Green Roofs on Commercial Buildings in Toronto

Bahram Farhang, the TTC's senior project engineer for roofing programs, perches atop the transit system's first green roof.


The plant mix used on the Eglinton West station roof is called the Carefree Evergreen Mix by LiveRoof, the company that supplied the TTC's greenery. The mix comprises eight varieties of sedum, a plant from the succulent family. Also known as stonecrop, sedums have fleshy leaves that retain water.



In a fresh bid to green the Red Rocket, the TTC has carpeted the roof of its Eglinton West station with an 835-square-metre garden.

The new strip of green offers transit users and motorists a more pastoral view at the Eglinton end of the Allen Expressway.

But the mix of flowering, drought-resistant plants called sedums comes with some invisible benefits too, says Toronto Transit Commission chair Adam Giambrone.

The green roof, the first of many planned for the transit system, will reduce stormwater runoff, improve air quality and extend the roof life of the station because the garden protects it from weathering.

Eglinton West was selected for the TTC's first green roof because the station's leaky old lid needed replacement.

A green roof at Victoria Park station, currently under renovation, will be about three times the size of this one. Besides green roofs, solar panels and cool roofs, which reflect the sun, are being considered for the Dufferin station renovation and five new car houses the TTC is planning for its Transit City streetcar lines, Giambrone said.

Green roofs cost more to install but can double the life expectancy of the roof to 40-50 years, according to Jonathan Wilder, the TTC's roofing consultant.

The Eglinton West project, which cost about $850,000, includes about 5,000 plant trays laid out in evenly spaced rows of rectangles, framed by gravel walkways. Installation took five days.

A conventional roof replacement would have cost about $500,000, according to transit officials.

Sedum is a good choice for rooftops because it requires so little water, about 2.5 centimetres a month, and no mowing, said Kees Govers. His company, LiveRoof, supplied the plants, which are grown in modular trays that fit together to create the roof's parterre design.

The plants lower the temperature by several degrees for about a metre above the growth, helping to reduce the urban heat island effect, a dome of hot air that builds up over cities.