The way to prevent humidity in a basement is to identify the cause of humidity and manage it. Typical sources of humidity include inadequate grading around the house, missing gutters and ineffective window design.
If the ground around the house slopes toward the foundation, pile dirt near the house walls. Grade it so that it slopes away from the foundation at a minimum of 1 inch per foot, according to the University of Minnesota. Continue this slope for at least 6 feet.
If the house is missing gutters or downspouts, have them installed. Ensure that the downspout extender points away from the foundation and directs water at least 4 feet away. If a window has been improperly constructed, have it rebuilt so that a drain tile extends from the window footing to the base of the window well.
Leaks are often the source of moisture in a basement. Look for water stains under large sources of plumbing, such as bathrooms and kitchens. Have any leak fixed.
Overall methods for controlling moisture include covering a dirt floor with plastic, which slows down the entrance of water vapor from the soil. Likewise, have any cracks or joints sealed with elastomeric caulk. Have vapor barriers installed on the warmer walls. Finally, use ventilation fans to keep the basement free of humidity.