Definition:
The green roofs are multi-layered structures, evenly distributed on the roof, allowing the plants to be vegetated on these surfaces.
The green roofs were already constructed in ancient Egypt, Babylon (famous gardens built by Nebuchadnezzar II (in 605-562 BC), Persia or in ancient Rome. They were also an important part of Scandinavian construction. The development of the green roofs took place in the 1960s and 1970s, then in Germany and Switzerland, the construction of buildings integrated with these green forms began. “Green roofs” can exist on the sites for about 100 years.
Today, they are commonly used as part of sustainable construction (important for LEED and BREM building certificates, etc.) and are also a kind of alternative to traditional green areas. They are used on single-family, multi-family and commercial buildings of different scales.
The popularity of green roofs is also gained by pursuing public policy, including financing their construction, or by tax relief in exchange for their installation, because their application provides major environmental, social or economic benefits for both the users themselves and the city.
Construction:
Green roofs can be designed on both existing and newly designed buildings. Their installation requires specialist knowledge, incl. in the field of construction (checking whether the building structure will keep the green roof when fully irrigated), architecture, they are performed by specialized companies (the most important thing is to properly seal the roof – laying the insulation). Used both on traditional and inverted roofs, on flat and sloping roofs (however, it depends on the type of green roof – up to 1% inclination intensive and extensive roofs, above 1% inclination only extensive roofs).
The multi-layer design consists of:
The insulation layer – hydroinsulation – protects the roof from moisture, must be resistant against the transmission of it through the roots of plants which green the roofs.
– Protective layer – protects the insulation layer.
– Drainage layer – drains excess rain water from the roof and stores rainwater.
– Filtering layer – Filter layer – protects the drainage layer against its silting.
– Vegetation layer – the substrate for the growth of plants on the roof, its thickness varies, depending on the type of green roof.
Installing green roofs has many benefits:
Environmental benefits: Reduction of the urban heat island (green roofs are much less heated than conventional ones), air purification, water purification, water retention, reduction of water flow to sewage systems, noise suppression, increased biodiversity (green roofs can serve as habitats for many animal species).
Social benefits: New recreational spaces, beneficial effects on the mental and physical health of local communities.
Economic benefits: Insulation of the building (the building is less heated and cools down less) – less energy consumption, less expenditure on roof maintenance than in the case of a conventional roof. They are increasingly becoming spaces used for food farming.
The green roofs are divided into:
– extensive
– intensive
– mixed
– brown
– semi-intensive
– wet
They are part of creating green networks in the city:
– raingardens, green walls, green streets, swales, bioswales, ect.
Implementing green roof systems in cities – learn more:
Strategy for implementing the green roofs in Hamburg:
https://climate-adapt.eea.europa.eu/metadata/case-studies/four-pillars-to-hamburg2019s-green-roof-strategy-financial-incentive-dialogue-regulation-and-science
https://www.hamburg.de/contentblob/12153692/10e26d1af7ebea6366cfc3902c31edcc/data/d-economic-evaluation.pdf
Sources and additional information:
Brachet A., Schiopu N., Clergeau P., 2019, Biodiversity impact assessment of building’s roof based on Life Cycle Assessment methods, Building and Environment, 158, s. 133 – 144Dover J., 2015, Green infrastructure. Incorporating plants and enhancing biodiversity in buildings and urban environments, Routledge, New York
Kania A., Mioduszewska M., Płonka P., Rabiński J., Skarżyński D., Walter E., Weber-Siwirska M., 2013, Zasady projektowania i wykonywania zielonych dachów i żyjących ścian, Agencja Reklamowo-Wydawnicza „Ostoja”, Kraków
Ociepa – Kubicka A., 2015, Zeszyty Naukowe Wyższej Szkoły Bankowej we Wrocławiu, 15/2, s. 289 – 296