Case Studies

Crawl Space Moisture Control Case Studies: Sealing and Insulating a Crawl Space in Lottsburg, VA

Friday, April 30th, 2021 by Nate Tetreault


A homeowner in Lottsburg, Virginia called us at The Drying Company to discuss possible solutions for moisture issues in their crawl space, and lack of insulation. We sent out one of our Home Performance Advisors to evaluate the situation and to propose a solution that would rectify the moisture problems.

Upon inspection, we found efflorescence all over the foundation walls, an indication of moisture infiltration. When moisture seeps through these porous cinderblock walls, it pulls the inner salts and sediments to the surface, creating a chalky, powdery residue. Open vents lining these walls also allow outside air and moisture to enter the crawl space and become trapped, affecting the relative humidity and environment.

We also noticed that a 6-mil vapor barrier was installed to cover the dirt crawl space floor. However, many openings and gaps exposed the earth/ground, allowing the moisture from the earth to rise, affecting the environment of the crawl space, and raising the relative humidity. Puddles of water were also forming on top of the vapor barrier, most likely due to the relative humidity reaching 100%, and allowing condensation to occur.

As a result of moisture infiltration and high relative humidity, the fiberglass batts were quite damp, and sagging or falling out of the floor joists. Fiberglass insulation will absorb moisture, and the fibers will pull apart, causing the insulation to sag or fall to the crawl space floor in heavy chunks.


Our Home Performance Advisor proposed several solutions to help control the relative humidity and protect the crawl space environment from outside influence. Our production team quickly got to work and began by removing all fiberglass insulation batts and fallen debris from the crawl space. We also removed the existing 6-mil vapor barrier, giving us a clean slate to work with.

The next action we took was to cover the crawl space floor with a 20-mil CleanSpace liner. This heavy-duty 7-ply vapor barrier will protect the crawl space from any moisture rising from the earth. We wrapped the liner around each pier and mechanically fastened it on the foundation walls, six to eight inches above outside grade. The vapor barrier also comes with an antimicrobial, called UltraFresh, built into the material to help prevent mold growth on the liner itself.

After the vapor barrier was installed, we then proceeded to insulate the foundation walls and cover the open vents lining them. We covered the open vents using foam board sealed with foam and then proceeded to cover the foundation walls using an R-10 value of closed-cell spray foam. This will act as an air barrier and moisture retarder and keep the crawl space of the home insulated.

Finally, we added a SaniDry Sedona dehumidifier to help regulate the relative humidity of the crawl space. This efficient dehumidifier circulates dry air around the crawl space and pulls excessive moisture from the air. A hygrometer was given to the homeowner to monitor both the temperature and relative humidity of the crawl space and inside the home.

If you are experiencing any of these issues in your crawl space, then please give us a call at The Drying Company to schedule your free estimate and appointment. We are always happy to answer any questions you may regarding your home’s efficiency. Let us help you keep the outside, outside!

our service area

We serve the following areas

Our Locations:

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

The Drying Co./ThermalTec
Mailing Address
P.O. Box 637
Toano, VA 23168
Unable to process this phone number