April 9, 2025
196 - Fire spread through external walls pt. 1 with FSRI
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In this podcast episode, we host Rebekah Schrader, Joseph Willi, Daniel Gorham and Gavin Horn, all from the FSRI, to cover their recent experimental research on fire spread through external walls. This is part 1 of the interview - the background, rationale and context. In part 2, we cover the experiments themselves, findings and actionable guidance from the experiments.
This research is conducted within the context of structure-to-structure fire spread, potentially in urban conflagration scenarios. The subject is most relevant, as when wildfires meet urban areas, they transform into something far more destructive – "wildfire-initiated urban conflagrations." These events devastate entire communities as fire spreads rapidly from structure to structure, overwhelming firefighting resources and leaving widespread destruction in their wake.
The Fire Safety Research Institute has embarked on a comprehensive research initiative examining exactly how these conflagrations develop and spread. What started as a response to their advisory board's call to action in 2018 has evolved into a groundbreaking exploration of the complex interactions between wildland fires and the built environment.
We break down the three primary mechanisms of fire spread – radiant heat, direct flame contact, and firebrands – while highlighting specific vulnerabilities in modern construction, particularly windows and cladding systems.
What makes this research particularly valuable is how it bridges traditionally separate disciplines: wildfire science and structural fire engineering. The team explains how they've translated complex wildfire scenarios into controlled laboratory experiments that yield actionable data for improving building codes and community design.
Whether you're a fire safety professional, community planner, or homeowner in a wildfire-prone region, this conversation offers crucial insights into how we can create more resilient communities in the face of this growing threat.
In the next episode, we will cover in depth the details of three experiments mentioned today.
Find the research papers at:
- https://onlinelibrary.wiley.com/doi/10.1002/fam.3278
- https://link.springer.com/article/10.1007/s10694-024-01685-8
- https://link.springer.com/article/10.1007/s10694-024-01656-z
And additional resources at:
- https://fsri.org/research-update/journal-article-reports-heat-transfer-through-different-window-constructions
- https://fsri.org/research-update/journal-article-investigates-role-residential-siding-materials-spread-exterior
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The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.
00:00 - Introduction to External Walls Research
06:13 - Understanding WUI and Urban Conflagration
11:42 - FSRI's Research Methodology
18:35 - Fire Spread Mechanisms Between Buildings
27:12 - Window Vulnerabilities and Technology
36:08 - Structure Hardening Against Wildfires
43:38 - Engineering Fire-Safe Communities
WEBVTT
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Hello everybody, welcome to the Fire Science Show.
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My mission in this podcast is to curate a listening list for you covering the most important interesting research happening around the world, and my attention came to a very interesting and big piece of research recently that is constantly published by Fire Safety Research Institute, fsri, and their research orbits around the topic of external walls and fire spread between buildings, fire spread through external walls and different aspects of that fire spread.
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And when I've looked into the papers, it was immediate to me that this is a fantastic piece of research.
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It's a piece that covers a very important knowledge gap that we have in fire safety and, what's even more interesting, it does not just cover the fire spread on its own.
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It puts it in the context of wildland, urban interface, fires entering urban habitats and fire spread like the ones that we've seen, perhaps, in LA Palisades fire recently.
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You know the urban configuration, types of fires that are really the most threatening ones, the ones that we really worry about the most.
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So, beyond just studying fire physics, beyond just studying compartment fires, beyond studying fire spread, this research literally bridges two disciplines wildfires and compartment fire science, and that makes it really, really interesting, and therefore I've started digging, started connecting myself with the colleagues at FSRI and organized this interview, and boy, this project is much bigger than I thought.
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So what you're about to witness is a two-part episode.
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Actually, in this first episode published today, we are covering the background, the rationale, the why, why are they pursuing this massive research set, what questions do they try to answer and what's the scientific context of the considerations.
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And in the episode that will be published in the next week, we will go more in-depth into the experiments performed, the experimental setups, results of those experiments, how they interplay together, what we've learned new from those experiments and how fire engineers can use that.
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My guess first time, I'm doing an interview with four different guests at the same time.
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So those are Rebecca Schroeder, joseph Willey, dan Gorham and Gavin Horn, all from FSRI, all involved in this magnificent external wall research project.
