Sealing & Insulating a Crawl Space and Between Floors in Carrolton, VA
Challenge
This Carrolton, VA homeowner contacted us after battling concerns with mold growth between their first and second floor and in their crawl space. They had already had the insulation removed and mold treated in the crawl space. In the living space, they had the ceiling of the first floor removed to treat the mold.
They were looking for options on just replacing the fiberglass in the crawl space and sealing the crawl space completely. They certainly didn’t want to incur the mold treatments and tearing their home apart again but wanted to understand their options. We reviewed both routes with them.
Ultimately, the homeowners decided to seal the crawl space as well as air seal the rim and band between the first and second floors.
Solution
In the crawl space, we began by removing the existing 6-mil vapor barrier and any debris. We then installed a heavy-duty vapor barrier. The liner is overlapped and sealed at all seams, so there are no gaps in the system. We wrapped and sealed all of the piers and attached and sealed the liner to the foundation walls about 6 inches above outside grade. This seals the crawl space off from any moisture rising from the ground and raising the relative humidity.
Next, we sealed all vents, the rim and band, and the sill plate with foam. These spaces are all gaps in the home’s construction that allow air carrying moisture to flow in and raise the relative humidity. Next we applied Closed Cell Spray Foam to the foundation walls, leaving a 2” viewing strip for termite inspections. The foam is sprayed at an R-10 and at this thickness it is both a vapor retarder and air barrier. A friction fit door is then installed behind the exterior crawl space access to provide an R-10 of insulation and air sealing, behind what I otherwise a large hole humid air can flood in through.
The final step in the crawl space is installing a dehumidifier and hygrometer. The dehumidifier is powerful enough to keep crawl space air dry by removing moisture from the air when it increases over 55% relative humidity and circulating the dry air throughout the entire crawl space. The hygrometer sensor is placed in the crawl space and reads temperature and humidity. In the home, there is a readout for the sensor that also monitors the home’s temperature and humidity. This allows homeowners to assess the conditions of their crawl space and offers an indication if there is ever an error with the dehumidifier.
To address the concerns between the first and second floors. Our team prepped out the home with plastic to protect the homeowner’s belongings and applied an R-10 of closed-cell foam at the rim and band. This provides air sealing properties and a vapor retarder to help prevent air carrying moisture from impacting the space between the floors again.
These solutions help the homeowners protect their space from future microbial growth. In addition, they will have the benefit of healthier indoor air quality, lower energy bills, and more comfortable living space.
