The space inside your home can usually be considered a controlled environment, where you can raise or lower the temperature by adjusting the thermostat. Heat is sealed inside during colder months to ensure that everything inside (including you!) can function normally, and in the summer, the air conditioner reduces the heat inside the home, keeping the temperature relatively consistent throughout the year.
However, one aspect of environmental or climate control that often goes overlooked is the humidity inside the home. The ideal relative humidity level ranges from about 40 percent to 60 percent humidity indoors. If the relative humidity is too high, then the excess moisture in the air can increase the risk of wood rot and mold growth throughout the home. Low indoor humidity under 40 percent is also a problem that can cause significant damage to the home, such as causing the floorboards, cupboards, and other wooden furniture to become warped.
What Is Low Humidity?
Low humidity means that there is a small amount of water vapor in the air, making it feel very dry. Typically, low humidity is when the relative humidity is below 40 percent.
Regularly check the relative humidity level in your home, especially during the colder months of the year, so that you can take action to deal with low humidity when it occurs, instead of after the home has been damaged. Learn more about what it means to have low humidity in your house.
In order to learn how to spot low humidity in your home and how to increase the humidity, it's important to have a firm understanding of relative humidity. Relative humidity refers to the amount of water vapor in the air relative to the current temperature. Warm air holds more water vapor than cold air. This means that a cold home with 50 percent relative humidity may actually have the same amount of water vapor in the air as a warm home with 40 percent relative humidity, despite the difference in relative humidity.
The percentage of water vapor in the air is used to express the relative humidity in your home based on the current temperature. If the humidity is over 60 percent, then the air is considered to have a high relative humidity level. If the humidity is under 40 percent, then the air is considered to have a low relative humidity level. For instance, if the relative humidity is 50 percent, then the air is currently holding only half of the water vapor that it could, while a humidity level of 25 percent means the air currently contains just a quarter of the water vapor that it could potentially hold.
How Low Humidity Affects the Home
High humidity levels are regularly associated with hazards like wood rot and mold growth, which are typically high on a DIYer's list of repair and maintenance concerns, but low humidity can also cause significant damage to a home if nothing is done to raise the humidity level to an acceptable percentage.
If this level of relative humidity continues, then the home may begin to show the results of long-term exposure to low humidity. Look for signs of shrinkage, warping, peeling, and cracking in your hardwood floors, wooden furniture, cupboards, drawers, counters, wallpaper, paint, windows, doors, and even houseplants. Another sign of low humidity is increased potential for electrostatic shocks when you touch a certain surface, so if the number of daily shocks you receive after walking on the carpet or handling laundry starts to increase significantly, then it may be a good idea to check the humidity levels of the home.
Causes of Low Humidity
There are many potential reasons for low humidity, but the most prevalent cause is the temperature outside. During the colder months of the year, the air outside the home cannot hold as much water vapor as it could during the warmer months of the year. This means that the relative humidity of the air is typically much lower when it's cold outside. An open door or window will allow the dry, cold air from outside to come into the home, where it can warm up and expand. However, this ultimately reduces the overall relative humidity of the home.
Additional causes for low humidity in the home include the excessive use of air conditioning or of a dehumidifier. Also keep in mind that some locations do not need to be cold to have low levels of humidity outside, like cities or towns located in desert regions. In these places, low humidity is a constant hazard that needs to be combated with a low maintenance solution, like a whole-home humidifier.
Target Humidity Levels
If you're wondering what the humidity level is in your home, there are a few ways to check. First, many thermostats, especially smart thermostats, may provide a humidity reading that you can check on the thermostat screen or even through an app on your phone. If the thermostat doesn't track or record this information, then investing in a small, inexpensive device called a hygrometer is the best method to check humidity levels.
The relative humidity should be between 40 percent and 60 percent in order to keep your home from suffering any negative effects. If the relative humidity level is above 60 percent, then you will want to bring the humidity level down, but if the relative humidity level is below 40 percent, then it's important to increase the amount of water in the air until there is a balanced level of humidity.
How to Increase Humidity
After testing the humidity level in your home, you may find that the air is too dry, but this shouldn't be cause for panic. There are many ways of increasing the humidity in your home that are both inexpensive and easy to do. Leaving the lids off boiling pots of water while you cook or keeping the door open to the bathroom while showering are great ways to increase humidity. Another option is to leave the water in the bathtub after a bath until the water cools.
Adding houseplants to your home will also increase the humidity level in the air, though if these more passive methods fail, you can also purchase individual humidifiers for each room or a whole-home humidifier. Just make sure that you don't increase the humidity level too much, so you have to deal with high humidity problems.
Let’s Clear the Air: Using Ventilation Practices to Promote Healthy IAQ in Schools. United States Environmental Protection Agency.
Moisture Control Guidance for Building Design, Construction and Maintenance. United States Environmental Protection Agency.
How Humidity Damages Your Home and How to Fight it. Building Performance Institute.
Make Humidification Adjustments. Energy Star, U.S. Environmental Protection Agency.
Han KT, Ruan LW. Effects of indoor plants on air quality: a systematic review. Environ Sci Pollut Res Int., vol. 27, no. 14, pp. 16019-16051, 2020. doi:10.1007/s11356-020-08174-9