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So what else to add, you'll figure out yourself.
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Let's spin the intro and jump into the episode.
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Welcome to the Firesize Show.
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My name is Wojciech Wigrzyński and I will be your host.
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This podcast is brought to you in collaboration with OFR Consultants, a multi-award-winning independent consultancy dedicated to addressing fire safety challenges, established in the UK in 2016 as a startup business of two highly experienced fire engineering consultants.
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The business has grown phenomenally to eight offices across the country, from Edinburgh to Bath.
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Colleagues are on a mission to continually explore the challenges that FHIR creates for clients and society, applying the best research experience and diligence for effective, tailored solution.
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Ofr will grow its team once more and is keen to hear from industry professionals who would like to collaborate on fire safety features this year.
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Get in touch at OFRconsultantscom.
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Hello everybody, I am here joined today by quite a crowd from the Fire Safety Research Institute.
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Hello guys, I'll start with Rebecca Schroeder from FSRI.
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Hello, rebecca, nice to meet you.
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Hi, nice to meet you On my screen.
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Next is Joseph Willey hey, joseph, how's it going?
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Dan Gorham hey Dan, okay.
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Yeah, nice to meet you On my screen.
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Next is Joseph Willey hey, joseph, how's it going?
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Dan Gorham hey Dan, okay.
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Yeah, good to see you.
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And Gavin Horn Welcome back, sir.
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Thank you, great to be here.
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Oh, and really amazed that we've pulled this over, and I'm really happy to record this podcast episode.
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So, to go straight into the important stuff, you guys are inside of a very interesting project related to external walls, heat exposures, fire spread into the buildings from the buildings, all rotating, revolving around external walls of our buildings in in the most interesting context, combining a wild and urban interface with built environment civil engineering.
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I love it, love it.
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I love the way how you are applying this.
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So, before we start talking nitty gritty about your experiments and the setups that you've done, tell me what made you start this work, because I assume it was not just a random coincidence that you run into this massive undertaking.
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So what was the initial trigger to go into this research, joey, would you like to start?
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So at FSRI we have an advisory board that we kind of consult with, filled with fire experts from all different types of fields whether that's the fire service or fire protection engineers or fire researchers and they kind of help guide our research.
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And so we have an annual meeting where we tell them, get them up to speed on the kind of research we've been doing over the past year, and then we have a session where we ask what do you think our next topic should be?
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What are some spaces we're not exploring that we should explore?
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And so we had one of those meetings, and was it 2018,?
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I think that we should explore.
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And so we had one of those meetings, and was it 2018?
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I think.
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And by far the number one issue that we hadn't been addressing was wildland or WUI fires, and that makes sense.
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It's been a hot topic, especially over the last couple of decades, as these fires increase in frequency, severity and size.
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So, based upon that, we started planning out what our research would look like, what we would focus on, and our first goal was to kind of look at structures.
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We've always focused on structure fires.
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Fsri started with the fire service and looking at fires inside of structures.
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So our idea was we would be looking at fires outside of structures kind of exterior fire spread into the structures.
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And so a part of researching that, our first round of experiments we conducted in a large-scale fire lab in Northbrook and we had three different phases of experiments.
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Our first phase was looking at different types of building material, construction materials, samples, when they're exposed to a well-characterized heat source in the form of the heptane spray burner and kind of how they would react.
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So we set them at distances that gave us approximate heat fluxes of 10, 20, and 30 kilowatts per meter squared.
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And we were looking at materials from roofing materials, siding materials, decking materials and then small window samples with glass panes in them.
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So we looked at how they reacted at those different levels of exposures.
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And then we also wanted to kind of characterize what the heat flux exposure from a compartment fire would be.
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So the second phase was looking at a compartment fire that had an attached facade to it with different siding materials to see if the different siding materials would contribute to that overall exposure from a compartment fires.
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And then our third kind of experimental phase was okay, we have the compartment fire that we characterized in the second phase what happens if we put a target facade across from it at a separation distance that you would see in a community with a high population density, and how would that target facade react to this compartment fire exposure?
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So we were looking at different types of siding materials on the target facade.
