Copenhagen is the largest city in Denmark and has a population of 2 million people. It has a goal to achieve carbon neutrality in the city by 2025, the first city in the world to do so. One part of their strategy is that they are making green roofs a requirement for every new build with a roof slope of less than 30 degrees. The hope is that this policy will bring up to 5,000 square meters of new development every year, all with green roofs.
Green roofs are beneficial for several reasons. Firstly, they can absorb as much as 80% of rainfall which helps to reduce stress on stormwater systems. Secondly, they lower temperatures in urban areas with the heat island effect (which you can read about here), which improves air quality and reduces harmful gases such as SO2 and NOx. Their natural way of collecting dust particles also improves air quality. Green roofs protect room membranes from UV rays produced by the sun – this can extend its life to double what a normal, unprotected roof would have! Finally, and one of the most significant benefits, green roofs reintroduce biodiversity into city centres and provide new pollinating plants and habitats for animals. This can help to grow the population of certain animals, insects and plants. Recently, a green roof in London saw an orchid that was said to be extinct, growing on a green roof!
There are two kinds of green roofs, intensive and extensive. Intensive roofs need a strong structure and can be used as gardens, parks, and places to sit. These roofs need a thickness of 30cm, they will cost more and require more maintenance. Extensive roofs are usually for smaller projects. This may be a lawn or moss that can feed simply off the rainwater. These are more common in Copenhagen as they only require a thickness of 5-10cm.The urban rooftops in Copenhagen have huge variety. They are home to urban allotments, flower gardens, viewpoints, aromatic plants, bushes and even trails.
Copenhagen is ahead in many ways with its sustainability plans. 62% of people in Copenhagen ride a bike to work, 76% of their electricity is generated by wind, biomass or nuclear and almost all their waste is recycled. They are taking initiatives that are inspiring other cities and countries to do the same. Canada, Switzerland and France are planning to install green roofs as a key part of their sustainability policy in their cities.
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