I recently went to Copenhagen for the first time; it felt like having landed in a haven of well-being, green and leafy. Copenhagen is one of these cities concerned with a certain harmony between urban environments and natural habitats. Back in Brussels I discovered that the Copenhagen City Council adopted a mandatory legislation to increase the number of green roofs last year.
From now on, any flat roof with a pitch of 0-30° will be planted with green vegetation as much as possible. The City will also encourage financially projects to grow green roofs on existing buildings. There are already a few green roofs in Copenhagen, but the city wants to increase the pace of change in order to get ever closer to achieving its 2015 climate plan (PDF).
The City of Copenhagen approves of the green roofs if they meet at least two of the following requirements, all of which can be achieved by a green roof:
- absorb 50-80% of the precipitation falling on the roof area
- create a cooling and insulating effect on the building and minimise the reflection
- contribute to making the city greener in order to reduce the so-called ”heat island effect” and in this way counteract increased rises in urban temperature
- contribute to a visual and aesthetically pleasing architectural variation which will have a positive effect on citizens’ quality of life
- double the roof life since the roof membrane will be protected against the destructive effect of UV rays
Initiatives like that of Copenhagen’s have multiplied in recent years; local governments realize that green roofs are an excellent tool to meet the environmental and health challenges of densely populated urban areas. For example, the City of Toronto was one of the groundbreakers in the green roof revival, followed by New York City or London (Find an audit here) where things have been moving albeit slower.
But the best example is perhaps Chicago, where Mayor Richard Daley initiated an ambitious set of incentives to encourage the private sector to follow the City’s leadership. Green roofs have literally blossomed in Chicago, as this map shows, with over 600 green roofs now.
View of a green roof from the Sears Tower in Chicago– flickr, photo by Eveliz Vega Marzan
The benefits of green roofs are undeniable but unfortunately, traditional substrates tend to be difficult to install. This problem will soon be history because Huntsman developed a polyurethane substrate for green roofs that is up to 60 times lighter than traditional substrates, thus bringing down one of the major hurdles standing in the way of green roofing: it can be a hassle.
So far, the development of green roofs has been exclusively encouraged by local initiatives, usually under the leadership of individuals who decided to improve the quality of living in their city, be it political leaders such as Richard Daley or volunteer organizations such as Seeding the City in New York City.
Green roofs should be encouraged, and with the appropriate technology, we will perhaps see the blossoming of European buildings; sooner rather than later.
Send us your pictures of green roofs and let us know about initiatives in support of green roofs in your city.
The Polyurethanes Team