Sweating floor joist can lead to an infinite number of problems. The “sweating” or “condensation” can become a feeding ground for mold and mildew and a plethora of other science experiments growing beneath your home. These critters can negatively affect your health, and can lead to accelerated wood rot. Moisture is also attractive to termites. There are several things that you can do: · Insulate your floor to reduce the chance of condensation. · Improve evaporation by increasing the number of foundation vents. · Lay plastic down on the floor of your crawl space in hopes of trapping the moisture at ground level. · Modify watering at the perimeter of you home in hopes of keeping it dry down there. · Prune back shrubs and hedges so that sunlight can get to the perimeter of the crawl space.