Safety focus turns to embers

On a sweltering morning recently in Portola Valley, Devan LeBlanc led a homeowner on a walk around her house, pointing out all the ways it could catch on fire.

“We think about that every day,” said the homeowner, who requested anonymity to protect her privacy. “What would happen if this place burned down? Where would we go?”

LeBlanc, co-founder of a small company based in Marin and Reno called Ember Wildfire Defense Systems, inspected the vegetation and debris around the home, the roof gutters and the tile patio out back, noting his observations. Then he turned his attention to the golf ball-sized ventilation holes drilled into the home’s attic and the rectangular foundation vents near the ground. A single ember, carried on the wind from a fire across the valley, could potentially get sucked into the home through one of those openings and start a fire, he said.

“It’s the smallest little details that can save a home,” LeBlanc told the homeowner.

In the past three years, wildfires in California have destroyed more than 40,000 structures. The alarming scope and scale of these disasters has made home “hardening,” the practice of armoring a building’s exterior against fire ignition, an urgent priority for homeowners across the state.

While the notion of wildfire threat conjures images of a wall of flame sweeping through homes in wooded areas, fire experts say that structures a mile or two from wildfire fronts can be threatened by windblown embers, a long-overlooked but increasingly common cause of structure fires. The smoldering specks travel beneath garage doors, into attic vents and through open windows, sometimes igniting homes from within. As many as 90% of building ignitions in the U.S. are caused by embers, according to recent research published by the Insurance Institute for Business and Home Safety.

“More and more what we’re finding out is that it’s not the eucalyptus tree next to your house that’s the biggest problem,” said Rich Shortall, executive coordinator for Firesafe Marin, a nonprofit focused on wildland fire safety. “It’s these massive winds that are blowing embers a mile or two from the fire front to people’s homes.”

Powerful wind gusts that often accompany the worst wildfires — the Diablo winds, as they’re known in Northern California — scatter embers long distances and can ignite homes directly (say, by landing on combustible wood siding) or indirectly (by landing in a pile of dry debris in a backyard).

It’s unclear exactly how many structure fires in California can be attributed to embers, but they have intensified some of the biggest wildfires of the past three years, including the 2018 Mendocino Complex Fire, at the time the most destructive in state history. The 2018 Woolsey Fire, which burned homes in Malibu, was fueled in part by Santa Ana winds that sent embers cascading across the region.

“You can see the real-time propagation of embers up in Wine Country right now,” Shortall said during the Glass Fire that burned parts of Napa and Sonoma counties starting in late September. “It’s empirical evidence that you can’t miss.”

California’s building code mandates that new homes erected in the so-called wildland-urban interface incorporate fire-resistant construction elements. But much of the state’s housing stock was built in the 20th century, some during a subdivision spree, when ignition-prone redwood was a preferred building material.

The emphasis on embers stems from a surge of wildfire research in the past five years that has spotlighted certain weaknesses of home building and design, said Steve Quarles, a senior scientist for IBHS who lives in Mill Valley. In one recent test, IBHS built a single-family home replica inside a warehouse in South Carolina and showered it with embers until it caught fire.

“Ten or 15 years ago, once you got beyond ‘replace your wood shake roof,’ there wasn’t a lot to say about the built environment, so the public messaging was about defensible space,” said Quarles, who is a Firesafe Marin board member. “But with new research coming out, there’s much more to say.”

Organizations like Firesafe Marin are trying to get the word out among Bay Area homeowners. They host public webinars and workshops on new homehardening products and techniques. But they’ve found that interest fluctuates.

“We need to simplify the information so it’s easier for people to understand,” said David Shew, a former incident officer for Cal Fire who lives in Napa and runs a consultancy called Wildfire Defense Works. “It’s easy for people to throw up their arms and say it’s too overwhelming.”

The circumstances have opened a niche market in wildfire home protection. Some companies are offering rooftop sprinkler systems that soak houses in water-foam solutions. Others market a water-soluble fire-retardant gel that homeowners can spray onto their stucco.

Many fire departments in the state offer home inspections, and several companies focus on defensible space, but fire experts interviewed for this article said the ember-focused company offers a new and unique service.

“It’s actually hard to find people who do this,” said Shortall. “There’s a lot of opportunity there.”

During the recent home inspection in Portola Valley, Le­Blanc and his business partner, Adam Iveson, slid a customized foundation vent from the bed of their truck. Made by a manufacturer called Vulcan Vents, it is outfitted with a fine mesh screen designed to block embers. A temperature-activated coating on the screen rapidly expands when it senses firelevel heat, sealing the vent off completely.

“We’ll put these in all around this house,” Iveson said. “Every home should have these.”

Gregory Thomas is the Chronicle's editor of lifestyle & outdoors. Email: gthomas@sfchronicle.com Twitter: @GregRThomas