CRITICISM: A striking presence on the Berlin skyline, the DEBIS TOWER, by the Renzo Piano Building Workshop, revives the skyscraper

Architectural Record, October 1998

The extended hangover of commercial overbuilding in the United States and the implosion of Asia's building boom might suggest that there's not much reason to build tall office buildings anymore. But a trip to Berlin can be bracing. Take the U-Bahn to the Gleisdreieck stop, then stroll west along the Reichpietschufer, which follows one of the city's canals. As you round a curve, a crystalline sliver, some 20 stories high, appears with a delicate zigzag ascending it. This proves to be an exit-stair enclosure at the southernmost extremity of Renzo Piano’s Debis Tower, a landmark within the Potsdamer Platz redevelopment, one of the largest commercial-building projects recently undertaken in the world.

Translating the mundane need for egress into an object of such athletic elegance is just one way in which the new Debis Tower transforms the office-building type. Debis looks not like one tower but several. The architect has carved the typical office-building box into a grouping of bundled slabs, alternating sheer glass elevations with ones clad in ocher terra-cotta panels and rods.

Piano’s accomplishment here lies not only in the creation of an urbanistically sophisticated, environmentally progressive, and technologically advanced workplace. He and his firm, the Renzo Piano Building Workshop, which is based in Genoa, Italy (though the project was executed through the satellite office in Paris), may have single-handedly recaptured the long-lost romance of the skyscraper. Such an outcome could not have occurred without an extraordinarily committed client and a well-considered site master plan–also designed by the Piano office.

But the project is also the progeny of monumental political change. Flash back to November 1989, when the Berlin Wall came crashing down. Not long after, East and West Germany were united. In the ensuing jubilation, Berlin was seen as the gateway to the entire former Eastern bloc, a half-continent expected to grow rapidly as capital flowed in to bring East into economic parity with West. A 728,000-square-foot, mostly empty chunk of former barbed-wire-entangled no-man's-land went on the block. The wedge-shaped acreage was tantalizingly located, hugging what once had been Potsdamer Platz, one of Berlin's liveliest intersections before World War II. Daimler-Benz, parent of the famous Stuttgart-based carmaker Mercedes-Benz, purchased the land. The chance to rebuild one of the key sites in the city was close to the heart of Edzard Reuter, head of the company, who was the son of the city's first mayor after the war.

Before the site could be developed, Berlin's Building Senate held an urban design competition for it, which was won by the Berlin architects Hilmer and Sattler. They redrew the axial boulevards that had once met at Potsdamer Platz, divided the site into parcels, and determined a street-wall height of 35 meters (about 115 feet) pursuant to the “critical reconstruction” tenets that have guided the reuniting of Berlin. The idea was that the new Berlin would have an urbanistic continuity with what remained of the prewar, pre-Wall city.

Daimler-Benz then held a competition for an architect to take the scheme to a more detailed level, which Piano's office won with Christoph Kohlbecker. At the unveiling of the scheme, Piano said that it “draws out the past for its foundations, while keeping its modernity through discipline in the use of materials and of all the technology at our disposal.” An international roster of architects was hired to design buildings for all 19 parcels, including Jose Rafael Moneo, Richard Rogers, Arata Isozaki, Lauber + Wohr, and Hans Kollhoff. Some of the key parcels were assigned to Piano, including the largest and southernmost, on which grew the tower for Debis, a Daimler-Benz subsidiary created in 1990 to handle real estate development and management, financial services, insurance, information technology, telecommunications, and media services.

Out of this plan came a project that was as much a symbol as a building. It was an emblem of Daimler-Benz's commitment to a united Germany and a rebuilt Berlin. Under such circumstances, no bland, American-style developer's hulk would do. But Piano's own master plan did not make designing the building too easy. The parcel is a long rectangle, with its northwestern corner stretched into a wedge. Its planned density would have been high for Berlin, but floor-area limitations meant that the envisioned tower -- a kind of exclamation point for the whole development -- could not be bulky.

