Several years ago, an empty urban lot in the city of Peterborough, Ontario, sparked an interesting and exciting debate among our faculty at The Endeavour Centre, a nonprofit sustainable-building school based in the city: What would it take to build the “greenest” home in Canada? And could such a home blend into an existing neighborhood and meet conventional cost and building code expectations?
In 2012, we set out to answer those questions, as the design and construction of such a house became the focus of our six-month Sustainable New Construction program. A group of eight students joined our faculty and guest instructors to attempt to meet the highest standards we could imagine for a residential construction project.
Sustainable Home Building Goals
From the outset, we knew that meeting our goals would involve a lot of research, as we weren’t prepared to make assumptions about the sustainability of any element of the project. We created an ambitious list of attributes we felt we’d have to prioritize in selecting all the materials and systems for the home:
• Environmental impacts. We would strive to ensure that all of our choices would have the lowest possible impact on ecosystems.
• Embodied energy and carbon. We would always choose the lowest-embodied-energy options and aim for a carbon-neutral building.
• Energy efficiency. Our building would far exceed the code requirements for energy efficiency, and we would aim to be a net-zero-energy home.
• Indoor environmental quality. We committed to ensuring that no materials with any questionable chemical content would be used inside the building.
• Waste generation. Our target was to produce less than 10 percent of the typical landfill waste for a construction project, and to reuse and recycle as much as possible.
• Code compliance. We knew that we would be challenging some code prescriptions in our efforts, but we wanted to work with code officials and use alternative compliance pathways to ensure that the entire project was legal and aboveboard.
• Durability and maintenance. This home needed to be simple to operate and not require any additional effort for the homeowner to maintain and keep functional.
• Cost. We wanted to keep the home within the price range of conventional custom home construction in our region.
• Aesthetics. The exterior of the home needed to fit into a neighborhood of brick and wood-sided century homes as well as post-war bungalows without copying its neighbors. Inside, we wanted a clean, open, and modern feel.
We found a formal path toward meeting these lofty ambitions when we registered for the Living Building Challenge. The Challenge first came to my attention in 2010, and I felt an immediate connection to its aspirations. I had been working for 15 years to create buildings with net-zero energy and water use out of local, nontoxic materials, and I was thrilled to see a codified standard aiming to make the best possible buildings with the lowest possible environmental impacts.
Building a Sustainable Home: From Concept to Design
So, with all these fine intentions, what exactly did we do? The project began with a deliberate planning process that included running the design through the Passive House Planning Package, software that creates a very accurate energy model of a building. While we didn’t pursue certification because of the extra cost, we used the software to get to a target of using 75 percent less energy than a conventional code-built home — a figure we could achieve with little extra cost, and which would result in immediate payback via energy savings. This would also get us into the range in which a net-zero-energy strategy could be affordable.
Soon, the house began to take shape. For the shell of the house, we used a blend of conventional and natural building approaches; whenever possible, we used off-the-shelf building materials and products that met our high standards. If we couldn’t source from a conventional building supply outlet, we went in search of better options elsewhere.
Energy-Efficiency Targets and Sustainable Building Materials
We made a conscious decision to build the house so it wouldn’t require fossil fuels. The electricity used to heat and power the home comes from a grid-tied 5-kW photovoltaic system on the roof. A contract with Bullfrog Power ensures that we’re using renewable energy even when our system isn’t directly providing power.
A Mitsubishi air source heat pump provides the heating and air conditioning for the building, and an energy recovery ventilator supplies pre-warmed ventilation air.
Two solar hot water collectors provide about 65 percent of the home’s annual hot water needs, and an electric on-demand tankless heater provides the rest. The building is rainwater-ready, and we’re looking forward to setting up that system soon.
In the end, we succeeded in building a home that earns about CA$1,500 more than its annual utility costs. (All figures are in Canadian dollars.) It uses 70 percent less energy and 71 percent less water than comparable homes, and, in the building process, we reduced the environmental impacts of construction by 47 percent and cut construction landfill waste by 89 percent. See the complete breakdown of figures in Calculating Energy Costs and How the Home Stacks Up.