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We had two double-hung, double-paned windows mounted in the target facade.
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But then a third thing we were looking at is the fire spread between them and what type of potential fuels could you have in between two structures that would kind of initiate fire spread from the compartment to the target facade?
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So we ran three experiments with three different types of what we referred to as ladder fuels.
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We looked at the impact of a car in between two structures.
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We looked at the impact of an attached deck attached to the target facade, and then we also examined a shed small shed in between the two structures.
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And so, based upon these three sets of experiments, we decided that we would plan our next experiments to be a bit more focused and look at the impact of different siding materials or exterior wall assemblies, as well as look more into window failure.
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So you said it started like 2018.
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What did the environment, like scientific environment, in this regard look like?
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Was it like a blank spot?
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Where did you find the biggest gaps in knowledge in solving those problems?
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Because I think 2018, I would say that was already the wildfire.
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Research was already pretty intense.
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I think one of the things that makes the WUI fire, or community conflagration fire, that a challenge is because of the complexity, the spatial scale is because of the complexity, the spatial scale.
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If we talk about a high-rise building that's 20, 50, 100 stories tall, you can think about them as individual structures, but you have that primarily vertical component, whereas at the community scale we have this horizontal component.
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In addition to the vertical component we have multi-story residential structures or commercial structures component, have multi-story residential structures or commercial structures, and so it really is that complexity of oftentimes it's not a single fire scenario, it's oftentimes multiple fire scenarios.
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So that might be your immediately adjacent structure that has burned from a kitchen fire or some other typical fire problem, but in a community conflagration event, where the fire transitioned from the wildland into the built environment, oftentimes it's multiple structures.
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So it's your neighbor next to you and across the street and three houses down, and so now we have multiple thermal exposures for multiple vectors.
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There's also the complexity of fuel continuity.
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Joe was talking about that in some of those initial experiments looking at the intermediate or ladder fuels between structures.
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If we think of structures and buildings as the primary things in the built environment, that being damaged or destroyed is the biggest loss.
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There are all the things in between and the residential communities.
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That can be cars, that can be ornamental vegetation, that can be your kid's play set.
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So there are a lot of these complexities that differentiate this WUI or G&E conflagration problem from other fire safety problems.
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But that is.
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It has also created an opportunity to learn from and lean on the experience and the knowledge base that we have in that space to translate it over.
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But we have to add compounding factors like that sprawl, that spatial component, the ambient factors like temperature, relative humidity and wind.
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And then another important component of FSRI's research is fire service intervention.
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When we think about structure fires or fires within the compartment, we oftentimes think about ventilation limited and water suppression.
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But in these configuration events, water supply is oftentimes limited.
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There's oftentimes more fires than there are resources, whether that be engines or responders, and so this is why the fire safety problem is big and something that FSRI is compelled to address safety problem is big and something that FSRI is compelled to address.
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FSRI is known for giving good fire safety considerations to the firefighters.
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A follow-up question, going from a general weave problem or even urban conflagration problem into actionable research items.
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It's not something you just simply sit down and research.
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It's too big, so you had to narrow down.
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So how did you come up with this research program in which this, I understand, there was a preliminary research, but how does it tie Like why, in particular, this fire spread through the external walls, why this was the gap that you've tried to fill out.
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So, as far as windows go, there've been post-Wooey fire investigation that have identified windows window failure as a potential point of fire spread to structures.
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Once a window fails, there's now an opening for hot gases, fire and embers to get through and ignite interior contents.
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However, there has been some research in the past that looks at window failure.
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Some of that is more than 20 years old and windows have developed since then then.
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But also there's not a whole lot of research out there that's more on the full scale side.
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So that's one gap that we were trying to fill with this research so with the modern technology I also.
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I think window technology and in general, facade technology is perhaps one of the biggest innovative areas of civil engineering and construction.
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Is it also the case for uh, private housing and dwellings and smaller?
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developments I would say so.
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I mean, you know energy efficiency has become a large thing over the last few decades, so with that you have kind of ever-changing window technology.
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Yeah, and the other aspects.
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You started listing them.
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I interrupted you.
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Yeah, yeah, no, I was just going to mention that.
