Editor’s note: David Burchfield is FAC Net’s Member Services Associate and a frequent blog contributor. In this piece, David introduces the National Institute of Standards and Technology’s Hazard Mitigation Methodology, a framework culminating from years of research on how wildfires impact the built environment. 

What if you’ve followed every home and parcel hardening recommendation down to the letter? You’ve cleared away brush from your ignition zone, replaced your roof, and set back your shed a long way from your home, but still… you could lose your home because one or more of your neighbors hasn’t done their homework as well. Perhaps there’s an auxiliary building too close to you on their side of the fence, or a wooden fence that runs too close to your neighboring wall. This kind of cross-parcel perspective on wildfire hazard mitigation is exactly what drives the Hazard Mitigation Methodology (HMM) by the National Institute of Standards and Technology (NIST). This past month, NIST released an online summary of resources to help practitioners and residents apply their Hazard Mitigation Methodology (HMM) in the real world. To give some context on how and why to use this methodology, let’s unpack the origins of the HMM with some of its creators.

The Hazard Mitigation Methodology Framework

The HMM is a framework for home and neighborhood ignition prevention and damage mitigation developed primarily by Alex Maranghides of NIST and his research team (Eric D. Link, Steven Hawks, Jim McDougald, Stephen L. Quarles, Daniel J. Gorham [a FAC Net member!], and Shonali Nazare). I got to talk with Maranghides and Hawks about the framework’s conception and creation. According to Hawks, he and Maringhides went to visit the 2018 Camp Fire in Northern California 4-5 days after the initial ignition, and they “really saw the connection of fire across parcels.” The Camp Fire destroyed 18,804 structures, making it one of the most destructive in California’s history. According to Maranghides, the HMM is “the culmination of 20 years of case studies of reconstruction. We are now on the fourth study of the Camp Fire. We’ve been studying the WUI fire problem, and we take that knowledge from the field.” 

This led the team to look beyond parcels of individual land (the most commonly used scale for regulation and study) to the community scale. “The part which makes [the HMM] very unique is that it’s truly a community system, because exposure comes from across parcels. You don’t want to say ‘Oh, homeowner B, you get a gold star, your home will be fine.’ Because homeowner A or C could burn your house down.”

The HMM gives many clear examples of how this might work. For example, it states: “Existing codes are parcel centric. Residential structures are similarly located in Scenario A and B; however, the parcel division in Scenario A allows placement of an auxiliary structure too close to the neighboring primary structure when the parcels are considered independently.” 

Illustrated graphic depicting parcels of land and relative placement to other parcels.

See page 21 of the PDF version of the HMM for additional context and details on this graphic. Image credit: NIST

As Maranghides said: “This is not designed to be an approach a homeowner takes. It’s designed to be an approach taken by a community… It has to be thought of as exposure-centric, not parcel-centric.”

Applying the HMM

The HMM considers preparing structures for wildfire, or hardening them, around two main threats: flames and embers. While partial hardening against flames can be somewhat proportionally effective, the methodology stresses that partial ember hardening does not equate proportional survivability with that threat. In other words, flames may be deterred by some actions, but embers can set a building on fire with even the smallest chink in your hardening armor. When we harden a structure, we do all that we can to reduce its flammability against both kinds of threats. Most important to the thinking beyond parcels, partial hardening against flames or embers isn’t just a risk for the parcel in question, but also for neighbors, especially in denser neighborhoods and communities. The PDF version of the framework offers exhaustive ember hardening recommendations in Table A (see page 58), including replacing plastic skylights with multi-pane glass, replacing shake roofs, adding noncombustible gutter covers, and others.

Tables B and C (pages 62 – 63) “evaluate the spatial relationships of fuels on surrounding parcels and on the parcel where the structure of interest is being protected.”. Should Tables B and C trigger hardening, Table D (page 64) explicitly addresses suggested hardening actions, including replacing exterior wall materials, screening windows, etc. 

Maringhides stresses that “you have to think of the three R’s of hazard mitigation: reduce, relocate, and remove the hazard.” This prompts residents to think about wood piles, outbuildings, etc. as hazards to not only themselves, but also their neighbors. 

Two side by side images: Image on left depicts a disattached model of a residential wall with a wooden structure on fire about five feet from it. Image on the right depicts a similar scene, but the flame lengths are much bigger than in the image on the left.

NIST conducted trials to determine the efficacy of different mitigation techniques. Photo credit: NIST

Hawks has seen some early adoption of the methodology in some California Office of Emergency Services (CalOES) efforts, specifically where one community has received FEMA funding to apply some community-wide hardening efforts. Hawks says “HMM was designed for [programs] like that.” 

This points to some of the promise of HMM, but also some of the challenges. As Hawks says, “What will drive that person to take the action that’s necessary? It’s not just one thing, it’s the whole suite of things. How can we drive people to want to take action? And those that want to but don’t have the resources, how can we support them to take those actions?”

Costs of total, community-wide hardening and fuels mitigation can be significant. The creators chose to exclude considerations of the cost of hardening measures from the HMM. Maranghides stresses that the framework was meant to survey what would work to significantly reduce or stop structure loss altogether in large fire events from a physical science, not an economic, perspective. This raises further questions which may prompt next steps in further adoption and application of community-wide resilience thinking: If we have a clear sense of how we collectively share risks across parcels (as the HMM provides), how will we choose to collectively address the work (and costs) to mitigate those risks? 

For me, this is the biggest impact of the HMM: It provides hard, specific, physical science support for the notion that we cannot view wildfire risk in isolation from our neighbors. But what do we do with that? Do we apply these costly, exhaustive measures to every single new home and retrofit all the rest throughout the whole country? Is that even realistic? Hawks points to some growing interest in code development guidance around cross-parcel Structure Separation Distance (SSD), at least in California. This may provide some promise for applying the HMM in permitting for new developments there, which is indeed exciting, but we know that wildfire risk extends far beyond that. This implies some important questions about how we understand community, private property and property tax, and so much more. Code guidelines in California that apply the HMM will provide the test case to see how well these ideas can work in one context, but the broader implications about how and why this framework can (or cannot) be applied more broadly raise enough questions for much more consideration. Perhaps we’ll get into those in another blog post on the topic….


National Institute of Standards and Technology (NIST), Maranghides, A., Maranghides, A., Link, E. D., Hawks, S., McDougald, J., Quarles, S. L., Gorham, D. J., & Nazare, S., WUI

Structure/Parcel/Community Fire Hazard Mitigation Methodology (2022). Retrieved January 5, 2023, from https://nvlpubs.nist.gov/nistpubs/TechnicalNotes/NIST.TN.2205.pdf


Leave a Reply

Your email address will not be published. Required fields are marked *