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Hannover, is the capital of the Federal State of Lower Saxony and is situated on the river Leine. As a major commercial, business and administrative centre in northern Germany, Hannover was chosen as the site for the World Fair, Expo 2000.
Due primarily to its size, 75,000 m2, the new headquarters building of Norddeutsche Landesbank is located in the city centre between the commercial centre to the north and the residential districts to the south.
The street level area of the development is accessible to the public and occupies an entire city block. The plan (Fig. 3) shows City Hall immediately to the west alongside Maschpark, (sports and recreation). Aegidientorplatz, to the northeast of the site and Friedrichswall are both subjected to heavy traffic.
Planning guidelines dictate that the perimeter of
the building is aligned to the existing streets and restricted accordingly in height to 4 to 6 storeys. Stepped height variations up to 70 metres are then mitigated by the existing massing of the surrounding city. Viewed from the surrounding streets and park, the development appears to be a conventional city block (Fig. 1, Fig. 2).
However, at the centre of the plot is a large courtyard development. This provides numerous public amenities in a generously planted landscaped environment which includes large reflecting pools.
The cafes, galleries, restaurants and shops provide a haven in the city protected from the traffic emissions and noise experienced in the surrounding streets (Figs. 3, 4, 5, 6).
80 Norddeutsche Landesbank | Hannover | Germany | Fig. 1 above | Fig. 2 opposite | Fig. 3 next page
Along with the recreational amenities, the
central courtyard also provides access to the daily operations of the bank (Fig. 6, Fig. 7). From the base of the courtyard the seventy metre high headquarters building rises and rotates as a series of glazed, stacked cubes (Fig. 4, Fig. 5). The architects, Behnisch, Behnisch and Partner in collaboration with Transolar Klima Engineering, devised an extensive environmental strategy for the Norddeutsche Landesbank. Taking into account the urban nature of the location and the building’s function, the main considerations were the comfort and well being of the occupiers and the pursuit of low energy building systems. To eliminate conventional air conditioning units totally, the designers made full use of the naturally occurring elements and climatic conditions.
To optimise daylight and reduce reliance on artificial lighting, both blind and glazing systems were designed with the assistance of computerised shading studies of the site. The upper slats of the blinds were angled independently to upwardly
direct daylight toward reflective ceiling surfaces. Glazed corridor walls further optimised day lighting (Fig. 7, Fig. 9).
A policy of natural ventilation was designed by utilising a double facade system. This has the additional benefit of reducing noise transmission from the streets. Clean air from the courtyard micro-climate is introduced into the void of the double facade, naturally ventilating the internal space through opening windows and corridor wall vents exploiting stack effect with heat recovery units mounted at roof level (Fig. 8, Fig. 10). Outdoor air temperatures in the region exceed 22 degrees Centigrade during less than 5% of the year. When supplementary cooling is required, the building superstructure is actively cooled by flushing with water. The heat is exchanged into the ground to be used in the winter months with the aid of a heat pump. The circulation pump requires conventional power, however, the annual energy balance for heat introduced into the ground and extracted breaks even in the temperate climate.
Fig 7 above I Fig 8 below
Fig 9 above I Fig 10 below