Why Use An Inline Bathroom Fan For Ventilation?

The main benefits of installing an inline fan in your bathroom are to keep the air fresh, stop moisture build-up, and eliminate excess heat and humidity. 

They are more powerful than a regular bathroom extract fan, easy to install, can handle longer duct lengths, and run from the bathroom light switch.  They are mostly silent depending on the install location. 

We tell you all you need to know below.

What is an Inline Fan?

An inline fan is a powerful motor that can move and expel heat, moisture, and bad smells from a room!  This type of fan is way more efficient at the job than a regular extract fan, which is generally found in things like cooker hoods, kitchen extractors, and indeed a lot of bathroom extractors. 

But the inline fan is a far better choice of extractor for your bathroom due to the benefits below.

Inline Exhaust Fan vs Regular Exhaust Fan

The main benefit of the inline fan over a regular exhaust fan is that it has a way more powerful extraction rate and therefore does the job a lot quicker.  This type of fan can also work in duct lengths of 10 meters whereas a standard extract fan mounted in the wall or ceiling can usually only work efficiently at a max of 4-meter runs.  The inline fan can also handle bends in the ductwork without losing power.  

The powerful inline duct fan is often found in situations such as computer server rooms and grow tents where keeping the desired atmosphere in the area is key.  This is because they are so much more efficient at extracting excess heat and moisture from the environment than a regular exhaust fan.  

Regular exhaust fans are generally nowhere near as powerful as the inline exhaust fan and quite often don’t do a great job.  Although they use less energy, their inefficiency at the job outweighs this.

Why Use An Inline Fan in a Bathroom?


OK, so we know this type of fan is super-powerful so already it’s easy to understand why it would be great in a bathroom, but there is another key factor.  Because this type of fan sits in an attic space or ceiling void, it means there are no extra electrics installed within the bathroom – definitely a safety plus!  

All you will see is a little grill or similar in the bathroom itself but behind the scenes, it has ducting that connects it to the inline fan that is safely situated up in the attic (or ceiling void) that then shoots everything along the ducting to the exterior of the building. 

It is simply wired into the existing light switch circuit so that every time you flick the light, the fan will trigger on.

Extra Extract Points

If you have a lovely, flashy big bathroom, you can even fit two extract points in the ceiling and connect them to a Y-piece that then connects along to the fan itself.  The fan then vents to the exterior with its usual single duct tube.  

If you install a regular extract fan in your bathroom it really needs to be fitted to an external wall to work efficiently, but many bathrooms in apartments don’t have external walls these days, so it has to travel along a length of ducting, thereby reducing its efficiency.

With an inline fan, you can install the extract point directly over the shower, and have another over the toilet, and they will both extract safely and powerfully into the ducting above the ceiling.  The inline fan then pushes everything through the exhaust tube to the exterior. 

Remember, we’re talking 10 meters instead of 4 meters of powerful extraction with the inline fan.   So you can see why this little baby would be far better than a regular extract bathroom fan.  

Noise Level

How annoying are those regular bathroom extract fans?!  Some of them are so loud it’s like you can hear them humming in your ears for an hour after!  I used to live somewhere that it was so loud and annoying I even used to imagine I was hearing it when trying to sleep!  

Well, that is a thing of the past as the inline fan is pretty much silent depending on where it is housed.  If it’s in the attic you’re in for a treat as you won’t hear it at all, but if you have it in the ceiling void you may hear a slight hum but nothing compared with the annoying regular extractor. 

So gone are the days when you can’t wait to hit the light switch to turn that irritating fan off again, despite the fact that the regular extract really should be run for 15 mins after vacating the bathroom!

What Exactly Does an Inline Fan Extract?

In a bathroom these are the things that we want to stop the build-up of:

  • Steam
  • Heat
  • Smell
  • Damp
  • Mold

The great news is that the inline fan can easily handle all of these!  But let’s take a look at them individually:


We all know what a nuisance it can be when you use a mirror in a bathroom full of steam!  An inline fan will suck all the steam from the room as it is produced and expel it to the outside of the building where it can no longer be an annoyance – so no more steamy mirrors!


This is another one that can be a real nuisance if you’ve just had a lovely hot steaming shower and find that you start sweating within minutes of getting out!  Having an inline fan installed will alleviate this problem as it will extract the build-up of heat along with the steam, making for a much more pleasant atmosphere.  


Oh yes, this is the big one – especially when combined with the two above!  An inline fan will get to work and expel any unwanted, lingering smells immediately, leaving the air cleaner and fresher in seconds.  So, no more feeling embarrassed when someone is waiting to enter the bathroom after you!


This can be a real problem in bathrooms without decent airflow or extraction.  Some buildings are worse than others with concrete buildings being an absolute nightmare as the walls just do not breathe!  All buildings need airflow and a lot of bathroom areas suffer from damp, which can spread to other rooms too.

Installing an inline fan will stop this problem in its tracks as it extracts all of the moisture in the air to the exterior of the building, drying out the damp atmosphere within.


Mold is a naturally occurring thing that has tiny spores living in the air all around us, which if left to build up, can pose a health risk!  So, if you didn’t already have enough reasons to fit an inline fan in your bathroom, this has to be right up there.  A healthy house – healthy you!

How Do I Calculate the Correct Size of Inline Fan?

This is easy to determine as it’s basically down to how big your room is.  So all you need to do is measure the space and multiply the length x width x height to give you the cubic feet or meters of the room. 

You will then be able to purchase a fan with the capability to extract from this space efficiently.  Inline fans are clearly labeled with their room capacity extraction per hour which will be written like this: 135m3/hr.  

Remember to check the physical size of the fan against where you want to install it to make sure it will fit into the designated space, for example, your ceiling void.  You will need to leave enough space so that it doesn’t touch the ceiling to avoid noise.

How to Install an Inline Fan

Installing an inline fan is a relatively simple job that requires basic electrical skills.  An experienced DIY enthusiast should be able to tackle this task successfully.  Once you have calculated the size fan that you need, as above, you will need to use the appropriate sized ducting to fit the intake and output points of your inline fan.  The ducting can be secured using the corresponding size of duct clamps. 

It is important to fit the fan securely to a solid surface to avoid vibration which could result in unwanted noise.  It is also important to make sure you can easily access the fan to clean it and perform general maintenance.

All you need to do then is run the intake length of ducting to the extract port in your bathroom, and run the output length to the exit point in the exterior wall.  It is always best to use a cowl or one-way vent cover on the external wall to avoid drafts and rainwater ingress.

Then it’s just a matter of hooking it up to the electric using the correct sized breaker required for the size of the fan and then to the light switch.  Always make sure to use the correct cable size to avoid fire hazards.

Well, that’s hopefully covered all you needed to know about why you should use an inline fan for bathroom ventilation.  All you need to do now is get one installed and enjoy a new sweeter-smelling, clearer, and cooler bathroom!