Wouldn’t you love to know your house was not only beautiful but designed to sequester carbon, reduce harmful emissions and promote neighbourhood liveability? Architect and Ryerson professor Cheryl Atkinson has prototyped a net-zero housing unit—one that also addresses the growing challenge of housing affordability. She spoke about the prototype in our event last week, “Innovations in Housing Affordability.”
In 2017, Atkinson set out on an ambitious project to not only design, but produce and construct a net-zero urban housing prototype, enlisting the collaboration of the Endeavour Centre, students from Ryerson and Ryerson professors Alan Fung and Philip Walsh.
This team eventually achieved their goal of a house boasting net zero energy use, construction waste, carbon footprint and cost differential to comparable housing. The design they built was taken from Atkinson’s proposal for the second storey of an attractive stacked town housing complex, which demonstrated how Passive House principles could work affordably as mid-rise urban infill on Toronto’s east/west arterial avenues.
Known as ZEROHouse, the 1,100 square foot, two-storey home was exhibited at the October 2017 EDIT DX Expo for Design, Innovation and Technology. Following the exhibition, it was dismantled and flat-packed then recently reconstructed on a permanent site near Collingwood by its new owner.
Atkinson spoke along with Heather Tremain, John van Nostrand and Leith Moore at our May 7 Urban Innovation Café on Innovations in Housing Affordability. We caught up with her to talk about ZEROHouse and how it reduces costs across its life cycle.
Q: Zero House uses modular construction. How does this work, and what are the benefits?
Our house was built using 33 separate wall roof and floor panels built as structural, hollow boxes that were lifted and fitted together on site within a single day by a crane. Prefabricated exterior and interior finish panels were installed by the Endeavour team within a single week for the exhibition. Insulation can be blown-in or installed in the factory. This obviously saves months of time on site, with much improved accuracy and quality control, significantly less construction waste, site transportation and associated emissions cost.
Q: How does ZEROHouse contribute to home affordability?
Factory construction, like all mass production, produces significant time and labour efficiencies over conventional manual work in the field. Also, midrise construction using wood framing is significantly less expensive materially to build than other mass-produced housing like concrete highrises, and offers a housing typology more suitable for families being close to grade and in existing residential neighbourhoods.
Q: What were the chief sources of emissions savings and energy efficiency in your design?
Emissions savings come from selecting locally produced materials grown by nature that sequester carbon. We used almost entirely a palette of wood products for structure, finishes and insulations. We also experimented with straw bale, cork and mycelium insulations. For durability and weight, we used a highly recyclable aluminum for the siding. We sequestered 25 tonnes overall rather than emitting the 45 tonnes of carbon a typical house through our material and construction choices.
Maximizing energy efficiency comes from good Passive House design, predominantly through providing proper orientation, a highly insulated and airtight building envelope, and using highly energy efficient mechanical systems and appliances. Building Integrated Photovoltaic systems produced the minimal energy then required by this more efficient building without the visual impact of conventional solar panels.
Q: How could the design for ZEROHouse and your stacked townhouses be employed in Toronto?
Toronto has many appropriate underused urban sites along existing east/west traffic arterials that would suit this kind of housing. They are well serviced by adjacent communities with adequate infrastructure and community services like schools, transit and green spaces to support this additional gentle density and height. Many of our east/west streets in Toronto used to be leafy residential streets before they were widened into traffic arterials. Lining these streets with three to four stories of housing over retail or commercial would create a pedestrian friendly streetscape and provide amenities while operating as continuous solar collector on its southern roof and facades.
Q: Would ZEROHouse be cost prohibitive to build again, land values aside?
It wouldn’t be cost prohibitive—but perhaps space prohibitive. The whole idea is based on factory construction, and a factory geared to this particular panel design doesn’t yet exist. We had a large tent in a field lent to us in Peterborough as our factory over the summer. Creating a real factory to make multiple panels for multiple residences would make this design even more affordable to build again. In Japan, a single factory can produce sixteen homes a day using digital fabrication, automation and advanced robotics!
Q: What are the next steps; how will this project evolve?
I am in the process of discussing this project with city councilors, planners and specific developers and prefabrication manufacturers to understand its viability as a type and a process for making housing.
The City is inherently supportive of infill with their recently approved guidelines for laneway infill housing in Toronto <link> and their support of urban intensification along existing arterials through their Mid-Rise Guidelines for Avenues.
I am trying to understand what restricts industry here from adopting significant prefabrication but facilitates it in places like Japan where it is commonplace. It is finally emerging here; large housing developers like Great Gulf have been developing their own state-of-the-art factory for much of their conventional wood frame housing, and have also built research prototypes of energy efficient single family houses.
I am optimistic that we are at a tipping point where we will start to see more mainstream adoption and integration of passive housing design and prefabrication processes. Given the continuing market pressure for affordable housing in this city, the lack of available sites and construction trades, and the fact that our buildings currently produce forty-five percent of Toronto’s carbon emissions (Toronto Atmospheric Fund 2016), coming up with alternatives for addressing these issues is critical.
The architectural design for ZEROHouse was led by Cheryl Atkinson with Ryerson U architectural science students. The house’s prefabrication was performed by students from Ryerson and Seneca College. The prefabrication research, design, and construction was led by Chris Magwood of the Endeavour Centre. Magwood also coordinated industry sponsorships key to the construction, and led the permanent installation in Collingwood. Professor Fung contributed innovative heating and cooling technology, and Professor Walsh contributed expertise into the future marketability and scalability of the venture.