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The other thing, specifically with reference to codes and standards that are used in the united states.
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So there's kind of three primary documents.
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There's nfpa 1140, chapter 7a of the california building code, and iwc.
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That are wii based codes and within them they address windows, but in a limited fashion.
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They're typically focused on the glazing or paint assembly and they make no mention of other window components such as frames.
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And then when it comes to the, the glazing or the glass, they have some variation between them.
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So for iwec and nfp 1140 they require either a tempered pain assembly or a multi-pain assembly.
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But with the multi-pain assembly they don't specify what type of glass should be used, so you can have a double pain, just plain glass assembly.
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And then with chapter 7a they require a multi-pain assembly with at least one pain tempered, but they don't specify which of the two or more pains should be the tempered pain did the preliminary research also guide you towards which, which are the most, I don't know, often found to be failure in wii scenarios, or was something that you only unraveled during your experiments?
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yeah, we saw.
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So we weren't.
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We were only looking at double-pane plain glass assemblies during those initial experiments.
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But with the phase three, with the target facade we had, like I mentioned, we had two windows.
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One of those windows had a low E coding on it and so we kind of based on our analysis of the data, saw interesting things with the window failure itself.
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We saw frames start to deform and whatnot, but also different types of failure with the panes, and saw maybe an indication that a low recoding could have may or may not have an impact on glass failure.
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If I understand correctly also this whole research, it was not just that the structure is a target of wild and urban interface fire, so you just understand how the structure responds to the fire, but you were also looking into a structure being a source of exposure to neighboring structures, also those interactions from in between.
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So it also kind of progresses to the influence of those external walls and how we build them as a factor that could contribute to an urban configuration scenario.
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I I would say like, if you ask me, uh, if you asked me, like last year, uh, about urban configuration, I would say, there, they, they don't seem to happen recently, but after what I saw in la uh just a few months ago, I'm not so sure if the age of urban configurations is gone.
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So, and you've started this in 2018.
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How did it look back then?
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Was it a part of your interest?
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Absolutely so.
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The best way I've heard these events described are as wildfire-initiated urban conflagrations.
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So it may start out as wildfire, but once it enters areas that are more populated, with a higher structure density, then all of a sudden there's a new fuel load introduced in the form of structures and the fire kind of spreads structure to structure throughout these communities.
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And that's where you see a lot of times the large amount of loss and devastation that's associated with those events is due to that time when the fire enters these kinds of communities.
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Is there also any specific context in how the structures are built, the distances between the structures?
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Was it also something that you've looked into?
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So we based our structure separation distances on kind of the worst-case scenario, or the highest population density areas or not the highest, but on the higher end and what kind of structure separation you'd see between there.
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So particularly we looked at anywhere from 1.8 meters to 4.3 meters separation distance.
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And in case, if there was a lot of fuel in between, did you also put the fuels between the structures and investigate that, or that was just preliminary, preliminary yeah, just during the preliminary.
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Okay.
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Now of course, in hindsight uh, looking at that, la fires was put up.
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It's obvious that this structure to structure fire spread was something you could expect in hindsight.
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Events like that did you observe?
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You must have went through the literature and and the previous fires.
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Have you observed events like that and how big part of your research plan was investigating fire behavior like we'd later observed in the lake?
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Yeah, and you know, when you look at the history of fire, particularly in the North American United States but across the world, I mean events like the Peshtigo Fire the same night of the Great Chicago Fire, I mean so many of those urban fires from the 1800s to the modern day.
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I mean over the past decade, the state of California alone has had some of their top 10, most destructive by structure loss count the Tubbs Fire, the Camp Fire, other parts of the country, the Marshall Fire and then just a couple of years ago now in Maui, hawaii, they had a series of fires.
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These were initiated as wildfires but in the case of the town of Wahaina, that brush fire or wildfire transitioned into the built environment, very similar to what we observed in the Marshall Fire in Colorado and many others around the world.
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And it's this transition from a wildfire or vegetation fire or a brush fire which has its ecological purposes, but as it enters into the built environment, it's that again, that fire safety or that fire phenomenon transition from a fuel that maybe needs burning, whether it be the vegetation or the shrubs, to the built environment where we have our homes and our communities that we don't want to burn, and that's the fire problem that transition from the wildfire into the built environment.
