30 St Mary Axe, Swiss Re Headquarters

30 St Mary Axe is rooted in a radical approach & technically, architecturally, socially and spatially. Commissioned by Swiss Re, it rises fortyone storeys and provides 76,400 m2 of accommodation including offices and a shopping arcade accessed from a newly created public plaza. At the very top of the building is a club room that offers a spectacular 360degree panorama across the capital. Generated by a radial plan with a circular perimeter, the building widens in profile as it rises and tapers towards its apex. This distinctive form responds to the constraints of the site: the building appears more slender than a rectangular block of equivalent size; reflections are reduced and transparency is improved; and the slimming of its profile towards the base maximises the public realm at ground level. Its profile reduces the amount of wind deflected to the ground compared with a rectilinear tower of similar size, thereby helping to maintain pedestrian comfort at street level, and creates external pressure differentials that are exploited to drive a unique system of natural ventilation. The tower's diagonally braced structural envelope allows columnfree floor space and a fully glazed façade, which opens up the building to light and views. Atria between the radiating fingers of each floor link together vertically to form a series of informal breakout spaces that spiral up the building. These spaces provide places for refreshment points and meeting areas and function as the building's 'lungs', distributing fresh air drawn in through opening panels in the façade. This system reduces the tower's reliance on air conditioning and, together with other sustainable measures, means that the building is expected to use up to half the energy consumed by airconditioned office towers.