Humidity and moisture wreak havoc in a vented crawl space. Moisture floods in through open vents, from the earth, and gaps in the substructure raising the relative humidity. The moisture is absorbed by the fiberglass insulation and the floor joists causing damage to the substructure of the home. This crawl space has a relative humidity of 72.5%, which is above the 60% threshold that allows mold to grow. The wood moisture reading is at 19%, where the potential for wood rot to occur begins.