home ignition zone Archives

Construction costs for fire-resistant home in California

Bill GabbertAugust 29, 2022August 29, 2022UncategorizedFireWise, home ignition problem, home ignition zone16 Comments

Mitigating destruction in the home ignition zone

Home steps on fire — Relatively fire-resistant homes can ignite during low-intensity wildfires if a path of combustible material, such as fences, stairs, decks, or support beams lead the fire to the home. Image from Texas Forest Service report about fires in 2011.

This is a portion of an article first published at Headwaters Economics in July, 2022. It is used with permission here.

Increasing home loss and growing risks require reevaluating the wildfire crisis as a home-ignition problem and not a wildland fire problem. A home’s building materials, design, and nearby landscaping influence its survival. Together with the location, arrangement, and placement of nearby homes, constructing a wildfire-resistant home is critical in light of rising wildfire risks. This report compares the cost of constructing a home to three different levels of wildfire resistance in California.

California is a leader in the country with a statewide building code and other property-level vegetation requirements addressing wildfire impacts to the built environment. Applicable to all new developments located in State Responsibility Areas (SRAs) and the highest fire severity zones in Local Responsibility Areas (LRAs), California’s Building Code Chapter 7A is intended to reduce the vulnerability of homes to wildfire.

Yet given the magnitude of California’s wildfire risks and increasing home development in wildfire-prone areas, constructing a home beyond Chapter 7A requirements may be needed to ensure greater wildfire resistance. Understanding the comparative costs of wildfire-resistant home construction in California can inform future wildfire policy and decision-making.

This report compares the costs for constructing three different versions of a wildfire-resistant home in California:

Baseline home compliant with the minimum requirements of Building Code Chapter 7A;
Enhanced home augmenting Chapter 7A requirements with a vertical under-deck enclosure around the perimeter of the deck and a noncombustible zone around the home (0 to 5 feet), including under the deck and extending five feet out from the deck perimeter; and,
Optimum home constructed to the most stringent, fire-resistant options (e.g., use of a noncombustible material), or in some cases, a “Code plus” option (an option not currently included in Chapter 7A). Optimum performance levels were selected based on recent research findings and best judgment.

Building materials and assemblies for five primary home components were considered, including:

Roof – roof covering, vents, roof edge, and gutters (including gutter covers and drip edge)
Under-eave area – eaves, soffit, and vents
Exterior wall – siding, windows, doors, trim, and vents
Attached deck – horizontal surface area, rails, and under-the-deck footprint
Near-home landscaping – the immediate five-foot perimeter around the home and attached deck (including mulch and fencing)

Cost estimates for individual building materials were provided through RSMeans, a national database of construction costs for residential, commercial, and industrial construction. Cost estimates included building material, labor, equipment, and contractor overhead costs such as transportation and storage fees.

In northern and southern California, building an Enhanced wildfire-resistant home increased construction costs by approximately $2,800 over the Baseline home. Constructing a home to Optimum wildfire resistance increased overall costs by $18,200 in northern California and by $27,100 in southern California.

Although the Optimum home was more expensive to build, it is likely that the increased costs will return greater long-term benefits in energy efficiency and durability. The roof, exterior walls, and near-home landscaping added the largest proportional increases to building costs. Each of the five components is described in more detail below.

Read the entire article at Headwaters Economics.

Researchers evaluate how fences can spread fires and ignite structures

Bill GabbertAugust 17, 2022August 17, 2022Uncategorizeddefensible space, fence, FireWise, home ignition zone, WUI10 Comments

Tests fire hazard fences — Examples of very high hazard fences and mulch: A) parallel privacy fences, B) double
lattice fences, C) wood-plastic composite #1 fence, D) good neighbor fence, E) rubber mulch. (From the NIST research)

Three weeks ago a television station in Dallas, FOX 4, streamed live video as a grass fire spread across a field and reached densely-packed houses, eventually destroying 9 and damaging another 17. There were several reasons why the structures were so vulnerable, including medium-heavy vegetation in the field adjacent to the property lines, very little impact from efforts of the fire department to stop the spread, no air support, and wood fences that connected all of the properties on the rear and sides of the homes.

fences burn fire Texas homes destroyed — Parallel fences burn as grass fire spreads into neighborhood in Balch Springs, Texas, July 25, 2022. Image from video by FOX 4 Dallas-Fort Worth.

