Humidistat vs Dehumidistat

There are many varieties of humidity sensors and an equal number of applications for them. The humidistat and dehumidistat are the most common humidity sensor types. These sensors regulate humidifying and dehumidifying equipment; their common goal is to maintain humidity levels in a preferred range.

Keeping a constant humidity level in your home is very important; especially for homes that host people with certain health problems. Apart from that, humidity regulators are important for preventing mold and protecting furniture and art from excessive moisture. Homeowners can lower or raise the humidity in the room with the use of humidity regulators.


A humidistat is a device on humidifiers to measure the level of humidity in particular area. Once the room’s humidity level drops lower than the set point, a set of electrical contacts closes which turns the humidifier on.

Humidistat Operation

A humidistat controls the functions of space conditioning units like humidifiers and air conditioners. It is attached to the humidification unit and adds water to the air. When you use it with an air conditioner, for instance, it rotates the system on and off based on the humidity level. This means that the humidity level is not based on the temperature that’s displayed on the regular thermostat. For instance, a humidistat that has been set to 70% relative humidity will rotate the air conditioner on when the relative humidity hits 70% or more even if the setting of the thermostat doesn’t require cooling. The relative humidity setting on the humidistat measures the water vapor amount in the gaseous mixture of water vapor and air.


A humidistat should be attached in parallel with the thermostat so each one can work individually. If used with an air conditioner, the advised settings are 70% for the humidistat’s relative humidity and 85 degrees for the thermostat. To check the right settings for your area, inquire from the manufacturer because wrong settings will lead to higher energy costs.


A dehumidistat works almost like a humidistat but instead of closing, its electrical contacts open up when the room’s humidity level is lower than the controller’s setting. When the room’s humidity increases, the electrical contacts close .The dehumidistat will then work to lessen the room’s humidity by removing extra humidity from the air. A dehumidistat is also commonly used to get fans to control the humidity of the crawl space and offer ventilation.

Dehumidistat Operation

When the room’s level of humidity goes over the specified setting, the dehumidistat activates high speed ventilation. The dehumidistat dial should be controlled according to the relative conditions outdoors. If the room is too dry, the dial should be set higher. If the room is too humid, the dial should be set lower.

If you encounter problems with the controls for these appliances, it is best to replace them even if there are parts available for you to purchase. The repair of these appliances is likely to be more expensive than just replacing the unit.