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Ductless Bathroom Fan: Is It up to Code?

Bathroom ventilation is a popular topic in the home improvement industry. But installing ducting can be a big job, or maybe you don’t have the space for it, so wouldn’t it be easier to use a ductless bathroom fan?

It sounds promising, and you won’t have to tear up your home to add the fan. However, once you start researching, you will find that not all appliances named “bathroom fan” are equal. There are other exhaust fans that can serve your ventilation and installation needs.


Ductless bathroom fans, unlike exhaust fans, do not comply with the code ventilation requirements. These fans are designed to remove odors from toilet rooms, but cannot remove humid air. It is viable if sufficient natural ventilation through a window is available.

How Do Ductless Bathroom Fans Work?

Ductless bathroom fans use a charcoal filter through which air is drawn. This helps to improve air quality in the bathroom by removing odors.

Activated charcoal filter

However, while the name is similar, these appliances are not the equivalent of a ducted bathroom fan. Ductless fans lack the duct that exhausts bathroom air (and odors) and removes moisture.

Being ductless makes the fan convenient where you cannot install exhaust ducts that lead outside. But this also means that they cannot provide ventilation for the bathroom as required by the International Residential Code (IRC) and local codes.

Ductless Fans Permitted With Natural Ventilation

According to Section R303.3 of the IRC, you can achieve natural ventilation with a window. The bathroom window must be at least 3 ft2 in dimension, and it must be able to open to 50%.

You don’t need to get confused with all the information in this section, as some of it pertains to providing natural light (note: the glazing area refers transparent part of the window) to the bathroom as well as ventilation.

With sufficient natural ventilation in the bathroom, you can install a ductless fan to take care of odors. The exception to this section is if your bathroom is provided with appropriate mechanical ventilation and artificial light, natural sources are unnecessary.

Ventilation Not Achieved With Ductless Bathroom Fan

If you don’t meet the requirements for natural ventilation in the bathroom, you are going to need mechanical ventilation in accordance with Section M1505 of the IRC.

Section M1505.2 requires that bathroom and toilet room air be exhausted directly outdoors and is never recirculated within the home (or other residences). This means that the fan is not allowed to vent into the attic or crawl space either.

Ductless bathroom fans take in bathroom air. It then passes through the charcoal filter and is released (or recirculated) back into the bathroom. This clearly doesn’t meet the requirements for ventilation according to the IRC.

Illustration of a ductless bathroom fan in a bathroom and explanation of how it works

Ventilation is, in fact, technically designed as both the removal of “old” air and its replacement. Ductless bathroom fans are capable of neither.

So, while the ductless fan will be good at removing smells from your bathroom, this does not make the ventilation in the room code-compliant.

Why Is Proper Bathroom Ventilation Important?

Proper bathroom ventilation helps to maintain air quality by removing odors, but the most important function it provides is to exhaust hot and moist air.

Whenever you have a warm shower or bath, your bathroom gets humid. Without a bathroom fan, the wet will build up in the room, which is the perfect environment for mold and bacteria to grow. Running your bathroom fan while you shower and for a while after will help remove the humid air.

Excess moisture can also damage the structure and fixtures of your bathroom.

The fan will also help prevent condensation from forming in the bathroom, which could lead to structural (like ceiling beams) and fixture damage in the room with prolonged exposure. Condensation will collect and can seep into the paint, grout, and drywall in your bathroom.

Humidity in your home above 60% can increase allergens and irritants that can impact your health and potentially cause infections to develop and spread. In addition, these conditions can exacerbate allergies and chronic skin and respiratory illnesses, such as eczema and asthma.

Will a Dehumidifier Bring the Fan up to Code?

A dehumidifier is an appliance that removes moisture from the air. Ventilation is about airflow. Using a dehumidifier in your bathroom may help to prevent water damage to the room, but it will not bring your bathroom fan up to code for ventilation and is not a substitute for an exhaust fan.

The charcoal, as mentioned above, doesn’t affect the moisture content of the air in any significant way. So, a dehumidifier is a good addition if you are dealing with moisture in the bathroom. However, ductless fans aren’t actually designed for bathrooms containing any form of shower or bathtub.

Good Bathroom Fan Options

So, maybe a ductless fan isn’t actually what you need. However, below are three types of bathroom exhaust fans that will meet the ventilation requirements.

Wall-Mounted (Through-Wall)

If you are short on ducting space, you should look at a through-wall exhaust fans that go straight through an external wall.

The Panasonic WhisperWall (amazon link) is one of the many great options for a wall-mounted fan, as it is effective, quiet, and durable. Although, you do need to cut a hole in your wall to install it.

Panasonic FV-08WQ1 WhisperWall Bathroom Fan, Thru-the-Wall Ventilation, 70 CFM

Pros

  • Doesn’t require ducting like ceiling-mount fans.
  • Easier to clean due to the lack of ducting.
  • Doesn’t require attic access.

Cons

  • More prone to back-drafting.
  • Less effective because of its position.
  • Generally louder than ceiling-mounted fans.

Ceiling-Mounted

These fans are installed in your bathroom’s ceiling, and the fan’s duct terminates at the roof.

This is a very popular mount for a bathroom fan, meaning you will have plenty of models to choose from, like the Panasonic WhisperCeiling (amazon link), which is relatively quiet and has different CFM and speed settings.

Panasonic FV-30VQ3 WhisperCeiling Ventilation Fan, Quiet Air Flow, Long Lasting, Easy to Install, Code Compliant, Energy Star Certified, White

Pros

  • In an optimal position for exhausting humid air.
  • Easier to install than other types.
  • Don’t take up wall space.

Cons

  • Harder to access for repairs.
  • If the vent leaks, it can damage the ceiling structures.
  • You have to protect the vent from animals.

Inline

An inline bathroom fan, like the Panasonic WhisperLine (amazon link), is actually set further back in the ducting. So, they do still need ducting, like the ceiling-mount fans.

Panasonic FV-40NLF1 Whisper Line Bathroom Fan

Pros

  • Allows you to vent multi-fan bathrooms or fans from multiple bathrooms with the same vent.
  • Quieter than other fans.

Cons

  • Difficult to install.
  • Can be ineffective with limited space or twisty ducting.

Sources

https://www.designingbuildings.co.uk/wiki/Glazing_area

https://homeairquality.org/bathroom-dehumidifier-vs-exhaust-fan/

https://www.thespruce.com/why-you-need-bathroom-vent-fan-1152643

https://www.nuckolsplumbing.com/blog/2022/march/why-bathroom-ventilation-is-important/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1474709/

https://www.getawair.com/blog/6-health-symptoms-associated-with-humidity

https://www.bobvila.com/articles/how-to-choose-an-exhaust-fan/

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