The Norddeutsche Landesbank in Hanover

The new Norddeutsche Landesbank in Hanover, Germany, by Behnisch, Behnisch & Partner is a self-contained mini-metropolis, rising like a sculpture of glass and steel boxes, piled one atop the other.

Hanover is not a city with a well-established tradition of risk-taking architecture. Close to the old East German border, it lagged behind the rest of West Germany in both economic growth and post-World War II reconstruction.

The locals had grown fond of the remaining old buildings and years of restrictive zoning had resulted in a rather low and uniform cityscape.

Even the cutting-edge architecture in the pavilions of Hanover’s Expo 2000 has not made any visible impact on the city’s contemporary architecture.

Within this cultural and physical milieu, Behnisch, Behnisch & Partner devised a massing that would create a transition zone between Hanover’s 19th century residential area to the south and its denser historical centre to the north.

With shimmering elevations facing many different directions, the structure’s multiple orientations were intended as a way of connecting it with the surroundings so that the Norddeutsche Landesbank (Nord/LB) building wouldn’t seem to be turning its back on anyone.

The new building meets the busy arterial street with ground-floor shops beneath two floors of offices, embracing a publicly accessible inner courtyard with a reflecting pool and wooden decks.

The low perimeter block of offices surrounds three sides of this courtyard ? traversed at various heights by glass tube-like passageways connecting the wings of the building. (Incorporated into the new complex is the landmark 19th century Siemens Building, now used as a training centre with separate access.)

The nearly 230-foot-tall tower primarily houses offices and meeting rooms, with executive dining rooms and boardrooms at its top.

Crowning the tower is a 65-foot-high sculpture of glass panes, coated with a metal film that changes colour with the position of the sun and armed with night-time illumination by diodes.

The lobby is a four-storey high, semi-public space ? the actual bank offices and security installations start on the second floor ? covered by a sloping glass wall with louvers for climate control.

On one side is the “forum”, a space that doubles as art gallery and lecture hall. In the lobby, an extraordinary floor bridges height differences not with stairs but through a seemingly infinite number of slightly ramping triangular planes, keeping the space fluid but sometimes playing fleeting tricks with your sense of balance.

This entry area also provides access to a two-level underground parking garage and the ground-floor company restaurant.

The restaurant’s roof is abstractly shaped like butterfly wings.

Behnisch, Behnisch & Partner won an international competition for this building in part because of the firm’s skill in reducing energy use, bringing in daylight and ensuring worker comfort.

In Nord/LB, the ground floor plays a key role not only in mediating between existing neighbourhoods and providing an enjoyable setting, but also in achieving the building’s energy goals.

The offices have no air-conditioning ? unusual in German commercial high-rises, most of which have either air-conditioning or mechanical ventilation systems with controlled fresh air supplies and exhaust air extraction.

Here, the tower’s load bearing structure ? consisting of two 3-foot-thick columns with concrete cores wrapped in heating spirals ? is cooled by a low-energy system using cold ground water, pumped from 66 feet below the ground, about 6 feet below the water table. The tower relies on concrete ceilings for its storage mass.

Water, running through pipes in the tower’s ceilings, gets cooled in soil heat-exchanger tubes in 120 foundation piles, where the heat is removed in summer and can be stored for winter use.

The importance the architect attached to creating a pleasant and comfortable work atmosphere is apparent everywhere, not only in the nuances of shading, the refreshing courtyard, and the operable windows.

Although many workers had to adjust to the distractions and lack of privacy created by glass walls onto interior corridors, the daylight admitted was welcome from the start.

Hanover, in spite of being located in a developed country, and its new landmark have plenty to offer for developing countries like India where energy saving is a growing concern. Here is an example where excellence in engineering did not compromise the aesthetics of the structure.