Bushfire Shelter and Earth Covered Homes: Earth Integration of buildings protects from Bushfire storms

David Baggs

The events of Black Saturday in February 2009 are tragic, almost mind numbing in their repercussions and human tragedy.  They remind us once more with graphic images and untold human and animal cost of the power of fire. To the writer, they are also extremely sad and frustrating. Following is an extract of an article written by the author in 1987 a few years after the Ash Wednesday fires, at a time my family and neighbours were experiencing the feelings and indeed the panic of impending bushfire.

Figure 1:  D. Baggs' family home Castle Hill in 2000: Street Frontage

baggs family home.pngIt was raining charred leaves, bark, and ash. Strong winds were bringing the smell of fires kilometres away right to our front door. The radio told us that another fire had started. This one however is at the bottom of the valley.

Seventy homes were being evacuated. For the moment, the winds were blowing down the valley and away from us. Our neighbours sat on their third floor balcony with binoculars, looking for the tell-tale smoke plume that would tell them the fires had 'spotted'  into the valley below us. Fortunately, none forms that day, and a change in the weather provided a welcome reprieve, for the time being, for our valley at least. Many others had not been so lucky.

Backing onto beautiful remnant Sydney Hills District Forest in the Excelsior Reserve and Darling Mills State Forest was a wonderful environment to live and raise a family. However, for the third time in seven years, the home had just avoided being in a bushfire. This time was by far the worst prospect, as the rest of the world knows, with the worst fires in the history of New South Wales, several of the closest raging within four to ten kilometres of our home.

Having spent the afternoon cleaning the leaves out of the gutters of the home of one of my neighbours, and watering the roof and garden of one of the other neighbours who was on holidays, I did spend a little time trimming the garden and overhanging branches. But for the most part I was confident, that if a fire came, the house would survive intact, our children were also calm and relaxed.

baggs2.pngFigure 2: Excelsior Reserve bush frontage

But it was not always so. On the first occasion some years earlier, when the house had been unexpectedly enveloped with smoke quickly filling the street to the point the sun became a dull glow in the west. We had no idea where the smoke was coming from, it seemed a fire-front was imminent and the children became very distressed. My wife of the time was in a real panic as she had just driven home through the almost impenetrable smoke that filled the street.

I hurried them all inside and in calming them down, there was great deal of comfort and satisfaction in my being able to say to them, 'there's no need to be afraid. You're inside now, you're safe - you live in one of the safest houses in the world.'

baggs interior.pngFigure 3:  Interior of Lounge Room overlooking Excelsior Reserve

It had a remarkable effect on them to hear that, and it had a great effect on me, to be able to say it. This sense of security was also shared by my sister and her family when they came to shelter from the fires near her house on the northern peninsula of Sydney.

So, why the supreme confidence? Well, it comes from the strategies employed in the design, specification and construction of the earth covered home, and from the experience of others in the 1983 Ash Wednesday Fires in South Australia.

The facts were, the home was an earth covered, concrete home backed into a sloping site and backfilled with earth behind and over the roof, with radiation shutters on every window, a separate underground air supply and no exposed combustible materials.

Would such a home have survived in the incredible conditions of Black Saturday or future, similar conflagration?

Based on historical precedent, yes it would have. The concrete structure elimination of combustible materials from the outside of the home, protection of all glazed areas from radiation and solid, protected, windowless underground spaces in some of the rear, earth contact areas of the home would have increased dramatically the safety of occupants and likelihood of survival. There is no question the home would have survived. The certainty is as a result of historical facts.

Such a home did survive the worst of the Ash Wednesday fires at "Eagle-on-the-Hill" in the Adelaide Hills. Everything around the home, including the neighbours' houses, had been burnt to the ground - yet the earth-covered home survived with nothing but a cracked window. The windows had not been protected in any way, yet because of the "mass" nature of the home, and the enveloping soil, it survived.

Yet when the bushfire code was rewritten thereafter, the best possible housing typology they could imagine and managed to give credit for was a double brick home- so where is the incentive to try to do better???

The authorities need to look more deeply at the options and consider better solutions - be creative and allow for innovation and recognition that there are better, safer options in earth integration and reflective radiation protection. It may well be that additional supplies of bottled air might be required. But one thing is for sure - it is hard to imagine living in bushland in anything but an earth covered, fire-protected building and from personal experience - the feeling of safety and the reality of the security this provides - is priceless.

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Figure 4: Wildfire Safety Bunkers - over 40,000 installations throughout Australia. Source: http://www.wildfiresafetybunkers.com.au/ accessed 22/5/12

During the Black Saturday fires, a number of people were saved in underground bunkers and some were killed due to the inadequacy of the bunker and their preparation. Earth covering can save lives, but adequate research, careful design, detailing, construction and preparation are required to ensure protection is successful. A number of specialist companies manufacture prefabricated bunkers with one, claiming to have installed over 40,000.

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Figure 5: Wildfire Safety Bunkers -. Source: www.wildfiresafetybunkers.com.au

As at January 2011, the Australian Building Codes board has developed both a draft Standard for Private Bunkers and a Regulatory Impact Statement to support an imminent decision relating to possible inclusion in the Building Code of Australia as the Board considers a range of options to include a code for bunkers in the BCA. (see www.abcb.gov.au).

An extract from the foreword of the Standard by the ABCB states:

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The obvious question is - why bother building both a house (that will burn down) and a 'shelter'? Why not consider an alternative… build your house as a shelter using earth to shelter from the fire storm. To achieve this one would incorporate a fully sealed shelter section within the home, with compressed air supply combined with carbon scrubbing cartridge air filters (ref BCA Standard) at the rear wall of the house where radiation is minimized. It would require its own lighting and emergency power source and numerous other safety items and features, but it is entirely feasible. A storeroom or utility room that does not normally require daylight could easily be adapted at design stage.

This way, any family could live daily with the comfortable modified temperatures, quiet ambient environment and solid, stable investment., but more importantly, the security and peace of mind about the family's safety and security.

Download the full Draft Standard.

David Baggs CEO of ecospecifier is a multi award winning architect who now consults to designers and architects on the design and construction of earth covered buildings having designed and built over 40 such structures including a school, museum and many homes. He is also co-author of the book Australian Earth Covered Buildings first published in 1985, republished in 1992 and fully updated and upgraded in 2009 to include Green roofs. Australian Earth Covered and Green Roof Buildings is now a searchable pdf book in DVD format. Download your order form here.