Do I Need A Bathroom Ventilation and Exhaust System?

Do I Need A Bathroom Ventilation and Exhaust System?

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Proper bathroom ventilation is the economical choice, and here’s why

The Building Code of Australia (BCA) requires that you must have openable windows that are at least 10% of the floor space as a primary source of ventilation. However, if the room does not have a window for ventilation, then an exhaust fan must be installed.

Coles Air Conditioning and Refrigerationknows that ventilation is very important for your bathroom, not only for the toilet, but also for those hot steamy showers we love to take. When you’re regularly taking hot showers, baths, or even running the dryer in your bathroom you’re increasing the moisture in the air. When not properly ventilated, through an open window or exhaust system, this can lead to the growth of mould, mildew, and other microorganisms. In extreme cases the build-up of moisture can even lead to the deterioration and breaking down of the room materials such as gyprock, paint, trims, and doors.

What problems can be caused by poor bathroom ventilation?

What problems can be caused by poor bathroom ventilation?

Bad ventilation can result in:

  • Accumulation of warm, moist air.
  • Growth of mould, mildew, and microorganisms.
  • Damaged bathroom walls, floors, ceilings, and fixtures.
  • Breaking down of wallboard, wall paint, and trim.

If your bathroom has a musty smell, you should consider increasing your room’s available ventilation as this is an indicator of an unhealthy environment. If caught early this can be easily fixed by cleaning the affected areas and installing an exhaust system.

Bathroom vents vary in size and style, including ones with all the bells and whistles from lights and heat lamps to Bluetooth capability and a speaker. Just imagine that you’re in the bath, taking a shower or using the toilet and your music or story is playing while you relax in your bathroom oasis without needing to have your phone in a bag or other waterproof container.

Air flow rate requirements

Air flow rate requirements

The HVAC industry typically uses the 25L/s air flow for toilet ventilation and odour control. However, Coles Air Conditioning and Refrigeration’s experience is that this air flow rate is often insufficient to adequately ventilate a bathroom when a shower is running, particularly in cool or humid climates. For a bathroom with shower to be free of condensation (and its inconvenient and harmful effects) an exhaust rate of between 50 to 100 L/s is recommended.

When installing an exhaust system, you need to make sure that it can be properly vented outside or into the roof space if it is not lined with silver paper insulation and has adequate air leakage to outside. You will also want to ensure there is enough room underneath the door, or that the door has an intake grille to avoid creating a vacuum inside your bathroom.

What to look for when shopping for a fan

What to look for when shopping for a fan


Aside from the size, colour, and gadgetry of available fixtures, it is also important to pay attention to the sound ratings of the fans. Vent fans with a sound rating of 1.0 or less are ideal for when you’re having a nice relaxing soak in the tub, or if you just don’t want your bathroom to sound like a helicopter pad!


Fan capacity is another thing to look for, you don’t want too much or too little pressure in your space. Their capacity is measured by the volume of air moved by the unit, in cubic metres per minute.

  • Less than 5 square metres: 1.4 cubic metre per minute.
  • More than 5 square metres: 0.03 cubic metre per minute.
Where should a bathroom ventilation system be positioned?

Where should a bathroom ventilation system be positioned?

You can get away with positioning the fan in the middle of small bathrooms, however in larger spaces you may want to consider having it where the most moisture would be. Contact Coles Air Conditioning and Refrigeration to speak with one of our experts about what location would be best for your bathroom, but the best locations are:

  • Over the sink.
  • Near the shower.
  • Midway between the shower/tub and toilet area.

Building Code of Australia bathroom ventilation stipulations

If the toilet is separate, consider a second vent fan and also keep in mind that the BCA stipulates the following rules:

  1. If the roof is not lined with sarking material (silver paper insulation) and is clad with roofing tiles or decking with adequate air leakage to the outside, fans can be mounted in the ceiling exhausting into the roof space.
  2. If the roof is lined with sarking material, then the air needs to be ducted to the outside atmosphere through the roof or eaves.

Comment ‘2’ is now more the rule than the exception, as energy efficiency regulations require full insulation of building roof spaces. This means that most roofs are now sealed from the atmosphere and thus require exhaust ventilation to be discharged to the outside.

Outside discharge

Outside discharge

Available solutions to achieve outside discharge are:

  1. If the bathroom/toilet has external walls, then a wall or window-mounted fan can be used to exhaust air directly to the outside, or you can also have a roof mounted exhaust grille and exhaust through the eaves.
  2. If the room is below an external roof that is exposed to the atmosphere, then a roof-mounted fan can be used to exhaust air directly to the outside.
  3. If the room is enclosed within a building, then it will be necessary to exhaust the air through an exhaust system to the outside atmosphere.
What does a bathroom exhaust fan do?

What does a bathroom exhaust fan do?

Bathroom exhaust fans are necessary for your bathroom because they perform the following functions:

  • moisture, smells, smoke, and heat elimination.
  • Improved air circulation.
  • Movement of hot or cool air.
  • Reduced levels of steam, reducing mirror and benchtop wipe-down.
  • Decreased probability of mould or mildew

Choose Coles Air conditioning for your ventilation solutions

There are many different ventilation options, depending on the location they will be installed in. The best way to ensure the correct system is installed is to speak to us at Coles Air Conditioning and Refrigeration, in Broadmeadow, Near Newcastle, NSW.

We are here to help you decide which system will be the best for you, your family, and your home. Contact us to speak with one of our expert team members today! Call us on 02 4957 0221or visit us at 141 Lambton Rd, Broadmeadow, NSW, 2292 to find out more. Alternatively, just click here to send us an online message and one of our friendly team will contact you right back.

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