What Is the Ideal Humidity for a Finished Basement?

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There are ways to improve the humidity level in a finished basement.
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A finished basement is partially or fully below the ground, and that means there will be humidity problems that you may not have in the upper parts of your home. Because they're underground, basements tend to retain more humidity. However, there are ways to ensure the humidity level in a finished basement is at an acceptable level.

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The ideal humidity in a finished basement is about 50 percent, although that fluctuates from 30 to 50 percent through the seasons. Winter humidity is usually much lower than summer humidity, so you may want to run a dehumidifier or an exhaust fan in the basement in warmer months to lower basement humidity.

Why Is Ideal Humidity Important?

Basements often provide ideal storage space, workout space or space for a family room, extra bedroom or extra bathroom. However, this below-grade space is subject to excess humidity in the summer. You can tell if your humidity level is too high by using a digital humidity meter gauge.

Check your gauge regularly as the weather changes in order to monitor the humidity level. Although 30 to 50 percent is ideal, anything above 60 percent is considered excessive. If your basement feels damp, it's probably too humid. You'll need to take action, or you risk accumulating mold, mildew and fungal growth and the creation of ideal termite conditions.

If you are using your finished basement for living space, you don't want your humidity level to be too low either. That can happen if you live in an area with hot, dry summers. Low humidity can lead to sinus and other respiratory problems, dry skin and scalp, peeling paint and air conditioner problems. A whole-house humidifier may help in this climate.

Getting to Ideal Humidity

If you live in a humid area, your basement humidity level will probably be too high. Using a portable dehumidifier can be a quick solution. These dehumidifiers will absorb moisture, and typically, they shut off when the tank is full and must be emptied. You can also get a dehumidifier with a pump that automatically drains the water.

Another option is to install a basement exhaust fan that is vented outside. This will push the humidity out of your house, and you don't have to worry about emptying a dehumidifier. Many of these exhaust fans also come with fresh air fans to pump fresh air into the basement.

There are some other ways to combat basement humidity. One is to open windows if the outside temperature is cooler than the inside temperature. That will increase ventilation. Also, if you have carpet, it can breed mold, so if possible, replace carpet with tile or vinyl.

Other Factors to Consider

Basements are often poorly insulated. This means that outside air can creep into the basement more easily and can influence the basement's temperature and humidity level. If your finished basement is heated, be careful about lowering the heat too much in cold weather.

Even when not using that part of your house, keep the heat at around 60 degrees. All that constant warming and cooling can create moisture, leading to the growth of mold and mildew.

If you have any holes or leaks in pipes or in the foundation that allow outside air into your basement, seal these holes. These can increase the moisture level. Sealing them will prevent that.

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Karen Gardner spent many years as a home and garden writer and editor who is now a freelance writer. As the owner of an updated older home, she jumps at the chance to write about the fun and not-so-fun parts of home repair and home upkeep. She also enjoys spending time in her garden, each year resolving not to let the weeds overtake them. She keeps reminding herself that gardening is a process, not an outcome.

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