There’s a new initiative springing up on Toronto rooftops these days. Green roofs make good sense — as long as they’re on the right building and part of a comprehensive approach to green living and design.
Today’s green roofs differ from traditional rooftop gardens in many important ways. These are vegetation-based “systems” that start with a thin layer of growing plants, teamed up with drainage layers, a root barrier and a waterproof membrane.
When you look at most green roof installations, you’ll see a low-lying expanse of vegetation that requires little maintenance. This is called an “extensive” green roof, perfect for greening existing buildings where roofs were not designed to take extra weight. This type of green roof is distinct from what’s called an “intensive” green roof (or “living roof”) that uses a thicker layer of soil and is planted much like a traditional garden, with large plants and even trees. Intensive green roofs can be found on new buildings where allowances for extra weight can be made at the design stage.
Green roofs offer many environmental benefits, mostly for the wider community. The most important benefit may be that they help reduce “heat island effect.” In cities, temperatures can be up to six degrees higher than in surrounding areas, because of the number of flat, dark, heat-retaining surfaces such as rooftops and roads.
When you get rid of black surfaces, you reduce the overall city temperature.
In addition to reducing heat island effect, green roofs provide other benefits. They reduce the amount of rainwater that flows into the sewer system, they provide a small amount of insulation that can reduce cooling costs for the building, and they’re pretty to look at.
Green roofs make the most sense on lowrise buildings with lots of flat-roof surface like big box retail stores, warehouses and single story office buildings. High-rise towers can make use of green roofs on the lower-level, broader surfaces usually at the podium level. At MintoMidtown at Yonge and Eglinton, a green roof is being installed on top of a six-storey podium, providing both environmental and aesthetic value.
A green roof can be a great addition to your condominium — as long as other essential green-building high performance features have been addressed first. Forward-thinking design elements will give you more green for your buck and more effectively contribute to a healthier planet. Ask questions when you’re condo shopping.
For example, do residents have the power to conserve by providing an “all-off” switch in their suite to turn off all lights and fans at the flick of a switch? Is fresh filtered air brought in directly to the suite through a heat recovery ventilator (HRV)? Is the development a candidate for LEED® certification from the Canada Green Building Council?
A green roof by itself does not make a building green. When the basics of healthy living and natural resource conservation are covered, you can be confident your condominium is truly green.
For more information about Living Green contact Andrew Pride, P.Eng. LEED A.P., Vice President of Minto Energy Management. He champions the green design elements of MintoUrban Communities condominium and rental buildings.