Posts Tagged: Steve Quarles
Can homes be designed to withstand wildfire?
In 2018, the Camp Fire destroyed nearly 19,000 structures in Northern California, including most of the town of Paradise. The structures left standing by the conflagration provided researchers an opportunity to investigate how housing arrangement – such as the size of the lot, the distance to a neighboring home, and surrounding vegetation – influenced which homes survived. They also looked at whether changes to the California Building Code in 2008, through the addition of Chapter 7A, improved the chances of homes built in the wildland-urban interface to withstand wildfire.
Both housing arrangement and surrounding vegetation likely influenced the survival of homes during an extreme wildfire, according to new research from the USDA Forest Service and the University of California Agriculture and Natural Resources analyzing the Camp Fire aftermath, which will be published Oct. 3 in the journal Fire Ecology.
“Our team found a reason for hope and information that can help Californians, building contractors and policymakers better prepare for future fires,” said co-author Yana Valachovic, University of California Cooperative Extension forest advisor.
The 2008 code, which applied to the city of Paradise, requires the installation of vents that resist flames and embers and other elements that help harden a home to wildfire. This chapter of the California Building Code added requirements for construction materials to California's existing two-zone fuel and vegetation modification guidance, known as “defensible space,” which applies to the vegetation and fuels out to 100 feet from a home.
The researchers found that the age of the home was a significant factor in predicting survival. But the key year wasn't 2008. Improvements in performance happened earlier. Only 11% of single-family homes built in or before 1996 survived, compared with 40% for homes built after 1996. Older homes were, on average, placed closer together and had more overstory tree growth near the home. Overall, the greater the distance between structures, the lower the likelihood of a home being destroyed by the Camp Fire. And the less overstory tree canopy cover, the higher the likelihood of a home surviving.
During a wildfire, structures can be threatened by the flaming front of the fire and by embers that are lofted ahead of the fire and land on fuels such as vegetation or mulch next to the house, igniting new fires. Embers can also enter homes through open windows or vents. Heat radiating from adjacent burning buildings or vegetation can also impact home survival.
“Despite the unpredictable nature of wildfire, strong associations with home arrangement and overstory vegetation cover indicate home survival is at least somewhat predictable,” said lead author Eric Knapp of the USDA Forest Service. “The silver lining is that this also suggests steps can be taken to substantially improve the odds of homes surviving a wildfire.”
One of the biggest drivers of home loss in the Camp Fire was the heat radiating from the large number of structures that burned. Over 73% of homes destroyed in Paradise had a structure burn within 59 feet. The distance to the nearest destroyed structure or total number of destroyed structures within 328 feet was a primary predictor of home loss.
“Exposure to the heat of a nearby burning structure can break glass in a window, for example. Once the glass is broken, embers or flames can enter the house,” said co-author Steve Quarles, emeritus UC Cooperative Extension advisor and retired chief scientist for the Insurance Institute for Building & Home Safety.
This finding suggests that denser developments, built to the highest standards, may protect subdivisions against radiant heat from a vegetation fire, but density may become a detriment once buildings ignite and radiant heat loads increase as well as the increased potential for direct flame contact.
“This research suggests a strong neighborhood effect, where the condition and proximity of an outbuilding or a neighbor's home can have a significant influence on a building's survival given the radiant heat exposure from a neighboring building burning,” Valachovic said.
Tree canopy cover was also associated with home loss, with a higher probability of home survival where tree cover was moderate or less.
“Trees provide shade, which is important where summers are hot. But to have the amenities trees provide without undue fire hazard, the key is to clean up the leaves and dead wood trees produce,” said Knapp. “This includes keeping roofs, gutters, garden beds adjacent to the structure and spaces under attached decks, free of leaves.”
The researchers detected no significant increase in survival for homes built from 2008 to 2018, under the new building code, compared to homes constructed during an equal time period, 1997 to 2007, immediately preceding the adoption of the new code. Houses built during the last two decades resisted wildfire better than older homes, indicating an overall improvement in common construction standards and the performance of building materials.
“It is important for Californians to understand that homes and immediate surroundings need to be well-maintained to resist embers, survive extended radiant heat exposures and minimize direct flame contact,” Quarles said. “Fortunately, all building codes get better with time and Chapter 7A is no exception – Californians have benefited from it. California's Building Code is reviewed every three years, and it is evolving as new knowledge becomes available based on research and post-fire assessments.”
To enhance wildfire protection at the neighborhood scale, the researchers recommend coordinating efforts with neighbors.
