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Can homes be designed to withstand wildfire?

This photo captured by a drone shows a house that survived the 2018 Camp Fire among others that were destroyed. Photo courtesy of Butte County

 

[This story was originally published Oct. 4, 2021, and updated Dec. 21, 2022]

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.

Aerial image over Magalia post-Camp Fire illustrates a gradient of fire damage to overstory vegetation with distance from destroyed homes. Photo by Owen Bettis, Deer Creek Resources

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.

In 2022, during a visit to Laguna Niguel after the Coastal Fire, Valachovic saw that defensible space had prevented flames from reaching homes. However, some houses had burned from the inside out after embers penetrated attic vents and ignited combustible materials.

“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.

Steve Quarles, UC Cooperative Extension advisor emeritus, looks at a garage attached to an older house in Paradise where the radiant heat from a nearby fence and line of planted vegetation ignited and were sufficiently hot enough to break the single pane glass. Photo by Yana Valachovic

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.

At a home built after 2008, embers ignited combustible mulch and vegetation and led fire to break the first pane of double-pane windows.

“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:

Posted on Wednesday, December 21, 2022 at 12:02 PM
Tags: Steve Quarles (4), wildfire (167), Yana Valachovic (21)
Focus Area Tags: Environment

Free wildfire publication simplifies understanding fuel-reduction permits on private land

In this restoration treatment, encroaching conifers are removed from an oak woodland to bolster fire resilience. Photo by Jared Gerstein

UCCE forest advisor helps landowners, community groups determine best project options

As Californians prepare for another year of drought and an anticipated intense fire season, landowners and organizations across California have been working to reduce forest fuels – flammable woody material – that can endanger their properties and communities.

For many of them, however, their urgent efforts hit a sizable speed bump: a massive rulebook that describes, amid a thicket of other information, the permits required before people can treat or remove fuels – as well as a litany of attached requirements, restrictions and stipulations.

“The California Forest Practice Rules are 410 pages, in font size 6,” said Yana Valachovic, UC Cooperative Extension forest advisor for Humboldt and Del Norte counties and registered professional forester. “Trying to figure out what permit vehicles make sense in the rulebook is not easy even for the experienced professional forester.”

To assist private landowners and community groups in deciphering the rules and determining their most cost-effective options, Valachovic took the lead in writing a new guide, “Planning and Permitting Forest Fuel-Reduction Projects on Private Lands in California,” available as a free resource in the UC Agriculture and Natural Resources catalog.

A portion of the decision tree framework that breaks down what permit applicants should consider when weighing their choices.

“We tried to create a system where all the permits are laid out side-by-side, and put in a decision tree framework to help make it easier,” said Valachovic, highlighting the publication's tables that break down the project goals and parameters a permit applicant should think about when weighing their choices.

Considerations include whether the project is pre- or post-wildfire, the location and dimensions of trees targeted for removal, the conditions of the site before and after the project, potential time limits, commercial options, and, crucially, budget constraints – given that the permitting process could comprise up to one-third of total project costs.

A primer for planning and preparation

Chris Curtis, the unit forester for CAL FIRE's Humboldt-Del Norte Unit, said that he and his colleagues are grateful for this new tool and plan to use it as an “over the counter” handout for community members. He added that the charts summarizing timber-harvesting regulations and possible funding sources are especially helpful.

This cut-to-length harvester is useful for small-diameter tree harvesting. Photo by Yana Valachovic
“These give a landowner a starting place to sort through the many commercial timber harvesting documents and fuel-modification project funding source options available,” Curtis said. “A landowner is self-guided to a few options that will seem most appropriate, and this will facilitate a resource professional to assist that person in selecting the most appropriate permitting.”

The publication helps prepare the landowner or community entity (such as Resource Conservation Districts, Fire Safe Councils or other concerned groups) for the types of questions that might come up in preliminary planning conversations with a registered professional forester or RPF.

Just as a homeowner would talk with a contractor before tackling a construction project, landowners and community groups must consult with an RPF, Valachovic said. RPFs have the specialized knowledge of forest practice rules and regulations related to water, air quality and endangered species protections, and the license to file the permitting documents.

“That's what I do in my job: Landowners come to me and we start talking about goals and objectives,” she said. “We start thinking about potential timelines – which goals are short-term, which are long-term – and how we can put an operational plan together to help those landowners achieve their goals.”

Long-term projects, short-term actions

Among the many practical tips outlined in this guide, Valachovic emphasized one in particular: for landowners dipping their toes into fuel reduction for the first time, keep the project “simple and realistic.”

In this forest restoration treatment, fuels are piled and will be burned later in the season. Photo by Brita Goldstein
And while even smaller projects could be more expensive this year due to higher costs for gas, equipment and supplies, she said that now is still “a great time to plan,” as fuel-reduction projects can take months to develop and execute.

In the short-term, however, Valachovic stressed that the extremely dry conditions across the state make it imperative for Californians to harden their homes, manage the fuels (i.e., landscape plants, stored wood, tall grass, etc.) immediately adjacent to their homes, and devise and review family emergency plans; see UC ANR's Wildfire Preparation page for detailed information and resources.

“There are a lot of immediate actions that people can be doing this year to help mitigate their wildfire risks and prepare for the unexpected,” she said.

In addition to Valachovic, co-authors of “Planning and Permitting Forest Fuel-Reduction Projects on Private Lands in California” are Jared Gerstein of BBW Associates and Brita Goldstein, UCCE staff research associate in Humboldt and Del Norte counties; both are registered professional foresters.

