A guide on Building Code of Australia (BCA) ventilation requirements

by | Jan 16, 2024 | Advice & inspiration, Building basics & regulations

Ventilation plays an essential role in the comfort and upkeep of your home. A ventilation system helps with the exchange of outside and inside air, helping improve the air quality of your home. It also is crucial for moisture control and removing harmful pollutants from your house. Like anything else when it comes to a new house, the Building Code of Australia (BCA) has a few things to say when it comes to the requirements of your ventilation system. So let’s vent on ventilation systems, look at the guidelines you need to follow, delve into why ventilation is such an essential part of any home build, and how you can ensure you have an effective cross-ventilation system that is up to code.

What are the BCA ventilation requirements?

Overview of BCA Ventilation Provisions

The overall goal of the BCA ventilation requirements is to ensure a home will have acceptable indoor air quality and remain safe for inhabitants. One of the key provisions is that windows need to be a minimum of 5% of the size of the floor space. The area may be calculated as a single enclosed room or the entire floor space of connected rooms (for example, an open floor plan where the kitchen, dining room and living room are part of a single area). Any openable window in a room will be considered a primary source of ventilation.


Ventilation provisions also cover allowing natural light into your home with the provisions being as follows:

  • Your windows will need to be at least 10% the size of the floor space to allow in natural light.
  • You install roof lights that are a minimum of 3% of the floor space
  • A combined set of the above leads to an equilivant result.

Ventilation Strategies

There are three key strategies for house ventilation which are:

  • Natural ventilation
  • Mechanical ventilation
  • A combined set of the above.

What the best option is for you will depend on a variety of factors including where you live, your budget, and the layout of your home.

What are the requirements for habitable rooms?

It’s a requirement that, for the purposes of ventilation windows must be at least 5% the size of the floor space. This can be made up of numerous windows and if this requirement is met, you won’t necessarily need an exhaust fan (though it may be a good idea, even if it isn’t a legal requirement.

If one particular room doesn’t have a ceiling fan or mechanical ventilation system installed, the room will need openable windows placed in a way that will achieve effective cross-ventilation

What is Sick Building Syndrome?

Sick building syndrome (SBS) is a term you may come across when researching ventilation. Basically, sick building syndrome is a building that doesn’t have adequate airflow, ventilation or issues with air quality. Many studies show that natural light and fresh air are essential to good health, so therefore, any house that impedes this is going to potentially cause harm. Some potential side effects of living in an SBS home are eye, nose and throat problems and hypersensitivity. If you or a family member has allergies, asthma, or immunity problems, a sick building could worsen these problems.

BCA ventilation requirements for different rooms

BCA ventilation requirements for wet Areas (Bathrooms, Laundries, Kitchens)

Ventilation plays an essential role in removing moisture build-up in bathrooms, laundries and kitchens. Areas with high moisture are vulnerable to water damage, mould and even structural damage to the house in serious cases. Below are the requirements for each type of room:

Bathroom ventilation system requirements: You’ll need a bathroom exhaust fan capable of a minimum extraction of 25L per second

Kitchen ventilation requirements: Requires an exhaust fan that is capable of a minimum of 50L per second. This is often achieved through a rangehood or similar setup.

Laundry ventilation requirements: You’ll need a fan capable of 20L extraction per minute.

Toilet Room requirements: You’ll need an airflow of 25L per minute.

BCA ventilation requirements for enclosed Spaces (Car Parks, Garages)

What are mechanical ventilation systems and when are they required?

There are four main types of mechanical ventilation systems which are:

Exhaust: Exhaust fan systems de-pressurise your building, thereby making the air pressure in the house lower than the outside atmosphere. Exhaust ventilation is best suited to colder climates (southern states more than in Queensland). They’re a fairly inexpensive option, both in terms of purchasing the system itself and installation.

Supply: These ventilation systems are in a way the opposite of exhaust fans because they pressurise the building. This keeps heat and pollutants from outside from entering your home. A supply system is also one of the more affordable options and is ideal for warmer or hot climates.

Balanced: A balanced system differs from the previous two entries in that it neither de-pressurises nor pressurises a building. Instead, they introduce and exhaust inside and outside air at an approximately equal rate. These are perfect for rooms where people spend a lot of time, such as bedrooms and living rooms. These systems can work in any climate, however, they’re more expensive than exhaust or supply systems.

Heat recovery: A heat recovery system transfers warm exhaust air to the cold supply air. The purpose of this is to prevent incoming air from affecting the temperature of the inside air, while still having the benefits of rotating air. Heat recovery systems are the least common type of ventilation system, partly due to being the most expensive system on the market. However, they’re also the most energy efficient and could have lower running costs so it might be a great investment in the long run.

What Energy Efficiency Considerations are there for mechanical ventilation systems?

Mechanical ventilation requirements include:

  • The system must be able to be turned off when not in use.
  • Any habitable building must have a means of allowing outdoor air in.
  • The system must provide odour control and remove harmful toxins and chemicals.
  • Air must be disposed of in a means that doesn’t disturb neighbours or other people.
  • There may be noise restrictions depending on your area and building type.

How to ensure you remain compliant with BCA ventilation requirements?

The National Building Code of Australia (BCA) is readily available to everyone if you wish to double-check any requirements.

Which professionals can help with BCA ventilation requirements?

Your builder should be aware of all National Building Code regulations as should any licensed contractor. Building inspectors can also visit your site to ensure everything is up to code, as can a building broker, like Buildi.

Buildi is here to help you throughout your building journey!


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