The May 2010 Australian Nanotechnology Alliance Newsletter presents the results of testing on houses built almost entirely of steel that have been subjected to a range of bushfire conditions. Read on:
“CSIRO scientists have \’flame-tested’ a steel-framed house near Mogo on the NSW south coast to see how the structure withstands realistic bushfire conditions. Constructed almost entirely from steel and featuring a non-flammable roof cavity, the house may provide a straightforward and affordable building option for bushfire-prone areas.
CSIRO bushfire researcher Justin Leonard says experienced fire researchers consider that a house constructed predominantly of steel should be able to survive in the flame zone of a real bushfire, assuming that windows or other external openings have not been breached. The concept is that the entire non-combustible building faade, insulation and frame acts to protect the habitable space.
A range of bushfire conditions were used in the test, from ember attacks to engulfing the structure in flames.
“The flame-test will also provide information for building policies relating to bushfire areas by providing supporting evidence for use by building authorities across Australia,” says Mr Leonard.
The test house is a small low-rise building approximately 8m x 4m x 5m high and includes most of the features of a domestic house. It consists of an elevated steel framed floor, steel wall framing with steel cladding and plasterboard lining and a steel truss roof with steel roof sheeting and a plasterboard ceiling. The house includes steel fascia and various soffit linings. The side that will face the fire front has two windows and a door.
New building codes, introduced after the Royal Commission following the Victorian bushfires in February 2009, specify that: “A building that is constructed in a designated bushfire prone area must be designed and constructed to reduce the risk of ignition from a bushfire while the fire front passes.”
“This means that the building needs to be resistant enough to protect life and minimise the loss of the building,” says Mr Leonard said. “This test house has been designed to meet this requirement and the trial burn will test how it shapes up against the performance requirements of the new building codes.”
The test was staged at the Eurobodalla Rural Fire Service Training Facility near Mogo in NSW the only facility in Australia with a bushfire flame front simulator that enables testing of different materials in the open under realistic bushfire conditions.
Bushfire researchers from CSIRO and the Bushfire CRC observed the house burnover from a safety area where they can monitor live feeds of data from numerous sensors and heat measuring devices embedded in the house fame.
The “home” was constructed in two weeks in March, almost entirely of Colorbond steel and contained materials that are affordable for the average Australian homebuyer. Data gathering instruments were placed throughout the interior of the building, to analyse the performance of the materials. The building received a mixed score card after the event.
“The floors and roof performed well but, with the walling system, we have a bit of work to do,” says Mr Leonard.
“What we were doing was trying to isolate certain parts of the house to see how they performed. We could have used the most expensive doors and windows, but we wanted to test the affordable options. Had the windows and doors held, there is every chance that the occupants could have survived.”