A relative humidity of 30 to 50 percent provides the most comfort for indoor air. Too little or too much humidity can cause problems with the health of the home's occupants and can cause structural problems in the home.
Having low humidity levels in the home causes dry skin and leading to itching and chapped lips and dry nose and throat, which can make the occupants more susceptible to getting sick. High humidity levels make it difficult for the body to cool itself and can cause asthma and allergy problems.
Low humidity causes the wood in the home to dry out and contract, which can cause gaps and air leaks in the home. High humidity causes mold to grow and wood to rot.