The grass is looking greener on rooftops around the worldDecember 15, 2017
When considered for their aesthetics alone, green roofs are kind of awesome. But when you account for the fact that they can save energy, manage stormwater, decrease pollution, improve thermal performance, and provide a habitat for urban birds and bees, well, green roofs go from awesome, to Oprah-levels of amazing (you get a green roof, you get a green roof, everybody gets a green roof!). From an archeological museum in Denmark to a wine cellar in Italy and a private residence in Singapore, green roofs are an international favourite. In this post we take a look at why green is good.
The History of Green Roofs
According to an article from Sustainable Architecture and Building Magazine, “The use of green roofs for aesthetic and recreational purposes can be traced back to the Hanging Gardens of Babylon which were built in the 7th century BC as a diversion for the aristocracy.” Given that our great nation is only 150 years old, that nearly three-thousand-year-old pedigree is kind of a big deal. But despite their popularity in ancient Mesopotamia, the current iteration of living rooftop design only gained popularity in the early 1970s, when environmental concerns began to sprout.
What is a Green Roof?
The Environmental Protection Agency defines a green roof as any “vegetative layer grown on a rooftop” and they come in two forms:
Intensive green roofs are basically elevated parks. They can sustain shrubs, full-grown trees, walkways, and benches. They require additional structural design for irrigation and drainage and, as a result, can be quite heavy (anywhere from 36-68 kg per square foot).
Extensive green roofs include hearty native ground cover that requires little to no maintenance. They’re usually purpose-built for their environmental benefits and don’t function as accessible outdoor spaces. Compared to their intensive counterparts, extensive green roofs are pretty light (anywhere from 7-23 kg per square foot).
6 Benefits of Green Roofs
Benefit No.1: They reduce energy consumption and costs.
Green roofs are a bit like your favourite down duvet – they keep you warm in the winter and cool in the summer. No one knows how they do it, it’s like nature’s magic, but it works.
Actually, that’s not entirely accurate – scientists know exactly how they do it (and thankfully the brilliant landscape architects who plan these verdant spaces). The details are a little beyond the scope of this post but basically green roofs absorb heat and provide natural insulation for buildings, keeping temperatures steady. According to one study conducted by the National Research Council of Canada, even a six-inch extensive green roof can reduce summer energy demands by more than 75 percent, that can add up to big bucks for larger buildings and for the residents that live there.
Benefit No.2: They reduce stormwater runoff.
While you may not have heard of it, stormwater runoff is a major source of flooding and pollution worldwide. It happens when rain falls on the nonporous surfaces of an urban environment (surfaces like pavement and standard building rooftops normally made of tar) and, unlike in a natural environment, isn’t absorbed.
A typical city block generates five times more runoff than a wooded area of the same size, but a green roof can offset that, absorbing the rainwater, using it for plant growth, and releasing it slowly over an extended period of time, reducing the risk of flash floods and sewer overflows.
Benefit No.3: They provide a habitat for wild flora and fauna.
Bees get a bad rap thanks to their sharp posteriors, but these little buzzers are actually an incredibly important part of the global ecosystem. They pollinate over 80% of all flowering plants (including 70 of the top 100 human food crops). One third of all our food is derived from plants pollinated by bees. So if you like to eat, then bees are your best friends.
Green roofs can offset the land-use changes (from nature’s playground to city sprawl) affecting the bee population. A 2009 York University study showed that green roofs in urban areas offer suitable habitat for a variety of bee species. The Fairmont Royal York agrees – in 2008 the hotel introduced their own rooftop hives, providing the honey served in their restaurants down below. Ain’t that sweet?
Benefit No.4: They extend the life of the roof itself.
Green roofs actually last longer. Why? Regular temperature fluctuations cause physical stress to a conventional roof due to expansion and contraction. But green roofs reduce those fluctuations and can extend the life of roof by two to three times!
Benefit No.5: They help clean the air and reduce the urban heat island effect.
In a country that deals with six months of winter each year, the urban heat island effect might sound tempting (bring on the tropical heat!) but it’s actually pretty scary. UHI refers to the overheating of urban environments, with temperature differences of up to 6°C from city to country in some spots. It increases energy demands and air pollution and can lead to poor water quality, increased greenhouse gas emissions, and heat-related illnesses.
Green roofs moderate heat gain and release water, which cools the air and reduces the ambient air temperature. They also trap carbon dioxide, filter out pollutants, and give off oxygen, contributing to cleaner urban air.
Benefit No.6: They provide a killer setting for sunset cocktails or outdoor events.
Helping the environment is super important (Leo would be proud). Why not celebrate with a cocktail or two on your… green roof. Green roofs are the epitome of form and function. While they’re busy doing good in the world, they also provide gorgeous landscapes visible across the city skyline. Studies show that looking out onto green space can reduce stress, increase productivity, and create a stronger sense of wellbeing. Projects like The Biophilic Cities Project are putting those claims to the test, promoting proximity between urbanites and nature in an effort to keep us connected to what matters most. Live better. Live greener. Sign us up.
Lead photo courtesy of Jamie Sarner