3D-printed homes: Gimmick or affordable-housing solution?

Here’s how a non-profit partnership and a robot that squirts grey goo are turning southwestern Ontario into a testing ground for new housing tech
By Josh Sherman - Published on Dec 09, 2021
Fiona Coughlin is Habitat for Humanity Windsor-Essex's executive director. (Habitat for Humanity Windsor-Essex)

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Ian Comishin likes to joke that his company is “in toothpaste construction.”

But Twente Additive Manufacturing develops industrial-grade 3D printers. And the toothpaste Comishin refers to is really a gooey, grey, concrete-like material that squirts out not from a tube but from the nozzles of these machines. “It almost has the texture of toothpaste,” he says. “What’s really cool about it is that you can very quickly build very solid structures that are virtually any shape you can imagine.”

Recently, Twente brought one of its 3D-printing robots, a hulking, 2.7-tonne device, to the University of Windsor. Tilikum, as the machine is named, is being tested in a lab before it’s sent to Leamington, in neighbouring Essex County. That’s where, this winter, the school and Habitat for Humanity Windsor-Essex are partnering to use the technology in the construction of four affordable tiny rental homes. “This, I think, is going to be a ground-breaking project both locally and for the entire country,” says Fiona Coughlin, executive director and CEO of the local Habitat chapter.

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Experts say it’ll be among the first examples of 3D printing in home-building in Canada and the province’s only to date. While they say the approach is faster, cheaper, and more sustainable than traditional building methods, they caution that much more fieldwork is required before the process, called additive manufacturing, can be widely adopted on construction sites.

For home construction, additive manufacturing has mainly been used to create interior and exterior walls (Courtesy of Twente Additive Manufacturing).

The Leamington initiative is part of the ongoing development of a larger, mixed-income community from local non-profit organization Bridge Youth Resource Centre, which plans to build 42 homes by 2025 and has already opened a new resource centre and supportive-housing facility — overall, it’s a roughly $13 million project. Bridge has agreed to purchase the 500-square-foot 3D-printed units for no more than $150,000 each; the money will go back into Habitat’s MicroBuild Fund to finance future housing construction. “We had … been looking at the 3D printing to find out whether it was something that could address the housing crisis,” says Coughlin, who wants to create a blueprint for other builders to follow. “Our hope is that at the end of this, the research will inform other affordable-housing providers, and they can take it to the next level — or we can take it to the next level.”  

Additive-manufacturing processes are already appearing in industries from aerospace and automotive to medicine and fashion (and, elsewhere in the world, housing). Modern 3D printing can be traced back to 1987 and inventor Chuck Hull’s first commercial 3D printer, explains Ali Radhi, a University of Toronto engineering lecturer who, earlier this year, launched the school’s first course in 3D printing. “Most people think of 3D printing as these small toy-like parts, but that’s definitely not true — 3D printing is here. You’re going to encounter 3D-printed parts somehow,” whether on a plane or in your mobile device.

In best-case scenarios, 3D printing costs about half of what traditional formwork would. (Courtesy of Twente Additive Manufacturing)

The process begins with a 3D model, which is drafted using computer-aided design software. Then code is written to direct the robotic printer’s movements. “In the grand scheme of things, 3D printing is really just a nozzle that’s moving around free space — usually a few millimetres above where you want to put material down — and then you’re squirting a material out,” explains Comishin, who co-founded Twente in 2018.

For home construction, additive manufacturing has mainly been used to create interior and exterior walls, rather than, for example, foundations or ceilings, and the Leamington build is no exception. Unlike a wall, which can be built up layer by layer from the foundation, there’s nothing underneath a ceiling. “Building things with a horizontal shape [like a roof or a ceiling] is quite difficult, as there are no structural supports underneath when the concrete is deposited from a nozzle,” explains Radhi in a follow-up email. Given this, Comishin estimates that his technology can be used to construct about 20 per cent of a house: “That’s where we are right now.”

In best-case scenarios, 3D printing costs about half of what traditional formwork would, Radhi says, and the automated process is less labour-intensive, as fewer workers are required and machines can log longer hours. There are material savings, too. “Think about having a honeycomb inside the wall instead of having one solid wall,” he says. “So they are structurally efficient and they are lightweight, so that’s why you have a huge reduction in cost.”

