Among many things, 2021 has already become the year of the 3D printed house. In March, the first resident moved into Austin’s Community First! Village, a housing development that features six 3D printed tiny houses built by the Austin-based robotics startup Icon Technology. That same month, Mighty Buildings announced the country’s first 3D printed community in Rancho Mirage, Calif., featuring 15 modern, single-family houses prefabricated in the company’s factory in Oakland, Calif. Weeks later, a group in the Netherlands announced the completion of a 1,000-square-foot home printed entirely out of concrete.
In the U.S., 3D printing has been marketed as an answer to two converging emergencies: the housing crisis and the climate crisis. Startups like Icon aim to address the former by significantly reducing the amount of time—and therefore cost—of residential construction, and the latter by reducing emissions associated with transporting building materials and construction waste. But as other publications have pointed out, some of these environmental claims ignore the reality of what makes up a house’s carbon footprint.
First, most 3D printed houses on the market are hybrid structures, featuring some 3D printed components but also steel or concrete elements. Second, in the case of a development like that of Mighty Buildings, the community’s location well outside of an urban center will lock in a certain amount of carbon emissions in the form of vehicle miles traveled.
Then there’s the printing medium itself. ICON prints its buildings out of a “proprietary Portland cement–based mix” called Lavacrete. Portland cement is the most carbon-intensive component in concrete. In other words, without a material revolution that finds a significantly less carbon-intensive binder than traditional cement and land use regulations that limit sprawl, 3D printing is likely to increase emissions, not cut them. “As 3D printing is taking off, it can potentially exacerbate the [climate] problem,” says Sarbajit Banerjee, a chemistry professor at Texas A&M University.
This reality has led some architects, working alongside 3D printing startups, construction scientists, and materials researchers, including Banerjee, to explore the possibility of using raw earth as a print medium. To date, the most tangible effort is TECLA, a 650-square-foot residential prototype designed by Italian design firm Mario Cucinella Architects and built by the Italian 3D printing company WASP (World Advanced Saving Project) outside of Ravenna, Italy. (The name TECLA derives from the combination of “technology” and “clay.”) The prototype was completed to great fanfare in April.
Unlike its American counterparts, TECLA uses no concrete and is nearly entirely 3D printed, with exceptions being its doors and skylights. The walls of the conjoined, hive-like domes are formed from a slurry of rice husks and soil excavated from the building site, an approach that both eliminates the need for Portland cement and long-distance material transport and creates novel end-of-life possibilities. Despite accounting for 10% to 12% of a building’s total emissions, the carbon emissions associated with demolition “are never considered,” says MCA architect Irene Giglio. With TECLA and other earthen structures, she says, “you have the soil, it’s transformed, you can live inside, and then once you don’t need it anymore, it just goes back to the soil in a continuous loop.”
TECLA is the culmination of years of research and experimentation. The goal was to create a wholly 3D printed architecture derived not from historic forms and assemblies but from the material and technological realities of 3D printing with soil. This led the team to the self-supporting, self-shading, and domelike forms of the realized prototype, which is divided into a living and dining space and a bedroom and bathroom space. By tweaking the amount of water, fiber, and chemical binder that goes into the soil mix, the team believes the TECLA system can be adapted to a range of climates and site contexts, including extreme or post-disaster environments.
While the approach holds promise as a low-carbon form of architecture, the technology is still in its infancy. Transforming soil into structural material presents a number of challenges. According to Banerjee, who is part of a different interdisciplinary team working to develop its own material formulation that can be adapted to any soil type, one primary challenge is “getting the viscosity [and] rheology of the fluid down, so [it can be extruded and] cure not too fast or too slow and bear enough strength that you can put on the next layer. It’s a matter of getting the chemical kinetics of these reactions to [occur] relatively soon, but not so soon that your printer gets clogged.”
The finicky process is also influenced by the size and configuration of the structure being printed. “It’s incredibly difficult to control the characteristics when you work with soil,” Giglio says. For example, MCA and WASP team had printed a partial mock-up of its building, she says, “and we have noticed that the building and the mock-up work very differently for two reasons. First, [in the mock-up,] the material was pumped from a closer distance, and that makes a lot of difference for the quantity of water that is contained within the mix. Second, since the slice was very small, the printer was passing on the same spot every 20 minutes, instead of every 2 hours.”
Even with a completed prototype, Giglio says the process is far from perfected. TECLA’s highly textural, layered surface creates opportunities for water to pool; despite a spray-applied waterproofing layer, the building already has several leaks. Solving this challenge will require either alternative waterproofing products or smoothing out the layers so that the structure sheds water more easily, Giglio says. The team is currently testing strategies on a portion of the structure.
Perhaps the biggest challenge is the spatial requirements of the operation itself. Giglio says 3D printing with soil is only suited to remote, rural, or exurban sites—places where relatively homogenous, uncontaminated soil is abundant and where enough open space to house the equipment and facilities required by the soil-mixing process is available. Also, the technology is currently limited to producing one- or two-story-tall structures—which means that, in the United States at least, a fundamental mismatch occurs between where housing is most needed—in cities—and where this technology can be deployed. “You cannot [build this way] in very crowded places; otherwise, the soil costs way more than buying concrete,” Giglio acknowledges.
Where the model may be most viable is in rapidly urbanizing areas, where the need for housing is acute and undeveloped land is available. On its website, the TECLA team describes the potential of printing “new autonomous eco-cities that are off the current grid.”
To facilitate this future, WASP has developed the Maker Economy Starter Kit, which includes the Crane WASP 3D printer, a tools and raw materials kit, and a smaller 3D printer that can produce furniture components, all designed to fit inside a single shipping container. The kit, which is marketed as a way to provide for basic human needs using digital construction techniques, could be purchased by municipalities or other government entities to produce affordable housing for its citizens. Depending on the context, however, such efforts will still have to overcome the challenge of local building codes, which are unlikely to permit 3D printed structures outright.
At its best, TECLA represents an attempt to contend with the embodied carbon of 3D printed housing. It’s a starting place, Giglio says, and a necessary one. “If we want to give everyone a house while also bringing emissions down to zero in the next 30 years, we have to start a small revolution in the way we build,” she says. “This thing is definitely not the answer. But it’s a proposal for this revolution."