October 27, 2015

Study turns the hose on sprinklers this bushfire season

The use of water sprinkler systems as a way of protecting homes in bushfire-prone areas is being put to the test.

The severity and frequency of bushfires is predicted to increase due to the changing climate and as urban expansion into the green fringes of Australian cities continues to put more buildings - and people - at risk.

For many people, readily available sprinkler systems are used as a primary defence against the threat of bushfires. Yet, little is known about how they fare against the heat and winds of bushfire conditions, and even less is known about how to design and install a system that provides a home with the most effective protection.

To find answers to both those questions, UOW PhD student and mechanical engineering graduate Alan Green is using high-speed cameras to measure the size and speed of water droplets from four common sprinkler heads used in bushfire water spray systems.

The study into sprinkler systems, the first of its kind in Australia, is part of the contribution the Sustainable Buildings Research Centre (SBRC) is making to develop bushfire-resilient homes.

The data will then be fed into computer simulations of bushfire conditions and the use of sprinklers as a defence to inform better building design specific to the home, where it is being built and the prevailing weather conditions.

“Bushfires cause many deaths and destroy a large number of houses in Australia and building resilience is an integral part of the adaptation that is required to mitigate this risk,” Alan said. “Many people think of water as a primary method of defence and there are certainly a wide range of building water spray systems on the market.

"Yet, some of these systems have never been validated to truly test their effectiveness and it’s difficult to find evidence-based justifications for their use.

"There is a danger that a homeowner could be lulled into a false sense of security, without really knowing how effective the sprinkler system will perform in high winds and temperatures.”

"People will continue to live in bushfire-prone areas so it’s important we have engineering solutions for the buildings they live in." - PhD student Alan Green.

Alan said the Australian Standard contained some guidelines but, if more scientific evidence were available, could potentially be made more helpful to building designers.

Following the 2009 Black Saturday bushfires in Victoria, which claimed 173 lives and destroyed more than 2,000 homes, the Bushfire Royal Commission recommended Standards Australia “expeditiously” develop a standard for bushfire sprinklers and sprayers.

“There’s been very little experimental work done on bushfire sprinklers before so this is one of the first in-depth experimental studies,” Alan said.

Tests in a controlled environment will be followed by full scale outdoor tests to validate and improve the accuracy of the computer model. The research will complement the ecological studies being done by Professor Ross Bradstock, Director of the Centre for Environmental Risk Management of Bushfires at UOW.

“The fire behaviour studies are helping us to understand the risk associated with building in bushfire-prone areas, and have shown that building resilience is important,” Alan said. “Ultimately, people will continue to live in these areas, it’s important to have engineering solutions for the buildings they live in.”

The study will allow engineers to compare water sprinklers against or in combination with other protection measures, such as observing the relevant building codes, using fire-resistant building materials as well as ensuring the property is well maintained and clear of combustible materials.

“It’s incredibly important that people don’t see a sprinkler system as the silver-bullet for protecting life and home,” Alan said. “They need to understand the limitations of defence systems such as sprinklers and the building materials they’ve used to get a complete picture of the risk they face, so they can make decisions based on that collective information.”

The project will be one of several initiatives on display at the second annual SBRC Open Day on Saturday November 14.