The Importance of Ventilating Your Crawlspace

Crawl Space ventilation

The condition of your crawl space has a major impact on comfort, energy efficiency, home value, and indoor air quality. It’s easy to underestimate that impact, after all, your crawl space isn’t a place you visit on a regular basis. But the truth is that the condition of your crawl space really does have far-reaching effects that can cost you money while also compromising the value and safety of your home. Many of these issues are linked to your crawl space’s ventilation.

Why should I ventilate my crawlspace?

The air in your home rises from the crawl space, bringing with it moisture, mold spores, and anything else that may be airborne down there. As this air rises in the home, replacement air is drawn through the vents. This replacement air is made up of unconditioned outside air that enters through vents and other leaks. This natural upward air movement is called the “stack effect” – similar to how a chimney works.

Consequently, whatever is in the air at the lowest point of your home eventually flows up into the living areas. Almost half of the air you breathe on the first floor of your home comes from the crawl space. Moisture ruins houses by providing a hospitable environment for mold and other fungi, and insects that destroy wood framing. Crawl space moisture, and the mold and mildew that thrive in this environment, affect not only the floor system directly above but also the entire house.

How do I ventilate my crawlspace?

We suggest that you open and close the vents in your crawlspace seasonally, instead of deciding to seal off crawl space vents altogether. Opening the crawlspace vents in the summer allows outside air to circulate under the floor to prevent moisture buildup that, among mildew and mold, encourages wood rot. In the winter, when the air is drier, close the vents to reduce the chance that the pipes in the crawlspace might freeze.

How do I seal off my crawlspace for the winter? 

If you decide to not seal off crawl space vents year-round, the simplest way to close your crawlspace vents for the winter is to plug them from the outside with foam blocks made specifically for crawlspaces. Then remember to remove the plugs when the weather turns milder in the spring – and while you do, check to make sure that your crawlspace vent screens are intact so that insects and rodents don’t make nests under your house. You could also choose to go with automatic vents, which are designed to work without electricity, and open at approximately 70 degrees and close at around 40 degrees.