The recommended humidity level for a home is 35 percent to 45 percent humidity, according to About.com. This offers the best comfort and protects the home from too much moisture or dryness.
There is a range of 10 percent with average humidity levels because the air quality and climate somewhat changes the proper humidity level inside the home. If the humidity is too high, it causes extra moisture in basements and dark corners of the home, which then adds to the risk of mold and structural damage. Having a humidifier in the home helps keep the humidity level at the right percentage. Humidifiers should be placed on the ground a few inches away from a wall.
According to the charts for winter temperatures, if the outside temperature is between 20 and 40 degrees Fahrenheit, then the inside humidity should not be over 40 percent. If the temperature was instead -20 degrees Fahrenheit or below, then the inside humidity should not be above 15 percent. These percentages are based on a 70-degree interior room temperature.
By maintaining these levels of humidity, condensation or frost can be prevented on windows. If there is too much moisture, mold may grow.
In the summer, the humidity levels can get too high in a home. Too much humidity and the introduction of cool air from air conditioning can cause condensation. It's suggested that the relative humidity should not exceed 55 degrees Fahrenheit in the main level of the home during the summer. If, for instance, the wooden floors are starting to buckle, this can be a result of too much humidity. A dehumidifier can be used to help dry the house out when necessary.