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Do I Need a Humidity Sensor For My Bathroom Fan

A popular addition to a bathroom exhaust fan is a humidity sensor but what is it, what is its function and do I really need one? These are all great questions to ask. Lets take them one by one.

What is a Humidity Sensor?

A humidity sensor is a device that detects the humidity level of the room or surrounding area. You might hear them called humidistats or even dehumidistats. When is comes specifically to bathroom exhaust fans they are either located inside the actual fan or mounted on the wall. A wall mounted device will give a better indication of the overall room humidity where a sensor integrated into the fan will have a quicker response to a rise in humidity – especially when the shower is in use. When the sensor detects a rise in humidity it will turn the exhaust fan on until the humidity decreases. There are many factors that can contribute to how long that might take including items such as size of the room, how long the shower was on, how hot the water was, ambient temperature and so on.

What is the Function of a Humidity Sensor?

Removing the humid air is a key factor in increasing your home’s indoor air quality. If you allow the humidity level to stay very high (above 50%) items like mold and mildew will start to grow and if not mitigated can cause issues with rot as well as health concerns. If you notice a lot of mildew in your bathroom, paint that is peeling, or a musty smell, you probably have a humidity issue. A sensor is a built in way to monitor the humidity level of your bathroom and adjust accordingly without you needing to constantly be monitoring it. Sensors are able to be set for a wide range of humidity level usually from about 5% to 80% relative humidity. The lower the humidity level is set for, the longer the fan will run. The ability to set the humidity level allows you to adjust to your specific needs and geographic location. More humid climates will need to set the humidity level higher than less humid areas. A quick note. If the fan is continuously running, it might be because the normal humidity level is too high and air conditioning or some type of dehumidifier needs to be added.

Do I Need a Humidity Sensor?

As we stated above, humidity sensors provide an automated way to ensure the humidity level of your bathroom is where it should be. Sadly, the exhaust fans in many homes are not used properly or even turned on at all. It is recommended that the exhaust fan run for at least 20 minutes after the shower is turned off and that is in the best-case scenario. In more humid situations that time might go up to an hour or more. Having a sensor in place takes the guesswork out of determining if the humidity level of the room is where it needs to be. Considering if you need a sensor can be determined by answering the following questions:

  • Is my exhaust fan being used properly by everyone utilizing the bathroom? Is it being turned on and allowed to run for the set time needed to fully exhaust the humid air out?
  • Do I notice signs of mildew, mold, peeling paint that tells me I need more ventilation?
  • Are there any building codes in my area that require it? California CALGreen requires any exhaust fan in a full bathroom must have a humidity sensor.
  • Do I have a rental property? Having all the bathroom exhaust fans on a humidity sensor in rentals is a great way to ensure the fans are being utilized properly.

What to Do Next

If you are in the middle of a bathroom remodel or are looking to replace an old exhaust fan, this is a great opportunity to upgrade to one that has an integrated humidity sensor. If you already have an exhaust fan installed, adding a wall mounted sensor switch is a fairly easy way to ensure the humidity level of the room. We do caution that while this is a project most do-it-yourselfers can handle, if you have any questions or concerns to consult a license electrician. We also caution to make sure your exhaust fans can be used with a humidity sensor. All Air King exhaust fans are able to be used with a humidity sensor and in general most exhaust fan can be used with one, but there may be other brands that can not. One other item to consider when choosing an exhaust fan that will be used with a sensor is the sound level. Fans with sensors are most likely going to run for longer periods of time. If you have a really loud fan, this could cause a less than ideal situation. One of the main reasons people do not turn on the exhaust fan is due to the sound level. Look for a fan around 1 sone or less. These are very quiet fans and will probably provide a much better experience.

For more information regarding bathroom exhaust fans as well as fans with integrated humidity sensors such as the ENERGY STAR® certified Humidity sensing BFCH series, click on the links at the top of the page. To learn more about a humidistat view our video on YouTube.

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