“Because ember ignition of one house can put neighboring houses at risk, it is critical that fuel reduction happens at a community scale. Living with fire means doing all things possible to prevent one's house from catching fire,” said Valachovic.
There are simple actions that homeowners can take to protect their homes.
“From retrofitting with vents that resist ember entry or using tempered glass windows, to the simple things, like not placing bark mulch or woody plants next to homes, and using gutter guards to minimize leaf and needle accumulation in gutters, all will improve the chance of home survival,” Quarles noted. “It is a matter of how we choose to live in this environment.”
“Housing arrangement and vegetation factors associated with single-family home survival in the 2018 Camp Fire, California” by Knapp, Valachovic, Quarles and Nels G. Johnson is published in the journal Fire Ecology at https://fireecology.springeropen.com/articles/10.1186/s42408-021-00117-0.
For more information:
- Steps for hardening houses against wildfire can also be found at the Fire in California website: https://ucanr.edu/sites/fire/Prepare/Building.
- Reducing the vulnerability to buildings to wildfire: vegetation and landscape guidance https://anrcatalog.ucanr.edu/pdf/8695.pdf
Landscaping with wildfire exposure in mind can protect homes
What can Californians do to improve the chances that their homes will survive a wildfire? Simple actions taken around the home can substantially improve the odds that a home will survive wildfire, according to UC Cooperative Extension advisors.
During wildfire, structures are threatened not only by the flaming front of the fire, but also by flaming embers that are lofted ahead of the fire front and land on fuels such as vegetation or mulch next to the house, igniting new fires. Traditional defensible space tactics are designed to mitigate threats from the flaming front of the fire but do little to address vulnerabilities to embers on or beside a structure.
“Without attention to ember-related risks, defensible space efforts only address a portion of the wildfire threat—especially during wind-driven fires in which embers are the primary source of fire spread,” said co-author Yana Valachovic, UC Cooperative Extension forest advisor in Humboldt and Del Norte counties.
An updated University of California Agriculture and Natural Resources publication describes how embers, radiant heat, and direct flame contact ignite buildings and shares low-cost actions residents can take to create effective defensible space.
“The new publication is up-to-date with the changes in California's defensible space guidance, and it addresses Zone Zero, or the missing ingredient, in defense space,” Valachovic said. “The publication also provides a thoughtful discussion of plant lists and their limitations.”
The odds of a home surviving a wildfire can be substantially improved through careful attention to three things: careful design and maintenance of landscaping; awareness and management of combustible materials on the property such as leaf litter, wood piles and lawn furniture; and incorporation of fire- and ember-resistant construction materials with appropriate installation and maintenance.
“You don't have to spend a lot to protect your home from these wildfire threats,” said Valachovic.
Zone Zero, the area within five feet of the house, is the most vulnerable area around the home, according to the UC Cooperative Extension researchers. “During wind-driven fires, embers are the primary source of fire spread,” Valachovic said.
They recommend removing combustible plants, planter boxes, mulches and wood piles within the five-foot perimeter of the house and beneath attached decks.
“While it may be a radical change, clearing the area next to the house will reduce the risk of ember-caused direct flame contact and radiant heat exposure, which are responsible for many home losses,” she said. “Because embers can accumulate at the base of an exterior wall, it is also important to create a six-inch noncombustible zone between the ground and the start of the building's siding.”
Colorful illustrations in the publication depict the three-zone defensible space strategy and show how spacing out trees on a sloped landscape can prevent fire from climbing from tree to tree to reach a house at the top of the slope.
The 12-page “Reducing the Vulnerability of Building to Wildfire: Vegetation and Landscaping Guidance” is available free for download at https://anrcatalog.ucanr.edu/pdf/8695.pdf.
“Landscaping for fire is part of an overall strategy aimed at reducing risk to the home,” said co-author Steven Swain, UC Cooperative Extension environmental horticulture advisor for Marin and Sonoma counties. “To reduce the risk of home loss, start at the house and work out from there,” he recommended.
Swain, Valachovic and Stephen Quarles, UC Cooperative Extension advisor emeritus, are currently updating a publication on retrofitting houses for wildfire resiliency.
Steps for hardening houses against wildfire can also be found at the Fire in California website: https://ucanr.edu/sites/fire/Prepare/Building.
Protecting homes in wildfire-prone communities covered in new publication
A team of California and Nevada fire scientists have produced a booklet with step-by-step guidance on retrofitting an existing home to be more resilient to fire.
Susie Kocher, UC Cooperative Extension forestry and natural resources advisor and co-author of the new guide, said some homeowners feel powerless to protect their homes against California's increasing wildfire threat.
