Calgary is slowly catching on with environmental rooftops

Many people have spent hours working on their roofs to change the colour — some from the green of mossy invaders back to the favoured black shingles. But a movement taking root in the Calgary-area seeks to flip this equation by rolling out the welcome mat for our photosynthesizing neighbours.

Green roof living roof or ecoroof — call it what you like — the ancient design of coating a roof with plants has experienced a well-deserved renaissance in recent years. The basic concept is of a roof covered with plants and soil with a root- and water-repelling membrane installed beneath to prevent structural damage.

In the days before central heating and air conditioning sod roofs were a common insulating feature on Scandinavian dwellings to keep it cool in the summer and warm during the winter. Modern green roofs continue the energy efficiency trend: Environment Canada researchers have demonstrated a 10 per cent decrease in winter heat-loss and a 25 per cent decrease in air conditioning. Green roof benefits however go well beyond saving energy and fossil fuels burned to produce it.

Kerry Ross an accredited green roof professional and co-founder of local advocacy group Alberta Ecoroof Initiative (AEI) says the roofs are not only esthetically pleasing but they also serve as “a place for people to have lunch and enjoy an outdoor green space with a great view.” This aspect could slow down urban sprawl and make high-density housing more desirable Ross says. “It could attract people to downtown living to give up the yard and have a roof deck in its place — it’s nice and cool on a hot day.”

Cool places are at a premium in a summer city landscape. All that asphalt and concrete trap solar energy contributing to the “urban heat island” effect. The result: city centres that are significantly hotter than surrounding rural areas higher air-conditioning usage and in cities like Tokyo legislation mandating green roofs to combat the heat. Planting trees helps as well. It also re-creates lost habitat for bird and insect species that find our concrete jungles inhospitable.

Large-scale benefits become apparent when entire cities are capped in greenery. For example air and water pollution are filtered by the plants. A heavy rainfall can wreak havoc on a city’s storm water management system but drops falling on plants are utilized and slowly released decreasing the immediate stress.

Because of numerous benefits places like Germany Switzerland and Austria have mandated green roofs and created incentives for construction projects that include one in their design. Without incentives initial costs are high though studies have shown that green roofs can last up to three times longer than conventional ones saving money in the long term.

Without government investment in green roofs North America has lagged behind Europe for decades — but that is starting to change. Toronto recently became the first city on the continent to insist that new buildings of a certain size install living roofs and it bolsters the new law with financial incentives. Chicago offers similar stimulants and its city hall even boasts a honey-producing rooftop apiary. And in Vancouver the public library has an outdoor garden on its eighth floor and the new convention centre’s roof has six acres of greenery. As well Vancouver Island’s Coombs is home to the Old Country Market with its sod roof home for a herd of grazing goats!

So….

Calgary?

“A lot of people think that the climate is too cold to make a green roof viable but that’s not the case” says Ross “We’re not blessed with a lot of moisture but we have vegetation surrounding the city that doesn’t require any maintenance at all.”

Native plant species already adapted to the hardships of life in the area make for a good rooftop choice as they require little upkeep. The AEI a research and advocacy group maintains a study roof atop Calgary’s Alistair Ross Technology Centre and has had success with mountain goldenrod Jacob’s ladder sedums and alpine strawberries. (In case you’re wondering you can eat the locally grown fruits of your labour.)

On a recent chilly afternoon tour of the Bison Courtyard in Banff amongst the native shrubs grasses and limestone stepping-stones I sampled the fruits of a well-laden black currant bush. As I squeezed a juicy orb between my teeth I thought of Vancouver’s Fairmount Waterfront Hotel which grows an estimated $30000 of herbs flowers vegetables and honey. It felt as though I was tasting the future one of lower energy usage higher urban biodiversity cooler summer cityscapes cleaner air and water and a local-food-fed population. And that future I’m pleased to report is delicious!

For more information about green roofs take a look at the Green Roofs for Healthy Cities website at greenroofs.org.

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