Central Air Humidistat 101 – Guide to Setting Your Humidistat

A humidistat is a switch that often comes included with a thermostat in an HVAC system installation. As the name suggests, it controls humidity in the building. Dry winter air creates static as well as dry, itchy eyes and skin. If you feel static electricity, it could be a sign you need to add moisture to your air. No one wants a scratchy throat in the cold weather. At the same time, you don’t want an overly humid home either. This is where a humidistat can be helpful.

Central Air Humidistat 101 - Guide to Setting Your Humidistat

When it comes to central air, consider the ways to control the humidity in your home. A humidistat has three possible settings if you think about it abstractly: ON, OFF, or a specific percentage (0 through 100).


This is like setting the humidity to zero, because it is on the “zero” side of the humidistat knob. Basically, this setting gives the same effect as not having a humidistat at all. The system will run normally, cycling on and off based on the temperature in the building.


It is highly recommended to almost never use this setting. On the contrary to popular belief, setting a humidistat to OFF does not deactivate it. Rather, it prevents the HVAC system from running normally by shutting off crucial parts, in order to raise the humidity in the building.

0-100 percent

Ideally, you should set a humidistat to whichever humidity percentage you would prefer the building to have. Within the zero to 100 percentage range, there is a specific point where you will hear the knob make a “click” noise. That point is the exact humidity percentage that is currently in the building.

Consider this: for example, let’s say the building’s humidity is at 40 percent. If you set the humidistat to anything below 40, it is effectively “on,” but will turn off when it gets down to that humidity. If you set it anywhere above 40, it is effectively “off,” and will turn back on when it reaches the humidity you set it to. Review the above descriptions of ON and OFF to see the effects of these settings.

At Tri County Air Care, we provide friendly service for your heating, cooling and indoor air quality needs. Talk to us about air conditioning and heating repairs, installations, thermostats and filters for better air quality this year. For more information on our trained technicians working in the tri-county, Texas area, please contact us today.