Affordable 3D-Printed Housing: Hope or Hype?

Different 3D materials have vastly different carbon impacts and structural specs. Can they balance affordability with crack resistance and performance?

You have heard about BioHome3D, a printed house created in Maine two years ago as an example of how more benign materials might be used to mass produce homes that are high performing and affordable. The 600 sq. ft. home has “done well so far,” according to Habib Dagher, one of the key researchers on the project, when I contacted him this month.

I asked Dagher to clarify the “bio” aspects of the home. What makes it different from some of the cementitious 3D homes being printed elsewhere? He says the home is made primarily from a plastic-wood composite.

“The materials we use in our research work are a variety of bio-based resins, recycled resins,  and waste wood and other natural fibers,” he explained. “ BioHome3D was made using waste wood from the sawmills and a bioresin. We have been researching the durability of these material systems for two decades in the lab, and also placed them in various locations and environments ranging from equatorial South America to Maine to study their mechanical and durability properties.”

The University of Maine wood composite BioHome3D has already been subjected to two years of snow and sun

Concrete v. Plastic v. Recycled plastic v. Wood-Plastic Composite

To put that in context, most 3D homes built to date in the U.S. consist of a special concrete mixture known as “LavaCrete, according to Reuters. Aout 90 have been built in a Lennar community called Wolf Ranch, Texas, for example, using this material. 

To evaluate the green credentials of any 3d home, you have to take a deep dive into the material. The technology is so new that most experts are cautious but optimistic. They note that 3D printed homes are now part of the International Code Council’s Appendix AW, published in November 2021. “This is the building code modification that allows 3D printing to be used as an alternate building method. Appendix AW essentially requires the construction of 3D printed homes to comply with UL standard 3401, last published on Nov. 28, 2022.”

The biggest remaining questions are the obvious ones: Will the buildings crack over time? How fire safe are they? Will existing fire suppression systems work, especially in plastic-based structures? To answer some of these, you need to look at the materials themselves. Here’s a rough table I assembled, comparing some of the common characteristics of each assembly material. I’m no authority on the nuances of the 3D printing process, but it’s a baseline

Material Comparison Table

Table Notes: It’s assumed that the HDPE (plastic) here is 100% from recycled sources, explaining its “high” ranking in terms of sustainability. The production and disposal of wood plastic composites (WPCs) can lead to higher emissions due to the processing of both wood and plastic. It’s harder to separate the two at end of life stage. WPC created using waste wood, however, rather than virgin fiber, would be more equitable with recycled HDPE in terms of sustainability.

Zeroing in on Nature

Engineers have found that printing materials such as cement require a trade off. For example, in this dense article about the performance of 3D materials assemblies, 

“The attainment of both stiffness and toughness have been regarded as mutually exclusive in existing engineering fields, so interesting attempts to emulate or draw the gradient microstructures of biological systems have attracted massive attention in the past decade.”

To translate, engineers have found that nature, through eons of evolution, has been able to bend the rules, organically creating patterns and lattices in materials that make them stronger AND stiffer, a prerequisite for creating high-performance 3D printed homes (or other objects). Maybe this strength can be “captured” by combining high-tech with low-tech materials—which is where plastic and wood-plastic 3D homes enter the picture.

Plastic by Design

A  company called Azure Printed Homes has built a few homes using a large percentage of recycled plastic. I wasn’t able to reach them for this article, but they appear to be on track to ramp up production, having built several homes in the Las Vegas area. 

All Plastic. Available in various sizes and configurations, Azure Printed Homes offer an ADU model. 

Plastic and wood-composite.  I only know of the one Bio Based model that used this material. They paid special attention to sustainability by including waste wood, instead of virgin wood material in the mix.. The house has weathered two Maine winters, according the the researchers, with no significant problems.

Other Considerations

It’s safe to assume that a 3d-printed home will have extremely tight envelope walls, meaning that mechanical ventilation is non negotiable. 

You’ll need to keep the air moving. For hot climates, I’d want to see some data on how the Azure-type homes perform. HDPE can handle a significant heat extreme, It begins to soften at 120°C to 130°C (248°F to 266°F), but even black HDPE left in direct sunlight on a 115 degree day in Phoenix will only hit about 68°C. 

Plastic and wood are both flammable, however, so care should be taken to keep the structure clear of heat-producing mechanicals. It might be wise to include a sprinkler system as part of the initial build.

The promise of 3D printing is affordability by way of labor savings. These structures can be completed in 70 percent less time than their stick built alternatives, according to their literature. The ones to watch at this point are the ones using recycled and composite materials. These should not only offer low maintenance living, they also have the engineering in place to offer a low energy footprint for owners.