Once they have a foothold, severe wildfires can quickly overwhelm a community, particularly one that is densely packed. To shield houses against such a fierce threat, a thorough defense is key.
Establishing a deep and multifaceted defense in and around homes is the basis of a new report that offers direction for safeguarding residences from external fire threats. Developed by fire safety experts at the National Institute of Standards and Technology (NIST), the California Department of Forestry and Fire Protection (CAL FIRE) and the Insurance Institute for Business & Home Safety (IBHS), the guidance provides dozens of protective actions — and the context in which each should be taken — all backed by the latest fire science.
This new approach, which is already being implemented in California by the California Governor’s Office of Emergency Services (Cal OES) and CAL FIRE through a pilot program called the California Wildfire Mitigation Program, could spare homes and lives from the intensifying threat of wildfires.
“We've seen all these destructive wildfires come through and burn thousands of homes. The way we aim to reduce those losses is to upgrade structures and then create defensible space around them,” said Steven Hawks, CAL FIRE chief and report co-author.
The strategy described in the report is the keystone of the recently launched California pilot program, which is meant to provide support to communities statewide. While the guidance is available for anyone to implement voluntarily, the cost of putting it into practice may be steep for some.
“That's where the California Wildfire Mitigation Program really steps in and provides the expertise, the education, the funding to back all of those mitigation measures at the level of each individual property,” Hawks said.
With significant gaps in fire codes and regulations, such as the lack of measures that address fire spread between properties, CAL FIRE worked closely with NIST and IBHS researchers to produce a more comprehensive defensive strategy.
The authors of the report compiled methods to protect against wildfires’ two main weapons of choice: flames and airborne pieces of burning debris called embers.
For a home to be made fire resistant, or hardened, up to 40 different components — such as windows, gutters and the deck — may need to be upgraded, either by adding to or replacing them with less flammable material. And because of how pervasive embers are, all 40 boxes must be checked in the end for a homeowner to reap much of any reward.
“If you have literally a million embers flying about your home and you have vulnerabilities, they’re going to find them,” said Alexander Maranghides, a NIST fire protection engineer and lead author of the report. “Hardening half of your home is not going to give you 50% improvement. You cannot pick and choose.”
In contrast, flames exhibit a much shorter reach than embers, and the approach for fending them off is more tailored to a home’s individual circumstances. The authors advise assessing the types and proximity of combustible features on a home’s lot and surrounding lots to determine where potential flames are a threat and identify appropriate actions.
The first line of defense for flames is to either remove combustible items, such as wooden furniture or sheds, or push them away from a home by a distance the authors determined to be safe.
In cases where a combustible object, such as a neighboring home, is dangerously close and moving it is not a realistic option, the guidance recommends hardening specific home features that would be in striking distance as a last resort, Maranghides said. This might mean having just the wall facing a neighboring home clad in a noncombustible material, for example.
The implementation of this strategy by every residence is especially critical in crowded neighborhoods where only a few feet may separate homes, potentially linking their fates in the event of a wildfire.
In California, the guidance is already seeing action through the pilot program, with Cal OES and CAL FIRE using it to assess and upgrade the properties of homeowners in three pilot communities across the state, including San Diego, Shasta and Lake Counties.
For Maranghides, the hope is that California is only the beginning. With several other states already grappling with an ever-increasing wildfire threat, the new, holistic approach for protecting homes and thus communities could be broadly applied throughout the U.S.
Report: A. Maranghides, E.D. Link, S. Hawks, J. McDougald, S.L. Quarles, D.J. Gorham and S. Nazare. WUI Structure/Parcel/Community Fire Hazard Mitigation Methodology. NIST Technical Note 2205. March 2022.