Choosing a bathroom fan

This article gives you a full overview of all the specific details you need to know when purchasing a bathroom fan.

Bathroom Zones

The most important factor before choosing a bathroom extractor fan is the area you are installing it in. The UK Electrical Wiring Regulations split the bathroom into 3 zones, simply named Zone 1, 2 and 3.


Bathroom Zone information inline with current building regulatuions for where you can install a bathroom fan


Zones 1 and 2

Two types of fan can be installed in these areas. SELV fans – more commonly known as low voltage bathroom fans. They can only be installed in these zones if there is a transformer housed in Zone 3 or outside all zones. The majority of SELV fans come with the transformer but be sure to check, because there are a few that don’t!

IPX5/IP45/IPX4/IP44 – Any extractor fan that has an IP rated motor can be installed in zones 1 and 2. This IP rating means they are protected from jets of water at all angles.

The one major difference between both of these types of fan is the IP rated versions are much more cost effective, due to the low voltage fan needing more components. This increased price is also reflected within the installation as the SELV fan needs to be fitted alongside the transformer in the circuit too.

Here at Extractor Fan Shop we prefer to recommend IP rated bathroom fans due to them being more cost effective and easier to install. We also highly recommend a fully qualified electrician to install your bathroom fan, due to the complex details this will require and an electrician has to certify the integrity of the installation too.

Zone 3

Any type of extractor fan can be installed within zone 3, as this area is considered safe and far enough away from the shower and bath. Another type of fan that suits every type of installation in the bathroom is an Inline duct fan. These fans are perfect if you have loft space or ceiling void. They are housed in these areas so far enough away from any water source and the beauty of these fans is because they are in the loft, they are built to be extremely powerful. This means they can be up to 5x more powerful than the usual bathroom axial fan but they will still be silent as they are not installed within the room!

National Ventilation Bathroom Fans

            National Ventilations Leading Bathroom Fan & Inline Duct Fan                  


Domestic extractor fans come in two sizes. 100mm / 4 inch or 150mm / 6 inch. Almost all bathroom installations will only require a 4 inch fan. If your bathroom is larger than 10 meters squared that’s when we would recommend looking towards a 6 inch bathroom fan. Another scenario when a 6 inch fan may be applicable is in homes of larger families where the bathroom will be used for bathing/showering frequently.

The power of all extractor fans is measured in ‘metres cubed per hour’ (m3/hr) or ‘Litres per second’ (L/s). This is a vital attribute for all fans, as if the fan does not meet a minimum of 15 L/s then it will not meet building regulations in a domestic bathroom.

The majority of bathroom fans on the market nowadays meet this requirement, so it shouldn’t be something you need to worry about, but always be wary of this. We would always recommend looking at bathroom axial fans with a power of 90 metres cubed per hour, this gives you enough power to clear moisture within the room. However, if you are looking for an inline duct fan then you will need to be looking at powers of 240 metres cubed per hour or above. This power will extract steam before it condenses.


Every extractor fan will be installed into either a light switch or a separate remote switch which is usually a fan isolator switch. Along with these options for switching there are also different modes a specific fan can have.

  • Basic Model- This option is your standard on and off. Turn the switch on and the fan operates, turn the switch off and the fan will turn off immediately.
  • Timer Model – This mode can sometimes be confused, it is not to set an actual time for the fan to switch on. Like the basic model when you turn on the switch the fan will turn on, but when you turn the switch off the fan will overrun for a set period of time. Most fans can be set between 2-25 minutes. Some manufactures now are incorporating a delayed start function for these fans, this is to stop fans switching on if you are only nipping for a quick wee in the middle of the night.
  • Humidistat Model – These models will turn on automatically when humidity in the bathroom reaches a set level within the room, it will then continue too extract until the humidity levels drop back below the pre-set level. This specific operation is popular because you don’t necessarily need a light on when using the bathroom.
  • PIR Model (Passive Infra Red) – This operation will only turn the fan on if somebody enters the room, just like a floodlight outside your house!
  • Pull cord – The pull cord operation is slowly being replaced by the above mentioned operations, but they are fairly self explanatory. They have a localised switch point.

Throughout the last decade technology within the ventilation industry has been improving and with that is now bringing to the market; smart fans. We live in a world where we have household robots which can mop, vacuum and clean windows so why wouldn’t we have a smart and automated bathroom fan?

For example Vent-Axia have released the UK’s only odour sensing extractor fan!

Vent Axia Pure Air Extractor Fan

This technology is so advanced that when an odour is detected the fan will increase its airflow to improve the air quality within the room. This isn’t just a fancy gimmick either, these fans reach an output of up to 140 m3/hr and run silently so are keeping inline and even better than more standard models too. Alongside the great performance and pioneering technology it also has humidity control, light sensor and adjustable timer than can be of course… all controlled by Vent-Axia’s very own app that can be found on all IOS and Android devices.

The opening screen of Vent-Axia's IOS and Andriod free app! The opening screen of Vent-Axia's IOS and Andriod free app!


Noise is another very important factor to take into account when researching any bathroom extractor fan. Any decibel rating displayed on a product is measured from 3 metres away. Our advice is to look for fans that are 35 decibels (dB) and under. Anything under this amount is the equivalent to whispering but as mentioned from 3 metres. As technology is advancing and improving we are now seeing fans that are closer to 20 decibels which is moving closer to completely silent. For the best results inline fans will be a better option and as close to silent as you will get. Being installed outside of the room means they are further away and much closer to the 3 metre measurement that manufactures use.


When looking to buy a bathroom fan of course how it looks matters. You may save money on the basic looking box grille fans, but in the long term you are going to see this fan every day so you want it to be as attractive as a bathroom fan can be! However, similar to the noise inline fans are again highly recommended for this. This sits in the middle of the duct run and you can choose your own flush internal grille for the ceiling. You have various different options of design and colour, this also means that you won’t have a fan petrifying from the ceiling. These internal grilles will be flush.


Centrifugal Fans – These fans are most common in blocks of flats or basement bathrooms. Due to the design of their motors and impellers they duct much longer distances than a standard axial fan.

  • Axial Fan – 5 Meters
  • Centrifugal Fan- 12 metres+ depending on model and size
  • Inline Fan – 10 Metres

They aren’t as common and people tend to avoid them as due to their needs for being powerful over long distances they tend to be fairly large and similar to a box installed on your wall!

Continuous Ventilation – is becoming more and more common as time progresses. Especially since building regulations have stated they want greater control of air movement in and out of buildings. Specifically because homes are now becoming better insulated and air tight which means there is less air movement throughout the home. These fans help massively with the constant moving of air and a higher degree of control compared to axial and inline fans.

See our recommendations for all bathroom fan installations..

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