Does a New Central Air Conditioner Need a Separate Humidistat?

Air Conditioners Dehumidify

• When an air conditioner blows indoor air across cold refrigerant coils to reduce the indoor temperature, it also removes condensation from the air. When humid indoor air comes in contact with the cold copper coils, condensation forms on the coils and drips down into a condensate pan. The more condensation is removed from the air, the less humid your home becomes.

Humidity and Comfort

• A humid day "feels" hotter than the thermometer would seem to indicate because the human body uses evaporative cooling, through sweat, to get rid of excess body heat. In a high-humidity environment, the evaporation process is slowed down, and it seems hotter than it is. When an air conditioner is cooling a room, it will have to reduce the indoor temperature further to make the air feel comfortable during periods of high humidity. A temperature of 72 degrees Fahrenheit at 60 percent humidity may feel comfortable, but if the humidity is higher, 80 or 90 percent, you may feel compelled to turn your thermostat down several degrees lower.

Problems with High Humidity

• In addition to issues of comfort, high indoor humidity levels can lead to mold and mildew growth. The constant moisture can render interior walls and ceilings a perfectly hospitable place for all sorts of microorganisms to colonize and can decrease the indoor air quality. For this reason, in parts of the world with prolonged periods of very high humidity, a separate humidistat may be a worthwhile investment.

A Humidistat is Not a Necessity

• In most circumstances, a separate humidistat is not necessary. Air conditioners dehumidify as they cool, and in most instances, an air conditioner will be sufficient to reduce indoor humidity to a comfortable and safe level. If you are having an issue with a single room of the house, a separate dehumidifier may be a more cost-effective solution to high humidity.