Did you know that a 700 sq. ft. dirt basement can discharge up to 10 gallons of water a day? Even a concrete floored basement can discharge large quantities of water through simple evaporation. If you insulate the floor joists above this dirt floor, the insulation can absorb the water vapor and become soggy, presenting a condition that can lead to mold growth.
Excess water vapor trapped in a house can accumulate in the attic and may contribute to, or even cause an attic mold problem. Install a vapor barrier or concrete over the dirt floor. To help with prevention, remove any insulation from the ceiling over the dirt basement floor. You should also provide a heat source for the basement and keep humidity levels between 35% and 50%.