Did you know that 10% of all buildings in Germany have living roofs, or that green roofs been around for centuries in Europe but are only just starting to pop up in North America?

To kick off a week of sustainable innovations, we’re taking a closer look at green roofs, an architectural innovation that involves planting gardens on top of buildings to make them more environmentally-friendly. Now, if strange images of abandoned cities that have been overtaken by plants are coming to mind, your mental imagery isn’t too far off, but don’t freak out — for the most part, these rooftops are very well manicured and their benefit to us is immense.

As with most elements of building design, the degree to which living roofs are covered by grasses and other plants varies depending on the building owner. They can range from residential homes with patchy blankets of moss, to commercial buildings with parks on top of them, complete with trees, ponds and strolling paths.

So what makes a green roof, or living roof, so desirable? In addition to their financial benefits — which include their ability to increase real estate value, reduce energy use/costs, and in some regions grant real estate owners tax incentives — green roofs also have an array of environmental benefits. The list is extensive, but a few of the “green” advantages of rooftop soil and plants include helping filter pollutants and CO2 from the air, reducing stormwater runoff, filtering heavy metals from rainwater, and even reducing heating and cooling needs through insulation. Urban areas that are densely populated with green roofs have even been proven to experience a reduction in average summer temperatures.

Types of green roofs: intensive vs. extensive
“Traditional roof gardens, which require a reasonable depth of soil to grow large plants or conventional lawns, are considered intensive because they are labour-intensive, requiring irrigation, feeding, and other maintenance,” Wikipedia explains. “Intensive roofs are more park-like with easy access and may include anything from kitchen herbs to shrubs and small trees. Extensive green roofs, by contrast, are designed to be virtually self-sustaining and should require only a minimum of maintenance, perhaps a once-yearly weeding or an application of slow-release fertiliser to boost growth.”

I don’t know about you, but I like the sound of “self-sustaining” much better than “labour-intensive.” That being said, both can have a killer aesthetic, as well as bring a multitude of benefits. Let’s check out four green roofs from around the world that illustrate why this sustainable architectural element is becoming more popular.

Chicago’s City Hall was completed in 2000 and is one of the most famous green roofs on a North American landmark building. In addition to lots of greenery — 20,000 plants, to be exact — the rooftop also houses bees, birds and butterflies.

Via Verde, which means The Green Way, was the winner of the New Housing New York Legacy Competition. The renderings of the mixed-use development include green roofs that could potentially lower asthma rates in the area by cleaning up the air, and increased agricultural space for easier acces to produce.

The plant-roofed West Building of the Vancouver Convention Centre opened in 2009, and is green on a number of levels. The building is certified LEED Platinum, is heated and cooled by seawater, has a fish habitat, and colonies housing 240,000 bees on top of Canada’s largest (24,000 square meter) green roof.

In 2009, Toronto became North America’s first city to include a green roof bylaw that requires all new residential and commercial buildings to have a green roof.

Would you considering installing a green roof on your building? If so, what would you plant? Would it be more about function or design to you?