How to build bushfire-resilient communities for a changing climate
Designing bushfire-resilient housing is essential for the survival of homes and communities as we see increasing catastrophic weather events.
Overwhelming evidence now shows that climate change is causing a rise in temperatures globally. It’s also a major factor in the increasing number of extreme weather events such as bushfires. Drought, very dry fuels and heat are all aggravated by climate change, according to the Climate Council.
To understand the growing risk to communities, you only need to consider how many Australians live in urban areas surrounded by vegetation. The growing frequency of bushfires means they are more likely to lose their homes and livelihoods if buildings are not able to resist fire and heat.
So what’s the answer? Designing communities that are bush-fire resilient. Climate-conscious urban design encapsulates everything from fireproof material and safety zones to an understanding of how firebrands (embers) behave. Master those things, and you will be able to help save homes and lives.
Australian bushfires destroy communities
Memories of devastating bushfires are fresh in our minds. The 2019/2020 bushfire season was one of the worst in recent times with 17 million hectares burned in New South Wales, Victoria, Western Australia, South Australia and the Australian Capital Territory. Tragically, 33 people died and 3,094 houses were lost, 2,439 of those in New South Wales.
Disasters such as these are creating a growing economic toll, currently $38 billion a year on average, according to the National Emergency Management Agency (NEMA). Even with lower emissions, this figure is likely to reach $73 billion by 2060, it says.
We need to act. With a growing population putting a further squeeze on housing, that means thinking about how we design homes and communities. According to the Bushfire Building Council of Australia, 2.5 million of us live in high bushfire risk regions and 90 per cent of the buildings within them are not resilient. Human cost aside, this equates to $1 trillion worth of property at risk.
Bushfires and climate change
As we face global climate change, the University of Melbourne is acting to ensure that professionals are equipped with essential skills to assess and design fire-resilient properties.
Developed in consultation with Fire Protection Association Australia (FPA),The University now offers an online course in bushfire assessment that help learners work toward bushfire planning and design accreditation.
Long-term global warming is now 1 degree Celsius above pre-industrial levels, according to the Climate Council. It reports that nine of Australia’s top 10 warmest days on record have occurred since 2005, and that three of the four mega fire years – when more than 1 million hectares burns – have occurred since 2000.
Research by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) has also found that climate change is not only a major factor behind the greater number of bushfires, but also the main reason we’re seeing an increase in the size of bushfires, with the average area burned growing by 800 per cent in the past 32 years.
Another concerning finding is a lengthening of the fire season towards what were historically cooler months. A rise in fire activity in alpine forest in Tasmania and tropical rainforests in Queensland has also been documented.
While bad news on the climate front seems to just keep coming, building sustainable housing that is better able to withstand the impacts of climate change is a significant way to reduce the effects of catastrophic conditions.
What is a bushfire and how does it interact with buildings?
A bushfire is a wildland fire that burns through wild vegetation and has the potential to destroy homes and communities. Leaf litter, small branches and twigs, grass and shrubs, especially if they are very dry from heat and drought, can all provide fuel.
Dr Alex Filkov, Senior Fire Behaviour Research Fellow at the University of Melbourne, collaborates with researchers around the globe to understand bushfire mechanisms.
These include the behaviour of firebrands, the performance of structural materials and the properties of wildland fuels. He also studies how wildland fires become disastrous fire events in wildland urban interface (WUI) – where vegetation meets urban development.
Understanding how bushfires behave and interact with buildings is essential if we are to design buildings that will withstand the onslaught of extreme weather events, he says.
“Australian Standard 3959 prescribes what materials should be used in bushfire prone areas. But in recent bushfires we have still had houses lost. That tells us the protection levels are not perfect and we need to further develop bushfire-resilient design principles.”
Preventing fires from destroying homes once a bushfire has started is challenging because of the ability of firebrands or embers to spread kilometres, he says. These enter homes through eaves, gutters, vents or valleys in the building construction or accumulate on or around homes.