Posted on Tuesday, June 28, 2022 at 9:03 AM
Focus Area Tags: Environment, Natural Resources

Landscaping with wildfire exposure in mind can protect homes

Creating defensible space around a home eliminates pathways for wildfire to burn directly to the home.

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.

Zone Zero, the area within five feet of the house, should be cleared of combustible plants, planter boxes, mulches and wood that embers may ignite. Photo by Yana Valachovic

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.

To prevent a wood fence from leading fire to the home, consider replacing the five feet closest to the house with a noncombustible section such as a cinder block wall, metal gate or wire fence. Photo by Yana Valachovic

“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.

Space plants, shrubs and trees so they don’t lead fire to the house or into crowns of trees.

“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.

 

 

 

Posted on Tuesday, August 10, 2021 at 4:42 PM
Focus Area Tags: Environment

Climate change is converting cities into 21st century ghost towns

In California, most ghost towns were created when a local industry collapsed. Now, climate change is more often to blame when booming communities whither and die, reported Daniel Cusick in E&E News.

In an eerie horror story released just before Halloween, Cusick wrote about five towns around the nation that have died or are dying from climate-related disasters. Historic Shasta and Helena, Calif., are featured in one of the vignettes. 

"Those are two towns that are getting more ghostly," said Yana Valochovich, UC Cooperative Extension forestry advisor in Humboldt and Del Norte counties.

A 19th-century mining town, Shasta City had been a preserved tourist destination in Shasta State Historic Park since 1937 when it was burned in the 2018 Carr Fire, the seventh most destructive wildfire in California history. Helena, a 170-year-old pioneer mining settlement, burned in the Helena Fire of 2017.

There almost certainly will be more "dead towns" as fires consume more of Northern California, Valochovic added.

The Helena Fire of 2017 burned down a pioneer mining town. (Photo: U.S. Forest Service)
Posted on Friday, October 30, 2020 at 11:14 AM
Tags: climate change (112), wildfire (167), Yana Valachovic (21)
Focus Area Tags: Environment

Houses likely burned from the inside out, says UCCE forest advisor

Fire damage from the 1991 Oakland Hills fire. Buildings can burn quickly if embers get inside and fall on flammable materials.

Preventing embers from getting inside may save homes

Photos and video of the Northern California communities that have been hit by wildfires show buildings reduced to ash. How could so many homes and businesses burn so quickly in the 2017 Wine Country fires? Many houses that burned to the ground in the Northern California fires likely burned from the inside out, says Yana Valachovic, UC Cooperative Extension forest advisor for Humboldt and Del Norte counties.

Red hot embers carried on the wind can enter the attic via the venting. “In the case of the wind-driven fires on October 8, these fires created ember storms that blasted little coals into everything in their pathway,” Valachovic said. These embers also create small spot fires near the home that fuel new sources of embers.

Weather played a large role in these fires and generated a fire storm of embers that ignited grass, shrubs, trees and anything in its path. “While the landscape can be the fuse, the homes really can be the most burnable part of the landscape,” Valachovic said. “These embers likely lodged in the small spaces and openings of homes and buildings. A common location is for the embers to enter via attic venting or HVAC systems distributing little fires into the buildings.

“Embers also landed on receptive leaves, outside furniture, and other flammable materials outside the buildings that created fires adjacent to the buildings. Once enough buildings were engulfed in fire, the radiant heat of each building fire led to exposures on the neighboring buildings, creating a house-to-house burn environment.”

Embers carried on the wind can ignite dry plant material like pine needles and create more embers that may enter homes through vents.

Residents can reduce the risk of embers setting their house on fire by removing dry plants around the structure.

“These fires remind us that everyone in California could help the fire situation by managing the vegetation, leaves in the gutters and decks, newspaper piles, brooms and other flammable sources near to their houses now before they get the evacuation call,” Valachovic said. “If you are likely to have to evacuate soon, temporarily covering or sealing up the vents with metal tape or plywood can help harden your home to an ember storm.”

Steve Quarles, UC Cooperative Extension advisor emeritus, who spent his career studying fire behavior on building materials and around homes, created an online Homeowner's Wildfire Mitigation Guide at http://ucanr.edu/sites/Wildfire. Quarles, who did research for the Insurance Institute for Business and Home Safety, demonstrates how embers can ignite and quickly engulf a house in flames in a video https://www.youtube.com/watch?v=IvbNOPSYyss. After the 3-minute mark, video shows embers drifting up and flying through a screened vent into the house, where they could ignite combustible materials in the attic resulting in fire starting on the inside of the home.

To show homeowners how to harden their homes against wildfire, Quarles will be presenting a free webinar July 28, 2020, with UC Cooperative Extension forestry advisor SusieKocher and ChristinaRestaino, assistant professor and natural resources specialist with University of Nevada, Reno Extension and the director of the Living With Fire Program. To register, visit bit.ly/TahoeRetrofit.

“If you have time to prepare your home, use the wildfire last-minute check list at https://ucanr.edu/sites/fire/Safety/Evacuation/,” Valachovic said.

Valachovic has co-authored publications in home survival in wildfire prone areas http://anrcatalog.ucanr.edu/pdf/8393.pdf and how landscape plants near homes can create more vulnerability to wildfire http://anrcatalog.ucanr.edu/pdf/8228.pdf.

“Past wildfire events have shown that this is the common way homes in the wildland urban interface (WUI) burn, and this scenario was likely translated to the urban environment,” she said.  

Posted on Wednesday, July 8, 2020 at 10:53 AM
Tags: wildfire (167), Yana Valachovic (21)

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