Why Are Open Crawl Space Vents a Problem?

In an ideal world, ventilating your home would have no downsides. After all, as the weather starts to warm up, it can be tempting to try and get cool air circulating through all levels of your home, even your crawl space. After all, if you leave the vents open, your home will cool down—right? 

The temperatures in your home may drop, yes, but it may also become more difficult to control temperatures inside your home in the days to come. When you open the vents in your crawl space, you allow the space to fall victim to the stack effect. 

What Is the Stack Effect? 

The stack effect describes a phenomenon during which the air in your home travels up from the crawl space into the other levels of your home. As such, if there’s an excess of moisture in your crawl space, then the air circulating through the rest of your home will be uncomfortable and moist, as well. 

That moisture—which does not always come in through the vents, but which can be made more prominent when your vents are open—has serious impacts on the health of your home. A home with high levels of humidity can see its structural supports start to fail. Mold can also take root in a damp crawl space. These mold clusters can appear both in your crawl space and in your HVAC unit, making it extremely difficult to remove in its entirety from your home. 

What’s more, trying to control the temperature of your home when there’s excess moisture in the air is a near impossibility. Moisture cools the air in your home and will continue to do so no matter how you adjust the thermostat. In short, by leaving the air vents in your crawl space open, you will be losing money on an overly expensive energy bill and putting your home at serious risk for damage later down the line.