Is it possible to design a bushfire-proof house?
One part of the answer to designing a bushfire-proof house is an understanding of bushfire behaviour. A bushfire has five different elements which damage buildings: smoke, wind, embers, flames, and radiant heat – the latter two collectively called the “fire front”. Buildings play an essential role in increasing the chance of survival for people and their animals. Most homes in bushfire-prone areas are only built to the minimal code-compliance requirements. They are not designed with adequate bushfire resiliency strategies – to create defensible and robust structures, reduce risk and improve resistance to a bushfire event.
Just as importantly, the landscape plays an essential role during a bushfire, with the potential to affect the intensity and behaviour of fire. Climate and fire feed each other in a feedback loop which requires all of us to re-engage with the landscape, and to actively manage and maintain homes in bushfire prone settings.
While Australia has national standards for construction in bushfire-prone areas, it is important to remember these are the minimum requirements and provide overall guidance, not specific guidance tailored to your home and its unique circumstances.
Bushfire Design Principles
Bushfires affect buildings beyond the boundaries of a single land parcel. The surrounding land forms, wind directions, seasons, ecological communities and topography also affect the potential fire hazard.
Working in bushfire areas requires attention to some key principles to minimise risk:
Landscape
Landscape is the first line of defence and should be an integral part of designing for fire:
- Resist the urge to landscape adjacent to buildings. Create a landscape-free zone surrounding the building with fire-resistant materials such as gravel, paving or masonry that can be easily raked of leaves and debris
- Use paving materials which allow water to percolate back into the soil for moisture retention
- Moisture is held in the roots of plants and trees – tap into local plant knowledge to identify which plants are best at retaining moisture and resisting fire
- Careful orientation taking advantage of existing vegetation as wind breaks to protect from prevailing winds
- Manage existing vegetation – clear the understorey of trees, remove loose bark and utilise vegetation to block prevailing winds
- Collect water from roofs for both emergency services and regular usage in the garden.
Built Form
Understanding the building as part of a larger context helps to consider wind, heat, vegetation and other natural attributes. The goal is to create a building that is protected from hazards:
- Simplicity of built form and building geometry
- Earth and wind sheltered structures built low to the ground
- Stagger house positions to avoid house to house fire spread
- Use durable, low maintenance and non-combustible materials
- Use building, roof forms and materials to deflect winds and prevent ember attack
- Avoid roof attics and voids where embers can enter unseen
- Enclose sub-floors and line the underside of floors with non-combustible materials
- Have a static water supply for the exclusive use of fire fighting
- Protect glass and openings through screens and shutters
- Consider active systems such as sprinklers to complement passive strategies
Do not rely on a single strategy but incorporate redundancy.
Bushfire-proof house
The Eco House in Leura is located within a bushfire-prone area. Its design incorporates key principles for bushfire protection, including: locating the building to maximise protection from prevailing winds, non-combustible materials, minimal landscaping and an active roof-sprinkler system. The combination creates a robust building and does not rely on a single strategy for protection. The app-controlled roof sprinkler system ensures a level of ‘self-defence’ even when there are no people present.
Design Strategies
- Locating the building in a staggered position from neighbouring houses, preventing house to house spread of fire
- Multiple layers of fire defence, for example by both lining and enclosing the sub-floor
- Sprinkler system which doubles as a cooling system during summer heatwaves
- Simple roof form to deflect prevailing winds and re-capture water for continuous use of the sprinklers
- Dedicated rainwater tanks – a Static Water Supply for bushfire fighting
- Simple building form and durable, non-combustible materials
- No landscaping within at least 2m of the building
- Pervious paving for ground moisture retention
- Selected components of the building upgraded to BAL-40 standard for additional protection.
Lessons Learned
Knowledge of and attention to landscaping and ecological health are just as important as the design and construction of a bushfire-proof house.
Active systems, such as roof sprinklers, can be more effective and economical when designed to address multiple climate events, such as fire and heat.
Building form and material selections that are simple and robust remove the need for constant maintenance. A home that is low-energy and low-emissions is resilient to both climate and economic shocks.
An affordable house
The Eco-House Leura was built using a mixture prefabricated and standard construction components and materials. It was straight-forward to build and took only 6 months to complete. By not using complicated or unusual construction techniques we were able to save time and cost during the build.
All the materials for the build were locally sourced, minimising transportation costs and simplifying the construction process.
Passive solar design means the house is warm in winter and cool in summer without air conditioning. Rooftop solar provides the energy to power the house, and overall the yearly energy bills are 75% less than the average home in NSW.
The Eco-House Leura demonstrates it is possible to build a beautiful, sustainable and bushfire-proof house without having to compromise. The house is comfortable year-round, low maintenance and low-energy. The bushfire-proof design also provides peace of mind.
If you’re thinking of building in a bushfire-prone area, contact us to discuss your project.
Download the Design for Climate toolkit to learn more.
