Controlling Moisture in a Louisa, VA Crawl Space

Monday, April 4th, 2022 by Erin Dougherty

Challenge

This Louisa, VA homeowner had noticed some moisture damage in their crawl space and after some research, determined they wanted to encapsulate the space. Matt met with them to discuss the project, do an inspection, and help them determine which products and materials they wanted to use.

While inspecting and measuring the crawl space, Matt found that moisture had been seeping in through the foundation walls, evidenced by efflorescence and staining on the blocks. Areas of the crawl space were missing their vapor barrier, which was unsealed, and was allowing moisture from the ground to rise into the space. Open foundation vents were also a gateway for hot humid air to enter the space as well.

The fiberglass insulation in the floors was dirty, it had been acting as a "filter" for the air being pulled up into the living space via the stack effect (about 50% of the air inside your home comes from your crawl space). As the insulation has absorbed moisture, the fibers have begun to pull apart from one another and "drip" from the ceiling. The moisture makes the batts heavier, causing them to fall away from the floors completely.

The excess moisture in the space resulting in high relative humidity, and warm temperatures has created the right environment for microbial growth. Mold and mildew need an organic food source, in the crawl space, this is the floor joists, subfloor, and paper backing of the fiberglass insulation. (Usually, homeowners don't go in their crawl spaces, but they may notice musty odors and high humidity inside their home, this can be an indicator that there are humidity and mold/mildew issues in the crawl space.)

Already knowing they wanted an encapsulation, we reviewed the different material options with our client and put together a plan for getting the crawl space cleaned up and turned into a healthy space.

Solution

The first step was for Hasan and Mohammad to clean out all of the fiberglass, vapor barrier, and any debris that was in the crawl space. Next, they applied an antimicrobial to treat the mold and mildew growth on the floor joists and other affected wood in the crawl space.

With a clean slate, they set to work sealing the space. CleanSpace Light, a 10-mil crawl space is rolled out and attached to the foundation walls about 6 inches above outside grade, this directs any water that seeps through the foundation wall under the liner. The liner is overlapped at all seams and sealed, and wrapped and sealed around all piers. The crawl space is now sealed off from any moisture that rises from the ground.

Rigid Foam Board Insulation is then attached to the foundation walls and sealed at all seams. A 2" viewing strip is left at the top of the foundation wall per building code, this allows for termite inspections. All crawl space vents are also sealed and insulated from the inside and the rim band and sill plate are sealed to stop outside air infiltration.

Finally, a Dehumidifier is installed in the crawl space to control the relative humidity. While we've done everything we can to keep excess moisture out of the crawl space, we're still going to have some humidity, so the dehumidifier will help us keep it below the threshold that allows microbial growth to occur. The homeowner is also provided with a hygrometer which allows them to monitor the temperature and humidity of the crawl space from inside their home.