At Capacity: Is Your Exhaust Fan the Right Size?

Back to blog

Exhaust fans are not ‘one size fits all’. The capacity of the fan is vital to making sure that it operates correctly, and effectively ventilates the unwanted moisture from the room.

The size of the exhaust fan required depends on a variety of factors, such as the size of the room, available airflow and the wall/floor covering materials in the room. When installing an exhaust system in your home, Kenner Electrics calculates the volume of air in the room and the number of air changes required. This allows us to provide a professional, customised solution that suits your homes unique needs.

Under-Sized Exhaust Fans

If an exhaust fan is not powerful enough for the space, it will not be able to effectively remove the undesirable humid air from the room. The resulting moisture build-up can create the perfect conditions for mould to grow, which has significant associated health risks.

Over-Sized Exhaust Fans

If an exhaust fan is too powerful for the space, it will cause drafts and make you feel cold (not great when you get out of a warm shower!). If the door is closed and there is not enough airflow under the door, the fan may also wear out too quickly because it is trying to suck more air out of the room than is available. This will also cause it to be noisier than it should be. As larger capacity fans are usually more expensive to buy and cost more to run, you don’t want to waste money on getting one that is too big for your space.

Kenner Electrics installs exhaust fans
Kenner Electrics calculates the best sized exhaust fan for your space and designs a customised exhaust solution for your unique needs.

How to Measure What Size Exhaust Fan you need

In Australia, the capacity of exhaust fans is measured in m3 per hour. This is the maximum amount of air that the fan can move within 1 hour. Knowing the size of the room (length x width x height in meters) and the desired number of air-changes per hour allows us to choose the perfect exhaust fan. The required number of complete air changes within a room per hour depends on the use of the room. For example, a separate toilet will typically require 6-15 air changes per hour, while a bathroom with shower will typically require 15-25 air changes per hour.

Universal Fans has a handy calculator to help you find out what sized fan will best suit your space.  

Kenner Electrics designs and installs ventilation systems to help avoid mould and moisture issues. Whatever the problem, we provide customised solutions and design the best exhaust system for your home.

There's plenty of ways to get in touch With Us Today


(03) 9996 0663

We're always ready to talk to you about your job.


Send through an email, and we'll respond during business hours.


Bottom right of screen

Chat with one of our friendly team members.

Fill Out our enquiry Form Below

As your local electrician, we promise friendly, professional customer service. On the job and after, you're safe with us.

Thanks! Your enquiry has now been sent and we will get back to you soon.
Oops! Something went wrong while submitting the form.