Buildings and bushfires (1989)
Many people believe bushfires create such an enormous amount of heat that, when surrounded by a bushfire, their houses may just explode in flames.
But researchers from CSIRO have found no evidence to support this popular myth. They have found, instead, that most houses catch alight in three ways: by direct flame contact, by radiant heat, and more importantly, by embers and combustible debris blown by the wind.
The outcome of their research has been a set of basic design principles for houses built in bushfire-prone areas.
[Image of a glowing sun with black smoke moving across it appears on screen]
Male: Almost the whole town has been wiped out by fire. [Image changes to show bushland and houses on fire]
Male: Every house in the area was burnt to the ground.
Male: And as late as midnight houses were suddenly bursting into flames.
Male: The fire just ripped through these houses.
[Image has changed to Dr Ramsay and researcher working in fire laboratory]
Dr Ramsay: The obstruction we constantly come against is this concept of the houses just spontaneously exploding due to the heat of the fire front. We just haven’t found any evidence to support that idea.
[Text appears: The Researchers]
[Image changes to show two men sunbaking, one is reading a newspaper and then to people engaged in different outdoor activities including cricket and windsurfing]
Narrator: In Australia sun worship is almost a national religion. The summer brings with it the promise of warmth, health and relaxation but who will ever forget the consequences of one searing hot summer a few years ago.
[Image changes to show bushland on fire]
Male: One minute it was just a tiny outbreak in a hill behind the town. The next it was searing down, engulfing everything in its path.
Male: In the summers following people looked to the skies with fear. It was Ash Wednesday.
[Image changes to show bushland and properties blackened by fire and still smouldering]
Narrator: Even as the embers of Ash Wednesday were cooling a wide range of people were on the scene of the devastation, house owners, clean-up teams, insurance assessors and researchers from CSIRO.
[Image changes to show Dr Ramsay and a colleague kneeling by a destroyed house and assessing the damage]
Male: The veranda post is still there though.
Dr Ramsay: Yeah.
Narrator: Dr Caird Ramsay and his team worked 12 hours a day, seven days a week to survey 1,150 of the houses involved. They made some surprising observations. [Image changes back to Dr Ramsay]
Dr Ramsay: You had one house virtually untouched and next to it on a similar block you had a house of apparently similar design and construction that was completely destroyed and the question why immediately comes to mind.
[Image has changed to show the burnt out remains of properties, the camera then pans over to property that was not affected by fire and remains fully intact]
Narrator: So began a project to find out why buildings catch alight and what factors contribute to their survival or demise. The evidence they collected gave a completely new picture of the way in which houses ignite and then burn down.
[Image changes to show Dr Ramsay and two colleagues reviewing and discussing photos and documents laid out on a table]
Dr Ramsay: The whole house was obviously ablaze.
Narrator: But any new theory would face tough opposition.
Dr Ramsay: Well I think when people think about bushfires and their houses they believe that the bushfire is going to create such an enormous amount of heat that their houses are just going to explode in flames.
[Image changes to show a house and small fire starting in a stack of firewood that’s piled up beside the house]
Narrator: There’s just no evidence to support this popular myth. What the researchers found instead was that houses catch alight in three ways, by direct flame contact, by radiant heat and most importantly, by embers and combustible debris blown by the wind.
[An animation of the three contributing factors plays]
These embers are by far the most common cause of house fires. At a recent demonstration Dr Ramsay and his colleagues showed just how this can happen. Burning embers ignite small fires and these gradually progress until the whole house is involved.
[Image changes to show researchers starting small fires in different spots around a weatherboard house and then changes to show the house fully engulfed in flames]
The outcome of the CSIRO research has been a set of basic principles for houses built in bushfire prone areas.
[Image has changed to show Dr Ramsay walking with a clipboard in his hands, around a house that features the principles discussed]
Houses should be designed to resist the onslaught of embers and flying debris, a simple roof shape with leafless gutters, window protection, enclosed underfloor space and no timber at ground level. But houses like this are the exception rather than the rule as Dr Ramsay has found when he visits fire prone areas.
[The camera pans over newly constructed houses and Dr Ramsay walking around inspecting them]
Dr Ramsay: Well the first reaction of course is despair when one sees that virtually every house has been built without any attention to the principles that we try and get across to people. We would believe that that indicates that the majority of people don’t take bushfires into consideration when they are designing and building their houses.
Narrator: In order to combat this combination of disbelief and apathy Dr Ramsay has made a video in conjunction with Melbourne University.
[Sections of the video Dr Ramsay has made play]
It explains the realities of bushfires, the principles of good house design for fire prone areas and how to survive in your house during a bushfire.
[Image has changed back to show Dr Ramsay and two colleagues reviewing and discussing photos and documents laid out on a table]
It’s based on CSIRO’s survey findings and years of exhaustive research and it’s already made inroads into the ignorance and mythology surrounding the threat of bushfires.
[Image has changed back to Dr Ramsay]
Dr Ramsay: Well we need to get the message across to people who don’t believe that there is anything that they can do in the face of a bushfire. We need to get them to understand that there are many things which they can do in building a new house or improving their existing house, even small things which will greatly improve the chances of survival of their houses during a bushfire.
[Text appears: For enquiries about the video CSIRO or Video Education Australasia. Tel: (054) 724799]
[Music plays and the CSIRO logo appears]