Wildfire season is no longer a far off worry for people living near trees and brush in the West. It is a yearly test of how well homes and neighborhoods are built and maintained.

New research says everyday choices, from your roof to the plants near your walls, can change the odds in a big way. The message is simple: what you and your neighbors do before a blaze arrives often decides what is left after.

The study was led by Michael Gollner, an associate professor of mechanical engineering at the University of California Berkeley.

Which homes survive wildfires?

The study suggests that combining home hardening with defensible space can double survival of homes in large California fires. Furthermore, clearing the first five feet around a structure can cut predicted losses by 17 percent.

The researchers analyzed five major fires, the 2017 Tubbs and Thomas fires, the 2018 Camp Fire, the 2019 Kincade Fire, and the 2020 Glass Fire.

The team paired field inspections with computer reconstructions to estimate how flames and embers hit each address, then trained a model that reached 82 percent accuracy at predicting whether a building survived or was destroyed.

One result stood out. Structure separation distance was the strongest driver of loss in dense areas where one burning house can ignite the next, while flame length and embers explained much of the risk elsewhere.

“CalFire maps are meant to highlight areas where you need more fuel clearing or more hardening for new construction,” said Gollner. He contrasted state scale hazard maps with the block scale modeling used in this work.

Why homes ignite in the first place

Most destruction in the wildland urban interface (WUI) happens when embers land on something that burns, or when radiant heat and direct flames expose weak points. Windows can crack, vents can suck in sparks, and dry debris near siding can light off and climb upward.

The study confirms that both external exposure and building features matter together. That is why a single change almost never tells the whole story.

Home hardening focuses on the weak links that let heat and embers get inside. Class A roofs, well screened vents, enclosed eaves, and multi pane tempered glass reduce the chance that a small ignition turns into a total loss.

Materials and details count because fires attack by heat, sparks, and time. Better windows, vents, and siding shorten that attack and give firefighters and residents more time to act.

Clearing cuts wildfire risk

California’s fire safety guidance describes three zones around a home, and it calls the first five feet the most important because most houses are lost to wind blown embers that ignite nearby fuels.

Zone 0 is the strip right against the building, and it is where wood mulch, stacked lumber, and plants against siding often start trouble. Clearing and hardscaping this narrow band does not erase a view or a garden, it simply moves burnable items a few steps farther away.

The new analysis shows that removing vegetation in the first five feet lowers predicted structure losses by 17 percent on average across the test fires. It is a small change on the ground with a large effect on outcomes.

Community action matters

The data here back that point. One hardened home can still be overrun if every house around it becomes fuel, while a street full of hardened homes with clean Zone 0 space breaks the chain of ignitions.

The model’s top feature, separation distance, cannot be changed quickly in existing neighborhoods. That is exactly why shared action on vents, roofs, windows, siding, and near home fuels is the practical lever to pull now.

Wildfire safety costs and home rules

Independent national assessments estimate that each dollar invested in hazard mitigation saves about four dollars in long run losses, which helps explain why insurers and public agencies reward proactive steps.

When a retrofit list feels long, start with the parts most likely to ignite and the places where embers land first.

New homes built to modern codes already gain many of these protections. Older homes can phase in upgrades, beginning with fine mesh vent screens, noncombustible six-inch siding clearance at the base, and replacing fragile windows in the most exposed room.

Cities and counties are updating their standards to ensure neighbors work together rather than at odds. Pairing inspections with small grants or reduced fees can encourage broader participation, especially in areas where a few holdouts might otherwise leave the whole community at risk.

The study is published in the journal Nature Communications.

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