Green roofs keep cities cool

As we work towards reducing the footprint of our cities we must consider all technologies and strategies. Increasingly popular, green roofs provide a wealth of benefits to increase sustainability. Though an ancient concept they reemerged in the 20th century with a new purpose.

One of the greatest benefits of green roof installation is mitigating the urban heat island (UHI) effect. This phenomenon is the result of buildings and paved areas absorbing solar radiation during the day and emitting it throughout the night raising urban temperatures above those of surrounding rural areas. Analysis of UHI mitigation tactics found that large-scale implementation of green roofs has the potential to reduce ambient air temperatures by up to 3°C. Additional benefits of green roofs include stormwater attenuation and reducing energy expended for cooling with some studies finding potential savings up to 48%.

There are many examples of green roofs within the city including the 35,000 sq ft green roof atop Toronto City Hall. The Ryerson community has also taken green roofs to heart and created the Ryerson Urban Farm atop the George Vari Engineering and Computing Centre. This 10,000 sq ft garden produces over 30 different crops and more than 100 varieties. The harvests are used in campus kitchens, sold at the Gould Street Farmer’s Market and distributed to those who purchase a subscription of fresh produce through the Community Supported Agriculture program.

Fourth-year Ryerson Environment and Urban Sustainability student Sabrina Guvenc was able to provide some insight on the value of the urban farm and her experience volunteering. A firm supporter of sustainability Guvenc believes that urban farms are “a great way to build a community as well as educate ... on the importance of eating locally. Too much energy is used shipping food around the world when it can be grown right here in the city.”

Green roofs provide many valuable ecosystem services in addition to economic benefit through reduced energy consumption. Furthermore they provide people with a tangible and accessible opportunity to get involved with sustainability projects and development. Thoughtful policy such as the Toronto Green Roof Bylaw (external link) , the first of its kind in North America, is a forward step towards sustainable cities and will hopefully encourage others to follow suit.

If you wish to get involved and volunteer at the Ryerson Urban Farm email them for more information or visit their website (external link) .