Constructive urbanity: an attempt to generate a large urban building which relates to the form and experience of city life, while offering varied office accommodation, has generated a result surprisingly related to Constructivism - Foster's Commerzbank in Frankfurt, Germany by Behnisch and Partners

Architectural Review, The, August, 2002 by Peter Blundell Jones

back.

Office variety

At first floor level the central node connects to the corridors of the peripheral office wings, and two glazed tubes span the ponded court as shortcuts. In five places the access corridors in mid plan are skewed, opening towards circulation nodes and breaking the monotony of endless passage. Often, too, glimpses are provided into inner courts or to outside world. For reaching further levels lifts dominate, but stairs are always adjacent, and local open flights here and there grant local connections from one floor to the next. A triple bank of centrally placed lifts services the tower, arriving in foyers which vary in shape from floor to floor and always allow a glimpse of view. As in other Behnisch office buildings, fully glazed partitions or partitions with glazed tops allow daylight into central passages almost everywhere. Varying plan depths in the wings are exploited to provide different sizes and types of office, from individual cells to big team rooms. A standard glass partitioning system was developed which can be adapted as needs change. The tower culminates, predictably enough, in board room and entertainment suite. It is interesting to observe how naturally the stepped forms and skewed angles blend into the top floor plan while accommodating and expressing pedestrian movement-directional spaces and a lively tower profile at the same time. This simple example reflects a policy which drives the whole.

The pursuit of radical energy and environment policies is a major interest of Stefan Behnisch, and perhaps the most obvious development he has brought to the firm's work. Surprisingly for such a large building, air conditioning is only used for underground rooms and service areas such as kitchens. Elsewhere are opening windows, and a system of largely passive ducts or 'air chimneys' to induce convection. On the outside faces is a typically Behnisch layered facade, with extra glass panels for acoustic isolation to the north, thermal glazing and external solar blinds on the other sides. Deployed blinds are specially designed to reflect a controlled amount of light inward to avoid leaving the room too dark Heating and cooling of offices is achieved by heat exchange through water pipes in the concrete floor slabs, whose mass provides thermal storage, and overall energy demand is reduced by heat exchange with deeply sunk ground pipes. These absorb heat in summer and provide it, stepped up from six degrees by heat pumps, in winter. Exchange with a district heating system is also involved, while solar water heating, photovoltaics and fuel-cells play minor and sometimes experimental roles. With all these measures, consultants Transsolar claim to have saved 1920 tons of carbon dioxide emission per year.

A state of flux

Some critics find the work of the Behnisch office too chaotic and imperfect, too unmonumental. Yet the advantage of their responsive approach most visible here is that a big building can be treated like lots of small ones, almost like a mini-city. This holds the scale down and allows flexibility, for without a great preconceived plan, there is room to incorporate site influences, existing buildings-Siemens House quietly absorbed-and to allow for growth and change. Most important of all, human scale is retained throughout and numbing repetition avoided. Every floor gains a different character: in the tower the lobby changes shape or an office wing cantilevers further. There are frequent views out for orientation. It was wise to give the ground floor back to the city with shops and cafes to animate the public realm, while the protected water court marks the beginning of the larger institution as well as helping the environmental strategy. Lively and memorable, the tower as landmark is different from each side. Its appearance is enhanced by areas of special colour-coated glass added for their reflective effect, part of a colour design policy which is another late Behnisch trademark. The high-tech brigade may fume about the catholic variety of details in this architecture, but professionalism does not necessarily entail the perfection of the machine. The issue is more profound: Mies's 'God is in the details' reflects a monumental architecture striving for the eternal in its perfection, and flexible only through its sheer indifference to change. Behnisch's situational architecture accepts a state of flux, always open and always developing, allowing for growth, interacting with life.