On August 10 the National Institute of Standards and Technology (NIST) published results of 187 experiments that examined how fire spread toward a structure is affected by combustible fences and mulch under conditions that may be encountered in a wildland-urban interface (WUI) fire. They looked at mulch only, fence only, fence plus mulch, parallel fences, and long range firebrands. The materials studied were western red cedar, California redwood, pine, vinyl, and wood-plastic composites. Fence styles included privacy, lattice, and good neighbor (board on board).

A small structure was located between zero and up to six feet downwind of the fence or mulch bed as a target for flames and firebrands. A target mulch bed at the base of the structure tested the ability of firebrands produced by the burning fence and mulch bed to ignite spot fires that threatened the structure.

While not many homeowners place store-bought mulch below their fences, it can be common for debris to build up along the base on one or both sides. The amount and flammability can be extremely variable, but the researchers’ use of mulch gave them control over the flammable material which could be consistently duplicated in their experiments.

The study found that firebrands capable of igniting spot fires downwind were generated by nearly all combinations of fence and mulch tested in this study. All wood fences with mulch at the base caused spot fires in the target mulch bed. Spot fires were often ignited within a few minutes of mulch and fence ignition. Shredded hardwood mulch and pine bark mulch burned and emitted firebrands for longer than an hour. Ignition of spot fires was also demonstrated from firebrands transported by the wind over distances as far as 156 feet from the burning item under high wind conditions and over a paved surface.

The research generated a number of recommendations:

Avoid parallel fences, to reduce exposure to large flames. Parallel fences can result in highly hazardous fuel accumulation corridors that are difficult to access and maintain. Spacing of 3 feet between fences is not sufficient.
Avoid proximity to other combustible fuels, to reduce fire intensity and limit fire spread. This includes fuels above the fence and fuels across parcel boundaries. Avoid mulch at base of fence.
Avoid proximity of combustible fences to residence, including neighboring residence, to prevent direct ignition.
Fire spread is more likely with wood and wood-plastic composite fences than with fences made of vinyl or noncombustible materials such as stone, brick, or steel.
Keep fence and yard clear of debris, to reduce the amount of fuel and potential pathways for fire.
Harden structures against firebrands to prevent structure ignition from embers produced by fences or other combustible sources.

The video from the July 25 fire in Texas does not clearly show the fences between the residences, but it is likely that they directly connected to the structures. An example is seen in the photo below of two homes in Superior, Colorado, one of the communities devastated by the Marshall Fire that destroyed 991 structures south of Boulder December 30, 2021.

Fence connecting houses fire spread hazard — File photo of fence connecting houses in Superior, Colorado. July, 2012 Google image.

The images below are from the FOX 4 Dallas-Fort Worth video shot July 25, 2022.

Most structures that burn in a wildfire are not ignited by direct flame impingement, but by burning embers that are lofted and carried downwind ahead of the fire. At Wildfire Today we first covered the role of embers in igniting structures in 2010, a concept brought into the public consciousness by Jack Cohen, a researcher at the Missoula Fire Science Lab. To reduce the chances of a home burning in a wildfire, the most bang for the buck is to concentrate on the Home Ignition Zone. The flammable material near the structure needs to be modified, reduced, or eliminated to the point where multiple burning embers landing in the zone will not propagate the fire and spread to the structure.

More information: Six things that need to be done to protect fire-prone communities

Thanks and a tip of the hat go out to Gerald.

Save communities by thinning forests or hardening structures?

Bill GabbertAugust 9, 2022August 8, 2022Uncategorizedfuel treatment, home ignition zone39 Comments

Moose Fire August 2, 2022 in Montana — The result of aerial ignition on the Moose Fire August 2, 2022 in Idaho. By Mike McMillan for the USFS.

Bloomberg Law has an interesting article by Bobby Magill about efforts to reduce the wildfire threat to homes. It discusses and compares forest thinning vs. hardening structures. Here are excerpts, but read the entire article.

