How Does a Bathroom Extractor Fan Work?

Let’s be honest — your bathroom extractor fan is one of those things you barely notice… until you really need it. But how does this humble hero keep your bathroom fresh and fog-free? Read on — we’ve got the answers!

You're in the bathroom. You stare up at the ceiling. You spy the extractor fan. You start to wonder... what does it actually do?! In the essence of helping customers broaden their bathroom knowledge, we've answered all your burning questions. How does it work? Where does all the air end up? What airflow is needed? We've got you covered.

What is a bathroom exhaust fan for?

The main job of an extractor fan is to whisk away unwanted smells and moisture, keeping your bathroom fresh and mould-free. Sure, it handles bad odours like a pro, but its real power lies in controlling humidity. Too much moisture? You’ll be dealing with peeling paint, mould, and damp spots before you know it.

A well-placed fan prevents all that. It’s a bathroom essential, especially if you want to avoid foggy mirrors and soggy walls after every shower. With the right extractor fan, you’ll keep your bathroom air flowing smoothly — and your mirror crystal clear.

How does a bathroom extractor fan work?

It’s simpler than you’d think. Powered by electricity, the fan draws in moist air, spins it through, and sends it out of the building via a vent. The air is pushed outside through an insulated duct, leaving your bathroom dry and fresh.

What is needed for a bathroom extractor fan to operate efficiently?

For your fan to work its magic, a few things need to be just right:

• Vented Outside: The moist air has to go somewhere — straight out of the building.
• Proper Airflow: Measured in cubic feet per minute (CFM), airflow is key. Bigger bathroom? Bigger fan.
• Good Ductwork: The air duct should be large enough, well-insulated, and as short and straight as possible.
• Makeup Air: Your fan needs fresh air flowing in, or it’s like trying to breathe with a blocked nose. 

Is CFM important?

As a rule of thumb, the bigger your bathroom is, the bigger your extractor fan should be. This is because the recommended number of air changes for any bathroom is 8 per hour. Most of the time, a bathroom exhaust fan is connected to an air duct.

Note: you have to ensure that it is as straight and short as possible and that it is adequately sized. Always remember: there is no problem with air ducts that are too big, but an air duct that is too small will waste electricity and make the fan unnecessarily loud.

Where does the exhausted air go?

What most new homeowners may not know is that a bathroom fan must always be directed outside. In fact, this is a building requirement almost everywhere in the world, and even if the building code in your area does not require you to do so, we strongly recommend that you do. When moving into a new place, you should always ensure that the exhausted air gets directed outside to prevent damage to your home which will be very expensive to repair. 

You can check this yourself or opt for a building inspector to check it for you. This is important because sometimes, Tradespeople direct the exhaust vents into the attic as it is much easier and quicker. This should not be the case because, in an enclosed space, the moist air will condense on the cold surfaces and result in mould and damage to walls and other surfaces. On top of this, redirecting the air outside prevents foul smells from being circulated throughout the rest of the house and will in turn improve the indoor air quality (IAQ).

Why does the exhausted air need to be vented outside?

Your Tradesperson may have attempted to save some money by venting your bathroom fan into your attic or elsewhere in the house. However, this may end up costing you thousands in repair costs and might even be worse than having no ventilation at all.

Here are a few reasons why the exhausted air cannot be vented in the house:

Redirecting the exhausted air into the crawl space under your house is not a good idea because, in the winter, the cold humid air that is redirected into the crawl space will condensate on the metal and wood, causing them to rust and rot. On top of this, mould will start growing in the crawl space in no time. With the wood, metal and mould, you will be looking at a pretty hefty bill for all the repairs.

Venting the air into the attic is also not recommended as it will saturate the insulation. This will decrease the R-value (how well something insulates) greatly and result in high electricity bills.

How do I know if the exhausted air goes outside?

An effective and inexpensive way to test if your bathroom extractor fan redirects the air outside is by using a fog machine. All you have to do is place the fog machine next to the exhaust fan and have someone on the outside see if the fog is redirected out of the house (don’t worry, the fog is harmless and is often used in concerts and parties). If there is no steam coming out of the house, it means that the exhaust fan terminates somewhere inside the house. This is also a great way to check for any leaks in your venting system.

Are bathroom extractor fans necessary?

As long as your bathroom has a window that can be opened, an extractor fan isn't a necessary requirement, according to building regulations. However, in most new-build properties, an extractor fan is a prerequisite. Whatever your bathroom situation, an extractor fan will help you avoid the issues that mould and damp can cause.

Conclusion

Extractor fans play a key role in ensuring that your bathroom is clean and odour-free. Now that you know the do’s and don'ts of bathroom exhaust fans, make sure that the one you choose meets all the necessary requirements.

Keep your bathroom and home clean and healthy

Taking all of the above into account, take a look at our fantastic range of extractor fans. We have something to suit every home, with a variety of sizes, speeds and features available to ventilate your home and reduce the chances of mould and damp forming.