These potential benefits have more than one Ontario group interested in 3D printing an affordable-housing complex. “What kept coming up, just in general discussions of what was in the news all the time, was the cost of housing,” says Anthony Zwig, CEO of Horizon Legacy, a Toronto-based renewable-energy company with roots in real-estate development. These talks inspired the company to put out an international-submission call last year to create a proposal for a triplex that could be built in the town of Gananoque, near Kingston, using new technology — and for less than $100 per square foot.

3D-printed home
A rendering of a 3D-printed triplex proposed for Gananoque. (Horizon Legacy)

Having purchased a two-acre parcel of land west of the Gananoque River this summer, Horizon is working with five selected applicants. Each is responsible for constructing a triplex that meets the cost challenge; four incorporate 3D-printing. Once the buildings are complete, they’ll be rented out for an “affordable” rate, says Zwig. Horizon will then choose one team to try a project elsewhere in southern Ontario: a 12-storey, 3D-printed apartment building. “It would be the tallest, the biggest in North America,” says Nhung Nguyen, Horizon’s vice-president of development.

Although local builders are beginning to break ground with the emerging technology, many challenges remain. Up-front costs are substantial, says Radhi, and Coughlin isn’t sure Habitat’s project would have moved forward without recent funding from the Canada Mortgage and Housing Corporation. “CMHC is a partner in this exciting project that will look to create more desperately needed housing supply by innovative means," a spokesperson tells TVO.org in an email. "Emerging trends in 3D construction have enormous potential to help increase the supply of affordable housing.”

An entry-level machine from Twente starts at about $350,000, Comishin estimates. Radhi says that, right now, only major developers could make the numbers work, by building in high volumes over several years. (Researchers from the University of Windsor, who are acting as project managers in Leamington, are conducting a cost-benefit analysis as part of the work they plan to share.)

“Another problem with them is they have a very low what we call margin of error,” explains Radhi of cement 3D-printers. Material rapidly hardens out of the printer’s nozzle, so blunders can be costly and time-consuming. “In normal approaches of form-working, if you figure out a mistake, you can easily fix that, but concrete 3D-printing is not easy to do because it solidifies very quickly.” Anticipating some trial and error at the Habitat site, Comishin has ordered 120 tonnes of “toothpaste.”

One more hurdle, according to Radhi: “The building is limited by the size of the printer — that’s why we don’t do a lot of high-rise buildings.”

Ali Radhi
Ali Radhi, a University of Toronto engineering lecturer, wearing his 3D-printed tie. (Ali Radhi)

Then there are Canadian winters. Performance varies by printed material, but Comishin says that what he’s using in Windsor can be printed only between 10 and 40 degrees Celsius. “This is definitely a hold-back in an environment such as Canada,” he adds, noting a heated tent is being placed over the site for winter construction.

“What people have to do is they have to do rigorous testing,” says Radhi. “All of this has to be tested.” Some of that work is already underway in Windsor’s lab under the supervision of engineering professor Sreekanta Das. Using a hydraulic system, researchers are simulating windy and rainy conditions to see how the walls printed by Twente’s robot hold up. “You cannot take a sledgehammer [to it],” says Das. “You’ve got to be a very strong guy to do that.”

Zwig, who’s working with Gananoque’s planning department on Horizon Legacy’s project, which the company aims to complete by next fall, is well aware of the difficulties posed by using unconventional approaches to homebuilding. “It’s a much woolier ride than just saying, ‘Okay, let’s use a tried-and-true technology and call us when the building’s done,’” he says. But, he notes, “You only live once.”

Coughlin, too, is optimistic: “There’s so much potential, and without the research, it doesn’t take flight.” If this proves successful, she’d like to see 3D printing somehow incorporated into the Bridge’s plans for the fourth and final phase of its development, which encompasses 30 homes.

She says Habitat wants to have the four homes finished by March 31 so that the milestone won’t be reached on April Fools’ Day. If that were to happen, she worries that people might not believe a 3D printer was used to build them: “It’s a little incredible.”


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