Australian building codes don’t expect houses to be fire-proof – and that’s by design


Raymond William Loveridge, University of Technology Sydney

More than 2,000 homes have been destroyed in Australia since the start of the bushfire season. More will certainly be destroyed before the season ends in March.

Could these houses have been built to better withstand fire?




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Quite probably. But that doesn’t necessarily mean Australia’s building regulations need reforming to ensure homes are made more fireproof.

Appropriate building codes are about weighing costs and benefits. Only analysing the reasons buildings were destroyed will tell us if more needs to be done.

Performances standards

Not all buildings are created equal. Newer buildings will generally be more fire-proof than older ones, due to building regulations having been improved over time.

In particular, national building requirements for residences in bushfire-prone areas were improved after the 2009 “Black Saturday” bushfires in Victoria, in which 173 people died and more 2,000 homes were destroyed.

Buildings are regulated by states and territories but governments have recognised the value of nationally consistent building codes through the National Construction Code. This code, among other things, sets minimum standards for the design and construction of new buildings on bushfire-prone land. (What land is deemed “bushfire prone” is defined by state and territory legislation.)

The National Construction Code is “performance-based”. It doesn’t specify how a building must be built, but how a building must perform. This means innovative designs, materials and construction methods can be readily approved.

A residential building on bushfire-prone land, the code states, must be designed and constructed to “reduce the risk” of ignition from a bushfire, appropriate to the risk from bushfire flames, burning embers, radiant heat and intensity of the bushfire attack.

The risk to which a building is expected to be exposed depends on the individual site and conditions such as vegetation type and density, and slope of land. Properties are assessed and given a “Bushfire Attack Level” (BAL) rating by inspectors.

There are six BAL levels that classify the severity of potential exposure to bushfire. The highest – BAL FZ – is for buildings exposed to an extreme risk, such as a house surrounded by trees that could produce direct contact from flames.

Lower BAL levels take into account risks from burning debris, ember attack and radiant heat. The lowest deems the risk insufficient to warrant any specific construction requirements.

Construction details for each BAL cover building elements such as floors, walls, roofs, doors, windows, vents, roof drainage systems, verandahs, and water and gas supply pipes. For example, fire-resistant timber may be required for floor framing, or windows may be required to use toughened glass.

Balancing competing interests

Are the requirements of the National Construction Code good enough?

If the aim is to minimise the number of buildings damaged or destroyed in extreme fire events, the answer is no.

But that’s not the aim. Like most government regulation, the code requirements are about balancing competing interests.

All building regulations are subject to cost-benefit analysis. They must demonstrate a “net cost benefit” to the community – that the cost of compliance will be less than the benefit delivered to the general community.

It’s a cold calculation about the risk and potential cost of homes being destroyed in bushfires versus the more certain costs involved in requiring all homes to be built to more stringent building codes.

Government policy treats potential property loss as a matter for owners to address through property insurance. There’s no reason to expect this to change any time soon.

Learning from experience

If the cost of building destruction in bushfires turned out to be greater than the cost of more stringent building requirements, there would be a strong rationale to improve the regulations. This is why post-fire analysis is so important.

A prime example is the royal commission into the causes and costs of the Black Saturday fires.

The commission’s final report made a number of recommendations for changes to the National Construction Code. These included new provisions to:

  • make protection from ember attack a performance requirement
  • address the design and construction of private (underground) bushfire emergency shelters
  • include design and construction requirements for non-residential buildings, such as schools and aged-care centres, in bushfire-prone areas.

All governments agreed to the first two recommendations, which were promptly implemented in the National Construction Code (in 2010).

The recommendation about non-residential building was not implemented at the time because governments considered that planning laws would not allow these types of buildings to be built in a bushfire-prone area.

However, the 2019-2020 business plan of the Australian Building Codes Board (which administers the National Construction Code, includes a “bushfire provisions for non-residential buildings” project, so it is reasonable to expect changes to the code in future.




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This season’s fires may also provide impetus for other changes to the construction code. One key factor that will be worthy of research is the age of the buildings destroyed.

