Basements can become breeding grounds for mold because they trap moisture and have little exposure to natural heat and sunlight. A dehumidifier can prevent humidity in the basement from rising to dangerous levels and contributing to mold growth, but in the wintertime, your need for a basement dehumidifier will depend on some important factors.
If you live in a region with extremely cold winter temperatures, a basement dehumidifier will have little use for you. Dehumidifier coils attract water vapor, and with low temperatures, the coils can freeze, rendering the device useless. For a dehumidifier to do you any good, the temperature in your basement should ideally remain above 60 degrees Fahrenheit. Some dehumidifiers are specially designed to work in much colder temperatures, as low as 42 degrees, but extremely cold temperatures tend to result in lower humidity anyway, thus negating your need for a dehumidifier.
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Relative Humidity Levels
You should only run a dehumidifier in your basement in the wintertime if the room maintains a high relative humidity. To monitor the relative humidity in your basement, hang a humidistat (sometimes called a hygrometer) on the wall. It works like a thermometer, constantly measuring the relative humidity in the room. Some dehumidifiers contain a built-in humidistat. If the humidity exceeds 50 percent, you would benefit from running a dehumidifier. Humidity levels above 50 percent carry a higher risk of mold growth.
Running a Dehumidifier
Keep an eye on the device if you decide to run a dehumidifier in your basement during the winter months. If temperatures get dangerously low, or if the room becomes too dry, turn off the dehumidifier. Some dehumidifiers allow you to set a humidity threshold, meaning that the device will automatically turn off if humidity levels reach a certain amount. If you can, set your minimum threshold at 30 percent. Any less humidity will cause the room to become too dry.
If the basement maintains high relative humidity levels in the winter but is too cold to safely run a dehumidifier, use an electric heater for at least a couple of hours each day. It will not kill humidity as effectively as a dehumidifier, but it will eliminate some of the water vapor while also reducing the temperature in the room. Keep an eye on your basement, and if you notice signs of mold growth, kill the fungus immediately using a natural fungicide like white vinegar, hydrogen peroxide or rubbing alcohol. Dry the room completely to stop the fungus from spreading.