Does Passive House Design Protect Buildings from Fire?

NEW YORK, Feb. 4, 2025 /PRNewswire/ -- With fires continuing to devastate multiple communities in Los Angeles, there is a growing awareness that the existing built environment is not compatible with changing climate conditions. As a result, many people are not simply asking, "How do we rebuild?" but how do we do so in a way that acknowledges these new conditions and makes communities stronger, more durable, and more resilient? Is there an existing knowledgebase that can help us achieve these ends? How does Passive House fit into this conversation?

The good news is that there are design strategies that can make buildings more resilient; there is a global network of engineers, architects, builders, and other technicians who have been refining these strategies for decades; and these strategies complement Passive House building techniques.

Passive House design principles are intended to create a healthier, more efficient, and more durable building. Fire hardening is not an explicit goal. However, as a result of smarter building practices in general and an effort to create a strong barrier between interior and exterior environments, there is significant overlap between Passive House buildings and structures where fire hardening is prioritized. Three things stand out:

1. Airtightness. The enclosures of Passive House buildings are extremely airtight. As a result, embers and smoke cannot sneak into the interior through small gaps that are common in more conventional buildings.
2. Compact form. Passive House buildings tend to have a smaller surface area to volume ratio, meaning there are fewer crevices or spaces where embers can easily settle.
3. High-quality windows and doors. Passive House homes are equipped with windows and doors that have multiple panes of glass and robust frames. As a result, the glazing on passive buildings is less likely to crack or break under the stress of a fire. As Andrew Michler writes in an article that was published in the Fall 2022 issue of Passive House Accelerator magazine, Building Forward in the Face of Fires, "By upgrading to tempered glass [emphasis added] the resilience of the assembly would be further improved, and the over insulation of the frame, another typical Passive House detail, will also reinforce the window's integrity."

Passive House Accelerator's Mary James, Editor-in-Chief of the Passive House Accelerator Magazine and a building science insider dedicated to protecting homes from the growing problems of wildfires, shares 10 steps you can take to increase resilience to wildfire events and minimize fire risk to your home. Watch the video here: https://youtu.be/626NQeQGH7s

Other fire hardening tactics that are more tangentially associated with Passive House construction, are covered more in depth in a video produced by the Accelerator above, but a shortened list includes:

• Removing any combustible plants or furniture from the perimeter of your home
• Keep your property clear of underbrush, dead leaves, and other material that can fuel a fire
• Install metal screens on all vents and apply intumescent paint that expands when exposed to heat
• Eaves should be boxed in with a fire-resistant material like fiber cement board
• Roofing should be made from Class A fire-rated materials, while siding and decks should be made from fire-resistant materials
• Nearby structures, including detached garages and sheds, should be air-sealed and fire hardened, too

Another aspect of passive construction that can help people who live in areas that experience a lot of wildfires and, consequently, excessive smoke, is mechanical ventilation. Mechanical ventilation systems use fans and ducts to draw in supply air from the outside. That supply air is then filtered. When smoke events happen (as the Accelerator documented in the article Wildfire Smoke Puts High-Performance NYC Buildings to the Test), the mechanical ventilation systems and sophisticated air sealing techniques of passive homes ensure that those inside are only breathing filtered air. In addition to protecting respiratory health, these systems can also prevent smoke damage to homes.

Passive House design does come at a small upfront cost premium. However, they also use up to 90% less heating and cooling than existing traditional homes and are far more durable. As a result, owners experience savings over time in the form of lower utility bills and reduced costs for maintenance. Passive House buildings also shrink owners' carbon footprints while providing healthier, quieter, more comfortable, and more resilient spaces.

There is a growing number of developers and owners who have decided to build to Passive House standards for precisely these reasons, and the Accelerator was founded in part to share their stories. To date, we have produced hundreds of written case studies, podcast episodes, and video presentations about smarter building practices. Some touch upon how passive design overlaps with fire wise building practices (such as Real-World Benefits of a Passive House Retrofit), while others share the stories of families in Colorado and California who have rebuilt their homes to Passive House standards following tragedy.

These are lessons that should be taken to heart as Los Angeles considers how it wants to rebuild the homes and communities that have been lost to the fires. Building in accordance with a combination of passive and fire wise principles can make the built environment stronger, more durable, and more resilient.

About the Passive House Accelerator: Passive House Accelerator LLC is a catalyst for zero carbon building. We cultivate a collaborative platform for sharing innovation and thought leadership in Passive House design and construction. We convene practitioners, institutions, manufacturers, and anyone concerned about buildings and climate change to dive into the details of creating better buildings. We work to accelerate both solution-making and solution-makers in the zero carbon building movement. We're nondenominational, so whether you're interested in PHI, Phius, net zero, Living Building, LEED, or just better building practice, please explore, learn, and engage!

SOURCE Passive House Accelerator