Why Green Roofs
are a part of
Sustainable City
A city is an ecosystem, but an ecosystem without plants is in unbalance, with regards to temperatures and water balance. Compared to nature, a temperate region city is more like a desert, where temperatures can become disturbingly high, and a rain will cause sudden floods. Because of all the sealed surfaces in a city, such as streets, parkings and hard roofs, water has difficulty infiltrating naturally. So humans have to solve that problem with technical drainage systems. This costs a fortune, and every time a new surface is sealed, the pressure on the system increases, and uncontrolled flooding events increase.

This is where plants come in. Plants help us taking care of the water, and evaporate it through their leaves – balancing both water and temperature at the same time! Being large, trees are the absolute best plants for this. But the space available for trees in a city is not enough to deal sufficiently with the problems. We need to get much more plants into our cities, to begin to reach the balance of a natural ecosystem.

That’s where the roofs come in, and the walls. If we use some of the vast acerage of roof space in the city for planting, we have the potential to reduce costs in stormwater management, and to increase comfort, and save energy. Buildings with green roofs and walls will loose less energy due to wind chill in winter, and be shaded and insulated from heat in the summer. The waterproof membrane of the roof will last longer when it is not exposed to UV-light, and, contrary to what many people believe – climbing plants on walls protect them, instead of damage them, when you use the right plant for the right façade.

Soil and plants also provide habitats for other species – so bringing in more vegetation turns dead space into living space. If we truly want to use the green roof as a sanctuary for birds, insects, spiders and other small animals, some extra thought needs to be put into the choice of soils and design.


Why green roofs and walls?
- Water management
- Temperature balance
- Biological diversity
- Air quality
- Noise reduction
- Insulation against heat and cold
- Longer life time of materials underneath
- Food production
- Aesthetics
- Health

    Photos and text © Grönare Stad AB - Louise Lundberg