Depending on how many homes lost were built after 2010, it might be argued that changes made after the 2009 Victorian fire have been insufficient to keep up with evolving conditions.The Conversation

Raymond William Loveridge, Adjunct Professor – School of Built Environment, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Houses for a warmer future are currently restricted by Australia’s building code



Australians need better solutions for coping with the warmer climate of the future (and present).
TRACEY NEARMY/AAP

Anir Kumar Upadhyay, UNSW; Chris Lockhart Smith, UNSW, and Krishna Munsami, UNSW

Australian houses use significantly more electricity to stay warm or cool than estimated during the design stage.

To design a new house in Australia, the building needs to meet the national construction code. One way to do this is by using software to simulate the building’s thermal efficiency, to see if it meets the minimum requirements of the national house energy scheme. The scheme divides Australia geographically into 69 different climate zones and requires new houses to be thermally appropriate for their environment.




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Unfortunately, this software does not properly take into account our warming weather. Our recent report found the climate assumptions used by the government drastically underestimate the length and heat of summers in the near future.

In fact, buildings that perform best for heat waves predicted by 2030 are actually banned by the government’s building code. We urgently need to update our building codes to cope with our changing climate.

Understand the future local climate

We took Richmond in New South Wales as an example to understand the effect a changing climate might have on building performance. By taking predictions from CSIRO’s medium greenhouse gas emissions scenario, we analysed Richmond’s likely weather for every week of 2030.

The future outlook, shown below, is strikingly different from the weather files used to determine whether houses meet the minimum thermal performance requirement of the National Construction Code. In 2030, Richmond will experience a warm period almost four times longer than predicted by the official weather file.


Author provided

Design for the future

Based on the future climate scenario, the design strategy for buildings in Richmond should focus on well shaded and insulated buildings to avoid any heat gain in the warm period, but should also harness sunlight to warm up the indoors in the cool period.

The warm period will last from December to March, when keeping the house cool is the priority. Passive solar heating, such as northern windows and well-insulated walls, floor and ceilings, are important during the May to September cool months, while direct ventilation is largely all that’s needed during the mostly comfortable April and October to November.

To test how houses will perform in a hotter future, we modelled a house in Richmond using AccuRate software. We found a design and construction solution that performed well (achieving 7.6 stars out of 10) for the 2030 scenario failed to meet a heating threshold that is legally required in NSW. In effect, the house that makes the most sense for the immediate future, could not be built.

These thresholds for heating and cooling are based on assumptions that are out of step with current conditions, let alone the future. Between 2016 and 2018 Richmond’s annual average temperature was 17.8℃, whereas the NatHERS weather file assumes it to be 16.7℃. This difference is set to increase.

In a 2019 amendment, the National Construction Code adopted NSW’s approach to heating and cooling thresholds to other climate zones in other states. The heating threshold puts a restraint on designing buildings that are optimised to mitigate extreme heat events.

This highlights the limitation of out-of-date climate files, and the current regulation that acts as a barrier to developing energy efficient designs for a future warmer climate.

Build to perform

A 2013 CSIRO study found that houses with higher star ratings using more energy in summer.

One of the reasons is the trade-offs on the thermal performance of one building component against another in the Nationwide House Energy Rating Scheme (NatHERS) software. For example, a window without shading on the western façade is acceptable in a NatHERS simulation, whereas the same window would not be allowed if a glazing calculator developed by the National Construction Code were used to demonstrate the thermal performance of a house.

Other issues are trade workmanship, such whether a building is airtight. Airtightness in residential buildings is ignored in the national construction code. However, considerable energy savings can be achieved if a house can be made airtight.


Author provided

Similarly, missing or displaced insulation in the ceiling, as shown above, can cause significant discomfort and additional heating and cooling costs. We all, from builders to homeowners, need to understand insulation must be carefully installed and cannot be moved later, or even well designed buildings will become inefficient.

Windows are the main option for ventilating most houses. However, if you live in a high-pollution or noisy area, or in a place with very little wind, open windows might not be desirable or practical. Consequently, households may not be getting enough fresh air to maintain a healthy indoor environment. A mechanical ventilation system, which uses little energy, is an ideal alternative.




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The current weather files and heating thresholds used to develop minimum building standards are inadequate for our warming climate. Our report presents a framework for designing and building houses that consider climate change. We hope to see further research on other Australian population centres, so we can develop a comprehensive overview to help us build energy efficient and healthy houses for the future.The Conversation

Anir Kumar Upadhyay, Lecturer in Built Environment, UNSW; Chris Lockhart Smith, Director – ecodweller, UNSW, and Krishna Munsami, PhD student, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.