Building Better with Mud 

In the high desert of far southern Colorado, Ronald Rael, an architect with Berkeley, California-based Rael San Fratello, has been experimenting with adobe on his family’s historic ranch near the town of Antonito.

Consisting of a trio of earthen spires, Rael’s Casa Covida project has spaces for gathering, bathing, and sleeping. Old and new commingle here. On the old side is adobe, an earthen building material that dates back thousands of years. The new is a robotic 3D-printing system that’s helping Rael reimagine the way we could build in the future.

“The long-term aspiration was to test the idea, to see if one could build architecture using a 3D printer and earth,” he says. “The technique of manufacturing works very well. The history of it being used in architecture is completely solid for the last 10,000 years.” Rael says his ancestors built adobe homes in the region for millennia, and his ongoing experiment in Antonito is just the latest iteration. “How do you reintroduce earth into 21st century culture, both building culture and the culture of living?”

With innovations like earthen 3D printing, the time-tested material is primed for a comeback after a long period of decline, and sustainability is a big part of the story. “I really like to say adobe is the world's oldest high-tech building material,” says Ben Loescher of Los Angeles-based Loescher Meachem Architects, who founded its earthen materials arm, Adobeisnotsoftware. “In general, it’s a material that's readily available, so most of the world, just about everywhere except for Antarctica, has a tradition of building with earth because the material is beneath our feet.” Not only does that make adobe inexpensive, but also, it basically zeroes out transportation-related emissions. And its manufacturing process involves sunlight instead of carbon-emitting kilns, further reducing environmental impact.

Post-construction, adobe absorbs heat in the day and releases it at night, and it helps regulate indoor humidity and air quality. It’s also recyclable. “An earthen wall at the end of its life can turn right back into the dirt that it came from,” Loescher says.

The founder of Colorado Earth, a company that manufactures adobe and compressed earth blocks and designs and builds earthen homes, Lisa Morey is currently researching the thermal performance of adobe on a project funded by a grant from the National Renewable Energy Laboratory in Golden, Colorado. She says she expects it to be a good fit in climate zones three, four, and five, a massive area that spans from New Hampshire to Georgia to California and the Pacific Northwest.

Concrete and cement manufacturing accounts for as much as nine percent of greenhouse gas emissions worldwide, so earthen materials are well-positioned to help the construction industry reduce its footprint. Adobe has a much lower impact than concrete in terms of its Environmental Product Declaration (EPD) criteria, which are used to quantify the environmental life cycle of a product. Morey wants to scale her operation across the country with a second startup, Nova Terra, which is now working with quarries across the country to test buckets of waste material used to make Colorado Earth’s EcoBlox. In some cases, the material needs cement or lime to make a durable compressed earth block, whereas adobe does not require additives beyond soil, water, and sometimes straw. “If we can lower our cement or lime percentages, we can be even better than a wood-frame building,” she says of the carbon footprint of compressed earth.

Adobe remains a niche material outside of New Mexico, in large part due to construction codes that are unfriendly to adobe. That’s starting to change now: The Masonry Society (TMS) is working with Loescher and other earthen advocates to change the International Code Council (ICC) to allow for more widespread adobe use. About a decade ago, Loescher found that building codes made it nearly impossible to get an adobe project permitted in California. “We thought that it may be less work at the end of the day to just change the entire national building code for adobe than it is to permit one adobe home,” he says. Loescher soon found himself at the 2016 ICC conference in Louisville, Kentucky, where he discovered that there was a proposal to just entirely do away with adobe as a legitimate material in the code. “They didn’t think it was important enough to spend the time to draft language around it,” says Loescher. After “a stay of execution,” Loescher and his allies at the Earthbuilders Guild have endeavored to fix the code problem once and for all. “Some of the people that were trying to get adobe out of the code have actually helped us establish this new committee (under the auspices of The Masonry Society) that will fix that once and for all.”

In the wake of these successes, Loescher has obtained permits for several residential adobe projects near Joshua Tree National Park, California, where he’s conducted most of the 100 or so adobe workshops he’s led over the years. Rael continues to experiment at multiple locales in Colorado, while also consulting on adobe projects in Colombia, Uzbekistan, and California. During her career, Morey has supported about 60 earthen home projects, and she says that Colorado Earth is now the leading producer of compressed earth blocks in the U.S. There’s huge growth potential, she adds, but perception is a big hurdle. “It’s going to take a mind shift, a cultural shift in the building industry. And I think some of the pressures around insurance and EPDs will hopefully drive us towards adobe.”

The post-World War II building boom entrenched wood-frame housing as the national norm, primarily because it was cheap, says Morey. “It was meant to be a temporary form to put up housing, and it just stuck, and here we are. You know, the rest of the world doesn’t build with wood. In Mexico, my counterparts say, ‘A wood-frame house? That’s what we put the dog in.’” Other countries have already leveraged earthen materials in decarbonization strategies. Morey highlights Germany as “probably one to two decades ahead of the U.S.” in terms of adoption. “They’ve already obtained EPDs, and the concrete industry is purchasing earth block manufacturers to layer into their operations.”

Climate resilience is another consideration. While wood-frame construction can have a better carbon footprint than adobe, wood is notably flammable. With earthen materials, “The dirt doesn’t burn, the walls don’t burn, they’re non-combustible,” Morey says. “We’ve kind of had this replacement mindset from a cost perspective, even though we know that we can build better,” she adds. “I think where we’ll see some of the potential change is insurance companies cluing in that these disasters are happening more often and they’re going to be losing their pants on having to replace so many homes.” Case in point: the Marshall Fire that destroyed more than 1,000 structures near Boulder, Colorado, in December 2021. Morey subsequently helped a family rebuild their home in the town of Superior with earth instead of wood. “The father and two children almost lost their lives in the fire,” she says. “They couldn’t imagine building back in the same way.”