Congress is spending billions to save communities from Western megafires by thinning large swaths of forests even as scientists say climate change-driven drought and heat are too extreme for it to work.

The money would be better spent thinning woods closest to homes and shoring up houses against embers raining down from firestorms, according to academics, former agency officials, and others who study wildfires.

“If our goal is to keep homes and communities from burning, the experts are telling us to focus from the home outwards. First, harden the home so it is less likely to ignite,” said Beverly Law, an emeritus professor of forestry at Oregon State University.

Megafires are sustained by drought and heat, and “no amount of thinning treatment will prevent such fires from occurring,” she said.

[…]

No Scientific Consensus
As the federal government focuses on forest thinning, no scientific consensus exists that removing vegetation, especially at a landscape-scale, will save communities in the paths of firestorms amid the West’s historic 23-year drought.

The science is clear that “there isn’t a great connection between home loss and these fuel treatments,” though they sometimes help firefighters gain a foothold on some fires, Cheng said.

Randy Moore, the Forest Service chief, said the agency is confident that as homes are built deeper and deeper into the woods, its research shows that removing “overstocked” trees is the best way to protect them.

“We know where we do nothing, or where we do a little, we’re seeing the evidence out on the landscape,” Moore said, referring to recent megafires. “We feel compelled to do something.”

Some homes being rebuilt in Paradise, CA will be very wildfire resistant

Bill GabbertJune 1, 2022June 1, 2022UncategorizedCalifornia, Camp Fire, home ignition zone, home safety, Paradise12 Comments

Based on the quonset hut design used extensively by the US military in World War II

A few of the 13,861 homes destroyed in the Camp Fire are being rebuilt using a particular design that is much more fire resistant than a typical structure. In 2018 the northern California fire burned most of the houses in Paradise after a failure on a Pacific Gas and Electric powerline ignited the blaze that raced through the town, doing much of its damage in just a few hours.

During World War II the US military purchased and installed thousands of quonset huts, a lightweight prefabricated structure of corrugated galvanized steel with a semi-cylindrical cross-section.

Design for a quonset hut style structure, via CBS News.

The steel itself is non-combustible of course, and if the rest of the exterior building materials are also, the structure should be very resistant to ignition during a wildfire. But it is important that everything within the home ignition zone is consistent with Firewise principles.

CBS News Sunday Morning produced the video story below of how this quonset hut concept is being used in Paradise.

Thanks and a tip of the hat go out to Gerald.

In a wildfire burning embers transported downwind are what cause most structures to burn

Bill GabbertMay 10, 2022Uncategorizedember attack, FireWise, home ignition zone, home safety, Jack Cohen12 Comments

Sheltering from the Creek Fire at the Mammoth Pool Reservoir — Sheltering from burning embers and the Creek Fire at the Mammoth Pool Reservoir Boat Launch, Sept. 5, 2020. Photo by Cameron Colombero, via Mike Ikahihifo.

The video below produced by the New Jersey Forest Fire Service elaborates on this concept. It is queued up to 1:42 where the issue is addressed.

More information is in our articles tagged “Home Ignition Zone.”

Research suggests Forest Service lands not the main source of wildfires affecting communities

Bill GabbertFebruary 18, 2022April 14, 2024Uncategorizedhome ignition zone, research25 Comments

They found that ignitions on Forest Service lands accounted for fewer than 25% of the most destructive wildfires

Research led by Oregon State University shows that fires are more likely to burn their way into national forests than out of them. The findings contradict the common narrative of a destructive wildfire igniting on remote public land before spreading to threaten communities, said Chris Dunn of the OSU College of Forestry.

The study, which looked at more than 22,000 fires, found that those crossing jurisdictional boundaries are primarily caused by people on private property. It also showed that ignitions on Forest Service lands accounted for fewer than 25% of the most destructive wildfires – ones that resulted in the loss of more than 50 structures.

“In the old framing, public agencies bear the primary responsibility for managing and mitigating cross-boundary fire risk and protecting our communities, with their efforts focused on prevention, fuel reduction and suppression,” Dunn said. “This has been the dominant management approach of years past, which is failing us.”

