. green roofs
Green roofs are literally islands of nature stacked amongst the concrete of the city, providing habitat, releasing oxygen, increasing insulation, improving water run off quality, and preventing heat from bouncing off buildings.
“It’s really valuable to replace natural landscape wherever we can,” says Jeremy Sturgess, a well-known Calgary architect whose new Beltline building named 614, will incorporate a green roof.
“We have a fair bit of area on the roof, just above the second level of the building, so by making that green, that’s just providing the nutrients back that are currently there on the empty site, back into the atmosphere,” he says.
Green roofs have been used for hundreds of years in Europe as an effective insulator, a place to grow some extra crops or as a more durable option compared with wooden shingles.
The process can be intensive, requiring a root-proof membrane that also protects against leaks, dirt and natural vegetation. In Tokyo, one issue has been the planting of non-native plants on green roofs, reducing natural insect and bird populations.
When planted with local vegetation, green roofs can provide habitat to insects and birds struggling to find a place within the city. The Beltline is a perfect example of an urban district that requires more green space.
Green roofs can also provide increased insulation for buildings, keeping them cooler in the summer and warmer in the winter. According to Environment Canada, a one-storey building with a green roof could reduce summer cooling needs by as much as 25 per cent, and reduced heat losses by 26 per cent. This saves money and energy.
Another advantage to green roofs is combating what is called the heat island effect. Heat island essentially means that the heat reflected off buildings and through human activity, warms the air in urban settings.
“This phenomenon describes urban and suburban temperatures that are 2 to 10°F (1 to 6°C) hotter than nearby rural areas. Elevated temperatures can impact communities by increasing peak energy demand, air conditioning costs, air pollution levels, and heat-related illness and mortality,” according to the U.S. Environmental Protection Agency.
Sturgess incorporates green roofs whenever possible, but says it requires a client that is open to the idea, and the extra cost.
“It’s a little more complex process to build, so it costs a bit more. If not properly done it can leak a bit more than other kinds of roofs,” he says.
Green roofs are gaining in popularity in Canada and could feature prominently in more Beltline buildings.