Damage analysis of 2017-2018 wildfires shows importance of mitigation

PARADISE, Calif., July 13, 2020 /PRNewswire/ -- Surveying the devastation in Paradise following the 2018 Camp Fire, the deadliest and most costly on record in the State of California, and data from six other California wildfire events in 2017-2018, researchers from the Insurance Institute for Business & Home Safety (IBHS) identified key factors influencing the survivability of structures during a wildfire. Released today, a summary of the IBHS Post Event Investigation: California Wildfires of 2017 and 2018 offers a new, more nuanced look at wildfire mitigation effectiveness.

Following the 2017-2018 wildfires, scientists matched Camp Fire field observations, along with those from other events, including the Tubbs, Woolsey and Carr Fires, to those seen during lab testing at the IBHS Research Center to further validate likely home ignition scenarios. Key findings and conclusions include:

• Mitigation is critical to give a home or commercial building a chance against wildfire but no guarantee of survivability.
• Mitigation efforts are most effective when building design, materials and surrounding defensible space are all addressed.
• Defensible space was an important characteristic of homes that survived the Camp Fire.
• Evidence of structure-to-structure fire spread was observed due to closely spaced homes.
• Firefighter intervention remains critical to saving structures, but that need can be reduced with effective mitigation.

While wildfires can ignite homes and businesses through direct flame contact, radiant heat exposure or wind-borne embers, the embers are the most serious threat and account for up to 90 percent of home ignitions. Although there is no guarantee that a home, commercial building or other structure will survive, ensuring those burning particles have nothing combustible to land on is key.

"Wildfires are influenced by available fuels, topography and weather conditions. Home and business owners can't change topography or weather, but they can reduce available fuels on and around their structures through creating and maintaining a five-foot noncombustible zone and selecting noncombustible building components," said Daniel Gorham, research engineer at IBHS.

Emphasizing the need to consider both building materials and defensible space, engaging in multiple mitigation steps to most effectively reduce wildfire risk, Gorham added, "Defensible space was an important characteristic of homes that survived the Camp Fire. However, rapid fire spread can breach even well-maintained defensible space, so it must be a multi-faceted approach for the best protection."

"Analyzing the damage in Paradise, along with data collected after other fires in 2017 and 2018, found no single repeatable absolute correlation between damage level and individual building features, such as roofing or siding materials. Vegetative clearance and topography had greater influence on damage level relative to building features, affecting thermal exposure to buildings during an event," said IBHS research engineer, Dr. Faraz Hedayati. "Firefighter intervention was critical in saving structures; yet the need for intervention, which is not likely in all scenarios, may be avoided with effective mitigation that resists ignition."

"While there is no guarantee, and with added uncertainly this year about the availability of firefighters due to the global pandemic, we urge home and business owners to make these critical improvements to their homes and commercial buildings to give them the best possible chance to resist embers," Hedayati added.

IBHS recommends starting with the following steps to reduce wildfire risk:

1. Build defensible space on your property, starting with a 5-foot noncombustible zone around your home or business.  
2. Ensure your roof has a Class A fire rating and do not allow debris to accumulate on it.
3. Remove debris and other combustibles on, around, and under your deck.
4. Create 6-inches of vertical clearance between the ground and noncombustible siding.
5. Install 1/8-inch metal mesh screening over vents (gable, soffit, and foundation).

For more information on these and other actions to take around homes and businesses, visit disastersafety.org/wildfire.

About the Insurance Institute for Business & Home Safety (IBHS) 

The IBHS mission is to conduct objective, scientific research to identify and promote effective actions that strengthen homes, businesses and communities against natural disasters and other causes of loss. Learn more about IBHS at DisasterSafety.org.

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SOURCE Insurance Institute for Business & Home Safety (IBHS)