August 1, 2011
by Canadian Architect
Text Pamela Young
Photo Jan Bitter
Ideally, the skin of a building would be a work of art that slashes energy consumption while keeping everyone within it exceptionally comfortable. If the KfW Westarkade in Frankfurt succeeds in becoming the world’s first high-rise with a maximum annual primary energy demand of a mere 100 kWh/m2, the built environment will have edged a little closer to perfection.
Recently named 2011’s Best Tall Building (Europe) by the Council on Tall Buildings and Urban Habitat and also shortlisted for the European Union Prize for Contemporary Architecture/Mies van der Rohe Award, the 39,000-square-metre expansion of KfW Bank’s headquarters was designed by Sauerbruch Hutton. Westarkade’s 10-storey tower rests on a sweeping four-storey podium that connects it to existing KfW buildings. Although the new building’s sustainable features include a geothermal system and state-of-the-art heat recovery technology, its most innovative aspect is the tower’s polychromatic, double-walled “pressure-ring” façade, developed by Germany’s Transsolar KlimaEngineering in collaboration with Sauerbruch Hutton.
The outer wall of the cavity surrounding the tower is sawtoothed. Vertical, coloured glass vents forming the narrow side of the sawtooth pattern alternate with the fixed, tempered-glass panels that form the longer edge. The inner wall has operable windows, interspersed with fixed, argon-filled insulated glazing units. Automated blinds within the cavity aid in controlling solar heat gain and glare. In response to data collected by a rooftop weather station and various sensors, the building automation system adjusts the angle of individual vents to introduce fresh air and maintain a ring of consistent positive pressure around the building. This shelters the tower from high winds, and it allows occupants to open windows on the inner wall year round without causing drafts or heat loss. Oriented and shaped to take advantage of prevailing winds, the tower benefits from natural ventilation most of the year.
Monitoring to determine how well actual energy performance measures up to the modelling is still ongoing, but the building is expected to be twice as efficient as a conventional European office building, and three times more so than the North American norm.
Sauerbruch Hutton defines itself as a firm intent on exploring how sustainable design can be “translated into sensual and stimulating spaces.” Its founding directors, Matthias Sauerbruch and Louisa Hutton, are known in particular for their striking use of colour. Westarkade’s façade incorporates varying shades of red, blue and green vents, with a different colour range dominating each elevation. Reds along the main frontage harmonize with historic sandstone buildings; blues complement an existing KfW building; greens form a backdrop to a botanical garden. Best Tall Building juror Peter Murray noted that colour is often used to mask otherwise unremarkable architecture. But in Westarkade’s case, he said that “it contributes an additional rich layer to what is already a remarkable building.” CA
Pamela Young is the editor of Canadian Facility Management & Design. Matthias Sauerbruch will deliver the architectural keynote address entitled “The Practice of Sustainability” at IIDEX/NeoCon Canada in Toronto on Friday, September 23, 2011 at 11:00am. For more information, please visitwww.iidexneocon.com.
Already a remarkable building with respect to its performance, the KFW Westarkade in Frankfurt transfixes with seductively rhythmic bands of colour and glazing.