> How does a Nopal build fair against fire?

In short, pretty darn well. While there’s no such thing as a fireproofed building, there are many ways to bias toward surviving a fire. Since this is an FAQ we will skip landscaping and focus on the building.

Let’s take a quick walk.

First, I’d like to say this one is hard to write. It has been a long time topic of conversation for us. Most commonly after a destructive fire, and then people stop the search. The current timing hurts, with the LA fires burning. For the same reason, this feels like a good time to share what we “know.”

Concrete, Steel and Glass is Not the Answer

We constantly hear touting of building out of “non-combustible” materials. While it’s true that concrete won’t burn, the rest of the house likely will. Large panes of glass will shatter and steel reinforced concrete will bend and fail with enough heat (although this applies more to larger buildings). There’s a chance (and there are examples) that your concrete and glass bunker with no landscaping and no insulation will be passed by when a fire shoots through.

But then your house is a carbon bomb and contributing to the exact change that leans toward more fires in the future.

Wildfires Burn Homes from the Inside Out

The most common path to a house burning in a wildfire is super hot air being pushed inside, igniting flammable things. If your house includes spray foam, that means a fire accelerant and toxic emissions.

Step 1 is building airtight. This is an area where extreme is good and good enough isn’t. We recommend building to at least a 1ACH50 blower door. Our builds routinely hit 0.4 and tighter. Also key, this airtightness has to be reached with durable materials and strategies. No spray foam, sparing use of Aerobarrier and no “airtight drywall” approaches. You need that tested airtightness to last for the next century.

Protecting the Openings

Glass, especially large panes in steel frames, flexes and shatters under pressure. Moderate openings with sturdy frames and triple pane tempered glass (common in high performance homes) resist both letting heat in and cracking under pressure.

ignition resistant insulation

Insulation should sail past code requirements without any tricker (I’m looking at you again spray foam). That means sticking a blowtorch to the insulation should result in charring, not flames. And we don’t want to get there by adding toxic chemicals.

Ironically, our best options here come from nature. Wood fiber insulation borrows from physics seen in Redwood trees and sheep’s wool is just amazing.

High Thermal Mass

Some magical insulations have a high resistance to heat moving through them (R value) AND a high resistance to changing temperature (thermal mass). This combo helps keep the interior temps down as the exterior heats.

Ember Resistant Cladding

Now that we have kept hot air and embers out of the interior we move outside. Here we have a similar mission to the insulation. Metal is one obvious choice, but many wood claddings are oddly resistant, like the trees they came from. We don’t have to turn to brutalist and high carbon materials like block and concrete to clad our homes.

System Approach

Like health and air quality, the right solutions are systems working together. Luckily, the systems that optimize for health, durability and low carbon are the same that work for fire resistance.

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