Abstract
Approximately 10 km2 of new green roofs are built in Germany every year. About 85% of these are Extensive Green Roofs (EGR). An EGR with several research features was installed on new buildings belonging to the University of Applied Sciences Neubrandenburg in 1999. The results of the almost 20-year permanent survey of the climate effects of the green roof in contrast to gravel roofs are presented here. High-quality sensors, similar to those used by official weather stations, are in use, and data is collected every 10 s and aggregated to hourly values which enable comparisons to official measurements made by the DWD in Neubrandenburg and Berlin. The results show the typical urban heat island effect (UHI) and the mitigation effect of EGR. Whilst the temperature increased over the years due to the urban heat island effect, the temperature within the growing media in the green roof remained constant. The EGR has a stabilization effect of 1.5 K. This is good news for all those seeking a UHI mitigation solution for city centers. In a best-case scenario, the green roof potential of cities in Germany is between 3 and 8%. A value of 50% can be achieved for all buildings; roofs represent about ¼ of urban surfaces, and the cooling effect of 1.5 K in 20 years is a reasonable contribution to cooling cities and achieving environmental goals by greening urban surfaces.
Highlights
Long-term studies are important for understanding the ecological functions of ecosystems [1].This is true for the natural system, and important for manmade urban ecosystems
In times of growing cities throughout the world, it is necessary to quantify how intensive vegetation-based solutions can contribute to mitigating the urban heat island effect (UHI); green roofs can make a contribution, but, in most cases, the real numbers are based on short-term studies or simulation
This article describes the effects of typical Extensive Green Roofs (EGR) on climate mitigation
Summary
Long-term studies are important for understanding the ecological functions of ecosystems [1].This is true for the natural system, and important for manmade urban ecosystems. In times of growing cities throughout the world, it is necessary to quantify how intensive vegetation-based solutions can contribute to mitigating the urban heat island effect (UHI); green roofs can make a contribution, but, in most cases, the real numbers are based on short-term studies or simulation. In addition to their positive effect on the climate, green roofs provide a number of further social and emotional values for the local population [2]. The author was inspired by Reinhard Bornkamm’s early green roof surveys in Goettingen [3] that were ecological long-term studies of these kinds of manmade urban habitats on buildings
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