The humidistat is essentially a gatekeeper installed ahead of the thermostat, which will only allow the thermostat to work when the humidity exceeds the desired percentage—and the usual setting is around 55%. If the humidity exceeds the humidistat setting, then the thermostat is allowed to turn on the system when the room temperature exceeds its own setting, which is recommended to be about 78º to 80º F. Newer thermostats include a humidistat function, like the one shown here.

    The energy savings is provided when the indoor temperature exceeds what you consider to be a comfortable idoor temperature, but the humidity is still low, and the system will not be activated. Turning the dial to far right to “ON” will override the humidistat and allow the thermostat complete control. 

Turning the dial to the far left to “OFF” will do the same thing except that, if the thermostat is not battery-powered, it will shut off the thermostat—which you definitely don’t want and, again, that is only for a thermostat without batteries. Also, if you set the thermostat too high (above 80º), the system may not turn on when needed to lower the humidity.

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  To learn more about heating and air conditioning systems, see these other blog posts:

• How can I find out the SEER of my air conditioner? 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• How can I find out the age of my air conditioner or furnace?

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

     Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.