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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. We think that's a myth, let us explain why.

Controlling Crawl Space Humidity

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've gotta have a dehumidifier to properly control humidity.

Just like standing water alone doesn't control humidity, a vapor barrier alone will not control humidity. You've got to address the standing water, install the vapor barrier, and still put in that dehumidifier that you don't want to put in. A dehumidifier is the only way to continuously control humidity in your crawl space.

Crawl Space Vapor Barrier

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!

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