At 19% wood moisture content, wood rot can begin. In this crawl space we found readings of 21%, indicating we had a big moisture problem. Some of the joists were compromised and needed to be sistered and Smart Jacks were installed to stabilize sagging beams.
Fiberglass insulation soaks up moisture like a sponge. The moisture reduces the R-value of the material and causes the material to separate from itself. The added weight from the moisture causes the batts to sag and fall from the floors. Even with the metal rods to help keep them up. Often the excess moisture rusts out these rods as well.
Mold is growing on the joists in the crawl space. To thrive, mold needs a relative humidity of 60% or higher, moderate to warm temperatures and an organic food source. In a crawl space, floor joists and the paper backing of insulation are that source. Inside the home, the homeowner may notice musty odors, high humidity, and even experience agitation to asthma or allergies.
A Heavy-duty vapor barrier called CleanSpace is installed to seal the crawl space off from the earth's moisture. It is sealed at all seams, wrapped, and sealed around all piers and mechanically attached and sealed to the foundation walls 6-8 inches above outside grade. The liner is durable enough to withstand service persons working in the crawl space, keeping the earth's moisture out.
This crawl space had a partial liner on the ground, allowing the earth's moisture to rise into the space and raise the relative humidity. The material is flimsy, unsealed, often held in place with u-shaped stakes that add holes to the liner, and cannot be attached to the walls without ripping off. It offers the crawl space little to no protection from water vapor.
After sealing the crawl space from outside air infiltration at the vent, rim & band, sill plate, and any penetrations to the outside through the foundation wall, we install insulation. This homeowner chose to use a vinyl faced fiberglass. The insulation is installed on the walls at an R-10, the required value for crawl space encapsulations per VA building code. Insulation on the crawl space walls extends the home's thermal barrier and
This homeowner contacted us with concerns about the joists under their home. At our inspection, we found that moisture had been wreaking havoc in the crawl space. We set to work developing a plan with the homeowner to repair the damage and prevent it from reoccurring.