A Brief History of Crawl Space Vents

Before we get into the long and winding road of crawl space vents, it's important to note that building codes and regulations are constantly changing as research leads us to the best solutions. Always consult current building code for your area before making any decisions!

Crawl spaces have long been a part of no man’s land when it comes to construction best practices. They’re not functional like a basement, which can be a usable part of the house, but they’re enclosed and so can’t be considered “not” a part of the house. So what are they? Mostly a headache.

Around the 1950s (all dates are approximate, as building codes vary throughout the country), it became best practice to ventilate a crawl space. It was thought that airflow would reduce moisture, thus reducing mold and the subsequent health and structural concerns associated with it. This isn’t the case, of course, but we’ll get to that.

There was always pushback as new research emerged, and building theory changed course in the 1990s as the Stack Effect was studied. Sure, vents allowed for airflow, but the stack effect (which explains the way air - hot or cold - moves throughout a home) meant that the conditioned air was going right out the window. Or in this case, the vents.

And besides literally paying to heat or cool the neighborhood, crawl space vents let a lot more than air into a crawl space. Moisture from the air, along with bacteria and vermin, could easily enter the crawl space; the house would be affected by the mold and bacteria as the air from the crawl space circulated the house.

For the past 20 years, crawl space ventilation has been on the decline, and the building codes have actually changed so that vents are no longer mandated. It is now recognized that a sealed, conditioned space is more beneficial to the health and safety of a home.

So what can you do?

If you live in, or are trying to buy or sell a home with a vented crawl space, get it sealed. We install vent covers as well as air and watertight crawl space access doors to ensure that there are no entry points from the outside. As for inside, a vapor barrier like our CleanSpace system will completely encapsulate the crawl space to ensure protection of the house. Installing a dehumidifier will go the extra mile to keep the home protected from the effects of mold and moisture.