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The importance of bathroom ventilation

A bathroom extractor fan

The bathroom is a place that can get very hot and steamy, making air circulation and ventilation incredibly important. Moist and stagnant air is a recipe for mould and mildew, so ensuring this air can escape and be replaced with fresh, drier air helps keep your bathroom running smoothly.

In a lot of bathrooms, an extractor fan or a fan-light combo can be switched on and the air will be taken out through the wall or a roof. When a bathroom doesn’t have a window, extractor fans are a fantastic alternative.

However, due to the design of some houses, it’s not always easy to vent air to the outside, so in this article we’ll look a how you can improve the ventilation in your bathroom space, whatever the situation.

How to spot ventilation issues

Building regulations make it a legal requirement, in new-build houses, for all bathrooms without a window to have an extractor fan to remove air and odours to the exterior of a building. Some people go even further and opt for an extractor fan in bathrooms with a window for those times when it’s too cold outside to leave the window open. This means that the vast majority of new houses are much better than older ones at bathroom ventilation.

That being said, all bathrooms can suffer the effects of indoor air pollution caused by a lack of ventilation. Mould is a particular problem, caused by too much moisture hanging around in the air and often manifesting itself as black patches on walls, ceilings and grouting. If left unchecked, mould can rot wood and create a dirty and unappealing look to your bathroom. At the more extreme end of the scale, mould spores can cause severe respiratory problems and allergic reactions.

If you’ve got some tell-tale signs of mould, such as those mentioned above, or even a damp smell, it’s likely you need to improve the ventilation in your bathroom.

What’s the best type of extractor fan?

Not all extractor fans are created equal, so there are some points for you to consider when selecting the right fan for you.


Extractor fans in the UK tend to come in two sizes – 100mm or 150mm. A general rule of thumb is that for bathrooms under 9sqm, you can use a 100mm fan, while for anything larger you should opt for a 150mm fan.

Extraction Rate

The air extraction rate is to do with how quickly the air is removed from your bathroom and, in the UK, tends to be measured in Metres Cubed per Hour (m3/hr). Though there are several different rates available, a standard air extraction rate is 85m3/hr, which more than meets the requirements of the Building Regulations.

Noise Levels

Even if you don’t have a fan in your bathroom currently, you will have been to a friend or family member’s house and heard the whoosh of the extractor fan coming on when you switched on the light in their bathroom. The noise of fans is measured in decibels (dbA), with the higher the number the louder the noise. If your bathroom is close to where you sleep, you may wish to consider a fan at the quieter end of the scale.


There are many options available when choosing a suitable extractor fan. Do you want the fan to come on with the light, or do you want an independent switch? Do you even want a manual switch or would an infrared motion sensor be more convenient? Will you choose a humidistat that detects the humidity in the room and come on accordingly? Should it have a timer than you can set to come on at certain times of the day? These are just a few of the many options you’ll need to think about.


This is the channel by which the air travels through the fan to the outside. Rigid metal or PVC ‘duct runs’ will be the best long term solution, but flexible-duct is a cheaper, if less durable alternative. The duct runs should be kept as straight as possible for ease of extraction, though the design of your house may make changes of direction necessary to reach the outside world. If there are changes of direction, ensure your fan is powerful enough to extract the air all the way outdoors.

Ventilation alternatives

Sometimes the journey from your bathroom to the outside of your building is not a simple straight line. Here are some alternatives to think about if channeling air outside is quite challenging.

Inline fan

If the route the air has to take to get outside is convoluted, you’ll need a more powerful fan to ensure the air gets out. A powerful fan can be very noisy. Another option is to install an inline fan somewhere along the route away from your bathroom. The air will still be extracted but you won’t hear such a loud noise.

Recirculating fan

These types of fans are very useful for small cloakrooms or under-the-stairs toilets where no shower is present. Rather than taking the air outside, the air is pushed through a filter that removes bad odours before being recirculated around the room. Excess moisture is rarely a problem in showerless rooms, but odours still can be and this is a great way of dealing with them.

Floor venting

If your bathroom is in a odd place that is nowhere near the roof or an exterior wall, another possibility would be to mount a powerful fan high up on the wall (to maximise extraction of hot, moist air) and then take it away via a channel that runs down the wall and under the floor to the nearest external wall. This is not always an easy install and will require planning and consultation with a professional.


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Tips for bathrooms without windows

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