A dehumidifier is a device that uses fans or turbines to pull moisture out of the air, lowering the humidity of an indoor space. The device is the functional opposite of a humidifier, which adds moisture to the air. Homeowners install dehumidifiers when signs and symptoms of excess moisture appear. While these signs and symptoms vary from case to case, all homes that require dehumidifiers typically have similar underlying causes for their moisture problems.
One of the most easily recognizable signs that indicates you need a dehumidifier is the appearance of wet stains on the ceilings or walls of your home's interior. These stains prove that moisture is permeating through your home's structure. Another indicator that a dehumidifier is necessary is the prolonged appearance of window condensation. Window condensation is the result of warm, gaseous water particles in the air changing to liquid form upon making contact with the cooler surfaces of window glass. Condensation from excess humidity in the home forms more readily on double- and triple-paned windows.
If the air in your home feels stuffy, heavy and uncomfortable, installing a dehumidifier can be a solution. This stuffy feeling is the result of high humidity levels. High humidity can make an interior space feel incredibly hot, even if the actual temperature is relatively low. This is because excess moisture in the air impacts how the body naturally cools down -- instead of sweat evaporating and readily leaving the surface of the skin, saturated air prevents this evaporation and sweat remains on the skin.
Humid home interiors can wreak havoc on wooden furniture, floors and other materials. When water molecules penetrate wood, the resulting moist conditions encourage the growth of microorganisms, which cause the wood to rot. In addition, moisture in the air can cause wood to expand or otherwise warp. This warping can make wooden windows and doors more difficult to open. If your home is suffering from such wood-related damage, a dehumidifier may be necessary.
Mold and Mildew
Excessively moist interior air can cause mold and mildew to develop on a variety of surfaces, including walls and ceilings. So if patches of mold and mildew are occurring regularly, a dehumidifier may be able to help. In addition to producing visible discoloration, mold and mildew can cause musty smells and can also aggravate the symptoms of people with allergies.
The basic, underlying reason why anyone would need a dehumidifier is that a home's air contains too much moisture. The source of this moisture is often the home's basement or foundation -- small cracks in concrete allow water molecules to penetrate a home's interior. However, other underlying causes of moisture can include leaking pipes and fixtures, poor ventilation and severe, perpetually humid weather conditions.