After our last post about green roofs at the University of Ottawa, I got a lot of questions about why we can't have green roofs everywhere on campus. If the answer was simple, I wouldn't have to write a entire blog post about it... but since I am writing a post... you can probably take the hint that this is a bit more complicated then a yes/no kind of thing. 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. 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 bo...