On the 5th and 6th of June 2019 representatives of 8 Polish pilot cities took part in the study visit in Hamburg, during which they got familiar with the city’s green roof strategy, observed how it changes the cityscape and visited the most interesting buildings and facilities covered with green roofs and living walls. And their number is increasing from year to year -  Hamburg’s objective is to cover with plants up to 100 ha of roof area within the city. New green roofs are constructed both on public utility and private buildings (residential and commercial) and significant part of them will be accessible for people.

The catalogue of presented model projects was very vast and included the ones shortly described below. Many of them have been realised within the strategy and support Hamburg in better management of rainwater and in flood prevention.

Building of Hamburg’s Ministry of Environment and Energy

The first building visited by the Polish delegation was the building of the Hamburg's Ministry of Environment and Energy, where the participants of the study visit met with the hosts and got familiar with the city maquette, history and development processes. Since one of the challenges that the city is currently facing are recurring foods, when planning revitalisation of existing or development of new areas Hamburg puts a lot of emphasis on the development of green and blue infrastructure. The green roof strategy implemented by the city since 2014 shall help in that. It was the first document of this kind adopted by any German city. After learning more about the strategy and the current status of its implementation, the participants had a tour around the building, which is covered with green roofs on different floors. These are both extensive and intensive green roofs with the total area of 10.000 m².

Green roofs on the Ministry’s building not only improve local microclimate and are the habitat of birds and insects (there are even beehives on them), but also support proper rainwater management within the city. Other environmentally friendly solutions used in the building include use of geothermal energy, application of solar protection integrated with external façade and use of advanced ventilation system with heat recovery (thermo-active ceilings).

Construction of the building in the period 2010-2013 was the largest project implemented within IBA Hamburg. It is the one of the most modern buildings in the city, which not only sets new visual standards, but also is highly energy efficient (with the energy consumption reaching 70 kWh/m²). The building received the DGNB Gold certificate.

Ministry’s neighbourhood: buildings with green roofs and system façades

After visiting the Ministry’s building, the participants of the study visit had a short walk around the neighbourhood, during which they saw few buildings with green roofs and façades. The most interesting of them included:

• BIQ building – residential building with usable floor area of 1 350 m² and an alga façade designed to improve indoor air quality through O₂ production and CO₂ absorption. Microalgae are cultivated in glass elements fixed to the external walls and are used to produce energy. The filled-with-algae elements also regulate the amount of light entering the rooms Moreover, the building has the PV panels installed on the roof. Likewise the Ministry’s building, BIQ was constructed within the IBA Hamburg.
• Smart is grün building – residential building with extensive green roof and green façade. The façade is made of climbing plants planted in pots with climbing supports. The whole building meets the sustainable residential construction criteria, has 5 storeys and 14 apartments in total
• Inselparkhalle building – sports facility including a swimming pool and a basketball hall. It has a classic green façade and PV panels on the roof. The façade is composed of four different surfaces (green façade, wood façade, PV panels…), which makes the building more distinctive and attractive. The ground floor is fully glazed and above there are vertical gardens and plantings, with gaps for information displays.

KerVita Senior Center

The Senior Center is composed of the residential building for elderly people (145 places) and the nursing home. It has an intensive green roof, which cost 43 000 EUR and was awarded as the flagship green roof project. Garden on the roof over the fourth floor was designed as a garden for people with dementia. They can safely take a rest and experience contact with nature there. The central part of the garden is a terrace with a gazebo, which might be used for cultural events.

HafenCity University

Green roof on the university’s building was built within the RISA research project. Other environmentally friendly solutions used in the building include: night cooling (heat removal via controlled night ventilation), advanced lighting control system using DALI technology (lighting control based on the amount of natural light entering the room, as well as on the presence of users), water-saving sanitary facilities and wind-powered ventilators.

HafenCity ecumenic forum

HafenCity ecumenic forum is a residential building, part of which is destined for religious observances and common initiatives targeting local community. The building has a green roof, which covers 300 m² and serves social purposes – on the roof there are organised different activities and workshops, e.g. joint planting of plants and beekeeping (so called urban farming).

Dock 71 Gbr building

Residential building with a part destined for commerce and services. It has extensive green roof, which can be used by inhabitants and visitors. Its trademark are roof terraces, social gardens and viewpoints. It has large inner courtyard which serves as a rest and meeting place.

Haus des Landschaftsbaus

Building occupied by the professional organisation of green space constructors. It has an extensive green roof.

Wegenkamp Primary School

Next, the participants visited Wegenkamp Primary School, where innovative drainage solutions were implemented under the city’s RISA program. They allowed for annual savings reaching approx. 3 300 EUR. The project envisaged involvement of pupils, teachers and parents, and was connected with environmental education, including education in the area of climate protection and adaptation.

„Kleine Horst”

Another project implemented within the RISA program, that the participants got familiar with, was the decentralised rainwater management system built on one of the new housing estates. The system uses different drainage elements: open canals, infiltrative beds, trenches and a quasi natural impounding reservoir (without fencing). The estate covers the area of approx. 9,3 ha and is composed of row houses (approx. 220 housing units). The cost of the project came to 1 Mio EUR and included purchase of land, as well as the cost of excavations, pipes and retention basins.

Moreover, the participants visited „Am Weiẞenberge” residential estate, where they visited one of the extensive green roofs with special retention functions (roof’s retention properties are being monitored by the HafenCity University within the framework of their research project), housing compound Seniorenheim Bethanien, which has a garden on the roof adapted to the needs of elderly people and people with dementia, as well as Parkside Lokstedt – another model RISA project: housing estate with part destined for commerce and services and with extensive and intensive green roofs. Also here decentralised rainwater management system has been introduced. Again, it uses different drainage elements including: green roofs, open gutters, infiltration wells, drainage canals and periodically flooded depressions vegetated with violas and other plants.