In the Home, what is Ideal Humidity?

Indoor humidity levels — the amount of water vapor in the air — can affect the occupants' health and can even affect the furnishings in a home. Indoor humidity comes from a variety of moisture-producing sources, among them cooking, running water for showers and baths or running a washing machine and dryer. Additionally, the climate and weather outside can directly affect the amount of moisture that is inside. All of these factors combined should result in ideal humidity level of about 45 percent. Although humidity cannot be seen, there are ways to measure it and help ensure that ideal humidity is maintained in the home.

A small device called a hygrometer can be used to give a specific relative humidity reading. A hygrometer can be either mechanical or electronic, and it can be free-standing or a part of a thermometer. Either style is relatively inexpensive. It should be noted that it might take a couple of hours to get an accurate reading. Even without a hygrometer, the signs of humidity levels that are too high or too low are fairly obvious.

Cold outdoor temperatures are a common culprit for low humidity, which generally is less than 30 percent. Part of the reason is that cold air cannot hold as much moisture as warm air. Low humidity can be an even bigger problem in homes with poor insulation or small openings around doorways or windows. These openings can cause drafts that allow cold air to seep inside the home. Traditional indoor heating warms up a home but does not add moisture to the air.

Some of the telltale signs of low humidity are a parched feeling, such as cracked skin and a dry, scratchy throat. More serious health problems might involve respiratory problems and a susceptibility to colds or other infections. Low humidity can affect the home by creating cracks in the walls or ceiling and by shrinking wood floors or wall paneling. Static electricity also might be prevalent when touching various items in the home. A table-top humidifier or a central humidifying system can be used to reverse low humidity and to create ideal humidity in the home.

At the other end of the spectrum are the problems associated with high humidity. When the humidity level in a home exceeds 50 percent, it becomes a potential breeding ground for mold, mildew and pests such as termites, cockroaches or dust mites. In turn, these conditions can aggravate allergies or other health conditions. High humidity also can be damaging to electronic equipment such as computers.

Too much moisture in the air also can be a hindrance to attaining the ideal humidity. Exhaust fans are one way to reduce the humidity in areas where there are high levels of humidity, such as a kitchen. A more cost-effective solution is to use a dehumidifier.