How to Choose a Bathroom Extractor Fan (and Avoid Damp)
An extractor fan is the least glamorous thing in a bathroom and one of the most important. It's the quiet workhorse that clears steam, protects your paint and grout from mould, and keeps that damp, musty smell from settling in. Skimp on it and you can undo a lot of the beautiful work you've just paid for; get it right and you barely think about it again.
The good news is that choosing one isn't complicated once you know what actually matters: a fan powerful enough for the room, sensibly controlled, and quiet enough that you'll happily leave it running. The features beyond that are nice-to-haves, not essentials, and it's easy to overspend on extras you won't notice.
Here's a calm way to choose one that genuinely does its job, in roughly the order that matters.
Questions worth asking yourself
There’s no single correct answer here. These are the things actually worth weighing for your room and the way you live.
Is it powerful enough for your room?
This is the one that really matters. A fan's extraction rate needs to suit the size of the bathroom — too weak and it never properly clears the steam, which is the whole point. There are simple guidelines based on room volume or air-changes per hour; an electrician or supplier can size it for you. A correctly sized fan in the right place beats an expensive one that's underpowered.
How do you want it controlled?
Options include a fan wired to the light switch, a timer that runs on for a few minutes after you leave, or a humidity-sensing fan that switches on when the air gets damp and off when it clears. A timer or humidity sensor is often worth it, because it keeps clearing moisture after a hot shower rather than stopping the moment you flick the light off.
How quiet does it need to be?
A noisy fan is a fan people switch off — which defeats the purpose. Quieter models (measured in decibels, or sometimes sone) are pleasant to leave running and worth a little extra if your bathroom is near bedrooms. If you'll be tempted to turn a loud one off, a quiet fan effectively does a better job.
Have you accounted for ducting and safety?
The fan needs to vent moist air outside, not just into a loft or cavity, and the run of ducting affects how well it performs. Placement also has to respect bathroom electrical safety zones near water. This is a job to confirm with a qualified electrician — the right fan badly ducted or wrongly placed won't do its job or won't be safe.
The honest bottom line
The single most important thing is a fan powerful enough for your room, ducted properly to the outside — get that right and you've protected your new bathroom from damp and mould for years. Beyond that, a timer or humidity sensor and a quiet motor are the upgrades most worth having, because they mean the fan actually runs when it's needed. You don't need the most expensive model; you need the right size, sensibly controlled, well ducted, and safely installed.
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Start your projectCommon questions
What size extractor fan do I need for my bathroom?
The right size depends on the volume of the room and how much moisture it needs to clear, which is why fans are rated by their extraction rate. The key is matching that rate to your bathroom — a fan that's too weak will never properly clear the steam, which defeats its purpose, while an oversized one is just wasted spend. Rather than guessing, it's worth having an electrician or supplier size it for your specific room using the standard air-changes-per-hour or room-volume guidelines, so you get one that actually keeps the room dry.
Is a humidity-sensing extractor fan worth it?
For many bathrooms, yes. A humidity-sensing fan turns itself on when the air gets damp — like during and after a hot shower — and off again once the moisture clears, so it does its job without you having to remember. This is genuinely useful because the steam often lingers after you've left and switched off the light, which is exactly when an ordinary light-linked fan stops. A simple timer fan (which runs on for a few minutes after you leave) achieves something similar at lower cost, so either is a sensible step up from a basic switch-linked fan.
Why is my bathroom still damp with an extractor fan?
There are a few common reasons. The fan may be underpowered for the room, so it never fully clears the steam; it may switch off too soon (linked only to the light) before the moisture has gone; or the ducting may be venting into a loft or cavity rather than outside, or be long and kinked so the fan can't push air out effectively. Poor sizing and poor ducting are the usual culprits. If damp persists, it's worth checking the fan's extraction rate against the room, considering a timer or humidity sensor, and making sure it vents properly to the outside.
Where should a bathroom extractor fan be placed?
Generally as close as practical to the main source of moisture — near the shower or bath — and positioned so it draws the steamy air across and out of the room, often with the duct run kept as short and straight as possible to the outside. Placement also has to respect bathroom electrical safety zones around water, which determine how close a fitting can be and what rating it needs. Because both performance and safety depend on getting this right, it's best planned and installed with a qualified electrician rather than guessed at.