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Yeah, and to bring this introduction full circle, this is how FSRI became engaged in the Wildland Interface research.
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Our colleague, derek Alconis at the time was the chief of the Air and Wildland Division at LA County Fire Department and was on our advisory board and he'd been responding to these fires that Dan just mentioned and including the Woolsey Fire and others that were there in Los Angeles County and year after year they were seeing these events that were occurring and were looking for answers on how they can better prepare their firefighters, prepare the citizens and be ready to respond to these fires but also make sure that the citizens themselves are as informed as possible and codes could be updated as well as possible.
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And because FSRI sits at a unique area where we were born from the firefighters St Jude Research Institute right, the firefighters have long been our core citizens, our incredibly important core audience for us, where we can take this full-scale research and address those concerns that exist.
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So after we saw a series of those fires in California, we began this program and identified, as Joe had just mentioned, windows as being one of the key vulnerabilities that there's some research that we can do at a scale that can help to fill in this gap and hopefully reduce some of those challenges that the fire department's facing, so citizens can have their structures prepared as best as they possibly can, and the firefighters can then respond as efficiently and as effectively as possible.
00:21:01.040 --> 00:21:06.982
So that's really how we really got to the area that we're at right now from a research perspective.
00:21:07.470 --> 00:21:11.801
Yeah, I'm pushing and chipping you to tell me the story, how you came into that.
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Because, like you guys are FSRI, you are the people who burn things down and do that in lab.
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That's like a normal Friday for you to burn down the house.
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I'm a fire researcher as well.
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I'm doing my time in the lab.
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Heat flux on my skin is not something I'm very unused to and, uh, in some odd way, you know, doing this research and doing all of those endeavors is our normal everyday's life.
00:21:40.923 --> 00:21:55.579
But there are hundreds of people out there fire safety engineers, civil engineers, architects who now have this problem of whole communities burning down, who wonder how do we solve the problem?
00:21:55.579 --> 00:22:03.359
And I would love people to understand how we, as scientists, how we figure out a high-level problem.
00:22:03.359 --> 00:22:09.603
In your case that's wildland-urban interface, initiated urban conflagrations.
00:22:09.603 --> 00:22:11.550
I love it because it nails down the problem.
00:22:11.550 --> 00:22:45.903
But here's it's a high level objective and by investigating, going through the history, going through the previous research, investigating evolution of the market, solutions, technologies, the ways how people build houses, looking into firefighters, reapers, you start narrowing down that big high-level problem into something that could be a window pane or a gasket or a facade technology and then in your laboratory, you can very precisely tell what makes the difference in this problem.
00:22:45.903 --> 00:22:56.642
That's the way of thinking that I want our audience to really understand, because if you understand the research process, one, you understand the research better.
00:22:56.642 --> 00:23:04.384
But two, if you have good ideas, you can send them to people like FSRI or me and we'll perhaps follow on that.
00:23:04.529 --> 00:23:11.280
But anyways, sorry for getting sidetracked, I just really had to say that and also admire your work a lot.
00:23:11.280 --> 00:23:17.019
Anyway, we know why, but one thing we still need to clean out.
00:23:17.019 --> 00:23:21.280
It was previously said that those fires spread through firebrands.
00:23:21.280 --> 00:23:26.849
We also mentioned heat fluxes, we mentioned ladder fuels, so fires in between the buildings.
00:23:26.849 --> 00:23:31.579
So perhaps let's clean out how the fires can enter the building and how fires can exit the building.
00:23:31.579 --> 00:23:33.384
I don't know, dan, maybe you can start.
00:23:33.849 --> 00:23:50.218
Yeah, so thinking about exterior fire or fire outside of the box, outside of the enclosure, and oftentimes we think about the box, the enclosure, the house, the building, the structure as the property or as the asset that's most important.
00:23:50.218 --> 00:24:00.584
And again, a lot of times when we think at these historical fires, what comes to the top is the acres burned, the unfortunate number of fatalities and structures damaged and destroyed.
00:24:00.584 --> 00:24:09.750
And so how do structures get damaged, how does fire initiate from the exterior into the building and then, ultimately, how can that cause it to be destroyed?
