Can Vapor Barrier Control Humidity? – Myth #10

This week we’re on myth #10 of our Crawl Space Myths Series!

A lot of contractors will tell you that installing a vapor barrier is enough to control humidity in your crawl space. The professionals at Crawl Space Ninja think that’s a myth!

Let us explain why. You can check out the entire 13 Video Myth Series Here.

Myth: You Can Control Crawl Space Humidity with Plastic

Okay, so we get asked all the time, “Does installing the vapor barrier control humidity?”

Yes, it does… but it doesn’t control humidity enough to where you still don’t need a dehumidifier. You should also install a crawl space dehumidifier to properly control humidity.

Just like standing water alone doesn’t control humidity, a vapor barrier alone will not control humidity.

How Do You Resolve High Humidity in a Crawl Space?

You’ve got to address the standing water, install the vapor barrier, and still put in that dehumidifier that you are on the fence about installing.

A dehumidifier is the only way to continuously control humidity in your crawl space!

Myth: Installing a Crawl Space Vapor Barrier Will Solve Your Humidity Problem!

Now keep in mind, the vapor barrier does not prevent all ground moisture from getting into the crawl space. It’s actually a retarder, so a vapor retarder keeps the humidity behind the vapor barrier, but that humidity can eventually escape through the seams and where it’s attached to the foundation wall.

So if somebody comes in and tells you, “I’m gonna put a vapor barrier down in your crawl space, Mr. Jones, and your humidity’s gonna be under 60%.” That’s not true. That’s a myth.

We hope that you’ve found this series helpful. Stay tuned as we continue next week!


Common questions around Vapor Barriers?

What Is a Vapor Barrier?

A vapor barrier, also known as a vapor retarder, is a material that prevents the diffusion of moisture through building materials. Its primary function is to restrict the flow of water vapor, which can cause damage to a home’s structure. While it doesn’t completely keep moisture out, a properly installed vapor barrier can significantly reduce the amount of moisture that passes through.

How Does a Vapor Barrier Work?

To understand how a vapor barrier works, it’s essential to grasp the concept of moisture movement. Moisture naturally moves from areas of high concentration to areas of lower concentration. This movement can occur through air movement, diffusion through materials, or heat transfer. In the context of a home, air movement is the most significant contributor to moisture transfer.

Air naturally moves from areas of high pressure to lower pressure, seeking the easiest path available, such as cracks or holes in the building envelope. By sealing these unintended pathways, you can effectively control moisture transfer. A vapor barrier acts as a barrier against moisture-laden air, preventing it from infiltrating the home’s structural surfaces.


Call Crawl Space Ninja for Help Installing a Vapor Barrier

Do you need help with crawl space encapsulation, fixing your crawl space humidity problems or installing a vapor barrier? If so, we can help. Please contact us to schedule your assessment.

Contact us if you need help fixing your crawl spacebasement, or yard drainage by clicking here.


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