(BDT_12_085) Swiss Re - Building Types Online

Description

The new headquarters of Swiss Re, the Swiss reinsurers, will be built only a stone’s throw from Richard Rogers’ Lloyds Building. The concept goes back to the “Climatroffice” of 1971, a joint project by Richard Buckminster Fuller and Norman Foster. “Climatroffice” encouraged a new, harmonious relationship between nature and the workplace: integrated gardens create a microclimate within an energy-conscious envelope minimised in relation to the enclosed space, where walls and ceilings dissolve into a continuous, triangulated skin. These seemingly utopic ideas developed thirty years ago are about to become reality in the building for Swiss Re.

The granting of building permission preceded heated debates following public opposition in London. The controversy was aroused less by the appearance of the project – it is called the “Erotic Gherkin” – than by the fact that erecting the new building required the demolition of the Baltic Exchange. Severely damaged by a bomb attack in the City of London, it had been sold to a Canadian investor on condition that it be rebuilt. Having sold the site to Swiss Re with the option of erecting a highly profitable high-rise, the original owner sued for loss of revenue. The conflict between the proponents and the opponents of high-rise development in the City of London was instrumentalised by the political parties. In the end it was thanks to the efforts of Norman Foster and the newly elected mayor of London, Ken Livingstone, that approval was won from the responsible government minister.

The new building, reminiscent of a projectile, will rise 40 storeys above a newly planned square, the design of which is based on a study of traffic flows by the London Organisation Space Syntax. Quality accommodation will be ensured by the round form of the building, for which wind tunnel tests and airflow simulations prove the absence of undesirable eddy currents. The ground floor is open to the public and accommodates retail shops and restaurants as well as the lobby. No private parking is supplied as there is sufficient public transportation. Providing bicycle stands and the accompanying showers and changing rooms will encourage the office workers to cycle to work.

The aerodynamic form of the high-rise offers a variety of advantages: in addition to the avoidance of eddy currents, the reduction of wind pressure reduces the need for stiffening so that the area occupied by the façade is minimised in relation to the enclosed space. Together, these lead to a more economical construction.

The main structure comprises a grid of steel A-frames that provide a double curvature outer skin that stretches evenly over the entire surface like a net. Developed using parametric modelling, a digital technology that originated in the aerospace industry, it provides the required stiffness. In this way, the core of the building is called upon mainly to carry weight and, with the reduction in the number of lifts and services as the building rises, can be made smaller, so that the office area can be increased correspondingly. The individual elements of the structural frame are minimised by the favourable weight distribution, whereby the weight of the construction itself is kept low and the proportion of net floor area to gross floor area is optimised. These two factors make the building very economical. In comparison, the neighbouring Tower 42, formerly the NatWest Tower, has in relation to the floor area and the core ratio 10% less usuable office space. Like the Climatroffice, the new building is enclosed in an energy-conscious façade consisting of external rhomboid thermal insulation glazing in front of the structural frame, solar protection in the interstitial space and an interior façade of flat glass elements, which gives spatial closure to the individual levels.

The most important element in the internal organisation of the skyscraper is the use of spiral atriums that are generated by the triangular cut-outs in the floor slabs. These cut-outs gradually rotate at successive floors forming the future „lungs“ of the building. Integrated into the design for the climate control system, they form sky gardens that provide a microclimate for every floor. The atriums relativise the scale of the building and promote internal communication, as local visual and spatial relations are enabled between levels. Unlike in conventional high-rises, several levels can be linked together this way to form not only an organisational unit, but also a communicative unit. The atriums are closed at every sixth floor in order to divide the building into vertical fire compartments. These floors are possible places for larger common areas like cafés or restaurants. Each floor is divided into six equal-sized segments. This makes possible a large number of office areas of different sizes that can be variously linked together, one of the most important factors for successful marketing. The geometry of the office areas results from a grid of 1.5 x 1.5 metres creating rectangular, more easily usable areas. Different office forms can be implemented: open work areas, combinations of open work areas, and private offices. The property developer’s brief to the architects was 10 m² of office space per person; although in all probability the building will never be used to its full extent, up to 4000 people can work in it at the same time. Swiss Re will be taking possession of its new headquarters gradually. The philosophy of continuous growth dictates that a building with twice as much space as currently necessary is being erected. Short-term leases will therefore be offered on the floors of the upper half.

According to the architects, the Swiss Re building will be the first skyscraper in London with partly natural ventilation. The pressure differences at the outer skin will be implemented to draw in fresh air through a vent running round the edges of the floor slabs. It will then be conveyed to the corresponding office areas via air outlets in the slabs. The waste air will be drawn off above the floors and into the space next to the façade, taking with it the heat being generated there, and then expelled either into the atriums or outdoors, depending on external conditions. The ventilation system is decentralized; each floor can be individually ventilated by means of a service plant in the core or in the slab areas. In addition to the natural ventilation, conventional air-conditioning can be switched in. This alternative option underwrites the flexibility of the office areas and takes account of the individual needs of future users. The atriums also contribute to energy savings through the high proportion of natural light they supply. Swiss Re stands out principally for uniting ecology and a high degree of user/occupant-friendliness with economic efficiency. Its planning entailed ecological requirements that were unusually stringent for high-rises in England, its structure is innovative and the organisation of the building is such that communication is fostered. This combination of qualities means that the future of the Swiss Re building is assured; it reacts to economic and ecological necessities, making it exemplary for commercial office high-rises in particular.