More than aesthetics

By Emily Jerome, Digital Engagement Assistant

Green roofs have an important role in climate action and sustainable, energy-efficient and biodiversity-integrated design and development.

Within one minute of sitting down under a pergola on the 5th-floor green roof, I spotted 15 native bees enthusiastically visiting each bright purple sage flower. I also heard the chatter of magpies amongst the snowberry bushes. I’m lucky to enjoy this little slice of nature while living downtown Calgary, but it isn’t just aesthetics that drew me here. Green roofs have an important role in sustainable, energy-efficient and biodiversity-integrated design and development. With a record-breaking heatwave sweeping through western Canada, green rooves also have a role to play in climate action. For municipalities, green roof bylaws are an easy step forward in addressing various environmental challenges and creating nature-full cities.

What are green roofs?

Quite simply, green roofs, also known as living roofs or eco-roofs, are where plants grow on top of buildings.  Instead of sealing buildings off with concrete tiles, green rooves have drainage systems, growing mediums for plants and then the cherry on top,  a diversity of trees, shrubs, grasses and flowers. Green infrastructure such as green roofs can be integrated into condos, industrial buildings, residential homes and schools.

Why are green roofs a big deal?

From social to economic to environmental, green roofs are jam-packed with benefits for humans, as well as wildlife. Here’s a fascinating list of benefits that will have you in awe:

– Increases energy efficiency by reducing heat flow. In some cases, green roofs can reduce air conditioning by 75% according to a study published by The National Research Council of Canada.

– Increases building durability by protecting the roof membrane from thermal and ultraviolet degradation. The longer the building life, the lower the environmental impacts of construction and repairs.

– Reduces stormwater runoff, therefore, reduces the risk of flooding and riverbank erosion.

– Improves water quality by filtering pollutants out of stormwater before returning to the watershed.

– Reduces air temperature and increases humidity, thereby reducing the urban heat island effect.

– Improves air quality by removing airborne pollutants from the atmosphere.

– Provides habitat for wildlife including pollinators, birds and more and increases the local biodiversity.

– Increases human well-being. There are many benefits to spending time in nature including increased cognitive function and decreased blood pressure, stress hormones and symptoms of anxiety and depression.

– Absorbs a significant amount of noise pollution including road traffic.

As you can see, green roofs really are the full package. Now, all we need are municipalities to step up to the plate and bat for green infrastructure and sustainable development. One Canadian city is way ahead of the game.

Toronto’s green roof bylaw

Back in 2009, Toronto became the first city in North America to enact a green roof bylaw. It required large new developments to cover 20% to 60% of the buildings with vegetation. According to The Nature of Things, there are now over 700 green roofs adding colour to Toronto’s skyline. If all these green roofs were “tetrised” together, they would cover around 73 football fields. Some of these green roofs even produce fruits and vegetables, a practice known as urban agriculture. Within the downtown core, Ryerson University’s rooftop farm produces an astounding 10,000 pounds of food per year. Green rooves and urban agriculture are a dynamic duo that can not only increase food security but help tackle the climate crisis.

Growing climate-resilient cities

With over 80% of Canadians now living in urban areas, it comes as no surprise that cities are hotspots for environmental impacts. According to UN Habitat, cities cover less than 2% of the Earth’s surface but produce over 60% of greenhouse gas emissions. One way that municipalities can become climate-resilient and contribute to climate crisis mitigation is by creating a green roof bylaw and/or incentive program. But, how can this green infrastructure help?

In an annual report, Green Roofs for Healthy Cities (GRHC), a Toronto-based not-for-profit, found that 3,112,818 square feet of green roofing was installed throughout the U.S. and Canada in 2019. It’s estimated that the plants and soil in these green roofs will sequester 120 tons (240,000 lbs) of carbon every two years and save 5.06 million kWh of energy every year. To give you a better idea, 5.06 million kWh of electricity would light over 700 homes in Canada for a year.

By storing carbon and saving energy, green roof bylaws could play an important role in working towards Canada’s goal of net-zero greenhouse gas emissions by 2050. So let’s turn traditional grey infrastructure into vibrant, biodiversity-filled green infrastructure. After all, the only things that look good in grey are silverberries, grey wolves and Meryl Streep.

How can you help support green roofs and urban biodiversity?

1. Contact your MP to encourage the enactment of a green roof bylaw and/or incentive program. 

2. To reduce stormwater runoff and increase urban biodiversity in your backyard, break up sealed surfaces such as pavement or asphalt with native plants.

3. Listen to our podcast episode of “What the f*** is biodiversity?” with Nina-Marie E. Lister, Graduate Program Director & Associate Professor, Director, Ecological Design Lab, School of Urban + Regional Planning, Ryerson University. 

4. Read ”What are nature-full cities?” by Dr. Rob Newell and “Cities are the next frontier for biodiversity conservation” by Nina-Marie E. Lister.