When a wildfire swept through 2,000 acres in the hills north of San Diego, California, in May, it left behind a curious checkerboard of destruction. One neighborhood was reduced to ashes and twisted metal. But houses nearby suffered little more than scorched grass and singed trees.
Captain Richard Cordova of the state firefighting agency, Cal Fire, visited the scene and quickly hit on one explanation for the fire's apparent favoritism.
Many of the homes that survived had little flammable brush in the area immediately around them. But others had dry grass and shrubs within feet of the walls. "Those were the ones that unfortunately did burn down," Cordova said.
As the summer wildfire season enters full swing in the United States, with more than 700,000 acres now burning in the Pacific Northwest and California, the difference between a surviving house and a charred husk could come down to details as small as screens over attic vents, trimmed trees, or pine needles in the gutters.
In fact, in the past ten years scientists have gained a whole new understanding of factors that can help a home survive a wildfire. And it turns out that saving a house has less to do with stopping a forest fire cold or creating a nonflammable moonscape for a hundred feet in every direction. It's more about lots of minor modifications and regular maintenance.
"It's the little things," said Michele Steinberg of the National Fire Protection Association, whose Firewise program works to educate American homeowners and communities about protecting themselves from wildfires. "That's the surprising fact for folks. I'm thinking I have to chop down every tree in the forest to protect my home, but what's really going to get me is the mulch up against the house or the doggy door that isn't sealed."
As wildfires grow bigger and more intense—the product of drought, disease, climate change, and buildup of flammable material from decades of extinguishing nearly all fires—and annual federal spending on firefighting surpasses one billion dollars, the new science of fireproofing has some experts asking if federal, state, and local agencies should be steering more money toward making homes and communities fire resistant.
Evolving Science of Fireproofing
For Steve Quarles, the new thinking on fireproofing crystallized in 2003, when he was sifting through ashes from the massive Cedar Fire in southern California. The blaze destroyed 2,200 homes, killed 15 people, and helped introduce the term "fire siege" into the local lexicon. Then a scientist at the University of California who was studying what happened to structures in wildfires, Quarles found green bushes and blooming flowers next to houses reduced to cinders. How would a fire leave such an odd pattern?
He went looking for a culprit that could set a house on fire without torching everything around it. He found it in tiny embers, or firebrands, as they are known among wildfire scientists. Blown far from a wildfire by the wind, these bits of burning debris can wreak havoc if they collect in flammable spots around a house: a gutter filled with pine needles, an unscreened vent leading into an attic, or a trash can left open against a wall.
That's different from an older belief—one still widely held by the public—that a wildfire's dramatic, towering flames march through a neighborhood, incinerating buildings in their path. Earlier scientific research into home destruction during wildfires had focused on how close a sustained fire, like a burning bush, needed to be to a home to set it ablaze.
But firebrands can shower a house that's situated a quarter mile or more from a wildfire. So they've become a central focus for Quarles, who now spends his days searching for the chinks in a house's armor as a senior scientist at the insurance industry-funded Insurance Institute for Business and Home Safety.
At a massive wind tunnel laboratory in South Carolina, he tries to set houses on fire. To figure out where firebrands cause the most problems, he builds small fires in a series of metal barrels, then lets a fan blow the firebrands onto a full-size house built inside the wind tunnel.
Mulch to Kindling
The experiments produced some surprising results. For one, landscaping mulch around houses turns into kindling when an ember lands there.
But the experiments also suggested that tiny modifications to a home can make a big difference. For instance, a metal cap can block embers from sneaking into the space between the roof and the fascia—the horizontal board ringing the roof's edge. Screens with gaps no bigger than one-eighth inch can stop embers from getting through vents leading to crawl spaces and attics.
Joe Stutler is putting that science to use on his home in the dry forests outside Bend, Oregon. A career firefighter with more than three decades of experience with federal wildfire-fighting agencies, he has stone pavers instead of a wooden deck, gutters designed to shed pine needles, a fire-resistant roof, and stone siding at the bottom part of the house's exterior.
Farther out, he's planted grass along the side of the house where a fire is most likely to come from, mowed the wild grasses to four inches high, and cut off the low-hanging limbs on evergreens to keep a grass fire from climbing into the treetops.
But he also knows his home's survival depends partly on what his neighbors do. If a single home catches fire, it can fling embers onto nearby houses. In dense developments, the heat of a burning house can ignite the house next door, setting off a chain reaction that overwhelms firefighters.
So Stutler, who advises his local county on wildfire policy, has rallied his neighborhood. Federal grants pay for free collection of flammable debris that homeowners rake from their yards in the spring. The grass and shrubs in vacant lots are mowed each year.
But he only has to drive to a nearby subdivision for a different picture. "Half of them have bitterbrush—what I call gasoline on a stick—growing over my head," he said. "It's just a matter of time before we have a significant fire and it burns a bunch of houses."
Fight Fire With Fire
So far, government spending on making homes more fire resistant has lagged far behind the amount expended on fighting wildfires. In 2013 the U.S. Forest Service spent more than $1.3 billion putting out fires. It spent just $2.6 million helping communities adapt to fire, and doled out an additional $24 million to states for similar programs and for clearing fire-prone forests.
The sharp funding imbalance frustrates Jack Cohen, a Forest Service scientist and one of the leading experts on wildfires and houses. The fear of forest fires consuming homes has helped drive decades of costly efforts to squelch nearly every blaze, he said. That policy has denied forests the natural fires that helped shape the landscape for eons. One result: forests cluttered with dead or overcrowded timber thats feed huge, intense fires.
Rather than focusing so much on putting out fires, Cohen said, attention should be paid to creating communities that can pass through a fire relatively unscathed. That would mean looking at the area right around houses, and at the structures themselves. (See: "NEXT: Simulating Wildfires.")
Cohen has repeatedly been called to the scene after a wildfire destroys homes around the West, to help figure out what happened. It nearly always comes down to homes and neighborhoods that weren't built or maintained to weather a fire.
"Basically, it's time to admit that there are going to be fires that we can't deal with, and ... we need to be compatible and not controlling," he said. "This is a home ignition problem, not a wildfire problem."
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