00:24:09.750 --> 00:24:20.522
So when we think about that fire progression, you know there are lots of ways to kind of from first order fundamentals, but one framework to think about it is the building ignition mechanisms.
00:24:20.522 --> 00:24:27.602
We can think about that as radiant heat, and so this is that heat transfer that doesn't require any form of medium.
00:24:27.602 --> 00:24:44.500
So whether it be from a crown fire, you know large, 100 plus foot flames causing radiant heat transfer to a structure fire, similar magnitude flames, no direct contact, but enough heat transfer via just radiation to cause material to ignite.
00:24:45.240 --> 00:24:48.667
How really, like I don't fully understand.
00:24:48.667 --> 00:24:51.574
Well, I understand it but I don't fully feel it.
00:24:51.574 --> 00:25:02.935
So if you have a crown fire and let's say it's 100 meters away, which is approximately 300 feet in your units, how big the radiant heat flux could be from such a crown fire?
00:25:02.935 --> 00:25:04.682
Is it really high enough to ignite?
00:25:04.682 --> 00:25:10.213
Or how close the house has to be to the crown fire for radiant heat to be really like a direct hazard?
00:25:10.599 --> 00:25:14.065
Yeah, no, that's a good point that you know that radiant heat transfer.
00:25:14.065 --> 00:25:15.445
You know Jack Cohen's work.
00:25:15.445 --> 00:25:22.615
Looking at crown fire, you know we can see from the fundamentals that radiant heat transfer decreases with the distance right.
00:25:22.615 --> 00:25:27.311
So the amount of heat transfer required would be very, very high.
00:25:27.311 --> 00:25:31.703
You'd need so much radiant heat transfer required would be very, very high.
00:25:31.703 --> 00:25:32.827
You'd need so much radiant heat.
00:25:32.827 --> 00:25:50.726
But an important factor that radiant heat plays in this space is that while it may not be that tipping over the straw that broke the camel's back to cause ignition, it can be the prelude to cause materials to rise in temperature, to dehydrate, to maybe evaporate some of those components that would reduce the time to ignition.
00:25:50.726 --> 00:25:53.326
So that radiant heat may not be the tipping point.
00:25:53.326 --> 00:26:10.400
But I think in a lot of cases, and again in these conflagration events, radiant heat plays an important role in that fire spread, in that building ignition because of that back and also, if you have a structural fire next to your structure, then we're talking about completely different heat fluxes.
00:26:10.317 --> 00:26:11.482
And if you have a structural fire next to your structure, then we're talking about completely different heat fluxes.
00:26:11.482 --> 00:26:18.420
And if you have a ladder fuel in between and that ladder fuel burns, then again we're talking about completely different radiant heat flux.
00:26:18.420 --> 00:26:28.434
So again, this way of thinking about just a single house ignition versus, you know, a whole scenario in which, house by house by house, they start going off.
00:26:28.434 --> 00:26:32.887
I guess the mechanisms, the mechanisms, the prevailing mechanism can also shift.
00:26:32.887 --> 00:26:34.631
So radiant heat flux, that's one.
00:26:34.631 --> 00:26:35.772
What are others?
00:26:41.900 --> 00:26:42.362
Yeah, another mechanism.
00:26:42.362 --> 00:26:43.586
You just mentioned how these oftentimes are not in isolation.
00:26:43.586 --> 00:26:47.078
I think in almost every case, barring some exceptions, there's some combination of them.
00:26:47.078 --> 00:27:12.025
And the next that I would think about is that direct flame contact has that radiant heat component but also has that aromantency.
00:27:12.025 --> 00:27:14.111
So we think about the convective heat transfer.
00:27:14.111 --> 00:27:26.701
And so this is where we start to think about the fuel connectivity and the horizontal and vertical components, about how it's not just the structure separation but it's also the fuels in between.
00:27:26.740 --> 00:27:32.150
So let's put ourselves in a scenario, maybe a typical suburban or urban community.
00:27:32.150 --> 00:27:40.951
My home and your home are separated by, let's say, 30 feet, but between our homes I have a privacy fence that connects to the property line.
