Ductless bathroom fans certainly sound like a convenient addition to a bathroom shower if you have a particular problem with humidity or if the shower is enclosed. Unfortunately, ductless fans are very different to exhaust fans and, as a result, have a very limited scope of use.
It can be very enticing to think you can find a solution for your home that doesn’t require you to actually destroy some of it first. There are definitely circumstances when a ductless bathroom fan is ideal, but not in this case, as you will see.
Ductless bathroom fans are not manufactured for use in rooms containing bathtubs and showers. The ductless fan cannot deal with humidity and will not provide ventilation, which is vital for the bathroom air quality and preventing moisture-related problems.
Showers Need Ventilation
What Is Ventilation?
Ventilation is the removal of “old” and stale air from a room and the provision of “new” and “clean” air to a room or building. The fresh air supplied to the room comes from outside.
It’s important to properly ventilate a bathroom.
Thus, the ventilation needed for bathrooms and showers is intentional. You are purposely ensuring that there is a fresh supply of air to the room, while the old air is removed from the room.
Why Is It Important?
Having good ventilation is important to maintain good air quality within your house. Ventilation gets rid of odors, dust, moisture, and pollutants in your home. Then this “dirty” air is replaced with cleaner air.
In bathrooms with bathtubs and showers, ventilation is important as it also serves the essential function of removing steam and heat from the room.
When there are high levels of humidity and condensation in a bathroom, it encourages mold and mildew to grow, and the moisture can cause structural damage in your home. It can also ruin the bathroom fittings and fixtures.
As a shower is the source of this moisture, it is the shower that requires the ventilation.
Who Says It Is Required?
The International Residential Code (IRC), an organization that aims to provide home and building regulations for health and safety purposes, requires proper ventilation.
Habitable rooms must be ventilated properly through an approved opening to outside.
According to Section R303.3, bathrooms (and similar rooms) are required to have natural ventilation provided by a window (at least 3 ft2 for the transparent part) that can open to at least halfway.
Exhaust Fans Ventilate Where Windows Aren’t Enough
Alternatively, if you cannot achieve sufficient natural ventilation, there needs to be an exhaust system (mechanical ventilation) for the bathroom that direct-vents to outside. This must comply with Section M1505 of the IRC.
Any exhaust system you install in a bathroom (of any sort) must be listed as able to provide 50 CFM intermittent or 20 CFM continuous exhaust rates (the minimum airflow) under ANSI/AMCA 210-ANSI/ASHRAE 51 ratings. These regulations can be found in Sections M1505.3 and M1505.4.4.
This means that your bathroom exhaust fan is an approved appliance for mechanical ventilation that can offer sufficient ventilation to the room.
The exhaust system in your bathroom must vent outside, as no air from bathrooms and toilets is permitted to be recirculated or discharged within the house, as per Section M1505.2.
This is what excludes ductless bathroom fans from this job.
Ductless Bathroom Fans Don’t Provide Ventilation
If you want to use a code-compliant ductless bathroom fan, you must adhere to the natural ventilation regulations as ductless fans cannot remove and replace the air in a room. These appliances can only filter odors.
Without ducting, the fan cannot do more than take air into the appliance and release it back into the room minus some pollutants. Ductless fans pass the air through charcoal filters that help remove pollutants, but the filters are incapable of dehumidifying or cooling air.
Adding a dehumidifier won’t suffice either, as these appliances only remove water content from the air and cannot provide ventilation.
Filters Can Get Soaked in Shower
Ductless bathroom fans are designed for use in toilet rooms/half baths, which do not contain a shower or bathtub.
I assume you want a fan in the shower to deal with one primary concern: humidity. Unfortunately, a ductless fan will not provide the function you are looking for. Additionally, the fan will be unable to function properly if you want to use it for its designated purpose.
The carbon filters are likely to become soaked by the steam in the shower. This sounds like it could get messy, and the moisture in the filter will block airflow through it and further inhibit the fan’s limited function. Not to mention the cost of needing to replace the wet filters regularly.
An exhaust fan will be able to handle the odors and moisture in the shower, making it a better option than a ductless fan.