Managing indoor humidity levels, all year round

How to keep your home comfortable in every season

Just like we adjust indoor air temperature with the seasons, it's important to be mindful of indoor humidity levels and adjust them when needed, because humidity plays a key role in both comfort and air quality.

What amount of humidity is the right amount?

Some humidifiers, dehumidifiers, and whole-home humidification systems will prompt you to set a humidification level. This setting on your humidification system is referencing relative humidity (RH), which is the percentage of moisture in the air compared to the maximum possible amount of moisture that the air can hold.

The ideal set point for your home can vary, and depends on a combination of factors including outdoor temperature, surface temperatures inside your home, and how well insulated and air-sealed your home is. Generally speaking, homes that are well insulated, well air-sealed, and properly ventilated face fewer humidity issues. Given these variables, it's important to be careful when you increase the humidity levels in your home.

Our bodies are most comfortable between 40 and 60 percent relative humidity. 

Avoid indoor humidity levels above 60% RH in the summer to prevent mold and bacterial growth. In the winter, our homes often need a lower RH than in the summer. When it is extremely cold out, 40% RH may still lead to problematic condensation on windows and wall surfaces. If you add humid air to your home and see evidence of condensation, be sure to lower your RH levels. Learn more about managing indoor humidity in winter below.
 

Preventing mold from high indoor humidity levels

When moisture condenses and sticks to surfaces like windows and walls, building material can experience water damage, which allows mold to grow easily on these damaged surfaces. Mold growth creates unhealthy indoor air and repair work can be expensive; therefore, avoiding high humidity levels is important for both your health and the durability of your home.
 

Safely adding humidity and preventing condensation in winter

During winter months in Minnesota, the outside air is noticeably very dry. This dry air can make its way into buildings, lower indoor humidity levels, and cause everything from dry skin to the shrinking of wood doors and furniture.
 
If your home feels dry in the winter, consider using a humidifier to add moisture to the air. This should be done carefully by only running the humidifier for short periods of time and setting low RH levels between 30%–40%. CEE’s energy auditors typically recommend individual humidifiers over whole-home humidifiers. Adjusting whole-home humidifier set points can be easy to forget about, which can lead to a rapid increase of too much moisture to your home, creating damage to the home from moisture issues.
 
Higher than natural humidity levels in the winter can lead to moisture condensing on cold surfaces like windows or exterior walls. If you start to see evidence of consistent moisture build-up on your windows or walls, it means there is too much moisture to the air. It is important that you turn off your humidifier and lower your RH set point before turning it back on.
 

Insulation helps prevent condensation build-up

If you are not using a humidifier in the winter but still have consistent condensation, it may be because of inefficient windows or under-insulated walls. To fix this, insulate and air seal these windows or your walls.
 
Insulating, air sealing, and properly ventilating your home will help maintain proper humidity levels. Having more insulation raises surface temperatures inside your home so that moisture is unable to cool and condense. Air sealing and adding a ventilation system gives you the element of control necessary to maintain more consistent humidity levels throughout the year.

When your home is properly insulated and air-sealed, indoor air can move freely throughout the home while keeping outdoor air out. Ventilation helps keep indoor air balanced by removing moisture, odors, and pollutants. In an improperly air-sealed and insulated home, leaks to the outside can create unintentional ventilation. When the home is properly air-sealed and insulated, those leaks are sealed, reducing the amount of airflow between inside and outside. Proper ventilation helps compensate for that change, ensuring the house can "breathe."

Additionally, these projects can help you use less energy and lower your utility bills. When CEE’s energy auditors visit homes in the winter and observe condensation build up, the solution revolves around properly air sealing and insulating the home. Similarly, if the home feels dry, it is an indication that the home is experiencing air leakage and would, again, benefit from proper air sealing and insulation.
 

Decreasing humidity levels in the summer

Minnesota summers bring more than heat; humidity is often just as much of a challenge.

The most effective way to reduce humidity is to use air conditioning. Air conditioners are effective because of their ability to remove moisture from the air in addition to lowering the temperature. If your air conditioner is old, undersized, or struggling to keep up, it may not be removing enough moisture even if the temperature feels fine. Upgrading to a high-efficiency system like an air source heat pump can improve both comfort and humidity control.

If you are not sure whether your current system is enough to manage your home's humidity, a Home Energy Squad® visit can help you find out.

Schedule your Home Energy Squad visit today
 

Humid basements in the summer

While air conditioners help make above-ground living spaces comfortable and less humid, dehumidifiers may offer additional help in the basement. Humid outdoor weather can make air in the basement feel stale and smell damp due to cooler basement temperatures and high humidity levels. For proper maintenance, most dehumidifier models need to have the water container emptied periodically or piped directly to a drain. Some efficient technologies, like air source heat pumps and heat pump water heaters, can also help dehumidify your spaces, depending on where they're placed and how they're run. Other solutions for high levels of humidity in basements may include adding more registers for better air flow, regrading the area around your home to reduce moisture entering the space, or installing a sump pump to pump moisture out of the home.

A basement dehumidifier should be set to 55% RH to prevent bacterial growth. If the air still feels too damp, lower the RH level.
 
If you are shopping for a new dehumidifier, purchase one that is ENERGY STAR® rated and has an energy factor (efficiency rating) of at least 2.0. The higher the energy factor, the more efficient the appliance is. 

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