Case Studies

The Drying Co./ThermalTec Case Studies: Solving Moisture Issues in a Newtown, VA Crawl Space

Thursday, May 27th, 2021 by Nate Tetreault


A homeowner in Newtown, Virginia called us at The Drying Company to discuss replacing the existing fiberglass insulation in their crawl space. They had hired a plumber who was unable to weave their way through all the fallen fiberglass. We sent out one of our professional Home Performance Advisors to evaluate their situation.

Upon inspection, we noticed that the fiberglass batts were indeed falling out of place in many areas. Many were blocking off different areas of the crawl space, others were just laying on the floor, rendering them useless. This occurs when there is too much moisture in the crawl space. The fiberglass soaks up much of the moisture and becomes too damp and heavy to stay in place.

We also noticed that many of the exposed wooden floor joists had mold and mildew growth upon them. When the relative humidity reaches over 60% during warm temperatures, mold and mildew can grow on any organic materials in the crawl space. It is also able to form along the paperbacks of the fiberglass insulation.

The next thing that caught our attention was the 6-mil vapor barrier on the dirt floor of the crawl space. Many areas of the dirt floor were not being covered by this vapor barrier, nor was there any sealing of any kind where the liner was present. This was allowing the earth's moisture to rise into the crawl space and raise the relative humidity, adding to the mold growth problem.

The mildew/mold growth can also be associated with the unsealed and uninsulated foundation walls of the crawl space. Moisture was seeping through these porous cinderblock walls and contributing to the high relative humidity. Open vents were also lining these foundation walls, which allows outside air and moisture to freely enter and affect the environment.

With these moisture issues in effect, mold and mildew growth is on the rise, and the fiberglass insulation batts are becoming more and more deteriorated. We proposed several options that would address these concerns.


The homeowner decided they wished to have us replace their existing fiberglass batts and vapor barrier. So, the first thing we did was remove the 6-mil vapor barrier, the fiberglass insulation, and any debris littering the crawl space floor.

The next step we took was to treat the mold and mildew growth using an antimicrobial, called Shockwave. This antimicrobial solution kills mold and mildew but does not remove any staining left behind. It is also important to note that the mold can grow back if the relative humidity and temperature are not controlled.

After the mold remediation, we installed R-19 fiberglass insulation batts between the floor joists. This will help insulate the subfloor. Our next focus was on the dirt floors of the crawl space, where the homeowner had us install a 6-mil vapor barrier, anchored by 12” stakes.

With the insulation and vapor barrier replaced in this crawl space, it will be much easier for service persons to navigate. However, without sealing the crawl space from outside air and humidity, moisture will still cause damage in the crawl space. If the homeowner wanted to prevent future mold growth and never has to replace their insulation or vapor barrier again, we recommend an encapsulation to control the amount of air and moisture entering the crawl space as well as the relative humidity.

This would be achieved by using an R-10 value of insulation on the walls, the entire crawl space would be insulated and brought into the thermal envelope of the home. If the crawl space were insulated from the walls instead of the floor joists, it would make it easier to control the relative humidity and environment.

We proposed using either a 10-mil CleanSpace Light vapor barrier or a heavy-duty 20-mil CleanSpace barrier. These liners are much more reliable and better protect the crawl space from moisture rising out of the earth and are more durable when service persons are working under the home.

We also proposed adding a SaniDry Sedona dehumidifier to the crawl space. This efficient dehumidifier is perfect for regulating the relative humidity while circulating dry air around the crawl space. This would help us to control the relative humidity, temperature, and environment of the crawl space, making it difficult for mold growth to occur.

If you or someone you know is experiencing similar problems in the crawl space, then please give us a call at 757-566-8622 to schedule your free estimate and appointment. We will help you to keep the outside, outside!

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

The Drying Co./ThermalTec
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P.O. Box 637
Toano, VA 23168
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