If you're building a more sustainable future, it's good to hold onto the past – and to bring warm clothes.

These are the lessons of a new building project by the environmental non-profit Evergreen, a renovation of a 53,000-square-foot structure at the Brick Works facility in Toronto. It will showcase tools and practices for building sustainable cities; to that end it will use innovative materials and advanced mechanical systems.

But the team of architects, engineers and builders working on the centre will also retain the existing building, and its array of drying kilns, firing kilns and glazing kilns, which once baked the earth of the Don Valley into the bricks of Toronto. And they'll do their best to leave it alone, while cutting its energy use to make it carbon-neutral.

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This is a strong formula for sustainability, and a crucial strategy as we move – slowly inevitably – toward mitigating the effects of climate change. "There are two items that contribute to the carbon emissions of our cities," argues Geoff Cape, Evergreen's CEO. "One is transportation, and the other is heating and cooling buildings." Figures from the Canada Green Building Council suggest that 35 per cent of all carbon emissions come from heating, cooling and lighting buildings. Other estimates are even higher.

And, as Cape argues, "the greenest building is one that already exists." This is a cliché among sustainability advocates, and it's little understood by everyone else. But just imagine the dumpsters next to any construction site you've seen, and then imagine the trucks full of rubble that emerged from the demolition site before it. Renovation is always, when possible, the greener option.

That is, as long as you're able to make an existing building function efficiently. That is the goal of this project: Evergreen hopes to make the building, right now an open-air shed, into "a national hub for innovation and the centre of sustainable cities in Canada … to bring academics, industry and the community to discuss and collaborate on the ways we want to build our cities." In short, it will be an event space; a new enclosure and classrooms, plus a partial rebuild of the interior will update it, and its walls will talk.

"The campus is at ground zero of a number of current sustainable issues, flooding, heritage, and brownfield remediation," Janna Levitt of LGA Architectural Partners says. Its location in the flood plain of the Don River makes it among the most flood-prone places in the country – and the number and intensity of floods has increased in recent years, something the new architecture will be built to deal with by strategically channelling and holding floodwater. "You can walk around this campus and say, here's what happens when something floods," Levitt says. "It's a test case."

Evergreen's goal of bringing different actors together here is important. The public and private sectors will have to work together to address a linked series of challenges: the growth of cities and central cities, and the global challenge of mitigating and adapting to climate change.

So the new building, which will be for education and "convening," will also try to show what that looks like in concrete and wood. The design, by LGA Architectural Partners and ERA, will be built by contractors EllisDon.

Technologies will play an important role in reducing the building's environmental footprint. It will employ geothermal heating, which uses ground heat, and solar thermal heating; new windows will be high performance.

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This lines up with a current project of the Canada Green Building Council, which has launched a call for buildings that are shooting for near-net zero carbon. "We wanted to change the conversation: How can we design buildings with carbon in mind, and how can we design buildings that are very low-carbon?" says the non-profit's CEO and president, Thomas Mueller.

That distinction is important: It allows for sources of energy, such as geothermal (or more controversially hydroelectric power) that keep the lights on without contributing to climate change. New buildings should be as energy-efficient as possible, but we all need to be conscious of where it is coming from. That makes for a practical yet useful goal.

The Evergreen project, part of the century-old former Don Valley Brick Works, breaks from the mainstream of green building, which focuses on efficiency and building performance. This is a century-old industrial shed. It's leaky. And an important piece of the design, LGA's Levitt says, will be accepting imperfections.

"One of the things we were interested in pursuing," she says, "was how do you take an artifact like this building, which is beautiful in its thinness, and make it usable without destroying it? For us that meant don't insulate everything. Don't use conventional heating and cooling. Push the limits of what the building code allows in terms of comfort."

So the centre will have radiant heating in the floors, because a small amount of heat at your feet generates a lot of comfort. And while new components will be "crisp and contemporary" in their materials and detailing, they won't come with all the paraphernalia new buildings often have. "In many historic buildings, the biggest challenge you deal with is, how do we insulate this thing? Where do we hide the ducts? We said, no. We're not doing any of that." The building functioned in the past without mechanical systems, as Levitt points out; that's a practice we should be able to learn from.

"And if it turns out you're a little bit cool," she adds, "put on a sweater."

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