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Exhaust fans - what to ask before you buy
If you're thinking of installing an exhaust fan into your bathroom, laundry or kitchen, these questions will help you make a better decision about which exhaust fan is right for you.
Click on a question below for more information.
- Need: Do I need an exhaust fan?
- Type: What kind of exhaust fan?
- Size: What size exhaust fan do I need?
- Shutters: Does the exhaust fan have shutters?
- Installation: Can I install the exhaust fan myself?
- Cost: How much does the exhaust fan cost to buy?
- Running Cost: How much does it cost to run an exhaust fan?
- Noise: How noisy is the exhaust fan?
- Cleaning: Is the exhaust fan easy to clean?
- Other features: What other things should I check when buying an exhaust fan?
1. Do I need an exhaust fan? 
Exhaust fans in kitchens, laundries, toilets and bathrooms will primarily be used to remove steam and odours, preventing them from circulating within the home. The right exhaust fan will also help to reduce mould by removing moisture from the air.
2. What kind of exhaust fan?
There are fans to suit installation in ceilings, walls, windows and skylights (both glass and acrylic). Make sure the fan you buy is suitable for the purpose.
You can buy combination light/heater/exhaust fan units which are installed in the ceiling. These require ducting to release the air to the outside. This is often difficult in apartment buildings, as the ceiling space in the bathroom is often full of drainage and water pipes for the apartment above, meaning it may be difficult to find an unobstructed path for any ducting to the outside.
3. What size exhaust fan do I need?
Fans come in varying sizes, to suit varying sized rooms, so measure the room to determine the size fan that is appropriate. Note that larger fans may be noisier, while having a fan that is too small may not clear the air at the rate you require. Check the specifications of the fan to see what size room it is designed for - fans are rated as to how many cubic metres of air they will move in an hour.
Domestic exhaust fans are generally from 150mm to 300mm in diameter but of course other sizes are available.
4. Does the exhaust fan have shutters or a cowl?
Exhaust fan shutters
Shutters prevent 'backdraft' where the wind blows into the room instead of out. Note that some exhaust fans are suitable for deliberately moving air into the room instead of out. If that's what you want, make sure the fan you buy is appropriate.
Shutters can be simply a couple of 'flaps' on the exterior of the fan. The flaps close when no air is being extracted. You can also buy fans with automatic shutters which only open when the fan is running.
In a high wind, the shutters can make quite a bit of noise slapping against the body of the exhaust fan. This may not be a problem in a garage, for example, but may be an issue at night in a residential property.
Exhaust fan cowl
A cowl is a fixed cover over the outside of the fan (which of course still allows air to be extracted to the outside!) The cowl will stop rain coming into the room via the exhaust fan, and because it doesn't move, it won't make the 'banging' noise that can occur with shutters in a high wind.
5. Can I install the exhaust fan myself?
The physical installation into a wall or ceiling can often be done by a builder or home handyman, however if the fan is to be installed into a window you may require a glazier to cut the hole in the glass. Note that glass must be sufficiently thick to support the exhaust fan - at least 5mm. Ensure any relevant standards are adhered to.
Some fans come with a cord and plug, so that once they are built in, they are simply plugged in and ready to go. Others will require an electrician to connect them.
If you are installing a fan in a multi-storey building where access is an issue (if, for example, you're on the 27th floor!) look for a fan that can be installed from the interior.
6. How much does the exhaust fan cost to buy?
You can pay anything from $30 to several hundred dollars for an exhaust fan. Cheap fans tend to be a bit noisier and have fewer features (may not have shutters, removable front grilles etc).
If you buy a wall fan to be used in a window, you're likely to have the added cost of buying a 'window kit'.
A smaller exhaust fan is generally cheaper than a comparable quality large fan.
7. How much does it cost to run an exhaust fan?
The cost of running the exhaust fan will vary depending on the wattage of the fan and whether it is on all the time, or only occasionally, or is on a timer. Generally, domestic exhaust fans use from 20-50 watts. Note that some fans are not designed to be run continuously, so if that's what you want check the specifications.
8. How noisy is the exhaust fan?
This is an important one. Most exhaust fans will have been rated for noise and you can compare these figures from their specifications.
Check if the exhaust fan comes with a 'gasket' to fit between the securing mechanism and the surface into which it is mounted. Some also have a flexible ring that fits inside the installation hole. Both of these measures will help to reduce the noise.
If your fan doesn't come supplied with this type of noise insulation, it's worth adding some. We have successfully used cheap foam 'draught excluder' tape (available from many 'dollar shops') to dampen the noise from a cheap fan
9. Is the exhaust fan easy to clean?
If the fan has a removable grille on the front, cleaning will be easy.
10. What other things should I check when buying an exhaust fan?
- Some exhaust fans will have a timer so that you can be sure they will operate regularly.
- Do you like the look of the exhaust fan? Once it's installed, you are probably stuck with it for a while. Some exhaust fans have a 'slimline' look while others are quite bulky.
- Is the plastic used in the fan UV stabilised? If not, it may eventually turn yellow and become brittle.
