In the forest fires in parts of southern Australia, dozens of houses and ancillary buildings were destroyed, reminding us once again how uncomfortable we are in the landscape of jungle fires. With 15 years of experience in designing and planning to mitigate the risk of forest fires, I found that the two main obstacles to affordable forest fire response housing are: incorrect information about construction costs in jungle fire-prone areas
It is difficult to provide an overall design approach that integrates buildings and their landscape into a risk mitigation/residence environment.
Error message about cost
More and more people believe that the construction of Australian Building Standards (AS 3959:2009) in areas with bush fires is unaffordable.
This can be attributed to the construction cost premium published in the six forest fire occurrence levels (BAL) outlined in AS 3959, from BAL-Low, BAL-12.5, BAL-19, BAL-29, BAL-40 to BAL-FZ . (flame area). The source of these costing calculations is the Australian Building Code Committee’s regulatory impact statement for AS 3959:2009. This cost matrix has been displayed on state and local government websites in Australian states, such as the Swan City of Western Australia, which makes the standard cost of additional “Australian Homes” of up to $20,885. These premiums stem from simple calculations, such as the upgrade of a fiberglass flying curtain net to a stainless steel ember net, or the replacement of float glass to a tempered safety glass. The problem with this costing approach is that it is assumed to be a given common base house style, such as a windshield structure and a high lightweight structure. Then replace or add elements, such as adding forest fire shutters to traditional windows.
This is a very basic costing exercise that uses a common family type and then replaces the elements, ignoring the factors that contribute significantly to cost when building a jungle fire-prone area. The biggest factor that usually causes cost is not the forest fire standard, but the national energy rating requirement. This is because the forest fires are very cold in winter and very hot in summer. In these climatic areas, you need a building with quality – such as masonry – and an open building with enough glass windows to capture the winter sun and natural cross-ventilated openings.
Constraints on integrated design
Good design is about cross-cutting – more at a lower cost. Therefore, what designers should look for here is the opportunity to integrate topography, thermal mass, radiant heat protection, insect control, flame contact, thermal comfort, shading, field access and escape into other overall aspects. A very practical example of this design approach is to eliminate the balcony cliffs and eaves – a proven weak link in forest fires – and replace them with perforated metal telescopic blinds on the windows.
These blinds then control the sun, insects, glare and wind, as well as embers and radiant heat. Our research has found that this can result in significant cost savings, but it is important that forest fire risk mitigation equipment is used daily rather than in emergency situations. That is to say, it is integrated into the daily life of the family – it is not a rarely used add-on.
Standards and planning
Further impeding the integrated design approach is the disconnect between AS 3959 and our state and local government’s site planning regulations for forest fires. For example, AS 3959 does not specify a residential escape route. Even more worrisome is that unless the site is officially declared as the designated forest fire-prone area for the first time, it is usually not necessary to apply this building standard. Western Australia is about to announce all areas about 100 hectares from the jungle, as forest fires are prone to occur.
Once announced, it is almost impossible to apply standards to existing homes through retrofitting. So we can have a situation that is not uncommon now, a well-designed jungle fire response house with a neighboring house with a flammable timber bungalow.
Security is still a mystery
Perhaps the biggest limitation to the integrated design approach is that the fire authorities and local governments across the country remain silent to support the two highest levels of forest fire design BAL-40 and BAL-FZ. The idea here is that for homeowners, building these levels creates a false sense of security that puts them at an unexpectedly high level of danger. The reality is that each BAL level represents the same risk level – the lower the BAL, the greater the distance between the home and the vegetation that is prone to forest fires. The higher the BAL, the closer the vegetation is to the residence. However, agencies are encouraged to build traditional homes with low to medium BAL levels – no higher than BAL-29 – and then expect homeowners to actively manage vegetation hazards. The problem we see in every fire season is that although there are many warnings every year for owners to prepare for forest fires, these measures are often not implemented.
For firefighting authorities, the promotion of this approach is somewhat contradictory, as the first principle of risk mitigation is to prioritize passive protection (such as establishing better forest fire protection) rather than proactive measures (maintaining harmful vegetation removal). The landscape is highly dynamic and reliable compared to permanent architectural features. The silence of agencies to promote better design reflects the misunderstanding of the cost of implementing building standards and the potential risk mitigation principles. The integrated approach emphasizes active vegetation management, which can be practically implemented and builds design solutions to address many aspects associated with living in forest fire-prone areas. Only then will we begin to see a reduction in the number of homes and properties when a forest fire strikes again.
Https://theconversation.com/we-can-build-homes-to-survive-bushfires-so-why-dont-we-35899