While flame itself obviously poses danger to both people and surrounds, radiant heat and heavy smoke can also cause serious damage. Radiant heat can be felt 10 metres away from a bushfire and has the potential to ignite structures as well as make conditions inside the home unbearable for occupants.
Smoke and the toxic fumes produced by bushfires can also impair vision and cause breathing difficulties, according to a risk framework research team of which Professor Trent Penman, a bushfire behaviour expert at the University of Melbourne Is a member.
What causes bushfires and how we can make buildings more resilient?
Bushfires can start from natural causes, such as lightning, or by people by accident or on purpose. “Radiant and convective heat, in addition to firebrands, is also a factor,” says Dr Filkov.
Both radiant and convective heat have the potential to pre-heat and dry out fuels such as garden vegetation or cladding making these easier to burn. While convection requires the flame to be in contact with a building to ignite, ignition by radiation can occur at a distance greater than that to which the flames extend.
While you may be able to protect your home relatively well from heat dangers if you minimise easy burning fuels around home, firebrands pose substantial danger. Generated by burning vegetation or buildings, they can land on structures from kilometres away.
A major challenge to saving homes from bushfires is that existing building standards do not take firebrands directly into account. “Houses inside the community, as opposed to those in obvious risk zones, are also built to lower bushfire resilient standards so once firebrands ignite fuel inside the community, house to house propagation of the fire is relatively easy,” says Dr Filkov.
A new climate-aware approach focuses on designing communities that are bushfire-resilient and can survive a bushfire event without defending them. “That means considering how we design every element of the community and layer of a home,” says Dr Filkov. “Instead of relying on quick fixes such as expanding fuel breaks or increasing the number of prescribed burns our approach should be strategic.”
To make buildings more resilient, some suggestions include:
Reinforced concrete for floor slabs and pilings
Shutters made of fireproof sheeting over glass surfaces
Fireproof insulation such as mineral wool or fibreglass
Corrugated sheeting for roofs, that can eliminate the need for gutters that collect combustible materials and catch embers
Bi-fold mesh screens around balconies that can be opened or closed to reduce heat load during a bushfire
More robust standards than prescribed for external walls facing each other.
Fire-resilient infrastructure that is affordable and sustainable
The technology to build fire-resilient infrastructure exists, but how can we make it more sustainable and cost effective?
Some sustainable, fire-resistant features you could consider include:
Materials such as stabilised compressed earth blocks that are cheaper than reinforced concrete. An ancient form of construction that is coming back in fashion because of affordability and climate challenges, they are eco efficient, sustainable and non-combustible, according to international research.
Metal shutters for windows that not only keep heat and flames out but give additional thermal mass for cooler seasons and reduce unwanted solar heat gain when it’s hot. The CSIRO’s Bushfire best practice guide suggests non-combustible shutters will also protect against embers and strikes from flying objects.
Rainwater tanks or water retention ponds that reduce water bills and feed a fire-fighting sprinkler system. You will need a non-combustible metal tank and pipe fittings rather than Polyvinyl chloride (PVC) and a diesel or petrol-driven pump in case electricity supply goes down. A minimum of 10,000 litres should be available for firefighting purposes.
Remember that even higher initial costs for fire-resilient infrastructure will ultimately prove to be more cost-effective in the long run. Houses that can experience bushfires without too much damage bounce back quickly after extreme weather events.
Building a better world
As climate change continues to escalate, old models of practice for infrastructure, agriculture and business no longer guarantee successful outcomes or even survival.
With record temperatures, more frequent droughts and rising sea levels, a rethink of how we obtain and use resources as well as evolve systems and supply chains within a fast-changing environment is necessary.
Communities and future generations need professionals at the forefront of trades and industry as well as services to play a crucial part in creating a safer, more eco-conscious world.
Want to help build a better future? Learn more about our Assessment of Bushfire Exposure micro-credential.