Destructive fires start on Forest Service or other land — Location of destructive wildfires (> 50 structures lost) between 2000 and 2018 that originated on (a) USFS lands, and (b) non-USFS lands. Fire locations are symbolized by magnitude of structure loss. Relatively few destructive fires originated on USFS lands. The most destructive USFS and non-USFS fires during this time are the Cedar fire and the Camp fire.

The findings, published February 15, 2022 in Nature Scientific Reports, follow by a few weeks the Forest Service’s release of a new 10-year fire strategy, Confronting the Wildfire Crisis. The strategy aims for a change in paradigm within the agency, Dunn said.

“We are long overdue for policies and actions that support a paradigm shift,” he said.

Scientists including Dunn and OSU’s Will Downing investigated 27 years of fires that crossed jurisdictional boundaries. The collaboration also included scientists from Colorado State University and the Forest Service’s Rocky Mountain Research Station.

Cross-boundary fires consumed just over 17 million acres during the study period of 1992 to 2019, and about half of the burned area was Forest Service land. The study area covered almost 141 million acres across 11 states and included 74 national forests.

Of all ignitions that crossed jurisdictional boundaries, a little more than 60% originated on private property, and 28% ignited on national forests. Most of the fires started due to human activity.

“The Forest Service’s new strategy for the wildfire crisis leads with a focus on thinning public lands to prevent wildfire intrusion into communities, which is not fully supported by our work, or the work of many other scientists, as the best way to mitigate community risk,” Dunn said.

Home Ignition Zone

“A substantial portion of the wildfire problem is a community destruction problem,” added Michael Caggiano of Colorado State. “The Forest Service can contribute to an advisory or facilitation role to address the home ignition zone, including fire resistant design and zoning, and fuels management on private lands, but states, local government and homeowners are better positioned than the USFS to manage those components of wildfire risk.”

A paradigm shift that could mitigate wildfire risk would begin with the recognition that the significant wildfires occurring in western states is a fire management challenge with a fire management solution, not a forest management problem with a forest management solution, Dunn said.

“The only way we are going to address the wildfire problem on large public lands at the scale of the challenge is through the effective and efficient management of wildfires over the long run,” he said.

Dunn said that means allowing some fires or portions of fires to burn to provide risk reduction and ecological benefits, identifying and preparing locations where suppression is likely to be effective, and developing strategies to rapidly distribute resources to where they are most needed and can do the most good.

“Our research has significant potential to inform and guide development of effective cross-boundary risk mitigation strategies, including identifying where and how work on the ground can be most effective,” he said. “The main source of our communities’ exposure to wildfire risk is clearly not our national forests.”

The study showed that in many cases, national forests were a net receiver of cross-boundary wildfire rather than a source, and that those fires tend to happen in areas with higher densities of roads and people.

Dunn credits the Forest Service for accepting the modern realities of wildfire and for embracing collaborative governance and cross-boundary partnerships. He added that managing fire in multijurisdictional landscapes has become a centerpiece of wildfire strategic planning and that evidence suggests fire transmission across boundaries will continue to increase.

Legislation

“As the Forest Service’s strategy moves forward, we think there could be opportunities to learn from what their state partners are doing, such as the more comprehensive policies passed in Oregon in 2021,” he said. “Oregon’s omnibus wildfire bill is a science-driven approach that recognizes the shared responsibility we all have in adapting to the fire environment.”

The legislation requires those homes at greatest risk to mitigate at the home ignition zone and also addresses landscape resilience and improved wildfire response.

Dunn calls it “the type of comprehensive policy we need to address the multitude of impacts wildfires have on communities, ecosystems, industry, etc. It recognizes that the Forest Service is neither the sole source of the problem nor the sole solution to the problem, but rather one of many pieces to a paradigm shift society needs to make.”

Matthew Thompson and Karen Short of the Rocky Mountain Research Station also took part in the cross-boundary fire study, which was partially funded by the Forest Service.

From Oregon State University.

Authors of the research paper: William M. Downing, Christopher J. Dunn, Matthew P. Thompson, Michael D. Caggiano, and Karen C. Short

Thanks and a tip of the hat go out to Kelly.