Case Studies

Crawl Space Insulation Case Studies: Remediating Crawl Space Moisture & Mold in Locust Hill, VA

Friday, June 26th, 2020 by Erin Dougherty


A homeowner in Locust Hill, VA contacted us when they noticed moisture and mold in their crawl space. They were interested in having the space encapsulated, so we sent out one of our Home Performance Advisors to inspect the space and review the homeowner’s goals as well as discuss their options.

At the inspection, our Humidity Meter indicated high relative humidity in the space, ranging between 62.8% - 72.5%. High relative humidity indicates there is an excess of moisture entering the crawl space. That moisture is absorbed by the fiberglass insulation in the floor and the joists themselves. Our Wood Moisture Meter indicated 19% - 21% wood moisture content in the joists. At 19%, wood rot can begin.

Moisture absorbs into the Fiberglass insulation reducing the effectiveness of the material. Moisture degrades the fibers causing them to delaminate and fall away. The insulation gets heavier as it becomes saturated and falls away from the floor.

The vapor barrier was not completely covering the floor of the crawl space and was even missing in some places allowing water vapor from the earth to rise into the crawl space and increase the relative humidity (RH). Another major contributor to high RH is crawl space vents. Warm, humid air floods in through vents, the rim and band, sill plate, access door, and any other small holes it can find.

The high humidity and warm temperatures allow mold and mildew to grow on organic surfaces. In a crawl space, this is typically the floor joists and paper backing of fiberglass insulation. As air from the crawl space is pulled up into the home via the stack effect, spores, dust, and allergens go along for the ride. Inside the home, the air quality is reduced and occupants with asthma and allergies are often irritated.


To encapsulate the crawl space, we first cleaned out the existing insulation, vapor barrier, and debris. Next, we applied Shockwave antimicrobial to the wood substructure to kill the microbial growth.

Then we laid the CleanSpace Vapor Barrier on the ground, sealing all seams and wrapped and sealed all piers. We run the vapor barrier 6-8 inches up the foundation wall above outside grade. We also used foam to seal and insulate the rim & band, seal the sill plate, and any penetrations through the block wall to outside. All vents were blocked and sealed from the inside of the crawl space as well.

Then we applied an R-10 of closed-cell spray foam to the crawl space walls for insulation. A 2 inch viewing strip is left per VA building code to allow for termite inspections. Insulating from the walls extends the thermal barrier of the home to the floor of the crawl space, making the environment easier to control. We also install a friction fit crawl space door to air seal and insulate behind the exterior access door.

Finally, we installed a SaniDry Sedona Dehumidifier. The Sedona is specifically designed to be effective and efficient in crawl space and basement environments. The unit only cuts on when the relative humidity increases to a preset 55%, we want to keep the RH below 60%. It pulls the excess moisture from the air, filters it, and circulates the dry air throughout the crawl space.

With this solution in place, the homeowners no longer need to worry about moisture causing issues under or inside their home. They can even monitor the temperature and humidity in their crawl space with the Hygrometer we installed as part of the system. The display unit sits in the home and reads the humidity and temperature for both the crawl space and inside the home, indicating to the homeowner if there is ever a concern.

If you are noticing moisture or mildew/mold growth in your crawl space, or high humidity and musty odors in your home, call your local Crawl Space experts at The Drying Co. Our Home Performance Advisors will discuss your concerns with you, do a thorough inspection, take photos and share their findings with you, then work with you to develop the right solution for you and your home.

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The Drying Co./ThermalTec
236 Industrial Blvd
Suite A
Toano, VA 23168

The Drying Co./ThermalTec
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Toano, VA 23168
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