What makes a neighborhood resilient to fires?

Firefighters around Los Angeles have been making steady progress against the massive, fast-moving blazes that erupted around the city this month. The containment perimeters around the Palisades fire and the Eaton fire are growing, but the risk of another explosive wildfire remains high amid dry conditions and high winds. 

The wildfires have so far killed at least 28 people, charred more than 63 square miles, and destroyed more than 15,000 homes, offices, and shops. 

Wildfires are a fact of life in California. They’re a natural phenomenon, clearing decaying vegetation, restoring nutrients to the soil, and helping new plants germinate. 

But their mounting devastation is a result of human decisions: More homes and businesses going up in wildfire-prone regions means a greater likelihood of igniting a blaze, and more destruction when one starts burning. Suppressing natural fires and not trimming back vegetation near structures means more fuel can build up. And as the climate changes, the weather in California is likely to see greater swings between rainfall and drought, enhancing the conditions that promote wildfires. 

The current blazes erupted after a sequence of record rainfall, record heat, record dryness, and high winds landed on one of the most populated parts of the country. The recent wildfires are on track to be the costliest blazes on record. The fires will only worsen California’s ongoing housing crisis and could reshape the makeup of the city as wealthy residents rebuild and poorer Angelinos are forced out. The scars of these fires will be borne by the region for years. As Vox’s Rachel Cohen wrote, “To merely restore what was lost — which will take years even with potentially rushed permitting approvals — won’t be enough to stem the mounting crisis.”

On the other hand, the fact that so many human factors are contributing to the rising destruction from wildfires means that there are decisions we can make to alleviate the harm. And as the flames die down and residents return, this moment presents an opportunity to think more holistically about reducing wildfire risk in Los Angeles and other fire-prone regions. 

“There’s a lot that we can do as residents and homeowners to really change that trajectory and make small, often inexpensive actions that can make a big difference in changing the outcome when our buildings are exposed to the pathways of wildfire,” said Yana Valachovic, a fire scientist at the University of California Agriculture and Natural Resources Fire Network studying resilience in the built environment. 

I spoke to her just as she was leaving Los Angeles after investigating the wildfire damage up close. She told me that she observed that the destruction was not simply a function of the materials used to build homes, but how they fit into their neighborhoods, how they interact with nature, and the sophistication of the firefighting response. 

This conversation has been edited for length and clarity. 

Umair Irfan

For people watching the fires from afar, one question keeps coming up as they see photos of the destruction: Why are so many houses in Los Angeles made out of wood? 

Yana Valachovic

From what I saw on both the Eaton and Palisades fires, we were largely looking at homes where the framing could be made of wood, but the exterior envelope was largely made of a stucco or stucco-like product. To me, it doesn’t matter what it’s framed in, whether it’s wood or metal, it’s really about how the design, the materials, the installation, and the maintenance that has taken place. All those elements need to work together. No one single product is going to save a home in the face of wildfire.

Umair Irfan

So wood isn’t necessarily a bad choice in a fire-prone region?

Yana Valachovic

I’m a licensed professional forester, so I will share my bias that I do like wood. We grow a lot of trees in California. It is our available natural resource, and I think it’s important to be able to use what you have in your community. The wood itself is combustible, but there are treatments that can make it fire-resistant. 

We have to think about this from a climate viewpoint and a natural resources viewpoint too. The environmental footprint of building with cement is pretty high. It takes a lot of energy to make cement, and we generally have to ship it from somewhere else, adding to the transportation footprint. 

Building materials made from wood are produced in California. Their environmental footprint is smaller, and through careful forest management, they really can be a very important sustainable resource that can also increase the resiliency of our forests.

People are really excited about mass timber construction and what the potential is for reducing fire exposure in multistory buildings.

But there are broader questions around what do we build with, where do we build, how do we build. There’s no clear winner that checks every box in terms of resiliency, environmental impact, and sustainability.

Umair Irfan

Is it true that at some point, any material can burn?

Yana Valachovic

I just want to step back for a second. It’s not just the building and how it’s constructed; it’s the coupling between the vegetation and other combustibles — how those directly touch or surround the building — that make a substantial difference in fire risk.

There are three types of fire exposures that buildings experience. 

One is the direct flame contact, which means that the fire is moving through some kind of combustible material. That can be wildland vegetation. It can be planted vegetation. It can be dry grass. It can be wood mulch. I think what the majority of people think about, this wall of flames that just slams at the house. 

