your typical shopping bag that you would get at the grocery or drug store is about .5 mil so that you can see, it is many times thicker.

Working with Professionals

Encapsulating a crawl space is a heavy-duty job that requires many different materials. On a scale of 1 to 10 for DIYers with 1 being the easiest level, this job is a solid 6. The job requires special tools, gear, and personal safety equipment, and can go very easily to 10 should there be complications with the foundation and surrounding drainage. Get an assessment from a professional crawlspace encapsulation company and make sure that the job is within your skills and reach.