Choosing and Using Dehumidifiers

What is a dehumidifier and how does it work?

A dehumidifier is essentially a refrigerator that forgot to get fully dressed. Really. The basic mechanical function of a dehumidifier is the same as a refrigerator. Compression and expansion of a gas is used to lower the temperature of metal coils to freezing temperatures.

However, instead of the cooling action being directed into a closed box, a dehumidifier is designed to blow warm moist room air over these cold coils. The moisture in the room air condenses on the coils to become liquid water. The water then drips into a drip collection pan, or to a drain. The room air, now freed of much of its moisture, returns to the room slightly warmer than it was. Dehumidifiers are controlled by a device known as a humidistat. This is an adjustable rotary switch which detects moisture in the room's air. It automatically turns the dehumidifier on or off as it is needed, based on the setting you choose. If you wish, you can set the dehumidifier to the maximum setting for continuous operation.

Why would I want to purchase one?

If you store anything of value in your basement, or if you use your basement as living space, it is important to keep the moisture level low. Unlike the rest of your home, the parts of your foundation that are below ground level, or "grade", is constantly in contact with moisture from the earth outside. Though some homes have adequate vapor and water barriers installed outside their foundations, many older homes have none.
This moisture can cause mildew growth and damage to furniture of all types, photos, carpets, and virtually anything except the dog. It is a sad fact that every year people unknowingly destroy their valuable possessions by not taking steps to lower the level of moisture in their basement's air.