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Common Moisture Issues Found In Vented Crawl Spaces

Tuesday, May 11th, 2021 by Nate Tetreault


Windsor, VA Crawl SpaceA Windsor, VA homeowner called us with concerns that many of our clients have, moisture in their crawl space. When we send an advisor to do an inspection, we always focus on the root cause of our client's concerns. In most cases, it is moisture, and moisture finds its way into a crawl space in a variety of ways.

In many crawl spaces, like the one in this Windsor, VA home, there is typically a 6-mil vapor barrier placed over the dirt crawl space floor. Unfortunately, these liners are not that effective at preventing moisture from rising out of the earth and into the crawl space. They need to be sealed at the seams, wrapped around all piers, and mechanically fastened to the foundation wall, lest there be moisture infiltration. The moisture that gets in raises the relative humidity of the crawl space, leading to mold growth or condensation. The dark and damp environment is also ideal for small critters and creatures, that will make their home in the underbelly of these houses.

There can be quite a bit of outside air and moisture leakage through the foundation walls of a crawl space, as well. Moisture will seep through these porous cinderblocks or bricks and affect the relative humidity. Efflorescence can also occur when moisture forces its way through the walls, bringing along with it the salts and sediments from within the walls to the surface, creating a chalky, powdery substance and staining along the walls.

Open vents also line the foundation walls, which will allow outside air and moisture to freely enter the crawl space. While vents were intended to allow hot humid air to flow in and out under the home in warmer months this is not what is occurring. Instead, any moisture entering through these vents becomes trapped, raising the relative humidity of the crawl space. Small critters and creatures can also sneak their way in via these vents.

For many homes, the crawl spaces can be subgrade, and water pools around the foundation. If the soil around the foundation is not dense enough, the added pressure from the water can expand and press against the foundation, which leads to cracks. Eventually, water will enter the crawl space through these porous and cracked foundation walls, adding to the relative humidity.

With there being multiple entry points for moisture infiltration, there are several issues that have arisen. Many crawl spaces, like the one in Windsor, VA, suffer from the high relative humidity and damp environment. The fiberglass insulation batts often found between the floor joists begin to sag and fall out of place. They absorb the moisture like a sponge, and the fibers begin to pull away from one another due to the insulation being wet, also when fiberglass is wet, its R-value is greatly diminished.

Mold and mildew growth is also an issue that arises in these damp crawl spaces. When the relative humidity reaches above 60% during warmer temperatures, mold and mildew begin to form along many of the organic materials found in the crawl space, such as the wooden floor joists and subfloor. Often, homeowners notice a musty or mildewy odor in their home because of the mold growth. Mold on Floor Joists

Condensation can also occur when the relative humidity reaches 100%, and the air can no longer hold any moisture. Water droplets will begin to form and eventually there will be puddles of water formed along the floor of the crawl space. As mentioned before, the water droplets will be absorbed by the insulation batts, pulling it apart and ruining it, leaving the subfloor exposed to the temperatures and conditions of the crawl space.

Moisture infiltration in a vented crawl space can lead to several serious issues, including mold and mildew growth, ruined fiberglass insulation, and in extreme cases wood rot, all of which can impact the health and durability of your home.

If you are experiencing any of these problems in your crawl space, or simply wish to learn more about crawl space encapsulations, click this link: https://www.thedryingco.com/about-us/blog/39154-6-steps-to-a-crawl-space-encapsulation.html or give us a call at 1-833-933-3111. We will help you to keep the outside, outside!

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