Fiery home invaders

Before dawn on Oct. 22, the Witch fire stormed through the chaparral-covered hills of north San Diego County toward Ron and Carol Bedell’s home.

As they fled through smoke and ash to escape the flames, the couple from Poway were optimistic that their new multimillion-dollar home would survive. It had been built to the highest fire standards, with a slate roof and tempered windows. And the Bedells were careful to keep brush cleared to 150 feet.

About 5 a.m., the fire roared up to their property, blew past and moved on, leaving the home intact. But eight hours later, with the wildfire burning miles away, their house caught fire -- the victim of smoldering embers that wafted through the dog door.

Fire officials believe that embers driven by raging winds through small openings or against exposed wood were responsible for igniting a majority of the 1,125 homes leveled by the Witch fire, the most destructive in California this year. In many cases the embers smoldered for hours before causing homes to burn.

A home “has to have a weakness for it to burn,” said Ernylee Chamlee, California’s chief of wildland fire prevention engineering. “It’s less random, or a case of luck, than you might think.”

In the Bedells’ case, a garage wall caught fire, but firefighters put out the blaze before it could consume the entire house. At other homes, the weak points were attic vents, broken windows or barrel tiles with openings that allowed embers to ignite a roof. Most of the homes destroyed in this year’s fires burned from the inside out, according to firefighters, a clear sign that the fires were caused by embers within, not flames attacking the outside walls.

An analysis of the Witch fire’s pattern of destruction points to deficiencies in long-held beliefs about building in fire-prone areas. Fire-resistant walls and roofs are helpful, and brush clearance is essential. But alone they are insufficient in the face of millions of burning embers flying horizontally more than a mile ahead of the flames.

Of 497 structures that burned in unincorporated areas of San Diego County during the Witch fire, more than half had fire- resistant walls and roofs, a Times analysis of government data showed. Information on construction materials has not been compiled for neighborhoods inside the cities of San Diego and Poway, but senior fire officials estimate that well over 75% of the destroyed homes had fire-resistant exteriors.

Truly protecting a house, fire officials say, requires more rigorous steps to close off the smallest openings through which burning debris might enter.

The ember phenomenon also raises a public policy dilemma. With the Witch fire, firefighters conducted one of the largest evacuations in California history and barred residents from their neighborhoods for days as they continued to put out hot spots.

Officials cite their aggressive evacuation policy as a primary reason that so few lives were lost in the fire.

But an untold number of homes were saved by people who refused to evacuate or sneaked back in to their neighborhoods before evacuations were lifted.

The Bedells’ home in Poway was saved only because a neighbor was around to spot the flames and call firefighters.

“Obviously, if my neighbor had not violated the curfew, my home would have gone down,” Ron Bedell said.

Firefighters conceded that residents who ignored evacuation orders played a significant role in saving homes, dousing smoldering embers themselves with garden hoses and summoning firefighters when flames erupted.

“We wanted them to leave, but we can’t force them,” said Jon Canavan, division chief of Poway’s fire department. “And a lot of people saved their own homes. . . . When an area is evacuated we no longer have the eyes and ears of people who live there and say: ‘Hey, my house is burning.’ ”

But he and other fire officials say there are too many pitfalls to allow people to stay or reenter prematurely.

Burned neighborhoods are dangerous places after a fire, officials say. Cinders can be smoldering, dangerous debris is everywhere, and smoke is heavy in the air. House fires might break out when a resident is sleeping or not paying attention. Gas lines may be ruptured and live power lines down. And busy firefighters do not want to be diverted from fighting the fire to save citizens who ignore evacuation orders.

“If it comes down to lives or the house, we’re going to choose the lives,” said Maurice Luque, spokesman for San Diego’s fire department. “Until it is safe, you don’t allow people back in. . . . We don’t want to risk public safety for a house.”

Until recently, there has not been much of an economic imperative to study the behavior of wildfires as they storm into suburbs. The flames make for dramatic news images, but their devastation is eclipsed by that of other natural disasters. Home insurer payouts nationally for fire losses are a small fraction of those from hurricanes, tornadoes and winter storms. And less than 1% of the 400,000 residential fires each year in the United States are the result of wildfires.

But the stakes are rising as local governments continue to let developers build in fire-prone areas. The California Department of Forestry and Fire Protection estimated in 2003 that more than 3 million homes in California -- the largest chunk in Southern California -- are at “significant risk” from wildfires. And the number is growing. A 2002 federal report said nearly 40% of all home construction in the West was pushing into wild lands.

In 2005, California began requiring homeowners to clear brush and weeds within 100 feet of their houses in fire-prone areas. And under new state building code requirements to take effect next year in those same areas, builders must take measures to prevent ember intrusion in all houses they build.

Some materials that have traditionally been viewed as fire-safe have come under new scrutiny. The barrel tile roofs that developers have turned to as an alternative to wood shake, for example, also can play host to embers. Because the tiles are arched, they leave flammable roofing materials exposed on the bottom-most row.

Some homes have a piece of tile that covers those holes, called a bird stop. Many do not.

“I’ve seen houses with embers stacked in those openings,” said Dave Hillman, chief of law enforcement and fire prevention for the California Department of Forestry and Fire Protection. “I call them catcher’s mitts.”

Under the new rules, developers will be required to close the gaps under barrel tiles with mortar or bird stops, screen attic vents, cover eaves, close off the underside of wood decks and install tempered glass in all windows so they don’t shatter in the heat.

The counties of San Diego, Los Angeles, Orange and Ventura already require similar measures, but the city of San Diego does not, according to the forestry department. Rancho Bernardo, one of the Witch fire’s hardest-hit areas, is part of the city of San Diego.

In a report on the fire, San Diego County official Kenneth J. Miller II concluded that the upgraded fire and building codes were “instrumental in saving homes” in county territory.

Much of the research behind the new codes stems from pioneering work by Jack Cohen, a fire scientist with the U.S. Forest Service. Cohen trekked a decade ago to Canada’s Northwest Territories, where officials allowed researchers to set sections of forest ablaze with flamethrowers and watch what happened to simulated houses they had built.

Cohen found that enough heat was generated to ignite wooden walls he erected 33 feet away from the forest’s edge, but not walls at 66 feet or 98 feet away. This was a critical observation: “Regardless of how big that wildfire is out there, how big the smoke columns and flames, by and large the potential for ignition of a house is determined by its immediate surroundings.”

In other words, buffer zones can keep flames out of reach. He suggested that homeowners eliminate highly flammable materials within 100 feet of their houses. But that still left the question of how to defend against flying embers. Although it long has been known that burning debris landing on a wood shingle roof was likely to ignite a home, Cohen said scientists used to underestimate the number of other ways embers could breach a home’s defenses, particularly in high winds.

Then they started studying why some homes ignited hours after a flame front had moved through. The answer, in many cases, was long-smoldering embers. That’s what played out on Cloudesly Drive in Rancho Bernardo. The Witch fire passed through at 4:30 a.m. Four hours later, with the wildfire long gone, San Diego Fire Battalion Chief Gerry Brewster came upon four homes on the same street that suddenly erupted in flames.

He suspected that a change in the wind sparked embers smoldering in a cavity of one of the houses, and the fire quickly spread to the others.

“That little change in the wind, and we had houses taking off.”

joe.mozingo@latimes.com ted.rohrlich@latimes.com ron.lin@latimes.com

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Times staff researcher Maloy Moore contributed to this report.