By | May 19, 2018

Bathroom And Toilet Exhaust Fans

Apart from local building regulations, it is important to ventilate well wet areas so as to avoid future humidity damage to walls and ceiling. Ventilation is also important in toilets to dissipate odors produced.
AS 1668.2 Supplement 1—2002
The use of ventilation and air-conditioning in buildings: Ventilation design for indoor air contaminant control

 The law states: “…Buildings shall have a means of collecting or otherwise removing: cooking fumes and odours; steam from laundering, utensil washing, bathing and showering; odors from sanitary and waste storage spaces; poisonous or flammable fumes and gases…”

This standard requires the minimum flow rate to be no less then 90m3/hr (25L/s) for shower, toilet, or bathroom area with a single fixture, with the rate increasing as the number of fixtures and room size increases. Air flow rates equal to or above the defined minimums will ensure steam; odours and stale air will be exhausted out, enhancing the environment for the occupants of the building.

Will any fan do ?
An exhaust fan needs to be sized according to the room size. This is quite logical as the fan moves air and the larger the room, the more air the fan needs to move. All exhaust fans should clearly display their air movement capacity to allow designers and consumers to make an informed decision on its suitability.

What capacity should the exhaust fan be ?
Generally 10 air changes per hour should suit most bathrooms, toilets and laundries. Work out the air volume in the room (height x width x length), then multiply by 10 and that will give you the capacity required of the fan.



Will the exhaust fan stop the mirror misting ?
The exhaust fan takes excess moisture out (but not all) and it is a good idea to let it run for a while after finishing a shower to clear the moisture. A strong fan can create a cold draught and take most of the warm air out of the bathroom, creating an unpleasant environment.

Where do I position my exhaust fan?
For an exhaust fan to perform at maximum efficiency, it’s vital that the exhaust fan has access to a balanced airflow. This means that the volume of air being exhausted by the fan must be matched by that flowing into the room. The best source of this in-flowing air is fresh air either from a window, vent or grille in a door or exterior wall, whatever the position its important to position the exhaust fan opposite this source of in-flowing air to encourage a cross-breeze which is essential to clear vapour and odours.

It’s important not to position an exhaust fan too close to a door/window as this will provide air circulation at the door/window but have little or no effect on the rest of the room.
For ventilation of bathrooms with a shower it’s recommended to use a ducted in roof mounted exhaust fan. This allows the extract grille to be installed directly above the shower for maximum efficiency whilst maintaining electrical safety with the fan being remote from any water spray.

Bathroom Exhaust Fan Position

Red squares are in position to indicate exhaust fan installation and blue arrows indicate balanced air flow needed for exhaust fans to work properly. There are a number of ways to balance the air flow in a room using a vents, door grill or simply opening a widow to allow air movement .



As long as your exhaust fan is not positioned to close to windows and door way the fan will work well in most positions. If your decide to install your exhaust fan under your shower or bath this installation will work well with the compromise of an air draft while in the shower.

It is also recommended to let your exhaust fan run after your shower or bath is complete for about 5 minutes. This will ensure moist air has been extracted to avoid moisture buildup on walls and ceilings.

 Common Exhaust fans

There are three common exhaust fans you can have installed in your bathroom and kitchen. The installation position and the way you use these fans are the same.

  • Ceiling exhaust fans – our electricians can arrange pull cord switch installation or wall switch installation.
  • Window exhaust fans with optional pull cord switch.
  • Wall exhaust fans with optional pull cord switch
  • Inline exhaust fan – this is a ducted fan unit that dispels moisture and smells outside and not in the ceiling space.
  • Another popular bathroom exhaust fan is “fan-n-lite” combination unit, with a fan and light in one unit more….. “fan-n-lite”

How to choose exhaust fans for your installation will depend on room size and if your property is two story or single ground level with roof access. Other installation questions to consider will be, whether you have the exhaust fan switched separate from the light or to be switched with the light, there are advantages for both installations we will talk about next.

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