Dirt doesn’t burn seems like an obvious comment but one that has been mostly abandoned by the U.S. construction industry. However, building homes with dirt is a possible solution to the problem of wildfires in the west of the U.S. Some people are rebuilding homes lost to wildfires. Only this time, they are using a material that they hope won’t burn.
Melanie Glover’s back window opens to a sweeping view of the Rocky Mountains. When she rebuilt her home in summer 2024, she wanted to keep this view.
On 30 December 2021, high winds had carried hot flames across these plains to her neighbourhood of Superior, Colorado, destroying her home, and nearly 1,000 others in less than half a day. Her husband, Matteo Rebeschini and her children were trapped in the front foyer for 30 minutes as their house burned, before they escaped unharmed once the fire passed. The fire brought trauma that lasts to this day, but Glover and Rebeschini were determined to rebuild. So they did, only this time, they used earth blocks.
This story is particularly poignant to me because I live as short distance from Superior, in Boulder, and I see the results of that fire regularly, as I drive through the area. The story was also of special interest because I’ve been horrified by the vision of many, many people rebuilding their homes using the same wooden construction as they had used before the fire – the building codes have not changed sufficiently to ban this type of “matchwood” construction. I reported recently on the increasing use of “adobe”, or dirt construction materials being used in certain parts of the world, but I am glad to see the trend has come close to home.
Earthen homes have a deep history throughout the world, from pit cave dwellings in northern China to the mud homes of Sana’a, Yemen. Indigenous communities in the south-western U.S. states of Colorado and New Mexico have used adobe, or “mud brick” in Spanish, to build earthen homes for thousands of years, using their thick walls to keep homes cool during hot summers and retain the sun’s heat during cold winters.
While earthen construction has been largely neglected by U.S. builders for decades, the material has an increasingly relevant use in modern times. As climate change increases the risk of wildfires through the western U.S., homeowners like Glover are beginning to turn to it for a new reason: as a strategy to protect themselves from fire. Their intuition is backed up by early research, which has found earthen homes could show extraordinary promise in resisting wildfires – and the structures could even strengthen after exposure.
In 2021, Michele Barbato, co-director of the Climate Adaptation Research Center at the University of California, Davis, and his students did a series of tests on compressed earth blocks, using soil mixed with water and chemical stabilisers. The researchers took a blowtorch to a compressed earth block at nearly 1,900C (3,452F), far hotter than an average wildfire. They also put a block in a 1,200C (2,192F) furnace. The blocks hardened and turned to red clay, similar to baking pottery in a kiln. More than just showing the earth blocks can withstand fire, the tests – which have been presented as a peer-reviewed conference paper but are not yet published in a journal – therefore indicate they strengthen after exposure.
They perform just as well in dry climates, Barbato says, while in wet weather, they even improve, as the material hardens making it tougher for water to penetrate.
For Glover, an avid gardener, her inspiration to build with dirt came from her garden. After the 2021 fire, she returned to her property and found flowerpots that had melted, leaving several unharmed piles of dirt behind. “I said to myself, dirt doesn’t burn,” she recalls. “We should build a house made out of dirt.
It didn’t scare me,” she says, whereas having a conventional stick-built American house really did.”
Not long after the fire, Glover drove past a billboard advertising Colorado Earth, a Brighton, Colorado company making compressed earth blocks, called EcoBlox, from waste material sourced from a local quarry.
The company’s earth blocks are made by mixing dirt with limestone and water, and then using an hydraulic press to compress them into solid blocks that are ready to use once they dry. Unlike bricks, they’re made without being heated, dramatically reducing the embodied carbon used to produce each block, Morey says. “It’s resistant to mould, fire and bullets. And bugs don’t like them either, she says.”
Glover’s completed home has thick, high-efficiency windows that, in a worst-case scenario, would take hours for fire to penetrate. There’s a total absence of protruding roof vents, which can give flaming embers an avenue to get inside. Instead, there’s a centralised ventilation system that can be closed in minutes when strong winds appear. “Fire’s not going to get into the gaps,” she says. “It’s completely sealed.”
Glover knows the house is not infallible. “I have never said that this house is fireproof,” she says. “The blocks are fireproof, but I can’t live in a house without windows and a roof. I’ve done the very best I possibly can.”
There is still an uphill battle for more earth homes to be built throughout the United States, where fast-paced construction, with environmentally unfriendly materials, is normal – in Colorado wood is the material of choice, which is environmentally friendly, sort of, but is a firetrap. Building codes have to be changed, and a longer-term vision of what a house “built with dirt” could do for the environment, and for house construction and insurance costs. That will take a cultural change, but one with great benefits, and few downsides. Let’s hope the current construction industry doesn’t try to kill the idea.
