Regnvandet

Soak Up the Rain: Green Roofs https://www.epa.gov/soakuptherain/soak-rain-green-roofs

EPA

Green roofs have a layer of plant material that absorbs water like a sponge. They capture water when it rains, slowly releasing it through evaporation and plant use. Green roofs can significantly reduce the amount of rain water that would otherwise run off an impervious roof surface.

Green Roofs Copenhagen https://en.klimatilpasning.dk/media/704006/1017_sJ43Q6DDyY.pdf

Green roofs support biodiversity. They lead to larger quanti - ties of rainwater being absorbed in a sustainable way and can curb the rise in temperature at the same ti-me.

Green roofs absorb the rainwater, and some of it evaporates. The roofs can absorb between 50 and 80 % of the annual rainfall. 

Water Quality, Rainfall Harvesting And Green Roofs https://livingroofs.org/water-quality-rainfall-green-roofs/

Livingroofs.org

Water quality can be improved when a green roof is installed on a building. Pol-lutants within the atmosphere and from roofs can cause run off from roofs to have poor water quality. Many studies in Europe and North America have shown that green roofs can improve the water quality of the stormwater that leaves a roof with vegetation and substrates on it. This benefit is in addition to reducing the rate and volume of the stormwater. 

Furthermore, It is possible utilise rainwater harvesting of a green roof contrary to claims from other industries. In fact it is quite common to harvest water from green roofs in Germany and Switzerland.