Case Studies

Crawl Space Insulation Case Studies: Mold Growth Remediation in Williamsburg, VA

Friday, August 20th, 2021 by Nate Tetreault


A homeowner in Williamsburg, Virginia was experiencing excessive moisture and mold growth within their crawl space. They called us at The Drying Company to discuss their options for protecting their crawl space from outside influence, so we sent out one of our highly trained Home Performance Advisors to evaluate their situation.

Upon inspection, we found that there was indeed mold and mildew growth on many of their wooden floor joists. This growth can form on organic materials of the crawl space when the relative humidity of the crawl space reaches over 60% during warmer temperatures. Musty odors can rise into the floors above and cause irritation to those with allergies and asthma.

The next thing we noticed was that the fiberglass insulation batts were sagging and falling out of the floor joists. This insulation becomes heavy when soaked with moisture and will tear apart and begin to fall to the floor in chunks. Water droplets pull apart the fine glass fibers, and gravity pulls the heavy pieces down, tearing the insulation into pieces and rendering it useless.

We also noticed that the existing vapor barrier, a 6-mil liner, was torn and pushed aside in many places, leaving the dirt flooring of the crawl space exposed. This allows moisture to freely rise from the earth and into crawl space, affecting the relative humidity and environment. This also makes it difficult for service persons to navigate through the space, and critters and creatures love to make this dark and damp environment their home.

Efflorescence was noticeable along the foundation walls, a clear indication of moisture infiltration. When water forces its way through these porous cinderblock walls, it brings along with it the salts and sediments from within the blocks to the surface, creating a chalky, powdery substance known as efflorescence. Open vents lining these walls were also allowing outside air and moisture to enter the crawl space. The moisture becomes trapped, raising the relative humidity, which just leads to moisture problems like mold growth and water damage.

We quickly drew up a proposal for many solutions that would not only help protect this crawl space but to help to create a more comfortable home and lower energy bills for the homeowner.


The first thing our team did was remove all existing fiberglass batts, as well as the 6-mil vapor barrier and any debris from the crawl space. Once the area was clear, we used an antimicrobial called Shockwave on all affected materials to kill any mold and mildew growth. This eliminates mold growth but does not remove the staining caused by it. It is important to note that mold and mildew growth can come back if the relative humidity and environment are not controlled and regulated.

The next step we took was installing a 10-mil vapor barrier, called CleanSpace Light, over the dirt flooring of the crawl space. This vapor barrier will help to keep the earth’s rising moisture from getting into the crawl space and raising the relative humidity. We wrapped it around all piers and mechanically fastened it on the foundation walls, six to eight inches above outside grade. This adds some protection the some of the moisture seeping through those porous cinderblock walls.

We had proposed that the homeowner let us apply spray foam onto their foundation walls as well. At an inch and a half thickness, the spray foam would act as an air barrier and moisture retarder. The spray foam would not only insulate the crawl space area but seal it from any outside influence. The open vents would be covered as well. Not only would the spray foam cover them, but we would use foamboard pieces to block them, ensuring no air or moisture can just freely enter through them.

The last step we took was to install a highly energy-efficient dehumidifier, called a SaniDry Sedona. This dehumidifier will help circulate dry air around the crawl space while maintaining the relative humidity at a set percentage. A condensation pump and drain line are also connected to the Sedona, pulling away any moisture collected to a predetermined location of the home’s property. A hygrometer is given to the homeowner to monitor the temperature and relative humidity of their crawl space.

The homeowners can now enjoy the benefits of sealing up most of their crawl space, such as lower energy bills and a cleaner and dryer environment underneath their home. If you are also experiencing any moisture issues or mold growth within your crawl space, give us a call at 757-566-8622 to schedule your free estimate and appointment!

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