“I'm happy to tell them that's not true. There are specific actions that we can all take to reduce the likelihood of our homes being burned in wildfire,” said Kocher, who lives in a forested area near Lake Tahoe. “We need to educate ourselves on the details of home construction that make homes less vulnerable to ignition.”
The free 20-page publication, How to Harden Homes against Wildfire (http://ucanr.edu/HomeRetrofitGuide) is now available online. It includes recommendations for 12 vulnerable components of homes in wildfire-prone areas, including roofs, gutters, vents, siding, windows, decks and fences.
In the past, agencies have focused on recommending changes in vegetation and establishing defensible space. However, Kocher said recent advances in wildfire science have exposed vulnerabilities of structures themselves.
“Managing vegetation and retrofitting the home are both needed to decrease wildfire risk and help our communities become more fire adapted,” she said.
CAL FIRE awarded funding to develop and publish the wildfire home retrofit guide, funding that is part of California Climate Investments, a statewide program that assigns cap-and-trade dollars to projects that aim to reduce greenhouse gas emissions, strengthen the economy and improve public health and the environment.
In addition to CAL FIRE, organizations that contributed to the document are University of Nevada, Reno Extension; University of California Cooperative Extension; Living with Fire, Tahoe; Tahoe Fire and Fuels Team; Tahoe Resource Conservation District; and Tahoe Network of Fire Adapted Communities.
The team also hosted three webinars to share home fire resilience information targeted to different audiences. Videos of the webinars are available on the Living with Fire YouTube Channel:
For the public: https://www.youtube.com/watch?v=YX114wpPwmg&t=327s
For building professionals: https://www.youtube.com/watch?v=ccIAIg6xONs
For fire educators: https://www.youtube.com/watch?v=lOsdyVSPxnA&t=177s
UC Agriculture and Natural Resources brings the power of UC to all 58 counties. Through research and Cooperative Extension in agriculture, natural resources, nutrition, economic and youth development, our mission is to improve the lives of all Californians. Learn more at ucanr.edu.
Wildfire preparedness bill puts UC research to work
Last week, Governor Gavin Newsom signed a series of bills aimed at improving California's wildfire prevention, mitigation and response efforts. AB 38, a bill aimed at reducing wildfire damage to communities, incorporates University of California research to help protect California's existing housing.
“Prior to AB 38, the State's wildfire building policy focus was centered around guiding construction standards for new homes and major remodels,” said Yana Valachovic, UC Cooperative Extension forest advisor for Humboldt and Del Norte counties. “How do we help incentivize homeowners to upgrade and retrofit the 10 million or more existing homes in California to help them become more resilient to wildfire? AB 38 is an attempt to start that important work and to protect Californians.”
AB 38, introduced by Assemblymember Jim Wood (D-Santa Rosa) provides mechanisms to develop best practices for community-wide resilience against wildfires through “home hardening,” defensible space and other measures based on UC ANR research. This bill is especially important to Wood because wildfires in 2017 destroyed lives and hundreds of homes in his district and because of his work as a forensic dentist following the Santa Rosa and Paradise wildfires.
“AB 38 was a huge effort by many partners as we sought the best policy solutions to address what is today one of our state's biggest challenges,” said Assemblymember Wood. “I could not have accomplished it without the support and guidance of the people at UC Cooperative Extension Humboldt-Del Norte, especially Dr. Steve Quarles and Yana Valachovic. Their expertise proved invaluable as we worked through this process.”
Studies conducted by Steve Quarles, emeritus UC Cooperative Extension advisor, and his continued work at the Insurance Institute for Business and Home Safety have identified building materials and designs that are more resistant to flying embers from wildfires. Embers are small, fiery pieces of plants, trees or buildings that are light enough to be carried on the wind and can rapidly spread wildfire when they blow ahead of the main fire, starting new fires on or in homes.
Evaluating the homes lost in wildfires that ravaged Paradise, Redding and Santa Rosa have also informed Valachovic and Quarles' recommendations.
Hardening a home to withstand wildland fire exposure does not have to be costly, but it does require an understanding of the exposures the home will experience when threatened by a wildfire.
Their recommended best practices for hardening homes against wildfire can be found in UC ANR Publication 8393 “Home Survival in Wildfire-Prone Areas: Building Materials and Design,” which can be downloaded for free. More information is also at the ANR Fire website https://ucanr.edu/fire.
What can we learn from the 14,000 homes lost during the Camp Fire?
