When constructed properly and with the appropriate air conditioning and ventilation, a basement should be dry. But many basements are particularly prone to dampness because of their poor design and ventilation. Dampness like this is a perfect breeding ground for mold and mildew, especially in basements where old books, magazines, clothing and suitcases are stored.
When the humidity level goes over 50%, the water vapor in the air can cause furniture to warp, moisture to condense on walls and floors and promote growth of fungus. It will also accelerate wood rot. For those family members with allergies, a basement dehumidifier is crucial to lessen the health risks linked to toxic mold and fungus.
But before you go off to purchase a basement dehumidifier, consider taking some time to investigate the reason behind the high humidity, and then repairing the underlying problems. For example, your basement should ideally be the same temperature as the rest of your house, and not an isolated cool temperature zone. Try adding weather-stripping to any basement doors and windows. If the basement is uninsulated, you’ll have to weigh the costs of adding insulation against that of running a basement dehumidifier.
Buying a basement dehumidifier will require a little planning. Know the cubic footage of the basement space that it will be going into. Also you will need to decide on getting a permanently installed unit versus a portable dehumidifier. An other shopping point is to consider are the size of the unit- will it fit in the space you are planning for it? Also be aware that some models are noisier than others, so ask for a demonstration before you buy.
A dehumidifier works on the same principle that refrigerators and air conditioners do. They pass the humid air over a bank of cold coils and in the process extract a good portion of the moisture via condensation. This condensation drips off the coils into collection pockets inside the dehumidifier. Meanwhile the dry air flow, heated somewhat by the extraction of humidity, is directed out of the unit back into the room.
Since the dehumidifier is in the basement and out of the way, many people forget that it requires some maintenance. It is important to empty and clean the collection container inside the unit periodically, otherwise it will be prone to bacterial growth. Some companies manufacture basement dehumidifiers which have no inner collection container, but simply a hose that can be run to a floor drain, and these are a perfect solution to the problem.