Crawl space vapor barriers, explained
Water vapor has the power to, over time, destroy the structural integrity of your home.
That’s why crawl space vapor barriers and crawlspace encapsulation systems are such an important facet of waterproofing your home – they prevent structural damping in the internal cavities of your home, which can lead to wood rot, mold and other forms of serious structural damage.
Crawl space vapor barriers prevent structural damage to your home.
Contact the experienced installers at Helitech.
But to answer your question—”Do I need a vapor barrier?”—truly understanding how vapor barriers work and what they do is important.
What is a crawl space vapor barrier?
Crawl space vapor barriers, or crawlspace encapsulation, are an impermeable or semi-permeable materials put in place to prevent interstitial damping in your home’s crawl spaces or attic.
Let’s break that down.
- Impermeable vs. semi-permeable crawl space vapor barriers
The permeability of particular materials gives you an idea of how resistant it is to the migration of water vapor through it. Impermeable materials might, for instance, permit less water vapor through, but prevent effective ventilation if your crawl space happens to get wet. For this reason, sometimes semi-permeable materials are selected over impermeable materials for crawl space vapor barriers.The American Society for Testing and Materials (ASTM), a third-party standards agency, grades vapor barriers based on their permeability as expressed in ”perms” in ASTM E96, and separates materials into three categories:
- Impermeable—Rated at less than one perm, these materials are highly resistant to the migration of water vapor through the barrier.
- Semi-permeable—Rated at one to ten 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.
- What, exactly, is interstitial damping?
Interstitial damping is just a technical word for structural damping. When water vapor comes through the wall and into the crawl space, it can condense on the wood or structural steel inside. Over time, if the water remains in the crawl space, it can corrode the steel or cause the wood to rot.Often, structural damping is difficult to spot until you have sustained significant damage. That’s why it’s important to have your crawl space vapor barrier installed correctly the first time by an experienced installer like Helitech Waterproofing & Foundation Repair.
Do I need a crawl space vapor barrier? And, if so, how will it help?
Good questions. According to the Building Science Corporation, crawl space vapor barriers serve two crucial functions: (1) keep moisture out and (2) allow 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. No water gets in—but then no water gets out. And, when your plumbing inevitably leaks or your dishwasher overflows, there’s no way for the excess moisture to escape.
Experienced installers—such as Helitech—will be able to install your crawl space vapor barrier, taking ventilation, dehumidification, and resistance to water vapor into account. This way, your vapor barrier resists the entrance of moisture but can allow water out if needed.
To answer your question, yes, you need a vapor barrier to prevent structural damage to your home. But you need it installed by an experienced team who will take all functions of a vapor barrier into account.
At Helitech, we’ve been doing this for over 30 years. We know how to install a crawl space vapor barrier like the back of our hands. We’ll evaluate your home’s needs and give you a free quote for your vapor barrier repair, replacement or installation.
We’ll give you, the homeowner, a free quote for your foundation repair.
We’ll get back to you with a cost-effective solution.