Protecting buildings during wildfires

The early bushfire season in Australia has brought heart-breaking stories of loss – of human and animal life, and of houses and other structures.

Uncontrollable fires have also been a destructive feature of summers in North America and Europe in recent years, with attendant loss of life and buildings.

With the climate crisis expected to increase the frequency and ferocity of such events, what more, if anything, can be done to keep from harm homes and buildings in the path of a wildfire?

In a study just published in Frontiers in Mechanical Engineering, American researchers reveal their work to scientifically assess the use of fire-protective blankets to protect buildings from fire.

“The whole-house fire blanket is a viable method of protection against fires at the wildland-urban interface,” says lead author Fumiaki Takahashi, from Case Western Reserve University, in Ohio, USA.

“Current technology can protect an isolated structure against a relatively short wildfire attack and further technological developments are likely to enable this method to be applied to severe situations.”

The work was motivated by people living and working in fire-risk areas who contacted Takahashi to find out if commercial products were available to help reduce the likelihood of built structures catching fire and improve public and firefighter safety.

In their initial investigations, the research team learned that the concept of whole-structure fire blankets isn’t new.

“I … found a US patent ‘conflagration-retardative curtain’ – a fire blanket – issued during World War Two,” says Takahashi.

“In addition, the US Forest Service firefighters managed to save a historic forest cabin by wrapping it with their fire shelter materials.”

There were other anecdotal reports of fire blankets protecting buildings from fires, but a marked lack of scientific evidence to back up these claims.

To rectify this, the research team conducted several experiments to test the ability of different blanket materials to shield structures against fires of increasing magnitude.

They tested four types of fabrics: aramid, fiberglass, amorphous silica, and pre-oxidized carbon, each with and without an aluminium surface.

Direct fire exposure tests determined how well the fire blankets protected wooden structures of various shapes and sizes, from a birdhouse in a burning room to a full-size shed in a real forest fire.

Laboratory experiments used controlled heat exposure and measured the heat-insulation capabilities of the four fabric types against both direct flame contact and radiation heat.

The laboratory and real-fire assessments demonstrated that fire blankets could protect structures from a short exposure to a wildfire, but also highlighted their technical limitations.

“The fiberglass or amorphous silica fabrics laminated with aluminium foil performed best, due to high reflection/emission of radiation and good thermal insulation by the fabric,” says Takahashi.

“New technology is needed to enhance the fire blankets’ heat-blocking capability for an extended period to prevent structure-to-structure ignition.”

He says that such advanced fire blankets will be more effective if dozens or hundreds of homes are protected at the same time, particularly in areas of high housing density areas that fringe bushlands.

Takahashi’s conclusions suggest it will take a lot of will and work to turn whole-building fire blankets into a reality, and that this presents entrepreneurs and investors with business opportunities.

“The implication of the present findings,” he says, “is that the technical community, the general public, and the fire service must work together to take a step-by-step approach toward the successful application of this technology.”