What is a Green Roof?

A green roof is a green space on top of a building. A green roof is an extension of the roof and includes a special waterproof and root repellent membrane (the roof’s skin), a drainage system, soil and plants.

"Extensive" green roofs contain light soil and low-lying plants that have very small roots. The soil depth is approximately 2" - 4" (inches)

"Intensive" green roofs contain deeper soil – 6" (inches) to 3' (feet) in depth. There are more vegetation choices such as trees and perennial garden flowers which require deeper soil so their roots can grow

Environmental and Public Benefits

Temperature Regulation

• Rooms under green roofs are at least 3-4 degrees Celsius cooler than the air outside when outside temperatures are above 25 degrees Celsius
• Reduces the heat a building gives off therefore reducing the heat of the air surrounding the building (Urban Heat Island Effect)
• Heat produced by buildings contributes to climate change
• Green roofs insulate buildings by preventing heat from moving through the roof

• Every 2-4 degrees Celsius represents approximately 10% of energy consumed to cool or heat
• Reduced green house gas emission (Co2 emissions) as a result of reduced energy use by air conditioners and baseboard heaters

• Green Roofs absorb rainwater
• In summer up to 80% of the rainwater that falls is absorbed
• In winter up to 40% of snow/rain that falls is absorbed
• Reducing water run-off and diverting storm water for irrigation reduces loading on the City of Toronto’s storm sewers

• A green roof filters the air moving across it
• 10 square meters of grass on a roof can remove 2 kg of pollution particles from the air per year – the Hugh Garner roof area is 1,925 square meters – that’s a lot of dirt cleaned from the air!

• Green roofs provide a habitat for songbirds and butterflies 

• Green roofs protect roofing membranes from extreme temperature fluctuations
• The life span of a green roof is twice as long as a conventional roof so decreases the need for re-roofing and consequently, less waste roofing and construction materials will end up as landfill

• The green economy benefits from a large project using local labour and materials
• A green roof this size on a residential building will serve to encourage conservation culture in the community
• The garden will serve as a learning environment for residents and the community on issues of energy, resource efficiency, bio-diversity, barrier-free gardens and gardening, storm water management and renewable energy sources
• More green space in a downtown neighbourhood that has the highest density of residents per square meter in North America
• A safe, enjoyable outdoor meeting space for use by co-op residents, community users and non-profit organizations that is a park in the sky
• Increased visual appeal for neighboring high-rise residents

• 5 inches of green roof can reduce sound by 40 decibels
• 12 inches of green roof can reduce sound by 46 to 60 decibels

• Merchandise Lofts in Toronto
• City Hall has one that is accessible to all
• Mountain Equipment Co-op will give tours if you book an appointment
• Eastview Community Centre
• Arcadia Co-op in Toronto
• Mary Lambert, private non-profit housing
• In Germany, Europe there are 10 million² (square) meters of green roofs – they have been building modern "green" roofs in Europe for over 20 years now
• In Switzerland, all new roofs must be green and all existing roofs must convert to have some "green" component to them as well as 20% green technology