The second component in fire exposure are embers, which are pieces of burning debris. They move all over and around a structure, and it’s pretty easy for them to find a pathway in to create new spot fires. For example, you leave the dog door open. The garage has a gap around it. There’s an open window, or a window that breaks. Those are all pathways for fire to get in.

We can do things that help harden the structure so that it’s less vulnerable to embers. We can upgrade our vents so that the vents are not of a size that are capable of letting an ember get inside to combust something.

Then the third element is something called radiant heat. Radiant heat is not directly in contact; it’s just the heat that’s transferred through the air that causes a failure in the structure. When you get all that radiant heat, what you see is the glazing that helps hold the windowpanes starts to melt, or the heat is so intense that it breaks the glass.

So, it’s a little more complex than just how the exterior building is finished, in wood or non-wood. It has to do with interrupting all those three pathways. I saw all three pathways lead to fires in the past few days.

Umair Irfan

Can you say to what extent improved building codes had an effect on which homes survived? Did newer homes under higher standards fare better?

Yana Valachovic

There’s some analysis work that needs to be done.

In California, in 2008, we started to implement a specific component of the California building code called chapter 7A. Its focus is specifically on improving fire resilience of the exterior components of the structure, not interior sprinklers, not about how to control fires from within. So, since 2008 or so we have had a whole new population of buildings in high fire hazard severity zones that are built to a higher standard.

Unfortunately, I didn’t get to see any of those buildings in my two days that I was out, but I’m really looking forward to the broader data collection to be able to see how those performed overall. That’s one of our key questions: Do the codes work? How well do they work? Do they need any more modifications?  

Umair Irfan

I did see some viral photos of individual homes that survived while the rest of the neighborhood burned down. There was one in particular that looked like it was paneled with wood. What do you make of that?

Yana Valachovic

I didn’t get a chance to see that building, but by and large that structure implemented many of the things that we’re talking about. It has another advantage: It has very shallow eaves. The eaves don’t overhang very much. Why that matters is that when a spot fire does occur, it starts to create its own heat, and you get an eddy effect, which is like a wind circulation pattern. That really puts pressure under the eave area. If your under-eave areas are pretty shallow, then there’s not a lot of area to be exposed.

It’s like a short-brim hat versus a wide-brim hat. The wide-brim hat gives you more sun protection, but it’s got a lot more area where you can get fire circulating its heat up and underneath.

Umair Irfan

What is it that’s preventing every home from using the best practices for fire resilience, beyond building codes?

Yana Valachovic

I just think it’s people’s lack of awareness. Also, most people don’t build new homes. They mostly buy from the existing housing stock or from someone else you know has put in a subdivision. I think the challenge is actually getting into the building community and the design community to help them understand.

We have an opportunity now after these fires to build back stronger and incorporate the best available information around so that homes are better prepared for these types of exposures.

Umair Irfan

As you’re heading out, was there anything you saw that was surprising or counterintuitive?

Yana Valachovic

There are two things that really surprised me, and I’ve done half a dozen research projects like this in events with fire loss. 

I expected to see more evenness in ember exposure. Why that matters is that I saw a number of buildings that survived, and what I concluded was part of the secret to their success was they just didn’t get as much exposure to embers, meaning that the wind didn’t bring embers everywhere consistently. The micro-topography really mattered in this. I think the temptation is going to be to say, “Oh well, that house had all the right ingredients and protections,” and I wish I could say so. What I observed is that there was just a variety of types of exposure.

I also observed that there was more firefighting response than I had anticipated. Based on the media, there’s so much discussion about lack of water availability, and not enough resources. But I saw a lot of great work that the firefighters did and they impacted the majority of homes that I saw that survived through both small and big actions. 

Umair Irfan

What were some of the small and big actions?

Yana Valachovic

A small one would be disrupting the fire from coming down a neighbor’s wood fence and then connecting to neighbors’ fences. A lot of these homes didn’t have a big distance between the edge of one house on the edge of the next house. There’d be a gate that would kind of close off the walkway on either side of the house. So there were folks that cut down wooden gates in particular to make sure that the fire didn’t run at the building. Firefighters were moving from house to house breaking those connections. In other places, a little bit of water went a long way just to stop the progression.

The big thing was having firefighting resources available to begin with. I think responders were moving quickly and efficiently through neighborhoods to help people in that situation. There are so many more resources in Southern California than other places I’ve been.