What Is A Vapor Barrier?

Water vapor has the power to destroy the structural integrity of your home.

That’s why crawl space vapor barriers and crawl space encapsulation systems are such an important facet of waterproofing your home: They prevent the accumulation of moisture in the internal cavities of your home. That moisture can lead to wood rot, mold, and other forms of serious structural damage.

Keep reading to understand how vapor barriers work and how they help preserve your crawl space.

Crawl Space Vapor Barriers, Explained

A vapor barrier is a crawl space liner made of impermeable or semi-permeable plastic material that prevents water from entering and accumulating in your home’s crawl space.

Vapor Barriers and Permeability

The permeability of particular materials gives you an idea of how resistant it is to the migration of water vapor through it. For instance, impermeable materials might permit less water vapor through, but they could prevent effective ventilation if your crawl space still happens to get wet. For this reason, crawl space repair contractors sometimes select semi-permeable materials over impermeable materials.

• Impermeable: Rated at less than 1 perm, these materials are highly resistant to the migration of water vapor through the barrier.
• Semi-permeable: Rated at 1 to 10 perms, these materials resist some of the migration of water vapor, but not all.
• Permeable: Greater than 10 perms, these materials do not provide much vapor resistance.

How Vapor Barriers Work

Installing a vapor barrier involves getting inside the crawl space and laying the chosen plastic material in an overlapping fashion over the entire floor. It is then taped or otherwise attached to the crawl space walls to create a barrier between the floor and walls.

Because most crawl space floors are dirt, water commonly seeps up from them during times of heavy rains or if you do not have appropriate drainage for your home. Water can also seep through crawl space walls or accumulate due to condensation from HVAC ductwork and plumbing pipes.

A vapor barrier prevents external water from coming into the crawl space, while also preventing excess moisture from condensation from damaging your floor joists, which can affect the stability and structural integrity of the floors in your home.

Choosing the Right Vapor Barrier

According to the Building Science Corporation, crawl space vapor barriers serve two crucial functions: (1) keep moisture out and (2) allow any water that manages to get into the crawl space to egress.

Inexperienced installers focus too much on the first function of crawl space vapor barriers, which means no water gets in—but no water gets out. Then when your plumbing inevitably leaks or your dishwasher overflows, there’s no way for the excess moisture to escape.

You ultimately need crawl space waterproofing to prevent structural damage to your home. But you also need an experienced team who will take your needs into account during planning and installation.

Experienced installers—like the crawl space repair experts at Helitech—take ventilation, dehumidification, and resistance to water vapor into account. We ensure that the crawl space protection method you choose will resist the entrance of moisture and will also allow water out if needed.

For a long-term waterproofing solution, you can opt for the professional-grade HydraLock encapsulation system instead of a traditional vapor barrier. This thick, polyethylene material prevents water, mold, mildew, and pests from entering your crawl space.