The building takes maximum advantage of natural light. This is largely thanks to the light wells that are one of the building’s hallmarks. The light wells create the distinctive spiral design that wraps around the exterior. These triangular cutouts, six in each floor, allow penetration of daylight and fresh air to penetrate deep into offices. Floor-to-ceiling windows also contribute to the sense of openness.
Natural daylight and ventilation
The six fingers of accommodation on each floor, configured with light walls between, maximise daylight penetration, reducing the time that artificial lighting is required. Light level and movement sensors prevent unnecessary lighting, reducing energy consumption and cooling loads.
Wind pressure differentials generated by the building’s aerodynamic form assist natural ventilation through the light wells and reduce the requirement for conventional air conditioning. As a result energy consumption and carbon dioxide emissions are significantly reduced.
External envelope
The ventilated double skin façade reduces heating and cooling requirements. Its performance can be tuned to maximise benefits that the prevailing internal and external environment might offer. Blinds located within the cavity of the ventilated double skin façade intercept solar gain before it enters the office environment, intercepted heat can then be reclaimed or rejected depending on the requirement for heating or cooling.
Environmentally, its profile reduces wind deflections compared with a rectilinear tower of similar size, helping to maintain a comfortable environment at ground level, and creates external pressure differentials that are exploited to drive a unique system of natural ventilation.
Building systems
The building’s primary fuel is gas, one of the cleanest available. Low energy light fittings are specified wherever possible. De-centralised on-floor plant offers the flexibility to supply and control mechanical ventilation on a floor by floor basis. By closely matching supply with demand, energy consumption is reduced compared to a central system for the whole building.
Transportation
Comprehensive public transport facilities surround the site to reduce dependency on private cars without placing undue load on any one element of infrastructure. The provision of cycle spaces within the basement is three times that of the minimum standard required, which together with shower and changing facilities, encourages this alternative means of transport. There are no private car parking spaces in the building.
The exterior form of 30 St Mary Axe explores a series of progressive curves with the aid of parametric computer-modelling techniques. The shape and geometry have affinities with forms which recur in nature. The pinecone for example, has a natural spiral and, like this building, opens and closes in response to changes in the weather. The buildings smooth shape also directs air movement around the building and minimises the amount of wind at plaza level to improve pedestrian comfort. The external diagonal steel structure is by virtue of its triangulated geometry, inherently strong and light, permitting a flexible column-free interior space.
A common definition of sustainable development is given by the World Commission on Environment & Development 1997: “…development that meets the needs of the present without compromising the ability of future generations to meet their own needs”.
The exterior cladding consists of 5,500 flat triangular and diamond shaped glass panels, which vary at each level. The glazing to the office areas consists of a double-glazed outer layer and a single-glazed inner screen that sandwich a central ventilated cavity which contains solar-control blinds. The cavities act as buffer zones to reduce the need for additional heating and cooling and are ventilated by exhaust air which is drawn from the offices. The glazing to the light-wells that spiral up the tower consists of openable double-glazed panels with a combined grey-tinted glass and high-performance coating that effectively reduces solar gain.
The building uses the double skin façade system, which means there are two layers of glass skins. In this case both of the skins are single glazed, with open able internal skin mainly for fresh ventilation and maintenance.
The ventilated double skin façade also reduces heating and cooling requirements. Its performance can be tuned to maximise benefits that the prevailing internal and external environment might offer. The way this works is by having an air buffer in the cavity of the two skins, this air buffer will prevent heat loss form the inside of the building.