Shades of brown and grey cast over bricks, cement, remnants of metal roofs and steel beams from manufactured and modular homes, collapsed stucco walls, BBQs, shells of washers and driers, along with an occasional tea pot—that is what you can see in and amongst living, but singed Ponderosa pine and California black oak trees where the Camp Fire burned. How did California's most deadly fire happen and what might be done differently to ensure a better outcome? These are difficult questions that California will wrestle with for a long time to come.
Last week I was able to tour some of the burned area in Paradise and Magalia to evaluate why some homes survived and others did not. This gave me a chance to look at homes that survived largely on their material selection, design details, the owner's maintenance efforts, and not necessarily with the aid of a fire crew or resident that stayed. Many of the buildings that were burned were lost on the first day or two of the fire while emergency response was focused on evacuating the communities. It will take months to make sense of this mess and tragedy, but during my tour some conditions rang true to me.
- Wildfire is not uniform. Not all fires are the same and not all houses experience the same type of fire. When you are looking at home losses and survivors, keep in mind that each home may not have had the same fire exposure. Some homes experienced significant ember exposure, while others ignited because their neighbor's home succumbed to fire and the heat of their neighbor's house caught their house on fire, while others were protected from the wind and its deadly embers. Paradise and Magalia have blocks and blocks of nothing but foundations, but amongst these bleak conditions are a few intact or partially damaged homes that have a story to tell.Remnants of a burned trailer park in Paradise.
- We saw homes that survived that had upgraded attic and foundation vents that meet the California building code for construction in wildfire prone areas. Some of these houses also included some extra efforts where vegetation and combustible mulch was virtually eliminated in the area immediately adjacent to the home. Our inspection team included UC's Dr. Steve Quarles, a national expert in fire-safe construction, who interpreted this to mean that meeting the 2008 Chapter 7 A standards, coupled with the enhanced defensible space, likely made the difference to ward off the assault of the ember-driven Camp Fire. We found evidence that burned homes in Paradise had ¼” mesh foundation and under-eave vent screens. Research has shown that these larger size screens let embers penetrate the attic and ignite the house from within. The 2008 California building code standards specify screen mesh size between 1/8” and 1/16”-inch, or vents that demonstrate their ability to resist embers and flames.A homeowner holds a foundation vent found in the rubble of her home. Her home was built before the 2008 construction standards and had the larger ¼ inch mesh screen size that may have allowed embers to enter her home.
- Our tour also confirmed that landscaping plants and wood mulch placed right next to the house creates vulnerability. While looking at the rubble of a home, it can be difficult to tell what happened; however, we saw several surviving houses with broken glass or otherwise damaged dual-pane windows that experienced heat exposures sufficient to crack glass in the windows, but the home still survived during these first two days when fire crews were rightly focused on community evacuation and not structure protection. For the houses that did not survive, we can interpret that in addition to the vulnerabilities in vents or a roof, heat can easily break glass in windows, especially if those windows are single pane, and can likely created a pathway for fire to enter the houses.Wood mulch and landscape plants burned adjacent to this newly constructed home. Several windows were broken from the heat from this fire. The home met the new construction standards and survived, but likely would not have been damaged if there had been a 5-foot zone around the home that did not contain combustible plants or other materials.
- Home placement makes a difference. A home at the top of a canyon or gulch can easily be overwhelmed by wildfire by taking on additional heat as the fire approaches and being blasted with embers. This is not a new concept, but the homes in the broader Paradise region were especially vulnerable when they were located above these gulches and canyons. Enhanced vegetation management is highly recommended that includes a 5-foot non-combustible zone immediately adjacent to the home.
Our team, which also included Dr. Eric Knapp from the USDA Forest Service Pacific Southwest Research Station, has been able to do a quick analysis of home losses by year of construction in Paradise. This cursory analysis shows that many homes built after the 2008 wildfire standards were adopted were lost during this fire, however, without knowing the specific details of each home (e.g., maintenance practices, proximity to other building, etc.), these statistics can be misleading. We will continue to work through the available data to try to look for patterns, however, in the meantime, it seems clear to me that the new construction standards can reduce the probability of ember intrusion and may have helped for some homes in Paradise. This week a new study reported that complying with these standards was not considerably more expensive. Additionally, the codes that help guide construction in California's wildfire-prone areas are dynamic and will be informed by the 2017 and 2018 wildfire seasons.
For me thinking about Paradise in the abstraction was easy. Visiting it was different. The name says it all. After my visit I could understand why someone would choose Paradise or Magalia; the views are awesome, the air is clear, the forest and woodlands are amazing. I can only imagine that the community was (almost) perfect. Rebuilding a more resilient community will take considerable thought, effort, and some radical new ideas.