Why Does My Crawl Space Smell Musty?

If you have a crawl space in your home, there is a good chance it has a musty odor. That musty smell might have started wafting into your home. Or, you're subjected to it whenever you access your crawl space. Do all crawl spaces have this unpleasant odor? Why does your crawl space smell this way?

South Central Services has insulated hundreds of homes with spray foam. Many homeowners in and around Mercersburg, PA contact us about musty odors and crawl space problems. In southern Pennsylvania, most crawl spaces smell musty. The good news is that we know why this musty smell happens and how to stop it.

By the end of this article, you will understand:

• What most crawl spaces have in common, in addition to musty odors
• Why crawl spaces have such strong musty smells
• How to stop the musty smell in your crawl space

Don't have time to read right now? Check out everything you need to know at a glance.

Most Crawl Spaces Are Left Open To Ventilation.

In southern Pennsylvania, most crawl spaces are vented. The idea behind vented crawl spaces is to use airflow to dry out a crawl space. If the crawl space gets enough ventilation, the movement of air can dry out the moisture of the dirt floor and the ground surrounding it.

Unfortunately, ventilation cannot dry out the crawl space. The ventilated air is already humid, so it cannot dry the crawl space. Ventilation is constantly fighting a losing battle, being open to the elements.

Since the open airflow cannot dry out the crawl space, the climate of that area fluctuates with the outside elements. This means a lot of cold and wet. It's no wonder your crawl space smells musty.

Think of this like a log in the forest in the summertime. The bottom of the log isn't exposed to direct sunlight, so if you roll the log over, it's wet underneath. This environment is the same as your crawl space. With no direct sunlight and humid air, nothing promotes the drying of your crawl space or the log.

Ventilation Leads To Musty Odors In A Crawl Space.

Since the crawl space is open to the elements, it stays wet. Vented crawl spaces do not intend to create a wet environment, but it is the reality. In this damp environment, mold and mildew are given the ideal circumstances to grow.

Even without the presence of mold, wet dirt does not have a pleasant scent.

Have you ever left clean, wet clothes in the washing machine for too long? As long as the lid to the machine is closed, you might not notice a smell at first. As soon as you open the door, the musty odor overwhelms you.

A vented crawl space has the odor of forgotten wet laundry, but there is no "lid" to keep the scent out of your home.

How Can You Cut Off Crawl Spaces From Ventilation?

Two insulation methods can help address the musty odors in your crawl space. You can either "put a lid" on the musty smell or cut off the ventilation entirely.

Let's examine each method in more detail.

1. You Can Insulate Your Crawl Space Ceiling.

Crawl space ceiling insulation is a common solution. Many vented crawl spaces have fiberglass batt insulation stuffed in the ceiling to act as a barrier.

Unfortunately, fiberglass batt insulation is as effective a barrier as a screen door. If you want to properly insulate your crawl space ceiling, you need to use closed cell spray foam.

Closed cell spray foam is the only product that can actually cut off the airflow between the living space and the crawl space. It creates an airtight seal and a vapor barrier, which prevents any moisture in the crawl space from entering the living space.

We don't usually recommend ceiling insulation, because we would rather address the root problems of the musty odors in your crawl space. However, there are some circumstances that necessitate ceiling insulation. Standing water in the crawl space is an example of a situation where ceiling insulation is the best approach.

If you opt for ceiling insulation, closed cell spray foam is the product you need. Fiberglass insulation is ineffective in this application.

Ultimately, insulation in the crawl space ceiling doesn't stop the crawl space from smelling musty. It just stops the musty smell from wafting into your house.

2. You Can Encapsulate Your Crawl Space.

If you want to address the root problems in your crawl space that cause the musty odor, you must encapsulate it. Encapsulating the crawl space cuts it off from cold and wet elements.

Insulating the walls and installing a vapor barrier on the floor prevents air from leaking at random. The seamless barrier also cuts off any ventilation holes in the crawl space.

An encapsulated crawl space's climate can be controlled, including keeping it warmer and dry. This can only be accomplished once the crawl space stops fighting the infiltration of air from outside the house.

Encapsulation stops a crawl space from smelling musty because it addresses the wet air and changes the climate. Any air that exchanges between an encapsulated crawl space and your home is clean and dry.

The Bottom Line About Musty Odors In Crawl Spaces

Most crawl spaces have musty odors because they are open to ventilation from outside the home. No amount of natural airflow in a crawl space can dry out the moisture from being below ground. In this state, your crawl space is a breeding ground for mildew, mold, and musty smells.

There are two solutions to musty odors in a crawl space: cutting the musty odors off from the home or cutting off the crawl space from the environment conditions that create musty odors.

Now that you understand why your crawl space smells musty, your next step is to:

• Decide if insulating your crawl space ceiling is best for you
• Consider whether crawl space encapsulation offers the benefits you want
• Discover how long encapsulation lasts