Structure Protection in the WUI - A Collection of Resources
Studies show that effective strategies to mitigate the risk of structural damage in wildfires include defensible spaces and home hardening. Structures in the western United States are especially at risk. Several jurisdictions have adopted codes that require implementation of these strategies. However, construction and landscaping professionals are generally not required to obtain credentials indicating their competency in mitigating the risk of structural damage in a wildfire. We discuss the implications of this policy gap and propose a solution to bolster competency of professionals in wildfire protection as communities further expand in fire-prone areas.
Short video (2:39).
Learn 5 key areas around your home to inspect when assessing your property’s wildfire risk.
Results were largely consistent with previously literature, finding that structural hardness factors (e.g. double-paned windows, enclosed eaves, ignition-resistant roofs and siding, no vents, etc.) are important in determining structure survival. Newer structures, built after California’s recent (2005 and 2007) fire safe building code updates, were more likely to survive, as were homes with higher improvement values. Mobile homes were far more likely to be destroyed. The role of fuel mitigation around structures was less conclusive; defensible space clearance had only a weak association with structure survival, although DINS+DSPACE results suggested a slight reduction in risk due to removing leaves and needles from gutters/roofs and keeping surrounding dead grass mowed.
Destructive wildfires are now a real threat in regions across the country and beyond what was once considered as the fire season, examples of which are the 2016 Gatlinburg Fire in the Southeast and the 2021 Marshall Fire in late December. Existing wildfire risk assessment procedures typically use simulation modeling to quantify the wildfire exposure to wildland-urban interface (WUI) communities, but rely on subjective estimates of the susceptibility of structures to fire in order to quantify risk. Thus, there is a need to better understand and characterize the effectiveness of different mitigation actions related to individual structure features and community layout on the resilience of a WUI community to fire. This presentation discusses findings from the analyses of past wildfire events and introduces a streamlined model to capture fire spread inside WUI communities to quantify structural damage. The proposed model can be used to guide mitigation actions in existing and new communities, and inform preparedness and response strategies by evaluating the likelihood of successful suppression based on the rate of fire spread.
The IBHS test chamber is a unique facility to study the effects of wind on fire. The test chamber area is equal to four basketball courts which allows researchers to perform large scale wind and fire tests. The test chamber is equipped with 105 fans that can generate gusty wind ranging from 12 to 120 mph. In this presentation, we will share our experience on creating realistic gusty wind and its effects on full-scale fire tests. Then, we will talk about our ongoing collaborative research projects with USFS, NIST and Cal Fire. Finally, we will describe our role in building codes and public policy.
Strong associations between both distance to nearest destroyed structure and vegetation within 100 m and home survival in the Camp Fire indicate building and vegetation modifications are possible that would substantially improve outcomes. Among those include improvements to windows and siding in closest proximity to neighboring structures, treatment of wildland fuels, and eliminating near-home combustibles, especially in areas closest to the home (0–1.5 m).
Wildfires, especially those that impact WUI communities, are driven by multiple factors interacting together that can determine the fire’s intensity and severity, including topography, wind, drought, relative humidity, and the condition and type of local vegetation. The behavior of larger wildfires can additionally be influenced by the weather systems they create, such as fire whirls and pyrocumulonimbus clouds.
Home survivability can be influenced by their construction materials, proximity to other structures and how these neighboring structures are maintained. Overall layout of the property, including landscape design and if materials are stored within proximity of buildings, can also have an impact.
This Guide includes specific recommendations for how to retrofit existing components of a home to withstand wildfre. Each section contains an explanation of how the component is vulnerable to wildfire and what can be done to improve that component. The illustrations throughout the Guide are intended to show best practices for reducing the vulnerability of a home to wildfire.
This study compiled and analyzed an extensive dataset of building inspectors’ reports documenting homeowner mitigation practices for more than 40,000 wildfire-exposed structures from 2013–2018. Comparing homes that survived fires to homes that were destroyed, we investigated the role of defensible space distance, defensive actions, and building structural characteristics, statewide and parsed into three broad regions. Overall, structural characteristics explained more of a difference between survived and destroyed structures than defensible space distance. The most consistently important structural characteristics—having enclosed eaves, vent screens, and multi-pane windows—were those that potentially prevented wind-born ember penetration into structures, although multi-pane windows are also known to protect against radiant heat. In the North-Interior part of the state, active firefighting was the most important reason for structure survival. Overall, the deviance explained for any given variable was relatively low, suggesting that other factors need to be accounted for to understand the full spectrum of structure loss contributors. Furthermore, while destroyed homes were preferentially included in the study, many “fire-safe” structures, having > 30 m defensible space or fire-resistant building materials, were destroyed. Thus, while mitigation may play an important role in structure survival, additional strategies should be considered to reduce future structure loss.
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Wildfires are a natural element of many ecosystems and have a great impact on society by destroying property and sometimes by taking lives. In the United States alone, thousands of individual fires occur every year and the number of both burned hectares and destroyed buildings are higher than ever since recorded fire history. Six of the 10 fires with the largest losses of lives and homes of the 20th century occurred in the wildland urban interface (WUI), and all of them occurred within the last 20 years. Given that billions of dollars are being allocated to fuel management and fire suppression and that the main fire suppression goal is to protect people and property, it is necessary to understand the factors related to vegetation, terrain and spatial arrangement that contribute to building loss from wildfires, and examine nationwide spatial patterns of vulnerability and rebuilding.