‘It’s Closing In On Us’: Wildfire Experts Push For Buildings Designed Against Encroaching Flames
Increasing devastation caused by wildfires in the Western U.S. and around the world has prompted calls for the hardening of structures to make them more resilient against fires.
In 2020, 4.4 million acres burned in California, and 10.2 million acres burned in the Western U.S., destroying 14,000 buildings and costing the economy about $20B, Feldman Architecture partner Chris Kurrle said during a Designing for Wildfire Resilience webinar on March 30 hosted by AIA San Francisco and the Center for Architecture + Design.
Following one of Feldman Architecture’s Bay Area projects being impacted by the Glass Fire that Cal FIRE data showed destroyed 1,555 residential and commercial structures in Napa and Sonoma counties last September, Kurrle floated the idea of convening a panel of experts to discuss strategies to protect the built environment from the conflagrations.
Among others, he was joined by Cello & Maudru Construction President Michael Cello, a Bay Area general contractor who said his company had to start considering the schedule of construction activities, as having exposed wood frames and sheeting during the height of fire season can pose even more significant risks.
“We are in a new reality,” Kurrle said during the webinar. “As the climate seems to be getting dryer — this year, another year case in point — we have about a century of combustible material that's been stored in our landscapes as we've tried to manage forest fires, and we as a society continue to grow and develop in these fire-prone areas.”
As development expands into forested areas and climate change leads to drier, windier conditions, the perfect storm takes shape, threatening the built environment and human life.
“Climate change is certainly driving extreme wildfire behavior,” Headwaters Economics wildfire researcher Kimiko Barrett said. “We know that wildfires are increasing in severity, duration and frequency. I think it's important to see that while a substantial 10 million acres burned across the country, that's still quite minimal when you look at historical trends. What is increasing is the severity of these fires and the pace with which they burn.”
In addition to cost concerns and market forces, Barrett cited false assumptions around what resiliency measures entail, including that it would mean people have to live in concrete bunkers, which she said is not the case. There isn’t incentive to build wildfire-resistant homes when people assume that firefighters will save them, she said.
Political conflicts are also at play, as a severe housing shortage and the state’s mandate that communities across California contribute to increasing the supply of homes means that residential units could be built in higher fire risk areas or places recently burned.
“The mandate doesn't say only build safe houses. It says just build, which really seems to be irresponsible,” Woodside Fire District retired Fire Marshal Denise Enea said.
When reviewing building plans during her career, Enea would often see what she called red flags in plan documents even after being approved by a city’s planning department and would make phone calls to architects and applicants, alerting them to issues.
Enea recalled an instance about eight years ago when a planning department required a homeowner to install a wood shake roof instead of a composite one in a fire-prone area in the interest of neighborhood conformity. When the resident was ultimately denied insurance coverage, the mistake cost them about $100K, she said.
“Planning departments are starting to understand fire behavior, which they didn't before, so I think we're starting to make progress,” Enea said.
Part of the understanding is knowing how wildfires behave, what building materials to use and how to design structures and properties for greater protection. A measure as simple as using rock mulch instead of wood mulch in landscaping can make a structure less vulnerable, Barrett said.
Enea cited several strategies to increase resiliency, but the main message was to use noncombustible building materials and provide sufficient defensible space between structures. Choosing tempered glass for a skylight versus a cheaper alternative could mean the difference between a stray ember causing ignition or not.
Other protective methods are emerging, such as adding exterior sprinkler systems to protect roofing and siding, but they come with increased costs and maintenance, Holmes Fire CEO Bevan Jones said.
“The biggest culprit behind structure loss during a wildfire event is embers, also know as firebrands,” said Barrett, who added that embers can travel up to 4 miles from a wildfire front, dismissing the notion that a wall of flames has to be bearing down to be in harm’s way.
Wooded, rural areas are no longer the only places at risk, as was learned in 2017 during the Tubbs Fire, which tore through the Coffey Park neighborhood of suburban Santa Rosa in Sonoma County. As the neighborhood was being rebuilt in 2019, anxieties about future losses to wildfires persisted, as reported by the S.F. Chronicle.
The Coffey Park wildfire event was a wind-driven one in which embers could penetrate structural vulnerabilities such as wood siding and older, nontempered windows, Enea said.
“Just because San Mateo County hasn't had their big one yet doesn't mean we're immune,” Enea said. “There's no protective bubble over San Mateo County. And if you notice, all the big fires are all around us every year. It's closing in on us, and it's just a matter of time before we have our big one.”