If Open Vents Increase Ventilation in Crawl Spaces, Why Not Keep Them Open?

One would think that leaving the vents in your crawl space open may seem like a good idea, especially since their purpose is to allow air through the crawl space to condition and dehumidify it. However, this can do more harm than good in the long run.  

Consider Your Local Climate 

Moisture and humidity are the enemies of crawl spaces. Indeed, open vents can exacerbate the problems that come with moist conditions. As such, areas that are at high risk for moisture damage in crawl spaces are those that experience a decent amount of rain and snow in the winter or humid days in the summer. 

Rush City, MN, is characterized by frigid, snowy winters and somewhat humid summers. The annual average rainfall sits at 32 inches of rain. This, combined with the annual snowfall average of 49 inches, can add up to a lot of water. Similarly, Fargo, ND, experiences similar climate trends, having around 24 inches of rain and 49 inches of snow each year. When the snow melts or when rainwater enters through any open vents into your crawl space, this can result in a multitude of problems.  

Open Vent Damages 

Water in any shape or form, whether it be rainwater, snow, sleet, ice, or fog, can enter your crawl space vents if they are open. This can result in many water-related damages, including but not limited to: 

• Wood rot 
• Dry rot 
• Mold and mildew 
• Structural damage 

Moisture in your crawl space is also an invitation for many common pests. Crawl spaces are typically colder than other areas of your house, but more comfortable than remaining outside. They are suitable for retaining moisture and protecting bugs from the elements. Furthermore, many humans do not even go near their crawl space, making it the ideal place to live and proliferate. Some particularly damaging pests that can enter through open crawl space vents are cockroaches and wood-eating insects, such as the termite, but other harmless insects can live in crawl spaces as well.