Let's Take a Look at uOttawa's Green Roofs

 

Let's take a moment to talk about the old proverbial green hat, more commonly know as a green roof. For years green roofs have been thought of as a nice to have but not really cost effective for most buildings. That perception started to change more recently; manifesting in new policies like the Toronto Green Roof Bylaw. Our campus got in on the action a little while back when we changed our building standards to prioritize green roofs as well.

This autumn, the first green roof under this design paradigm is set to be installed on the Perez Building. Since the building is a bit older, our engineering assessment found that a green roof isn't appropriate everywhere, but along the north roof the conditions are just right. This works out fairly well since this part of the building is lower than the other roof sections; meaning that occupants will be able to see the roof from their windows.

Stunning views of green roofs from an office or classroom window might be considered the cherry on top, but there plenty of reasons why green roofs are the way to go... even if the costs are sometimes hard to quantify. Here is a list of of couple of the reasons why green roofs makes sense at the University of Ottawa.


Climate resilience at its best

It's not hard to understand how green roofs play a role in climate change. Like all plant communities, a good green roof will soak up carbon. A study looking at the sequestration rate of green roofs in Toronto found that they can absorb 7.22 grams of CO2 per square metre every year. That can really start to add up after a while. Currently, there are approximately 3,800 square metres of green roof on campus, which capture 27.4 kilograms of carbon annually.


Storm water management 

Its not only CO2 that green roofs soak up; like a giant green sponge they also absorb prodigious amounts of water. Numbers vary depending on the kind of green roof (there are many different types) but one source estimates a maximum capacity of 80 L/m2. This is important in an urban setting such at the University of Ottawa. More precipitation is expected in Ottawa in the coming years because of climate change and green roofs might be one of the best ways to prevent flooding on campus.


Controlling temperature

There are actually two ways that green roofs can help regulate temperature. First, they create an layer of insulation on a building that can reduce heat from entering in the summer time, and prevent the loss of heat in the winter. 
The second way is through the urban heat island effect, a phenomenon that can dramatically increase the areas around high concentrations of concrete. So instead of just heating up a single building, entire neighbourhoods are affected. Green roofs help reduce the the amount of heat absorbed into concrete and thus reduce the overall heat island effect.


Of course all of these are great reasons to have a green roof, and we have even written about how in the long run, these roofs are cheaper than conventional roofs. However, I will circle back to my earlier statement about the beauty these roofs provide. Not every green roof on campus is visible to a building's occupants; but when they are, what a treat. 

When the choice is between a solid grey mass and a green field, there really is no choice. This fall when the newest green roof is installed on the Perez Building, it will join the family of green roofs already on campus and help us move another step closer to sustainability.

~jonathan rausseo - campus sustainability manager



No comments