Sourced from Link Magazine - BCIT
Across from NE1, students are on a roof, frantically planting as many ferns as they can. There’s a deadline to be met today and Dr. Christine Thuring has been racing it from the beginning. As she leads them, she quizzes them to keep their spirits up.
“How many species of bees do you think there are in BC?” she asks to no one in particular, but everyone is clinging to it.
“I don’t know… 39?” says a voice.
“No, over 400!”
And another plant’s been potted.
Why the deadline?
We’ll have to back up a bit first, and talk about what green roofs are, what they’re used for, and why, as students, we should be pretty excited about them. I’m sure we’re all on the same page when we hear the phrase “green roof” – a rooftop garden. And it kind of is. But not really. A garden, you have to water and tend to. Green roofs are installed on a “waterproofing membrane” that protects the building it sits on from water damage. Insulation, drainage and filter fabric are stacked on that. Then the growing soil.
Now that we know what these are, let’s talk about why we’d want to install one on a building. We’re going to look into three main benefits—energy conservation, water management and ecological benefits. These save a lot of energy—they reduce the cost of heating giant buildings via evapotranspiration; the combination of plant transpiration and evaporation. They can also reduce the cost of cooling in the summer via evaporative cooling; the cooling of air through the evaporation of water. A 2005 report from Ryerson University found that adding green roofs to 50 percent of the available surfaces in downtown Toronto would cool the entire city by up to 0.8 degrees celsius. How does this work?
As you get closer to the city, it gets warmer. As much as ten degrees. All the concrete and asphalt absorb heat during the day and releases it at night— so the city never really cools down. There’s lots of side effects from that; plants and urban organisms have slightly different life cycles than their rural counterparts. Cherry blossoms, for example, will flower sooner than they do in the country. It can even change weather patterns.
Green roofs offset those urban changes.