When moisture in the home is referenced, what will commonly be referred to is the relative humidity. The relative humidity is the percent of moisture in the air relative to the maximum amount of moisture. A relative humidity of 30% indicates the air has 30% of the moisture it could have for the temperature the house is at. A comfortable relative humidity is generally from 30% to 60%. Less than 30% can lead to skin and throat irritation, possible drying out of furniture/flooring/walls and producing high static. Higher than 60% can lead to mold problems and allergy problems.

There are ways to control the humidity in a home. When conditions are too dry, a humidifier will increase the relative humidity in the home. This is especially important when it is cold outside because when the air from outside it processed through the heating unit it will cause the relative humidity to significantly decrease since warm air has the capacity to contain much more moisture than cold air. Even if the relative humidity is high outside when it is cold, once that air is brought inside it can turn extremely dry. Showers and air drying dishes are other ways humidity will increase. The increase is temporary though thus if it is too dry it is helpful to use a humidifier.

When the home is too moist, a dehumidifier can be used. This will remove some of the moisture from the air causing the relative humidity to decrease to a more comfortable level. This is especially important if mold is an issue in the home. It also helps to check wall and window surfaces and keep them disinfected from any signs of mold growth. High humidity in the home is an issue for climates in which it is warm and humid outside. Refrigerating air causes the relative humidity to increase. Thus, warm and humid outside air will tend to keep the humidity in the home at a high level. Damage can occur to furniture and the home when the humidity is too high for a long period of time.