00:27:40.951 --> 00:27:47.143
On the side of my home I have some combustibles, like a garbage can and maybe my parked car, and you have the same.
00:27:47.143 --> 00:28:03.440
So now we have a scenario of the fire spreading perhaps from my structure to the fence, to the vehicle, and now it's not just the radiant heat from my structure and all those intermediary fuels, but now those fuels very close to your home can cause that direct and intermediate clean content.
00:28:03.941 --> 00:28:05.244
You said convective.
00:28:05.244 --> 00:28:07.371
How big a part of that is wind.
00:28:08.119 --> 00:28:10.917
Yeah, I think wind plays a really important role in these exterior fires and the convective how big part of that is wind?
00:28:10.917 --> 00:28:13.724
Yeah, I, I think wind plays a really important role in these exterior fires and the convective heat transfer.
00:28:13.724 --> 00:28:18.551
So if you think about, you know the, the gas temperatures it's superheated and if you're in that plume.
00:28:18.551 --> 00:28:22.044
But convective heat transfer can also play a role in cooling right.
00:28:22.044 --> 00:28:34.333
So we know about wind eddies and it's not always a straight line constant wind flow and oftentimes in these um, you know these urban communities, there's eddies and there's vortices and it's not constant.
00:28:34.333 --> 00:28:37.442
So convection plays both a heating and a cooling role.
00:28:37.442 --> 00:28:44.467
But I think when we talk about, you know that direct contact or, in the line of the plume, the convective heating.
00:28:44.467 --> 00:28:46.732
I think it's probably more dominant radiant.
00:28:46.732 --> 00:28:51.181
But convection is important enough that we shouldn't neglect it and firebrands.
00:28:51.240 --> 00:29:00.346
I think a lot of research I see recently is around firebrand ignition and how they can penetrate structures, so obviously that's a pathway right.
00:29:00.961 --> 00:29:14.900
Yeah, absolutely, firebrands, or embers or you know whatever you want to call them, these glowing or burning particles that are one generated by fuels, whether they be from the wildland or wildfire vegetation, as well as in the built environment.
00:29:15.181 --> 00:29:22.509
So once structures start to burn, once cars and RVs and kits placed that start to burn, they generate these particles.
00:29:23.080 --> 00:29:41.471
And one of the components of embers is they can travel beyond the kind of fire perimeter so they can travel distances reported of more than a mile, but even short range distances of tens of twenties of feet or, you know, tens of twenties of meters that can cause spot fires.
00:29:41.471 --> 00:29:45.160
Additionally, those firebrands can enter into the structure.
00:29:45.160 --> 00:29:55.602
So a lot right now we've been talking about kind of the, the building, the structure as a, as a, as an encapsulation, a force field if you will, and the flames and the radiant heat having to penetrate it.
00:29:55.602 --> 00:29:58.355
Well, these embers can penetrate into small little open.
00:29:58.355 --> 00:30:01.508
That might be through vents, into your attic, your crawl space.
00:30:01.508 --> 00:30:11.951
That might be through a window that hasn't failed from the heating mechanism but might have just been left open because people have their windows or some natural convection.
00:30:11.951 --> 00:30:26.807
So embers penetrating into the building or causing spot fires around the building can be that third, and oftentimes a large portion of building ignitions play a role in kind of three in combination of the mechanisms.
00:30:27.390 --> 00:30:37.912
So how does one turn a wildfire scenario or an external fire exposure scenario into laboratory-controlled exposure?
00:30:37.912 --> 00:30:44.200
Like, how do you go from wildfire into laboratory unless you're having a wildfire-sized laboratory?
00:30:44.200 --> 00:30:51.411
In that case it's perhaps easy, but how do you create this design exposure?
00:30:51.471 --> 00:30:55.911
let's say Well, really, whenever you're talking about fire exposure, there's a lot of different variables.
00:30:55.911 --> 00:31:02.593
With wildland fires especially, there's many including size of the fire, wind, etc.
00:31:02.593 --> 00:31:20.645
And so to kind of help control this, we came up with a scenario of a compartment fire that's venting out of an opening, the compartments flashed over, and that exposure from a fire venting out of an opening is not, it's going to be based on the opening size.
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