We managed to exclude any interior materials that contain toxic or questionable chemicals and any materials that could cause environmental degradation in the harvesting or manufacturing processes. We even sourced 90 percent of the materials within a 250-kilometer radius of the building site.
The home doesn’t look like a strange new form, either. Its wood and shingle siding fits so well into the Peterborough neighborhood that only the solar panels on the roof set it apart.
There seems to be a pervasive notion that building “green” is more costly and complicated than conventional options. This house was CA$185 per square foot, which is well within the average range for custom construction in our part of the world. The home would also be easy to reproduce — there was nothing complicated in the design or construction, and building of this sort can be done for single-family dwellings, such as this one, or expanded for use in multi-unit structures. With minor adjustments, it could be delivered as affordable housing.
Building a sustainable home with this level of environmental performance isn’t difficult to do, but it requires the homeowners, designers, and builders to commit to meeting clear goals and using strategies that have been crafted by the whole team. It requires research and careful vetting of all products and materials to make sure they fit the goals, and it takes conscientious construction to ensure that the energy targets are met. But the reward is an affordable, nontoxic, beautiful home that has a truly minimal impact on the planet.
Conventional Building Materials
Wooden, open-web floor joists. These joists use finger-jointed wood to create spans longer than solid-wood joists, and use less material.
Triple-pane, fiberglass-framed windows. Locally made windows from Inline Fiberglass provided sufficient thermal properties to meet our energy targets while remaining affordable.
Cellulose insulation. Used in the ceiling (with an insulation rating up to R-80) and in the framed walls around the windows (to R-40), this recycled-newsprint insulation has very low environmental impacts, no toxic off-gassing, and is very affordable.
Roof trusses. Engineered roof trusses use small-diameter trees from sources certified by the Forest Stewardship Council (FSC) to provide maximum structural capacity with the least amount of wood.
Recycled-content drywall and hypoallergenic joint compound. Where drywall was used, we were able to source board with a very high recycled content. The joint compound from Murco contains none of the toxins and chemicals found in typical drywall mud.
Steel roofing. Locally sourced steel roofing has a high amount of recycled content, will outlast other types of roofing, and will provide clean water for rainwater catchment.
FSC-certified hardwood flooring. Regionally sourced maple flooring is FSC-certified and comes with a nontoxic factory finish.
“Alternative” Building Materials
Durisol block foundation. Locally made insulated concrete forms (ICFs) made from waste-wood chips bonded with cement and Roxul insulation inserts. The basement wall achieves R-28 in a single, straightforward step and is chemical-free.
Poraver slab insulation. We bonded locally made expanded glass beads from Poraver with a homemade hydraulic lime binder that uses Poraver’s waste metakaolin as a key ingredient. The result is stable, impervious to water, and chemical-free.
Prefabricated straw bale wall panels. These straw bale walls were cast off-site and delivered as ready-to-be-installed panels. They cost less than any conventional wall system achieving R-30, and were made from locally sourced and chemical-free materials. They were also installed in a single day per floor, reducing labor time.
Solid-wood subfloors. As it’s impossible to find plywood or oriented strand board (OSB) that doesn’t contain formaldehyde glue, we used locally sourced pine to keep the interior free of toxins.
Clay and lime plaster. Many walls of the home feature clay or lime plaster in place of drywall. These site-mixed, wet-applied finishes are both beautiful and durable while having very low environmental impacts and no embedded toxins.
Locally sourced and FSC-certified siding. The house mixes FSC-certified pine siding with locally milled Eastern white cedar shingles that were finished with nontoxic coatings.
Natural clay, lime, and oil paints. Surface coatings were sourced from manufacturers that provide 100 percent nontoxic and biodegradable finishes that use clay, lime, or natural oils as their bases. As a side benefit, they’re also beautiful and durable.