Bathroom Ventilation


Bathroom ventilation. Looks great, now add odour

Looks great, now add odour

Bathroom ventilation dynamics for internal and external bathrooms

Best way to ventilate your bathroom is to ensure good air wash of the area otherwise problems will arise.

Bathroom ventilation

You want to ventilate a bathroom efficiently so place the exhaust fan opposite to ingress (window etc).
The most efficient egress (exhaust) is vertically, through ceiling to roof ventilator or eaves vent.
Horizontal air exhaust is noisier and less efficient.
This short circuits the flow and does not air wash (removing moisture ) the total area.
Low level air ingress is ideal for removal of toilet odour and high level ingress creates less draft when showering.
These are some of the considerations necessary when designing bathroom ventilation

Yes there are times when a rule cannot seemingly be implemented however this is a matter where understanding of fluid dynamics (air movement) is essential.
A non conventional alternative can always be found.


The most efficient ventilation has the exhaust fan placed over the shower area to where the highest heat & moisture content is created and removed.
It’s somewhat immediate removal can be achieved before it spreads throughout the room.
Egress, or exhaust, is a 240vac fan.
In addition to this the fan can be switched by infra red and or movement sensors so that you can avoid the fan being left on when unoccupied.
This guarantees positive and consistent flow which is needed for wet areas.
For vacating to atmosphere, the fan ca be ducted to within 30cm of the roof ventilator.

Heat Lamps

Try to install heat lamps over the personal drying area as this is where they are needed most.
Place lighting either, over the mirror, or overhead between you and the mirror.
Combined function or multi tasking units, as shown above, seem like a good idea but are inefficient, because of location, and noisy by nature, as you will discover should you install one.

Bathrooms can be vented efficiently once you understand the principles of what is required.

There are two types of bathroom locations in a building,
Peripheral‘: that has at least one peripheral (outside) wall available for air ingress, usually via a window.
Internal‘: no window for air ingress.

Peripheral Bathroom ( with one outside wall)

Have air entering the bathroom via a window on an external wall and exhaust via a ceiling fan located opposite, ideally over shower.
This allows positive low speed movement of air in the room and avoid creating drafts.

Internal Bathroom ( with no outside wall)

Bathrooms need fresh air ingress (external air) to replace that which is being exhausted by the fan.
Air ingress from an adjacent room in the building will not do.
The Ductdown system begins 200-300mm above ceiling down to approx 200mm from floor.
A negative pressure is created in the room when the fan is turned on, causing air to be drawn down from the roof void via the duct, replacing that which is being removed by the fan.

Low level ingress into the room will ensure good air washing of odour and moisture, without disrupting air quality values in the rest of the house.

Condor exhaust fans are available in either 240vac or 12vdc and are available in a variety of aesthetic presentation as well as protruding, ceiling line and recessed.
For further information contact Condor

Is this what you want in your bathroom?
Schematic of bathroom ventilation variables
Condor Hi Flow low noise adjustable speed exhaust fan
Dynamics of ideal bathroom ventilation using Condor Ductdown system
Go to Builders Notes
Air Transfer systems

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