Bush Fire Resistant Houses.
In november 2015 Baldwin O'Bryan Architects won the The Bushfire Building Council of Australia's Innovation Award for the best design concept.
In november 2015 Baldwin O'Bryan Architects won the The Bushfire Building Council of Australia's Innovation Award for the best design concept.
The obvious reason that earth sheltered buildings have such an advantage in bushfires is because the surrounding soil can provide a massive buffer to direct contact from flames and it can also insulate the interior against the extreme radiant temperatures experienced in bushfires.
Earth sheltered building generally have an entirely reinforced concrete structure which is unlikely to be damaged in a fire even without the massive enclosing earth walls. We have recently developed a low cost building system based around stabilised compressed earth blocks which is equally fire resistant.
However, most people would know that 90% of house loss in severe bushfires is actually caused by ember attack from distant fires rather than the fire front itself.
Earth sheltered building do not have the same entry points for ember attack as most conventional houses . There are no eaves, gutters, valleys, ridges or gables and embers cannot enter under gaps in roof tiles or sheet metal and perhaps most importantly there are no roof cavities.
Flame and embers can’t enter underneath the building which was identified as major cause of destruction in the recent Wye River Fires.
Even though it is a very unusual building type, there are quite a few reports of the resilience of earth sheltered buildings in bushfires.
These include several houses which were undamaged in both the Ash Wednesday and the Black Saturday Fires - All in communities where everything else around them was completely destroyed.
For various reasons and mainly to minimise the cost of retaining walls, earth sheltered buildings are generally designed with their openings concentrated in one or two zones.
This makes it easier to cover all the potential ignition points with either FZ fire rated panels or roller shutters. Of course the size of openings can be considerably reduced if bushfire resistance is the main priority.
The Newee Creek House shown above is on top of a ridge in a heavily forested high fire-prone area inland from Nambucca heads. This design won the Bushfire Building Council of Australia’s award for best design Concept.
It has is a minimum of 1500 deep earth cover on the roof and the earth mounds on the sides of the building are eight meters wide at the base of the building.
The buttress walls coming out perpendicular from the east and west facades were designed to partially shield the front and rear courtyards.
The walls surrounding the front and rear openings which face onto heavily vegetated bushland are 200mm thick reinforced concrete and all the openings are protected by FZ Shutters.
Properly designed Earth sheltered buildings can be very cost competitive against conventional buildings mainly because external finishes are minimised.
We believe that it is possible to design earth sheltered buildings that would survive even the very worst bush fires undamaged and we are hoping this technique can have a much larger role in improving the ability of buildings to better withstand bushfire attack.
There is always a competing interest between preserving natural bushland and the need for new buildings - which unfortunately often requires so much bushland to be destroyed for fire safety reasons.
It is in everybody’s interest to minimise the depletion of our beautiful native flora and fauna - and we hoping that the technique of Earth Sheltering could eventually contribute to moving the needle on this environmental dilemma - particularly for sensitive bush fire prone regions such as the blue mountains and on the edges of larger urban areas.
The construction system based on compressed earth blocks is the most economical system for bushfire resistant houses. It is highly sustainable and roughly 40% of the cost of reinforced concrete and it is considerably less expensive than most conventional building systems.
The system has exceptional bushfire resistance with just normal glazing as shown in the graphic above. This is mainly because there are no entry points for an ember attack- which is by far the most common cause of building destruction in bushfires.
However the the second more robust facade shown in the two graphics below is a relatively low cost adjustment and it can meet the requirements of the highest bush fire attack level in Australia which is called Flame Zone (FZ). The facade has magnesium oxide panels surrounding the glazing and a mechanised Fibre-shield fire curtain to cover the glazing in a bushfire event.
The system has exceptional bushfire resistance with just normal glazing as shown in the graphic above. This is mainly because there are no entry points for an ember attack- which is by far the most common cause of building destruction in bushfires.
However the the second more robust facade shown in the two graphics below is a relatively low cost adjustment and it can meet the requirements of the highest bush fire attack level in Australia which is called Flame Zone (FZ). The facade has magnesium oxide panels surrounding the glazing and a mechanised Fibre-shield fire curtain to cover the glazing in a bushfire event.
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