Reconciling the massing of the 482,000-square-foot building to the urban scale of Berlin was the chief problem posed by the site, explains Bernard Plattner, who was the architect-in-charge for the tower. The urban-design criteria mandated a street wall along the 600-foot western edge of the site. To break down the scale of this unappealingly long block, Piano carved recesses into the facade, dividing the elevation into four elements that almost appear to be separate buildings. (The tallest shaft is actually a ventilator for the vast underground area of the Potsdamer Platz development.) The architect scooped a monumental atrium out of the deep center of the block to satisfy German building regulations that limit the depth of the floor plate by mandating how far most workers can be from a window (about 25 feet).

Piano saw each element of the tower -- elevator core, stair towers, the ranges of offices facing east, south, and west -- as a potentially expressive element. He pulled them apart, with the recesses acting as visual membranes. The overall impression is of lapped slabs of solids and glassy membranes -- a kind of contemporary San Gimignano of towerlike elements.

The design of Debis is not all bravura. Building on experience gained on a number of past projects, Piano's office used glass and terra cotta to make what is among the world's most sophisticated skin. Like an increasing number of technically advanced German buildings, Debis has a double-wall curtain wall.

The combination of shading (provided by projecting the terra-cotta rod system in from of the window glass), the double wall, and operable windows reduces external warm-weather heat loads, winter cooling loads, and internal heat loads. The concrete floor slab is exposed at the outer edges of the floors, which enhances energy conservation by absorbing excess heat from the office space in the daytime and radiating it at night.

For the building as a whole, this means that air conditioning is supplementary, not mandatory. Yet office occupants can control their own environments more than those who work in sealed, constantly airconditioned buildings. At Debis, most people sit next to windows that can be opened. External blinds can be lowered to reduce glare.

In other respects, the interiors are conventional. Most of the staff is housed in one- or two-person white-painted private offices. The building recesses along the exterior signify sublobbies inside, which help people orient themselves in what otherwise could be a confusing racetrack of hallways.

The atrium is monumental in the time-honored corporate style, even though it invites public use through the provision of changing art exhibitions, an auto showroom, a coffee shop, and a cafeteria open to the public. Piano softens the effect by mounting angled, milk-tinted glass panels below skylights to gently diffuse sunlight into the six-story-high space.

Piano often speaks of what he does as marrying construction technique with an overarching design idea. At Debis, the close-up experience of the building is unusually tactile, rooted in the materials and the way they are put together. At some times of the day, the sun sparkles from the beveled bottom edge of the pivoting glass panels; at others, it picks out elements between the glass walls: the vertical glass returns, the metal facade-support structure, or the maintenance platforms. The terra-cotta elements don't move, but their raw-clay finish invites touch. The rhythm of open and closed cladding along with deepening and lightening shadows as the light changes through the day have their own sensual appeal.

Debis, as manager of the 19-building site, saw its own tower as a prototype for future corporate real estate endeavors. The company used the building to test innovations in energy-conserving building design and in environmentally sustainable techniques. In cooperation with BEWAG, the local electric utility, a new power plant is being built for the entire Potsdamer Platz site. Its waste heat will be distributed by pipe to heat or cool the buildings by the absorption method. A graywater system routes rainwater to sodded roofs over the Debis building's low-rise section. The excess fills the pond that surrounds the building. Building ecology experts Drees & Sommer advised on the use of lower-toxin products and construction materials.

The gigantic scope of the overall development also imposed limitations. To avoid overburdening local streets, most material was delivered to and waste removed via an adjacent staging area constructed for the purpose, served by freight rail and barges.

At the building's topping-out ceremony in 1996, the company celebrated by bringing in an orchestra and the conductor Daniel Barenboim. As the musicians played, 20 tower-crane operators around the 17-acre Daimler-Benz site moved their massive charges in time to the music. Since cranes have become the hallmark of Berlin's skyline over the years since the Wall crumbled, such a ballet of 150-foot-high mechanical storks was strangely fitting. The Daimler-Benz complex, if the Debis Tower is any indication, may offer this rebuilding city much to celebrate.