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Crawl Space Ventilation

Crawl Space Solutions by JES

Crawl Space Ventilation

Crawl Space Ventilation

In the past it was common practice to endorse crawl space ventilation. The idea behind this practice was that venting the crawl space would keep it dry. We now know that this just isn’t the case.

Crawl space ventilation, especially in humid areas, ends up doing more harm than good. The outside moisture that’s pulled into the crawl space creates the ideal environment for mold, mildew, insect infestations and wood rot. All of which thrive in environments that have a relative humidity that’s over 50%. According to the USDA, “Experimental studies have show that crawl space ventilation is usually counterproductive, especially in humid climates.”i

Experimental studies have show that crawl space ventilation is usually counterproductive, especially in humid climates.”

In fact, an Advanced Energy study found that crawl spaces with open vents stay above 70% relative humidity – well above the healthy humidity level of 50%ii. Even if a vapor barrier was installed, if there were open crawl space vents then high humidity continued to be a problem.

Open crawl space vents

Why Are Open Crawl Space Vents Bad?

Crawl space ventilation typically results in high humidity which will:

You can see that crawl space ventilation can lead to some major problems. It’s a good idea to protect your home, family and health by having a professional seal your crawl space. This is the only way to ensure that you won’t have a crawl space moisture problem.

Additional Resources:

Crawl Space Moisture Control

Crawl Space Encapsulation Code


i. USDA. Techline: Crawl Space Ventilation

ii. Advanced Energy. Housing Zone: To Vent or Not to Vent.

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