Glass Haus: With a host of green features and a clever layout, a new office building in Hamburg’s harbor is anything but ordinary.
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While the port is busy as ever, an under-utilized portion is undergoing a radical conversion. In 2003, construction began on HafenCity, or Harbor City, whose master plan calls for housing, shops, restaurants, offices, and cultural venues, including a concert hall by Herzog & de Meuron and a science museum by Rem Koolhaas. Billed as Europe’s largest inner-city redevelopment, the 390-acre district will increase the size of Hamburg’s urban core by 40 percent. It also will add pizzazz to this maritime city.
It is here that Behnisch Architekten has created a new eco-friendly headquarters for the Germany/Austria/Switzerland branch of Unilever, the 80-year-old consumer products company behind such household names as Dove, Lipton, and Skippy. Completed in 2009, Unilever Haus, as it’s called, has fast become a local landmark and gained international recognition: At the 2009 World Architecture Festival, it was named “Office Building of the Year.” The seven-story, 409,000-square-foot facility building is not just a lively addition to HafenCity; it also exemplifies Behnisch’s commitment to holistic sustainable design and offers fresh ideas about what an office building can and should be.
Behnisch Architekten—the 60-year- old, Stuggart-based firm known for such innovative projects as the Genzyme Center (2003) in Cambridge, Massachusetts— won the commission in 2006 through a competition. The brief: Unilever wanted a more open environment for its 1,200 Hamburg employees, who for decades had worked in a traditional high-rise that didn’t foster communication. “An employee on floor 17 did not communicate with someone on floor 12,” explains Michael von Rudloff, Unilever’s project construction manager and supply-chain director. The company also wanted more public visibility.
When it came to selecting a site, Unilever was drawn to the pioneering spirit of HafenCity, which seemed to mirror the company’s aspiration to develop a new work culture. And it picked a slice of prime riverside real estate, on HafenCity’s southern edge. “It was definitely a challenging and exciting site,” says Stefan Behnisch, Hon. AIA, founding partner at Behnisch Architekten. “It’s very prominent and exposed.” The design team took its cue from the water, creating a low-rise building whose bulky shape and white exterior resemble a ship’s hull. Inside the building, river views are ever-present.
The program brief required that part of the building be open to the public, which inspired a dynamic layout not often found in office buildings. Visitors enter a light-filled atrium, criss-crossed by walkways and ringed by interior facades with operable windows. The ground floor features an employee cafeteria and test kitchen, along with public amenities—a café, small spa, and grocery store stocked with Unilever products. Outside, a patio merges with stairs leading down to a riverside promenade.
At the center of the atrium is a glass elevator, in addition to a stairway that leads to Unilever’s reception area on the second floor. The upper levels contain open-plan offices and meeting rooms, along with slivers of communal space that overlook the atrium. These “communication” areas are furnished with blocky wooden tables and kitchenettes, giving employees an informal area to eat, chat, or conduct business. “We worked quite closely with Unilever to reconsider what an office building is,” says Martin Haas, partner at Behnisch Architekten.
Creating a pleasant work atmosphere while being mindful of the environment is a long-held tradition in Germany and was central to the design of the Unilever headquarters. Natural light was a primary concern and, Haas says, “you have to deal with all glass if you want to have a daylit building.” But ample glazing wouldn’t be energy efficient, and the design team didn’t want to use a standard double-layer facade. “Double facades are always so expensive and heavy and difficult,” says Behnisch. “We asked, ‘Is there anything new out there?’”
In the end, they conceived a lower-cost double skin that gives the building its unique character. For the inner layer, the team used a high-performance glass facade system with operable windows. To reduce heat gain and glare, they placed exterior Venetian aluminum blinds on all elevations but the north, where direct sunlight is minimal. A rooftop device that tracks the sun controls the blinds, although employees can override the system.
Due to strong winds in the area—up to 62 miles per hour—the blinds required shielding. And so the team wrapped the facades in a clear foil made of ethylene tetrafluoroethylene (ETFE). “This was something that required courage on both sides, the architects and us,” says von Rudloff. “We decided to go for it.” This protective membrane sits 1 to 2 meters from the inner facade and is supported by a steel and aluminum frame. Because the gap between the two membranes is open on the top and bottom, fresh air is able to flow into the cavity and through the operable windows, explains Jürgen Trenkle, an engineer with Form TL, the facade consultant.
To maximize transparency, the team used single-layer ETFE sheets rather than the more common double-layer pillows. Compression bars push the skin outward at various points, keeping the foil in tension and enabling it to better handle wind forces. The skin has a life span of 25 to 50 years and typically is cleaned with water.
The facade system works in tandem with the building’s interior layout. Narrow and irregularly shaped floor plates wrap the atrium in a terraced fashion, ensuring that natural light is able to deeply penetrate the building. When and where needed, artificial light is supplied by LEDs that are 70 percent more efficient than comparable lamps, notes Haas.
There is no overhead lighting in the offices, which allowed the project team to embed a radiant cooling system in the exposed reinforced-concrete ceilings. Raised floors in the offices accommodate two vital functions: mitigating sound transmission and housing the ventilation system (fresh air passes through filters before entering the building). In the atrium, the radiant cooling system is embedded in the floor slabs.
Unilever Haus is designed to use less than 100 kilowatt-hours of primary energy per square meter each year; a typical office building consumes four times that amount, according to Haas. The building contains other green elements such as waterless urinals, a graywater system, and a green roof. Its long list of sustainable attributes earned it a “gold” rating under HafenCity’s green-building rating system.
In so many ways, Unilever Haus is not your standard office facility. Its design appears to succeed on multiple levels: boosting Unilever’s profile, providing a satisfying work environment, serving area residents, and reducing energy use. Moreover, the architecture alludes to the city’s maritime character without being gimmicky. As HafenCity continues to take shape, this project will no doubt serve as an important benchmark. It also will help Hamburg— recently named the European Green Capital for 2011—demonstrate how an industrial city can help lead the green revolution.
Jenna M. McKnight is news editor at Architectural Record and an occasional GreenSource contributor.