What Humidity Level Should My Home Be Set at to Prevent Mold?

Mold can become a serious problem with high relative humidity. Mold grows in moist environments, and high humidity amounts to excess water vapor in the atmosphere. If enough of this water vapor exists, dormant mold spores can begin to germinate (grow). If your home is subject to high relative humidity indoors, you will want to control it in order to minimize your mold risk.

The Ideal Humidity

When attempting to maintain the ideal humidity level, you must consider more than just mold risk. While too much humidity can create a breeding ground for mold, a lack of humidity can lead to health issues like dry skin, nose bleeds and allergy attacks. In order to keep your mold risk at a minimum, the Mayo Clinic recommends keeping your indoor relative humidity below 50 percent. Note, however, that humidity below 30 percent can create dangerously dry conditions.

How to Measure Humidity

If you want to keep track of humidity levels in your house, install a hygrometer. It acts like a thermometer and sometimes even looks like a thermometer, but it measures humidity. It is sometimes called a humidistat. Some dehumidifiers contain built-in hygrometers, which constantly measure the humidity in the air even when the device is not running. If you have persistent humidity, a dehumidifier with a built-in hygrometer can be a very worthwhile investment.

Reducing Humidity

A portable dehumidifier can keep indoor relative humidity under control. You can also reduce humidity in your home by running a central air-conditioning unit. Do not use a swamp cooler, as this can make the problem worse. If you decide to use a dehumidifier, keep the filters and reservoirs clean, because mold feeds on dirt and a dirty filter can also elevate your mold risk. If you use a humidifier for dry air, keep an eye on your hygrometer and turn the humidifier off if the indoor humidity nears 50 percent.

Killing Mold

If mold has already started to grow on a damp surface, like a wall or carpet, you can still benefit from using a dehumidifier. Turn on the dehumidifier to dry out the surface before you apply any disinfectants to the mold. By drying the surface first, you neutralize the mold. Then you can kill the spores using a bleach solution (1 cup chlorine bleach per 1 gallon water) or undiluted vinegar.