Crawl Space Science: Vented Dirt Crawl Space Problems

Monday, May 23rd, 2022 by Paige Jackson

A house with a dirt crawl space is dysfunctional, and a dysfunctional house is not worth building at any price. -Larry Janesky

Quick question: Is your crawl space located on the inside or the outside of your home?

If your crawl space is vented with a dirt floor, and has no barrier, it is on the inside of your home.Crawl Space Science: Vented Dirt Crawl Space Problems - Image 1

Why is There Mold in Your Crawl Space

Crawl spaces are very prone to mold growth due to the often excessive moisture in these dark, underground spaces. And, because you most likely don't go into your crawl space often or at all, mold can go undetected for a long time. Vented crawl spaces are prime targets for mold growth because of their chronically high humidity levels, especially during the summer. The air in your crawl space circulates through your home, so if there's mold in your crawl space, you are likely breathing unhealthy air. Particularly in homes with family members who have allergies, a below-grade space should be maintained no differently than the rest of your house. Even if intermittent, a musty smell in a crawl space is a sign of mold growth. Mold spreads by its microscopic spores traveling on air currents to reattach elsewhere.

Crawl Space Science: Vented Dirt Crawl Space Problems - Image 2
40% of the air we breathe in our home comes from the crawl space.

Moisture inside your home is bad for what's in it. Have you ever noticed green/white spots on your clothes or shoes in your closets? That is mold and it is more than likely coming from your crawl space. This crawl space air gets into your home in one of two ways.Crawl Space Science: Vented Dirt Crawl Space Problems - Image 3



#1: The Stack Effect

“Stack Effect” is a term used to describe the way air moves throughout a home. As the air in a home warms, it rises to the top of the house and builds up air pressure. Since the pressure inside the top of the house is greater than the outdoor pressure, the warm air will leak to the outside. This happens primarily through all the gaps, cracks and openings in the attic floor.

If air is leaking out, it must also be leaking in, because a vacuum can’t be created under natural conditions in a home. The air will leak primarily in the basement or crawl space of a home, where the pressure difference between the inside (low) and the outside (high) is greatest.
“Leaky” homes suffer from stack effect more than other homes. Homeowners may spend more money to heat their homes in the winter, and cool them in the summer because the stack effect increases the amount of air changes occurring in the home in any given time. And this air needs to be heated and/or cooled!

Crawl Space Science: Vented Dirt Crawl Space Problems - Image 4

#2: HVAC System

Crawl space air can enter a home via the HVAC system. How so? Courtesy of your air ducts! You are breathing the crawl space air. In fact, we know that 1/3 to 1/2 of the air that you breathe on the first floor of your house came through your crawl space.


If someone sprays paint inside of your crawl space, do you think you would be able to smell the spray paint upstairs? Of course you would!


If you see (or smell) any of these issues inside of your home, it is time to contact the experts. A musty crawl space should be something you do not have to live with. Remember no matter what type of crawl space repair solution you need; Southeast has the experience and custom solutions. It's our job to make sure that the space is transformed into a cleaner, drier, healthier and more energy efficient space.

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