At fifty-three storeys, the Commerzbank is the world's first ecological office tower and the tallest building in Europe. The project explores the nature of the office environment, developing new ideas for its ecology and working patterns. Central to this concept is a reliance on natural systems of lighting and ventilation. Every office is daylit and has openable windows, allowing the occupants to control their own environment. The result is energy consumption levels equivalent to half those of conventional office towers.
The plan of the building is triangular, comprising three 'petals' − the office floors − and a 'stem' formed by a full-height central atrium. Winter gardens spiral up around the atrium to become the visual and social focus for four-storey office clusters
From the outside these gardens in the sky give the building a sense of transparency and lightness. Socially, they form focal points for village-like clusters of offices, providing places to meet colleagues or relax during breaks. Environmentally, they bring light and fresh air into the central atrium, which acts as a natural ventilation chimney for the inward-facing offices. Depending on each garden's orientation, planting is from one of three regions: North America, Asia or the Mediterranean.
The tower has a distinctive presence on the Frankfurt skyline but is also anchored into the lower-scale city fabric, through the restoration and sensitive rebuilding of the perimeter structures to reinforce the original scale of the block.
These buildings provide shops, car parking, apartments and a banking hall, and help to forge links between the Commerzbank and the broader community. At the heart of the scheme is a public galleria. With its restaurants, cafés and spaces for social and cultural events, it has become a popular pedestrian thoroughfare. Interestingly, on the day the Commerzbank opened, the Financial Times adopted it as the symbol of Frankfurt, just as it features the Houses of Parliament and the Eiffel Tower as symbols of London and Paris.
The building design responds to prevailing winds and solar orientation, to ensure optimum ventilation and daylight penetration.
The triangular shape and central atrium assisted in the creation of a zone of negative pressure, that drives natural ventilation through the building.
The building was designed to be naturally ventilated for 60% of the year, with the sky gardens allowing natural ventilation during shoulder seasons. This approach was expected to reduce energy consumption by up to 50% compared to an equivalent air conditioned office.
Cooling is provided by chilled ceilings, while heating is from perimeter heating. Windows are connected to the BMS to ensure that the mechanical ventilation only works when the windows are closed. Artificial lighting is connected to motion sensors and timers.
From 1st January 2008, the Commerzbank Tower has been supplied exclusively with green energy that is derived from renewable energy sources.
The central infill site location of the project, is also key to its connectivity and access as it is close to public transport links.
The development reused and restored the existing perimeter buildings which reduced materials consumption. Even before the existence of the Forestry Stewardship Council, all timber used in the building was taken from managed sources. Operational waste segregation facilities are provided and catering waste is composted.
To reduce potable water consumption, the condensate from the chillers was recycled, and used for WC flushing
Large sky gardens with a diverse ecological profile were used to provide informal break out spaces with views of the city. This incorporation of landscaping, and the other sustainable design responses, led to Commerzbank being dubbed as the world’s first ‘ecological office tower’.
The tower, built in the centre of Frankfurt, was designed with respect to existing historical structures and the buildings surround. The project reused and restored the existing perimeter buildings of the site, which helped to maintain the streetscape.
Designed with the end user in mind, office areas are naturally ventilated and flooded with daylight. Users can regulate their own environments and sky gardens act as a breakout space.
The tower has been embraced by the city, and Commerzbank is now regularly shown as an iconic structure of Frankfurt, and the German stock exchange.
As the first ‘ecological office tower’, the sustainable approach for the project was ahead of its time. The design planned for a future of increasing resource scarcity and cost, by minimising energy and water consumption, whilst providing solutions for enhanced comfort.
Post occupancy studies have shown that the tower actually consumes 20% less energy than predicted, and there has been a year on year reduction in energy consumption since 2000. This is largely because the building users have extended the period of natural ventilation up to 85% of the year, as opposed to the 60% designed for.
“"We now have five years' experience of running the building, and I am very happy to report that it is actually far more efficient in energy terms than was anticipated at the design stage. For example, whereas it was estimated that the building would be naturally ventilated for 60 per cent of the year, we are in fact able to use natural ventilation for more than 80 per cent of the time. This means that our present electricity usage is approximately 20 per cent less than predicted. As you might imagine, we are very happy." Peter Muschelknautz, the Commerzbank Facilities Manager 2002 "We now have five years’ experience of running the building, and I am very happy to report that it is actually far more efficient in energy terms than was anticipated at the design stage. For example, whereas it was estimated for 60 per cent of the year, we are in fact able to use natural ventilation for more than 80 per cent of the time. This means that our present electricity usage is approximately 20 per cent less than predicted. As you might imagine, we are very happy."Peter Muschelknautz, The Commerzbank Facilities Manager 2002 "We are given lots of praise when our office workers leave at night and tell us that they don't feel tired - this means that their productivity increases. This is more important to me than great architecture or sky gardens."Dr Horst Gruneis, director of Commerzbank's Central Building department quoted in Architectural Record, January 1998 "At last we can open the windows whenever we like, we can feel the air and the noises of the street - we feel freer."Unnamed Commerzbank employee quoted in Frame 1, December 1997 "As the interiors of Foster’s Commerzbank come together, the most striking effect is one of glistening transparency." Barrie Evans, The Architects’ Journal, 27 March 1997 "This architecture speaks of a better world – on the one hand, highly technical; on the other, ecologically defensible."Manuel Cuadra, Domus, November, 1997 "At last we can open the windows whenever we like we can feel the air and the noises of the street – we feel freer." Unnamed Commerzbank employee, quoted in Frame, 1 December 1997 "You sense that a kind of community has been created, one that could become familiar and intimate, so unlike the usual downtown tower."Mary Pepchinski, Architectural Record, January 1998 "With the Commerzbank we combined an ambitious structural and aesthetic vision with a quest for natural ecological solutions and the well-being of the individual. For me, it is in this synthesis of these themes that the real achievement lies."Norman Foster
Area: 120 736m²
Height: 298 m
Client: Commerzbank AG
Structural Engineer: Ove Arup & Partners / Krebs & Kiefer
Quantity Surveyor: Davis Langdon & Everest
M+E Engineer: Roger Preston & Partners/ RP&K Sozietat GmbH/ Petterson & Ahrens
Landscape Architect: Sommerland & Partners
Lighting Engineer: Lichtdesign
Winter gardens linked to a central atrium spiral up the tower to become the visual and social focus for four-storey clusters of offices.