Inadequate Vapor Barrier
Like most crawl spaces, the 6-mil vapor barrier that is in this crawl space is unsealed, damaged, and displaced. The purpose of the vapor barrier is to prevent water vapor from the earth from rising into the crawl space. Instead, the gaps in this vapor barrier allow vapor to impact the environment.
Mold Treated & Insulation Removed
The homeowners had an issue with mold between their first and second floor as well as in the crawl space, they have already had the mold treated and old insulation removed as part of that process. The microbial growth is a result of high relative humidity allowed into the crawl space through open vents and from the earth, warm temperatures, and an organic food source.
Heavy Duty Vapor Barrier
A heavy-duty vapor barrier is installed in the crawl space. The liner is overlapped and sealed at all seams, wrapped and sealed around all piers, and attached and sealed to the foundation walls about 6 inches above outside grade. This seals the crawl space from the earth's moisture and prevents water vapor from rising into the space.
Spray Foam on Foundation Walls
Closed Cell Spray Foam is applied to the crawl space walls leaving a 2" viewing strip. The viewing strip is a Virginia Building Code Requirement that allows termite inspectors to perform their inspections. The foam is applied at an R-10 the requirement for insulating from crawl space walls, and at this thickness is both an air barrier and vapor retarder.
Controlling Relative Humidity
The final piece of controlling the relative humidity in a crawl space and preventing future microbial growth is installing a dehumidifier. The dehumidifier will remove excess moisture from the air keeping the relative humidity below 60% and it will circulate the dry air throughout the crawl space. The dehumidifier will only turn on when the relative humidity rises over 55%, so it does not run all the time. A Hygrometer is also installed, a sensor is placed in the crawl space to send temperature and humidity readings to a unit in the home which reads temperature and humidity in the home and displays the results of both the crawl space and living space. This allows the homeowner to monitor the conditions of their crawl space.
