How To Fix It

How Do Humidistats Work? 

Measuring humidity in your home is essential to prevent property damage and minimize health risks. Luckily, you can rely on humidistats to maintain the humidity in your home. However, how does a humidistat work? 

A humidistat works by detecting the humidity levels in your home and adjusting them to the ideal level. After attaining the set humidity, it stops the humidifier’s water supply and turns the AC on or off. Humidistats are useful for preventing diseases and protecting property from mold. 

Read on as we talk a little bit more about humidistats. Find out how they work and what they can do to your home. 

What Is a Humidistat?

A humidistat is similar to a thermostat. Unlike a thermostat that measures temperature, a humidistat measures humidity. While the two are different, they can work together, especially in homes with central cooling systems. 

In a nutshell, a humidistat measures moisture in the air in a room. It’s often a significant component in portable humidifiers and dehumidifiers. 

The main problem with a humidistat in a portable humidifier is that it measures humidity only near the appliance. It means that the measurements can be inaccurate in a large room. 

A hygrometer can be helpful when you need to measure the humidity of a larger room. However, it cannot manage the room’s humidity. You’ll still need to use a dehumidifier or humidifier to keep the moisture at an optimum level. 

In contrast, humidistats work with the HVAC systems in your home. They will turn the AC on or off depending on the humidity in the room and the relative temperature. 

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Read: Dehumidifier Settings For Winter And Summer 

Humidistat: Elements and Their Functions

To better understand how humidistats work, you must know the different parts. 

The sensing element, a flat plate with a pair of metal conductors, is one of the significant components of a thermostat. It connects to a relay amplifier, which is responsible for giving accurate readings based on the signals transferred by the sensing element. 

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Variations in air moisture will cause electrical resistance in the conductors of the sensing element. Consequently, it dictates the next thing that a humidistat will do.

If the electrical resistance shows that the humidity is too low, the humidistat will turn on the humidifier and turn it off after achieving the right humidity level. When paired with the thermostat, the relative temperature and moisture will be detected and maintained at a comfortable level. 

For instance, if your humidistat senses a high temperature and low humidity, it will prevent the AC from running even if temperatures are high. On the other hand, if the humidity is too high, the humidistat will turn the AC on to reduce humidity

In addition, a humidistat connected to a whole house system will also control other HVAC components. For instance, it will adjust valves and dampers to regulate airflow and control humidity. 

Read: What Does An Attic Fan Do? 

Old vs. New Humidistats 

For a better understanding of how humidistat works, it’s also helpful to look at how the old and new ones differ. The main difference lies in the component that senses humidity levels

In the case of older humidistats, a hygroscopic material is a part of the sensing element. It can be made of animal hair or a specific type of plastic. The material expands upon the absorption of moisture in the air. This contraction, in turn, regulates the opening and controlling of the circuit that controls the humidifier. 

On the other hand, many newer humidistats do not have the older electromechanical components. Instead, they have electronic switching circuitry. The latter senses moisture in the air to control humidity in a room. 

Read: Does Furnace Reduce Humidity?

The Right Humidistat Settings 

It isn’t enough that you understand how a humidistat works. It’s equally important to know the correct settings. Doing so will help you ensure optimal settings for a healthy home and prevent damage to your property. 

The Environmental Protection Agency suggests that the relative humidity in your home should be less than 60%. Ideally, it should be between 30 to 50%. It’s vital to ensure that it does not go too high, as that can trigger the growth of mold and mildew. 

Humidistat Settings in the Winter vs. Summer 

Depending on seasonal temperature variations, the amount of moisture air can hold also changes. Air holds more moisture when it’s warm and the other way around when it’s cold. 

Earlier, we noted that the indoor relative humidity should be below 60%. In the winter, you’ll need to set the humidity even lower to account for the cold, as the cold prevents and reduces normal evaporation. Thus, we recommend setting the humidity to 30 to 40% in the winter

On the other hand, you can set the humidity to 40 to 50% in the summer. Although, this will still be highly dependent on the temperature outside. 

Setting the Humidistat When You’re Away 

If you’re leaving your home for a long time and it will be unoccupied, you must choose the right setting for the humidistat. 

The goal is to set the humidity at a level that will prevent mold and mildew while ensuring efficiency. Maintaining lower humidity can be costly, so if you are away for an extended period, consider increasing the humidity as far up as is safe for your home. 

Remember, mold and mildew can set in and ruin your home if the humidity is too high, so it is crucial to find the perfect balance. 58% relative humidity is a safe bet

Read: Why HoMedics Humidifier Is Not Working?

Do You Need a Humidistat? 

After learning how a humidistat works, you may be curious if you need one. In most cases, yes, you need a humidistat! It can come in handy when maximizing the benefits of your humidifier. Even better, it can help make your home healthier. 

Here are some reasons why a humidistat is useful. 

An Easy Way To Control Humidity

A humidistat takes the worry of maintaining an ideal level of relative humidity out of your hands. You don’t have to adjust your humidifier or dehumidifier by hand or be left guessing whether you need to turn the humidifier off. Instead, the humidistat automates the process for you

Minimize Health Risks 

When our bodies heat up, we sweat. It then evaporates from our skin, which is also what helps us stay cool. However, when the humidity is high, our sweat does not evaporate. In turn, we feel hot. Our body needs to work harder, which can trigger unhealthy responses and health issues

For instance, high humidity can increase the risk of dehydration, fatigue, heat stroke, and fainting

Meanwhile, low humidity isn’t good either. It can cause throat and nasal irritation, itchy eyes, and dry skin. 

Prevent Property Damage 

Aside from health risks, incorrect moisture levels in the air also cause property damage. Among others, high humidity can cause mold and mildew. These microscopic fungi are common in damp areas. More than being unsightly, they can also be health risks. For instance, they can trigger asthma and allergy. 

Additionally, humidity can also be the culprit for peeling wallpaper or paint. Condensation gathers when you fail to control humidity. When wallpaper starts curling or paint starts to flake, it can indicate humidity problems in your home. 


A humidistat uses a sensing element to detect changes in your home’s moisture. The element delivers this information using a relay amplifier to the humidistat. The humidistat adjusts moisture levels by adjusting your home’s AC, dehumidifier, humidifier, or valves.