DO GREEN ROOFS LOSE GROWING MEDIA OVER TIME?
It is traditionally thought that growing media with higher than traditional organic matter content suffer from loss of depth because of organic matter’s rapid nutrient cycling rate, and so over time there will be a gradual lessening of available media. But is this actually true?
From 2013 to 2015 the University of Toronto conducted a study of 33 green roofs in Southern Ontario to determine the physical and chemical changes of the green roof growing media over the lifespan of the green roof. Their findings not only contradict the conventional industry opinion on high organic matter growing media but also confirm Bioroof’s stance on the matter : more organic matter does NOT equal loss of depth.
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CAN A GREEN ROOF HELP COOL MY BUILDING?
Yes, it can! Sedum species, a succulent ground cover commonly used in green roofs, are specialized CAM plants that can store water in their leaves to minimize water loss by evapotranspiration in the heat of the day. By cooling themselves down in this manner these plants also help cool the roof of their building, reducing the need for internal air conditioning within the building and in turn reducing the Urban Heat Island effect.
The University of Toronto monitored the effects of this phenomenon on the surrounding air temperatures to determine the real difference in air temperature above a green roof and a traditional roof membrane. The conclusion? Green roofs can cool the air temperature around them by up to 2° Celsius - good news not only for individual buildings but also for the climate as a whole!
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ARE GREEN ROOFS GOOD FOR THE POLLINATOR COMMUNITY?
Pollinator communities are often the ‘canary in the coal mine’ when it comes to today’s climate change issues. Any detrimental environmental stressors on their populations are often felt soon after in other wildlife communities, and the ripple effect of decimated pollinator populations are far-reaching with serious consequences on food supply and biodiversity. Because of this, preservation of pollinator species is an absolute must - which is where green roofs come in!
Green roofs can act as ‘pollen banks’ in urban environments where vegetation is hard to come by and ground-level landscaping is often overtaken by concrete structures. On top of this, wider varieties of vegetation including native meadow species are being used on green roofs in order to encourage native pollinator populations to re-colonize areas where they have been overtaken by exotic species.
To read more about the effect of green roofs on urban bee populations, please click the button below.