KfW Westarkade

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Official Name KfW Westarkade
Structure Type Building
Status Completed
Country Germany
City Frankfurt am Main
Street Address & Map Zeppelinallee 6
Postal Code 60325
Building Function office
Structural Material composite
Proposed 2004
Construction Start 2007
Completion 2010

Companies Involved

Owner KfW Bankengruppe
Design Sauerbruch Hutton Architekten
Architect of Record Architekten Theiss Planungsgesellschaft mbH
Structural Engineer
• (not specified) Werner Sobek Group GmbH
MEP Engineer
• (not specified) Reuter Rührgartner GmbH; Zibell, Willner & Partner
Main Contractor Züblin
Other Consultant
• Energy Concept Transsolar Energietechnik GmbH
Material Supplier
• Elevator Schindler

About KfW Westarkade

One of the first office towers in the world predicted to run on less than 90 KWh/m² of primary energy per year, KfW Westarkade uses approximately half the average energy of European office buildings, and one-third of American. The building forms a 14-story extension to the KfW’s headquarters in Frankfurt, completing an existing ensemble of buildings from the last four decades. Situated in the city’s West End, it lies adjacent to the Palmengarten park and includes space for conference facilities and 700 new workplaces.

The streamlined shape of the tower integrates itself into the cluster of existing buildings. It acts as a colorful interface between two distinct urban spaces: while it appears as a slim slab towards the city, it presents a discreet backdrop to the park and provides open sightlines for the existing ensemble. Furthermore it exploits the prevailing wind direction for controlled natural ventilation of the offices by means of its unique double layered wind-pressurized façade.

The new building extends the grounds of the KfW Banking Group to the west with a four-story podium that clearly delineates the edge of the Zeppelinallee road. The tower above it is formed in such a way that it does not obstruct the view from the existing office floors of the main building. Together with the main buildings and the adjacent existing structure, the building’s south side creates a communal courtyard. The landscaped areas of the southern end of the Palmengarten are drawn through the site leading to this courtyard, resulting in a coherent and interesting open space.

The construction and use of the Westarkade is governed by numerous built and behavioral features to maximize sustainability, led by three factors: natural ventilation, activated slabs, and geothermal energy.

The Westarkade had as its primary aim to make a significant advance in the field of natural ventilation of tall buildings, as a significant component of their overall sustainability. The dynamically-controlled pressure-ring façade serves to neutralize external wind conditions which are otherwise too turbulent for operable windows, especially on higher floors. The façade’s outer layer contains sensor-controlled flap openings that maintain a constant and even air pressure within the ring. The inner layer has operable windows that allow the offices within to be ventilated. The air flow within the pressure ring is regulated to never exceed 6 m/s. The flaps are designed to adjust to five wind directions as well as outside temperature, solar radiation and pressure differences on the windward and leeward sides of the building.

Exhaust air flows through noise-attenuating overflow elements in the office partitions and along corridors until it reaches the cores, where the air, through stratification, is naturally driven upward to the roof through shafts.

As a result, the offices can be ventilated naturally for eight months of the year without creating drafts or undesired heat loss. Mechanical ventilation is required for less than 50% of all working hours. The double façade also functions as a passive thermal solar collector, as the flow of fresh air is pre-tempered by solar radiation within the double façade. In this way heat loss is minimized and heat energy is conserved. The outer skin of the double façade can be opened completely in order to avoid overheating of the building in summer.

The building employs thermally activated slabs, whereby a system of pipes built into the solid floors conveys water that serves as both a heating and cooling medium. This creates exceedingly energy-efficient, comfortable and constant room temperatures. Due to the high thermal storage capacity of the solid concrete floors, the rooms can be sustainably heated and cooled without the extremes in water temperature that are required with traditional radiators. For this sort of tempering, energy can be used that already exists in the building: the waste heat from the data processing center can cover half of this heating demand.

Geothermal energy is provided through an air source heat pump which complements the recovery-based heating system within the KfW complex. Largely contaminant-free air is drawn from the adjacent Palmengarten park, then tempered by traveling though a system of underground conduits before being distributed inside.

CTBUH Initiatives

KfW Westarkade Chosen as Featured Building
Dec 2011 – Featured Tall Building

Werner Sobek Presents on Engineering High-Rises for Sustainable Cities
11 Jun 2013 – Conference Video

Sauerbruch Hutton Present on KfW Westarkade
3 Nov 2011 – Awards Symposium Video


Beyond Green – Engineering High-Rises for Sustainable Cities
11 Jun 2013 – Werner Sobek, Werner Sobek Group

Best Tall Building Europe: KfW Westarkade: The Next Generation of Energy Efficiency
3 Nov 2011 – Axel Hinterthan, KfW Bankengruppe; Matthias Sauerbruch & Louisa Hutton, Sauerbruch Hutton

CTBUH 10th Annual Awards Dinner
3 Nov 2011 – Dinner 2011

More Videos

Videos Related to KfW Westarkade

Videos Related to KfW Westarkade

Beyond Green – Engineering High-Rises for Sustainable Cities
11 Jun 2013 – Presentation at CTBUH 2013 London Conference; Werner Sobek, Werner Sobek Group
High-rise buildings make an important contribution in the design of sustainable cities – provided they are planned accordingly and with a holistic perspective. In this…
Best Tall Building Europe: KfW Westarkade: The Next Generation of Energy Efficiency
3 Nov 2011 – CTBUH "10th Annual Awards"; Axel Hinterthan, KfW Bankengruppe; Matthias Sauerbruch & Louisa Hutton, Sauerbruch Hutton
One of the most energy-efficient office buildings in the world, KfW Westarkade is projected to use about half the primary energy of an average European office building,…
CTBUH 10th Annual Awards Dinner
3 Nov 2011 – CTBUH "10th Annual Awards"; Dinner 2011
The 10th Annual Awards Ceremony & Dinner was held in Mies van der Rohe’s iconic Crown Hall, on the Illinois Institute of Technology campus, Chicago. The 2011 “Best Tall…
Interview: Engineering the KfW Westarkade
3 Nov 2011 – 2011 Awards Ceremony/Symposium Interviews; Werner Sobek, Werner Sobek Group
Werner Sobek is founder of Werner Sobek Group, one of the world’s leading engineering consultancies. He speaks on sustainability and lightweight structures as well as…
Interview: KfW Westarkade
3 Nov 2011 – 2011 Awards Ceremony/Symposium Interviews; Axel Hinterthan, KfW Bankengruppe; Frankfurt and Matthias Sauerbruch & Louisa Hutton, Sauerbruch Hutton
The winner of the 2011 Best Tall Building Europe, KfW Westarkade in Frankfurt, is also the winner of the Overall Best Tall Building Worldwide. Axel, Matthias, & Louisa…

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