Toronto couple turns to green roof as city faces climate-driven flooding

National Observer

15-07-2025

When Julie Wang sees streets turn into rivers after another heavy downpour in Toronto, she thinks of the 600-square-foot patch of greenery on her roof — and feels a little less helpless.
'It's a fantastic feeling to know you're doing your part — for stormwater management and all the other benefits of the green roof,' said Wang, who lives with her husband, Edmund, in the city's east end. 'If everyone does their bit, the collective effect would be huge. That's why I believe every flat roof in the city should be green.'
The Wangs are among a growing number of Toronto homeowners turning to green roofs — layers of vegetation installed on rooftops — as a way to help the city adapt to climate change. Flash floods are becoming more frequent and intense, overwhelming aging infrastructure and causing costly damage.
On Monday, Toronto ranked among the most polluted cities in the world, with wildfire smoke and extreme heat triggering simultaneous air quality and heat warnings in the Greater Toronto Area (GTA).
Last year, flash floods shut down highways, swamped basements and pushed storm sewers beyond their limits in cities across the GTA. Friends from Julie's old neighbourhood in North York told her their basement flooded during storms.
While no single solution can stop these impacts, experts say infrastructure like green roofs plays a valuable role in helping cities adapt.
Julie and Edmund moved into their home on Gough Avenue about six years ago, bringing with them a shared commitment to sustainability — partly inspired by their daughter, who works in environmental conservation. A green roof was one of their top design goals.
As well as absorbing rainwater, green roofs can reduce energy use, improve air quality and cool cities during heat waves. They also offer habitat for pollinators and extend the life of roofing materials.
They weren't sure how effective it would be, but the results quickly exceeded expectations. Their top floor is cooler in summer and warmer in winter, thanks to the insulating effect of the green roof. Sedum plants cover the roof, supported by a system that retains rainwater and reduces runoff. They estimate it absorbs more than 70 per cent of rainfall in a typical storm.
They also received a rebate from the City of Toronto's Eco-Roof Incentive Program, which helped cover nearly half the cost.
One unexpected perk was the sound insulation. During construction, the couple had worried rain would drum loudly on the flat roof. Instead, the green roof muffled the noise so effectively that stormy nights now pass in near silence
'It's like sleeping under silence,' said Edmund. 'We barely hear it anymore. It's been great for our mental health.'
A small fix for a big problem
As well as absorbing rainwater, g reen roofs can reduce energy use, improve air quality and cool cities during heat waves. They also offer habitat for pollinators and extend the life of roofing materials.
Toronto was the first city in North America to require green roofs on certain new buildings. The Green Roof Bylaw, passed in 2009, applies to commercial, institutional and multi-unit buildings over 2,000 square metres. In 2024 alone, the city approved 41 new eco-roof projects, adding more than 63,000 square metres of green roof space.
To support smaller properties, the city offers up to $100 per square metre through its incentive program. Since 2009, the program has funded over 600 projects, helping divert nearly 19 million litres of stormwater each year. It has also cut energy use by more than 2,300 megawatt hours annually and avoided over 430 tonnes of greenhouse gas emissions.
But green roofs alone won't prevent flooding, said Darko Joksimovic, professor and chair of civil engineering at Toronto Metropolitan University (TMU). He said green roofs are more effective when they are part of a broader system engineers call a 'treatment train' — a layered strategy for managing water at multiple points, from rooftops to rain gardens to sewer systems.
'They capture rain where it falls, which is always better than rushing it into pipes and hoping for the best,' Joksimovic said.
He added that if every roof in Toronto were green, stormwater runoff could be reduced by up to 30 per cent — significant in a city covered in impermeable surfaces, such as roads and buildings.
Joksimovic also pointed to other benefits. At TMU, a rooftop farm produces several tonnes of food each year for underserved communities, showing how green roofs can contribute to food security and urban biodiversity as well.
Stormwater costs rising, cities seek solutions
Managing stormwater is expensive for Toronto, especially since the city doesn't currently charge property owners for runoff. Nearby cities, such as Mississauga, Vaughan and Markham, have long had stormwater charges to help fund flood prevention and infrastructure.
To help cover rising costs, Toronto also proposed a stormwater charge on commercial and residential properties with large paved surfaces. But the idea — quickly branded a 'rain tax' by critics sparked backlash and was suspended. Public consultations were cancelled.
Now, Toronto has set aside $4.3 billion over 10 years (2023 to 2032) for stormwater management, including $2.11 billion for its basement flooding protection program.
A separate proposal for a commercial parking levy — targeting large paved lots that contribute to runoff — was also paused. City staff say more engagement is needed with the provincial government and Municipal Property Assessment Corporation before it can move ahead.
The city is now shifting to a new green infrastructure program to help property owners reduce paved areas and install green infrastructure to soak up rain water.
Growing interest — under threat
Nearly 90 per cent of surveyed residents support more green roofs in Toronto, despite most being unaware of the city's green roof bylaw. Residents ranked air quality, habitat and cooling as top benefits.
The bylaw is part of the city's green building strategy to reach net-zero emissions by 2040. But that progress is now under threat. The Ford government recently passed Bill 17, which removes municipalities' ability to set their own green building standards. Critics warn the law could undermine local climate action and make flooding worse.
For Julie and Edmund, the motivation is both personal and political.
'We're losing so much green space,' Julie said. 'There has to be a balance. We can't keep building over farmland and wetlands and expect no consequences.'
At their home, nearly 80 per cent of the property is now green space — including the rooftop, front yard and garden beds. The only part left is the garage roof, which they hope to green next.
'We're doing this because we can, because we care,' Julie added. 'But also because the government isn't doing enough. So we're doing our part — one roof at a time.'