Wildfire Resilience Design Strategies for Architects and Homeowners

At any given time, wildfires are raging around the world, from California to the Amazon to Australia. In the United States, 4.5 million homes were identified at high or extreme risk of wildfire, according to a 2017 study by data analytics provider Verisk, with more than 2 million at-risk structures in California alone.

Despite knowing the risks of living in a threatened area, David Hertz, FAIA, and his wife, Laura Doss-Hertz, purchased a 47-acre ranch in Malibu, Calif. Hertz is the founder of Los Angeles–based practice David Hertz Architects and Studio of Environmental Architecture. Built in the 1930s, the residence was once owned by Tony Duquette, an artist who created fascinating set designs for stage and film, including The King and I. The house was later destroyed by the Old Topanga Fire of 1993. After the Hertzes bought the property in 2007, they named it Xanabu—an amalgam of Malibu and Xanadu—and reimagined it.

Hertz aimed to protect both the legacy of Duquette’s artistry and of the estate. However, the latter is, as he puts it, “perfect kindling for fire.” It hosts an Adirondack-style hunting lodge, an East-Asian influenced small village, a garden house, and a sunset pagoda, all constructed primarily of wood, and all surrounded by a mature landscape. “It is an ideal host of any kind of ember shower,” Hertz says.

Under Hertz’s stewardship, the estate survived the November 2018 Woolsey Fire, which burned nearly 97,000 acres of land in Los Angeles and Ventura counties, destroyed more than 1,600 structures, killed three people, and necessitated the evacuation of more than 295,000 people. The event prompted Hertz to add a resilience lab to his practice. The four- to six-person part–think tank and part-consultancy focuses on climate adaptation and survival for those living in wildfire-prone areas. It also vets and develops best practices and products for fire rebuilds and fire prevention for residential and commercial projects.

Hertz’s firm adheres to the Australian bush fire standards, the stringent and most carefully considered fire safety requirements the firm could find. Xanabu was preserved thanks to many of the strategies outlined in this article—and the couple continues to make improvements.

Hertz shared with ARCHITECT some do’s and don’ts related to wildfire-resilient residential design for new construction and renovation projects. Though living and building in high-risk areas are far from ideal, the land falling under this categorization is expanding due to climate change. As it stands, many desirable—and thus well populated—places to live are susceptible to wildfire and more will be added in the future.

Incorporate Design Fundamentals
Embers represent the largest threat to buildings in terms of fire, Hertz says. As a result, the overall design strategy should limit their potential to drift onto, settle, and ignite structures.

The 5-foot perimeter immediately surrounding a structure is the most crucial zone for defense. Within this zone—and beyond, if possible—designers should minimize landscaping, and homeowners should continually clear out dead, flammable brush. Avoid specifying timber hardscaping, such as wooden fences, which can become wicks that lead a fire straight to the house.

Other preventative landscaping design strategies are less obvious. For example, planting oak groves upwind of a house is an effective defensive measure; when mature, these groves can help to block wind, deter the growth of brush at ground level, and hold a tremendous amount of water within their root systems and branches. The recommended planting distance depends on the tree height and property size.

Architectural details can also affect a structure’s vulnerability. Features that increase fire risk include elevated decks, dramatic eaves, raised foundations, and attics. Façade niches and openings offer landing strips for embers. To reduce risk, architects should specify Class A fire retardant on all wooden structural members and all roof substrates, including roof tiles, decking, and membranes. Vent openings should be covered with wire-mesh screens to help prevent embers from infiltrating.

Support Emergency Personnel
To prepare for the worst-case scenario, Hertz suggests designating an area “where the fire department wants to be and where they feel safe.” This means providing clear egress routes to and from the property as well as turnarounds for fire trucks in driveways or yards.

During the Woolsey Fire, the California Department of Forestry and Fire Protection leveraged Xanabu’s accessibility, using it as a base from which to defend it and neighboring properties, including the 747 Wing House, designed by Hertz; the iconic residence incorporates the wings of a Boeing 747-100.

An independent, on-site water source and power supply, such as a generator, can significantly aid the fire department because these crucial amenities can be scarce during a crisis. Though a lap pool (a relatively common amenity in greater Los Angeles) is too narrow for the fire department to extract water, other forms of water storage or stormwater retention ponds can be useful. In terms of storage, Hertz adds, a gravity-fed source “is preferable … because [it] is not dependent upon electric-driven pumps, which can become inoperable without power.”

Invest in Fire Prevention Systems
For a client willing to invest upfront to reduce the risk of home loss and and the cost of rebuilding later, Hertz recommends a layered defense strategy comprising multiple zones. An example setup includes cannons mounted on 8-foot-tall steel poles, spaced 50 feet on center, along the property perimeter as the outermost layer. When activated, the sprinkler heads cast a fog of fire retardant, such as Phos-Chek, a nontoxic compound that prevents embers from smoldering into a fire. Ideally, nozzles mounted on the roof along with spinning distributors that drop from the soffits would also douse the building exterior.

However, fire-prevention systems often require someone staying behind to operate them. “You can have the most robust system, and [then] someone leaves a screen open,” Hertz says. His firm’s resilience lab is researching fully automated systems. “I am testing both infrared electronic fire-sensing equipment for early automated detection as well as heat-sensitive fusible links for activation,” he says. It is also developing simplified versions of other prevention measures, such as automated roll-down fire shutters made of fireproof fabric to cover windows and other fenestration.

Understand Codes and Costs
Municipalities have widely adopted established fire-protection codes in rural and suburban areas, in areas of wildland, and land that is uncultivated or unfit for cultivation. National Fire Protection Association standards are commonly referenced. The NFPA has also established the Firewise USA program to teach residents how to adapt to living against the constant backdrop of wildfire risk, and to encourage neighbors to help prevent infrastructure losses together.

One barrier to adopting these codes is perceived cost, but that may be unfounded. A study by Headwaters Economics, a Bozeman, Mont.–based nonprofit research group that aims to improve community development and land management decisions, found that “a new home built to wildfire-resistant codes can be constructed for roughly the same cost as a typical home.” That is, fire-resistant roofing, walls, decking, and landscaping construction materials are comparable in cost to their non-fire-resistant counterparts. It comes down to an architect’s knowledge and decision-making.

Designing for wildfire resiliency is complex and multifaceted, but Hertz believes architects must be better equipped to address the consequences of climate change. “What [architects] do very well is organize specialists,” Hertz says. Innovation, particularly in the form of automated fire-prevention systems, will help as well, he notes. “If people are able to become more resilient and defend their properties through technology, then less stress will put on infrastructures, municipalities, and communities.”