SACRAMENTO — Insurance companies are asking the same question that often mystifies homeowners after a disastrous wildfire burns though a community: Why do some houses and neighborhoods escape unharmed while others burn?

A study released Tuesday by the insurance industry-sponsored Institute for Business and Home Safety validates the importance of traditional fire safety precautions, such as fire-resistant building materials, but it also finds the characteristics of a neighborhood are just as important.

"Most people think that if they just take care of their own home, they're safe," said Julie Rochman, CEO of the institute. "But it's not just the perimeter homes in housing developments that are in danger of wildfires. Your neighbor's house becomes a hazard to your own if you don't watch out for each other."

The study analyzed damage caused by last fall's Witch Creek fire in San Diego County that damaged or destroyed nearly 1,700 homes, resulting in about $1 billion in losses.

Researchers found wind-blown embers were the cause of most property damage in the fire and few reports of homes being ignited as a result of direct contact with flames. The danger of embers affects homes on the interior of a development as well as those on the perimeter.

Rochman noted 63 interior homes in a single development were ravaged during the Witch Creek fire.

The study found that homes in so-called "shelter-in-place" communities were 100 percent better protected than those in traditional developments. Fire safety standards in those communities go beyond standard building code requirements and include such safeguards as minimum 45-foot spacing between homes, prohibitions on planting trees near the sides of homes, wider roads, the use of fire-resistant decking materials, in-home sprinklers and having a buffer of vegetation zones surrounding the perimeter of the development.

The study found that not a single home in such a development was damaged.

"Humidity, wind speed, slope angles, age of the structures, all add up to create risk to homes," said Rochman, "But maintaining vegetation around them, code compliance, using fire-resistant building materials and basic maintenance all add up to equal safer communities during wildfires."

New statewide fire safety building regulations went into effect this month that seek to address many of the issues raised by the study.

"California is leading the nation in its fire safety standards," Rochman said. "But that's not enough. We've got millions of older homes out there, built before the new codes were in place."

There are multiple resources on the Internet for increasing the safety of your home or community, including the Institute's Web site, http://www.disastersafety.org. There, you can find a checklist for vulnerable areas on your house, including the roof, windows, gutters, eaves, children's outdoor play equipment and landscaping.

Outdoor decks are another hazard.

"They act as a candle wick does to wax, sending fire from embers that land on it right to your home," said Rochman. Using concrete rather than wood is one way to prevent that risk.

"If you're going to live in your home, you might as well protect it," said Tully Lehman of the Insurance Information Network of California.

He added that renters can buy insurance even when the home they live in may not be up to code for fires.

CalFire Chief Dave Hillman said wildfires present a much greater risk to suburban homes than they did two decades ago. "The term Wildland Urban Interface, or WUI, didn't exist 20 years ago," he said.

Today, more housing is being built in areas that encroach on wildfire danger zones.

"We are building, building, building," said Rochman. "As we continue to build, wildfire risk grows."