FAQs - What if Every Roof Was a Green Roof at uOttawa
As a quick reminder, the University has a design imperative in place that implies green roofs will be installed in any case where the building can take the weight without a new support system, that the building is still going to be around in 20 years, or if the roof wouldn't serve better as a place for solar panels.
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| Photo credit - kingcounty.gov |
HOW MUCH CO2 COULD WE SEQUESTER?
First thing people were asking me about was sequester CO2. If roofs can take carbon out of the air, why not do more of this? Of course all plants sequester CO2 but a green roof can't do as much as a tree and certainly not as much as a peat bog (99% Invisible recently had a great episode about peat bogs and CO2 sequestration.)
- The most recent number I have seen is that green roofs sequester 0.375kg of CO2e per m2
- We have about 92,000 m2 of roof space on campus (but in all honesty this number is half this much because there are roofs that can't support the weight, or have there is equipment on the roof)
- So this means if we cover all the roofs on campus, we could sequester 36 tonnes of CO2 per year. That's the same as 1,568 trees according to Carbon Pirates.
COULD PLANT GREEN ROOFS AND ADD BEEHIVES TO MAKE HONEY?
Experience from other institutions and cities tells us that this isn't actually a far-fetched idea. Many places have installed apiaries of help pollinate local plants and harvest some honey. That being said, there are still many reasons why we might want to do this on campus, and not for the reasons you might think.
Most people might worry about the potential for bees to sting them, but honey bees don't really get aggressive like that unless they are threatened or they think their hive is under attack. Also, a hive or colony on campus could be on some of our more isolated areas, like the Lees Campus or at Peter Morand.
The amount of honey that could be harvested might not be as much as people tend to think. Certainly if we planted enough pollinator friendly flowering plants around the hive, that would help. But there is also the problem of what we would do with the honey. In order to serve it on campus, we would have to spend a lot of money to prove that it is food safe.
But the real reason is that honey bees are an invasive species in these regions. We tend to forget that because of our love of honey and some good PR campaigns. But they do outcompete local species, having a potentially harmful impact on our ecosystem. Jessica Forrest of the University of Ottawa Biology department has done a lot of research in this area.
CAN WE ADD GREEN ROOFS EVERYWHERE AND USE THEM AS LOUNGING SPACE?
That is of course the dream. People lounging all over the campus on roofs that have no shadows from other buildings. In between classes or at lunch time, you could grab some sun and enjoy the outdoors. Maybe the roofs could even be used for special events?..
Alas, there are many issues with using roofs this way. Let's set aside that idea that some roofs can't take the additional weight of greenery and people, and let's pretend for a moment that there aren't loud mechanical rooms on the roof of buildings.
There are many security issues with having people on a roof, including people getting too close to the edge or items falling from the roofs and hurting someone below. There would need to be large security barriers and other safety features. And of course, it would be very difficult to shade the area. In the winter time, intense sun sounds great but in the summer time, that kind of unfiltered heat can lead to dehydration and heat strokes. Trees are too heavy to put on the roof without extensive structural work, and the last think anyone wants is a patio umbrella getting loose and falling to the ground.
I hope you enjoyed our little FAQ post. If you have other questions you want us to answer about any sustainability topic on campus, please send them our way.
~ jonathan rausseo - campus sustainability manager
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