Most homes should maintain a relative humidity below 50 percent at all times. This prevents mold and mildew growth, dust mite infestations, and condensation from building up in your home.
The Environmental Protection Agency considers indoor air quality a top health threat. During the winter when the air outside is generally dry, the relative humidity of a home should stay below 40 percent to prevent condensation from forming on windows. During the hot summer months, air conditioning can cause the same effect, so it is advisable to use a dehumidifier. A high humidity level can also cause hardwood floors to buckle and bend.