The building sector represents 10% of greenhouse gas (GHG) emissions in Quebec. To decarbonize these buildings — and those to come — the solutions already exist. Visit of the Phénix, an emission-free building in the Saint-Henri district of Montreal.
From the vicinity of the Lionel-Groulx metro station, this large brick building from the 1950s does not evoke high technology. And yet, its renovation and its current equipment make it a building at the cutting edge of carbon sobriety.
The equation is both simple and sophisticated. On the roof, more than 300 solar panels bask under the greyish March sky. With downtown Montreal as a backdrop, the portrait is resolutely modern.
And inside, massive concrete columns rise proudly. Rather than building new, the architects wanted to capitalize on the already existing building stock to avoid using more high-carbon materials such as concrete and steel.
“We wanted to show that we could bet on the built heritage, on an ordinary building, and make it a carbon neutral building,” explains Hugo Lafrance, a partner responsible for sustainable strategies at Lemay, one of the largest architectural firms. in Quebec.
Under his feet now house the offices of the company. Two floors can accommodate 350 professionals. This project called Le Phénix, completed in 2019, serves as a proof of concept for the firm.
The “intrinsic” carbon of a building, that is to say associated with its construction, counts for a lot. Reported over half a century, these emissions can approach those associated with heating the building with oil or natural gas.
According to the report of the Intergovernmental Panel on Climate Change (IPCC) released on Monday, 20% of global greenhouse gas (GHG) emissions are attributable to cement and steel used for construction and renovation of buildings.
By opting for used, Lemay estimates that it released 577 tonnes of CO into the atmosphere.2 through the materials used. Building an equivalent building, but new, would have dropped 2,721 tons into the atmosphere, she estimates. A reduction of almost 80%.
And by focusing on the electrification of heating, the firm thinks it can lower the emissions of the Phoenix to 3 tons per year, rather than the 96 tons before the moult. A phased natural gas withdrawal plan is underway. To offset its residual emissions (intrinsic and operating), it buys carbon credits.
In Quebec, half of the total surface area of commercial and institutional buildings is heated with natural gas or oil, according to 2017 data. At least 46,000 buildings in this sector must therefore be decarbonized in the coming years.
Optimize energy performance
On the two floors of the Phénix devoted to offices, rare employees – pandemic extension obliges – survey the open spaces or strum on their computer.
Around them, details optimize the building’s energy performance: state-of-the-art LED lighting, triple glazing on the north face, solar preheating of outside air in winter, opening windows in summer.
The solar panels on the white roof supply the building with electricity and are even used for its heating. However, due to the intermittent nature of solar energy, designers had to think of ways to store these joules.
In the basement, a cistern containing 18,000 liters of water — the equivalent of a small above-ground swimming pool — serves as a “thermal reservoir”. The volume of hot water is so large that it compensates for the gap between availability and heating needs. Simple hot water radiators take care of the distribution to the upper floors.
To heat the water in the tank, the designers chose not simple heating elements, but rather heat pumps. By “pumping” some of the thermal energy from the outside, these devices inject four kilowatts of heat into the water for every kilowatt of solar electricity.
Alongside the giant water heater is an electric battery. If needed, this refrigerator-sized black box can power the building for half a day.
From a carbon perspective, solar panels do not outperform the hydroelectricity available on the Hydro-Quebec grid. However, in a context where the government corporation must increase its capacity by 50% to supply a carbon-neutral Quebec in 2050, every kilowatt counts.
And storage can help manage peaks in demand, observes Florian Pedroli, a research associate at the Trottier Energy Institute who co-authored a recent report on building decarbonization in Quebec. “The buildings produce their own electricity, they store it, and then they will use it at peak,” he explains.
For Lemay, the Phénix adventure did not generate any additional costs. The solar panels received a federal grant, and the project met a “standard budget for a 350-person office,” according to Lafrance. “The idea was not to skyrocket costs! he said.
By virtue of his investigation, Mr. Pedroli nevertheless believes that the decarbonization of buildings must benefit from a framework from the public authorities. “If we wait for the market to get the upper hand on carbon-free technologies in a ‘natural’ way, we will never get there in the time required,” he stresses.