“We don’t have a forest fire problem, we have a home ignition problem. As soon as you come to that realization, it changes your view on wildfire.”
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We have to learn to live with fire
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Jurisdictions need to develop standards for structures, the home ignition zone, and community infrastructure
Continue readingWildfire-resistant construction costs are similar to typical costs
With tens of thousands of homes being destroyed in the last year in California wildfires it should be a very high priority for home builders and local governments to swiftly adopt the practices that can greatly reduce the vulnerability of structures. It is not a given that if a large rapidly-spreading wildfire approaches a house it will ignite and burn to the ground.
Media reports sometimes marvel at how an occasional structure will be spared, and may describe it as miraculous or random. Instead, it is based on science. Some structures are designed, built, and maintained to be less vulnerable than others. The other half of the equation is what is within the home ignition zone — what will become fuel within 100 feet. If there is continuous vegetation or other flammable material in that zone that can carry the fire, especially close to the structure, it stands less chance of survival.
But for now let’s think about the structure itself. There are several useful reference guides for architects, home builders, and zoning boards containing information that can lead to designs and building codes that can help keep a fire from turning into a disaster.
• International Code Council’s International Wildland Urban Interface Code (IWUIC),
• National Fire Protection Association’s Standard for Reducing Structure Ignition Hazards from Wildland Fire (Standard 1144), and
• California Building Code Chapter 7A—Materials and Construction Methods for Exterior Wildfire Exposure.
Headwaters Economics compared the costs of new construction of a typical home vs. one with wildfire resistant standards for a three-bedroom, 2,500-square-foot, single-story, single-family home representative of wildland-urban interface building styles in southwest Montana. Below are excerpts from the article:
We examined costs in four vulnerable components of the home: the roof (including gutters, vents, and eaves), exterior walls (including windows and doors), decks, and near-home landscaping. Overall, the wildfire-resistant construction cost 2% less than the typical construction, with the greatest cost savings resulting from using wildfire-resistant fiber cement siding on exterior walls, in lieu of typical cedar plank siding. While cedar plank siding is typical in the wildland-urban interface of western Montana, fiber cement siding is already a common choice in many regions because of its relative affordability, durability and low maintenance needs. Wildfire-resistant changes to the roof resulted in the largest cost increase, with a 27% increase in gutters, vents, and soffits. The following sections describe the wildfire-resistant mitigations for each component.
Are planned communities safe from wildfires?
And, can we learn to adapt to fire?
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Continue readingResearchers study how the Fort McMurray fire ignited homes
A preliminary report report released by the Institute for Catastrophic Loss Reduction looked at how the 1,500,000-acre Fort McMurray Fire ignited some of the 2,400 structures in the Alberta city in May of this year.
Below are excerpts from the document.
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After evaluating the fire environment and clearances between homes and the forest edge, the investigator discounted direct contact from flames or radiant heat of the forest fire as being significant sources of home ignition at Fort McMurray. Instead, it was concluded that wind-driven embers were the most probable cause for the majority of early home ignitions in the zone where the fire made its transition from forest into urban neighbourhoods. Once established, the fire would have spread from structure to structure as an urban conflagration, accounting for the majority of home losses.
In all neighbourhoods studied, homes whose owners had adopted FireSmart guidelines survived much more frequently than homes where they had not, despite the extraordinarily harsh conditions.
Recommended FireSmart guidelines work. They are effective in reducing the probability of home ignition and wildfire losses. Home survival does not appear to be random or a matter of luck.
Home survival depends on conditions in the home ignition zone, for which owners are responsible.
While low total hazard rating is important, a single critical weakness can lead to home loss.
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NIST releases report on Waldo Canyon Fire that burned 344 homes and killed two people
The National Institute of Standards and Technology has released a lengthy report on the Waldo Canyon Fire that burned 344 homes and killed two people in Colorado Springs, Colorado in June, 2012. (It can be downloaded here, but is a large file.)
The 216-page document covers firefighting tactics, how structures ignited, defensible space, and how the fire spread, but does not address to any significant extent the management, planning, coordination, and cooperation between agencies, which were some of the largest issues.
The report was put together by five people, Alexander Maranghides, Derek McNamara, Robert Vihnanek, Joseph Restaino, and Carrie Leland.
At least three official reports have been written about the Waldo Canyon Fire, two from the city of Colorado Springs (here and here) and a third from the county sheriff’s office. However one of the most revealing was the result of an independent investigation by a newspaper, the Colorado Springs Independent, which revealed facts that were left out of the government-issued documents, including numerous examples of mismanagement by the city before and during the event.
The fire was first reported the evening of June 22, 2012 on the Pike National Forest. Due at least in part to the anemic response from the U.S. Forest Service, the fire was not located until after noon the following day. No aircraft were requested until firefighters were at the fire, more than 16 hours after the initial report.
The day the fire started there were eight large fires burning in Colorado and 16 uncontained large fires in the country. Four days later on June 26 when the Waldo Canyon Fire moved into Colorado Springs burning 344 homes and killing two people, there were 29 uncontained large fires burning in the United States.
However there were only nine large air tankers in the United States on U.S. Forest Service exclusive use contracts, down from the 44 we had 10 years before.
The 7-page Executive Summary of this newest report lists 4 primary findings, 37 technical findings, and 13 primary recommendations.
Primary findings:
- Defensive actions were effective in suppressing burning structures and containing the Waldo Canyon fire.
- Pre-fire planning is essential to enabling safe, effective, and rapid deployment of firefighting resources in WUI fires. Effective pre-fire planning requires a better understanding of exposure and vulnerabilities. This is necessary because of the very rapid development of WUI fires.
- Current concepts of defensible space do not account for hazards of burning primary structures, hazards presented by embers and the hazards outside of the home ignition zone.
- During and/or shortly after an incident, with limited damage assessment resources available, the collection of structure damage data will enable the identification of structure ignition vulnerabilities.
Three of the technical recommendations:
- Fire departments should develop, plan, train and practice standard operating procedures for responding to WUI fires in their specific communities. These procedures should result from scientifically mapping a community’s high- and low-risk areas of exposure to both the fire and embers generated during WUI events (as will be possible using the WUI Hazard Scale).
- A “response time threshold” for WUI fires should be established for each community. Fire departments have optimal “time-to-response” standards for reaching urban fires. Similar thresholds can, and should be, set for WUI fires.
- High-density structure-to-structure spacing in a community should be identified and considered in WUI fire response plans. In the Waldo Canyon fire, the majority of homes destroyed were ignited by fire and embers coming from other nearby residences already on fire. Based on this observation, the researchers concluded that structure spatial arrangements in a community must be a major consideration when planning for WUI fires.
Primary recommendations:
Radiant heat, embers, and the ignitability of structures
Here are a couple of interesting videos featuring Jack Cohen, a researcher at the Missoula Fire Science Lab. The videos explain radiant heat and how difficult it is for fine fuels and structures to ignite from that alone, and the role of embers in spreading fire and burning structures.