The 1,200-square-foot home has three bedrooms, two full bathrooms, and a covered front porch. Yet it took just 28 hours to erect the home’s concrete walls — that’s because they’re printed, reducing the standard construction schedule by at least 4 weeks. Using automated computer technology and a patented concrete mix, Habitat for Humanity recently completed the first of many planned 3D-printed houses in Williamsburg, Virginia and elsewhere.
The new owner, April Stringfield, and her 13-year-old son, are happy to know that the home will be theirs. Ms. Stringfield has worked as a laundry facilities supervisor for 5 years at a local hotel, however, her income totals less than 80% of the area median income. Needless to say, becoming a homeowner seemed out of reach — until being accepted for one of the Habitat for Humanity 3D-printed houses. “My son and I are so thankful,” she said at the home’s dedication. “I always wanted to be a homeowner. It’s a dream come true.”
Habitat for Humanity has constructed hundreds of thousands of affordable homes for people who need them.
3D printing is a fairly new technique in the construction sector, with the aim to improve the economics and alleviate environmental impacts. It is an innovative area that combines the knowledge of traditional construction with digital fabrication. The elimination of formwork plus several other major benefits has great potential and has caught the attention of the construction industry.
Why 3D printing?
- It saves up to 15% per square foot in building costs for contractors.
- It offers better retains temperature, reducing heating and cooling costs for homeowners.
- It is resistant to tornado and hurricane damage.
3D-printed houses are already being built and sold to the general public.
How 3D-Printed Houses are Constructed
The concept of additive manufacturing — the more technical term for 3D printing — dates back to the 1980s, but has become much more popular in the last decade. 3D printing begins with a digital file of a house design. Large robotic arms on a swivel produce fully functional houses as, layer by layer, they deposit material to build up the house in three dimensions, one layer at a time.
For Ms. Stringfield’s Habitat for Humanity home, Alquist used a patented concrete mix and extrusion machine to print exterior and interior walls, which were reinforced with steel during the printing process. Afterward, the exterior walls were sealed with a clear or tinted coating that keeps moisture from transferring through the concrete. The contractor incorporated traditional siding on the roof gables and used standard bricks on the porch pillars.
Homeowners can choose a standard gray concrete color or select from a range of attractive earth tone hues to give the home a custom look.
After Alquist finished printing the walls, traditional builders constructed the roof, ran plumbing and wiring, and installed interior flooring and other finishes. Through the Williamsburg chapter of Habitat, contractors, subcontractors, and other volunteers donated their time to complete the remaining parts of the house.
Life-Cycle Assessment of 3D-Printed Houses
The life-cycle assessment (LCA) framework is utilized to quantify the environmental loads of raw materials extraction and manufacturing, as well as energy consumption during construction and operation phases. Want the stats? A study conducted in the United Arab Emirates looked at the construction process of a single-story 3D-printed house to conduct the comparative assessment against traditional concrete construction.
The economics of the selected structural systems were investigated through life-cycle costing analysis (LCCA), that included mainly the construction costs and energy savings. An eco-efficiency analysis was employed to aggregate the results of the LCA and LCCA into a single framework to aid in decision making by selecting the optimum and most eco-efficient alternative.
The findings revealed that houses built using additive manufacturing and 3D-printed materials were more environmentally favorable. The conventional construction method had higher impacts when compared to the 3D-printing method with global warming potential of 1154.20 and 608.55 kg CO2 eq, non-carcinogenic toxicity 675.10 and 11.9 kg 1,4-DCB, and water consumption 233.35 and 183.95 m3, respectively.
The 3D-printed house was also found to be an economically viable option, with 78% reduction in the overall capital costs when compared to conventional construction methods. The combined environmental and economic results revealed that the overall process of the 3D-printed house had higher eco-efficiency compared to concrete-based construction. The main results of the sensitivity analysis revealed that up to 90% of the environmental impacts in 3D-printing mortars can be mitigated with decreasing cement ratios.
Environmental Impact of 3D-Printed Houses
Alquist — the company behind the Habitat for Humanity 3D-printing — uses the technology to create designs while lowering the cost of housing and infrastructure in economically distressed and under-served communities. Each Alquist home comes equipped with Virginia Tech’s proprietary Raspberry Pi-based monitoring system, which monitors the indoor environment, provides security and emergency management, optimizes energy consumption, and analyzes occupant comfort and space utilization.
Alquist also installs a 3D printer in the kitchen of every home it builds. The homeowner receives a downloadable computer file that will allow them to print knobs, light switch covers, and other replaceable parts.
While 3D-printed houses are still uncommon, the Williamsburg house symbolized the potential of affordable homes that limit the use of natural resources like trees. Every new home built by Habitat for Humanity Peninsula and Greater Williamsburg is EarthCraft certified. EarthCraft is a voluntary green building program that serves as a blueprint for healthy, comfortable homes and works to both reduce utility bills and minimize environmental impacts.
Construction of each home built by Habitat for Humanity Peninsula and Greater Williamsburg is a cooperative effort between volunteers, house sponsors, and the buyers of the home. Participating families provide at least 300 hours of work toward building their own and other families’ homes, called sweat equity. Habitat’s homebuyer program resulted in monthly mortgage payments of no more than 30% of Ms. Stringfield’s income, including her real estate taxes and homeowner’s insurance.
3D-printed houses are inherently resilient, cost-effective, and have sturdy construction. They can help make homes more affordable and are likely to become another tool in the toolkits to fight against homelessness and the effects of the climate crisis.
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