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Case Study 1: Unileverhaus

November 1st, 2010 / By: / Case Studies, Exteriors, Feature

HafenCity
Hamburg, Germany

Not every 3,000m2 corporate edifice is both design savvy and über-green, but Unileverhaus has managed to achieve both. Indeed, the more than 80-year-old consumer products company (Dove®, Q-tip®, Wisk®, Lipton) had a visionary program for its new Germany/Austria/Switzerland headquarters in Hamburg’s HafenCity (Harbor City), whose masterplan is founded on sustainability practices. The structure needed to evoke its industrial site on the Elbe River, adhere to the HafenCity masterplan of being open to the public, create visibility for Unilever and its products and be eco-friendly. The headquarters also needed to hold its own aesthetically in a rapidly rejuvenating urban core that boasts cultural venues by Rem Koolhaas and Herzog & de Meuron.

In a stroke of innovation and elegance, Behnisch Architekten of Stuttgart delivered. Designing a sustainable seven-story building with a soaring atrium and glass elevator, the low-rise Unileverhaus evokes a ship’s hull and provides river views from most perspectives. The first floor includes an employee cafeteria and test kitchen, in addition to such public amenities as a grocery store, spa, café and access to a riverside patio. The terraced, upper levels overlooking the atrium consist of open-plan offices, conference areas and communal overlooks for employee gatherings, formal or informal.

In addition to constructing an environmentally high-performing building, natural light and ventilation were Unilever’s primary goals. The company also wanted operable windows. A conventional double glass envelope was ruled out as too expensive and cumbersome. The solution? A single, high-performance glass envelope with aluminum venetian blinds installed on all exterior elevations except the north side, to reduce heat gain and glare. What Unilever and Behnisch had not initially anticipated was the site’s gale force wind load—often reaching more than 97kph—that stressed the venetian shading system. The risky and unorthodox solution was to wrap the façade in a single-layer transparent ETFE foil that would allow the shading system to function properly, even in high winds, and minimize the energy impact.

“The design team was looking for something new and light, and so EFTE was the appropriate material,” explains Bernd Stimpfle of formTL, the engineering firm that worked on the project. “To maximize the transparency, a single layer ETFE solution was chosen versus the more common double-layer EFTE pillow.” To better withstand the wind load, the 224 EFTE panels comprising the façade were designed with a curvature. “With plane foil structures in areas of high wind load like we have here in Hamburg, a very limited span is possible,” states Stimpfle. “Therefore, it is necessary to curve the foil.” An aluminum and steel frame installed 1–2m in front of the glass envelope supports the EFTE façade. Fresh air circulates between the two skins from both above and below. Moreover, with a lifespan of 25–50 years, EFTE is also free of plastic and will retain its transparency.

Aesthetically, the entire design program is compelling. Perched on the Elbe’s edge, Unileverhaus seems to be part of the water and of the land. The EFTE outer skin visually counters the structure, making it appear to float or to be a hovercraft of unknown origin. Unileverhaus is at once sensual and muscular, transparent and tactile. On a practical level the design and openness of the building foster employee interaction and is inviting to Hamburg’s residents and visitors.

Unileverhaus proves that excellent innovative design and sustainability are not contradictory, even in gale-force winds.

Mason Riddle, a contributing editor for Fabric Architecture, writes frequently about architecture, design and art for numerous publications, including Dwell, Architecture Minnesota and Public Art Review.

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