Crawl Space Encapsulation in Yorktown, VA
Challenge
This Yorktown, VA homeowner contacted us when they decided they wanted to encapsulate their crawl space. They were referred to us by one of our long-time customers after noticing some moisture issues under their home.
At our inspection, we first noticed that the existing 6-mil vapor barrier was not sealed. 6-mil vapor barriers are thin and flimsy, easily damaged, and tacked into place using U-shaped stakes creating holes in the material. All these gaps and holes allow the earth’s moisture to rise into the crawl space, raising the relative humidity (RH).
Next, we found that there was efflorescence and staining on the foundation walls. This indicates that moisture has worked its way through the porous cinderblock and collected on the walls. Open vents in the foundation walls allow air and moisture to pour into the crawl space throughout the year contributing to high humidity under the home in the summer and cold floors and drafts in the winter.
The excess moisture in the crawl space has raised the relative humidity above 60%. With moderate temperatures, mold and mildew have begun to grow on the joists. We did not find high moisture content in the wood, which is a good thing. High wood moisture content, over 19%, indicates that wood rot is beginning and can lead to structural concerns. Thankfully, we did not see any signs of this.
Mold in the crawl space is always a concern because it not only impacts the health of your home, but it can impact your health as well. Approximately 50% of the air inside your home comes from your crawl space. This means that the dust, allergens, and moisture are pulled up into your home impacting the indoor air quality. This generally irritates those with asthma or allergies, and in extreme cases can even cause asthma or allergies. Some homeowners notice high humidity in their home, musty odors, and might notice mold growth in closets. Our client had not reported any mold in the home, another good sign.
Despite not being on the extreme end of mold growth, wood rot, or moisture damage in the home, our client wanted to be proactive to ensure that their home was protected and have the added benefit of a more energy-efficient home. So, they opted to encapsulate their crawl space.
Solution
We began the project by cleaning the crawl space floor. We pulled out the old vapor barrier and removed any debris on the ground. Typically we would remove damaged fiberglass insulation at this point, however, the batts in this home were relatively new and undamaged, so the homeowner opted to keep them in place and have our team reinforce the batts with additional support.
Next, we installed a 10-mil vapor barrier. The liner is run up the crawl space walls 6-8 inches above outside grade, this allows any water migrating through the porous block wall to be directed under the liner. The liner is wrapped and sealed around all piers and all seams are overlapped and sealed. Properly sealing the moisture barrier is key to keeping the earth’s moisture out of the crawl space.
Our liner crew also sealed all the crawl space vents from the inside of the crawl space. This allows the exterior of the home to maintain its aesthetic. The rim and band and sill plate are also sealed with foam insulation. The sill plate is where the frame of the house sits on the foundation. There are gaps all around the sill plate and rim and band that allow air and moisture to flood into the crawl space.
The next step was to install a continuous R-10 of insulation on the foundation walls. The homeowner opted to use Foamboard insulation for this. The Foamboard is mechanically fastened to the crawl space walls and sealed at all seams and against the block wall. This prevents air and moisture from traveling through the block wall from entering the crawl space. A 2-inch viewing strip is left at the top of the foundation wall, per Virginia Building Code, to allow for termite inspections.
We have now done everything we can to prevent as much moisture as possible from entering the crawl space. However, because we can’t fully control how the outside temperature impacts the inside of the crawl space, and the substructure of the home is made of organic material, we need to control the relative humidity to prevent future mold growth and moisture damage to the wood. The final piece of the puzzle is to install a dehumidifier. In this crawl space, we used the Compact70, a unit designed for particularly tight crawl spaces.
The dehumidifier will turn on when the relative humidity reaches about 55% and will remove excess moisture from the air and circulate dry air throughout the crawl space. Keeping the relative humidity under control means that we can help to prevent future mold growth and wood rot. Our homeowner is also provided with a wireless hygrometer. The hygrometer is 2 parts, a sensor placed in the crawl space and a receiver with a screen that is kept in your home. The receiver displays the relative humidity and temperature inside the crawl space and inside the home. This allows our client to keep an eye on the conditions under the home without ever going in the crawl space giving them peace of mind that their home is protected.
