City Hall, London
City Hall is the headquarters of the Greater London Authority (GLA) and serves as the official office for the Mayor of London and the London Assembly. Located on the south bank of the River Thames in Southwark, the building was designed by the award-winning architect Norman Foster, who drew inspiration from his earlier work on the renovation of Berlin's Reichstag. It was constructed at a cost of £43 million and opened in 2002.
The building is part of the More London development that encompasses retail, business and restaurant space on the south bank between London Bridge and Tower Bridge. Adjacent is the sunken amphitheatre The Scoop, designed to look as though the City Hall building has been scooped out of it.
It has a distinctive bulbous design derived from a modified sphere which means the building has no conventional front or rear. Each level is slightly offset from the one below, making it hang over one side of the building. As such, it has been compared to a motorbike helmet, a misshapen egg, and a woodlouse. Former mayor and inhabitant Ken Livingstone referred to it as “a glass testicle”, while his successor Boris Johnson opted for the nickname “The Onion”.
The top of the building houses an exhibition and meeting space called 'London's Living Room' with an open viewing deck across the Thames, said to represent the idea of transparency, which is open to the public on occasion.
The building was designed using advanced computer-modelling techniques that 'enabled a radical rethink of architectural form' according to architects Foster + Partners. The unusual shape was intended to achieve optimum energy performance by maximising shading and minimising the surface area that is exposed to direct sunlight.
The building's almost-spherical shape means it has around 25% less surface area than a cube building of the same volume, and so less heat escapes during winter and the building avoids overheating during summer. However, critics have pointed out that the excess energy consumption caused by the exclusive use of glass far outweighs any benefit of the shape.
Inside, a 500 m (1,640 ft) helical walkway spirals up to the full height of the 10-storey building.
 Energy efficiency
The energy efficiency of City Hall has been the subject of some confusion and controversy.
It was specifically designed to keep carbon emissions as low as possible. In addition to the building's shape, cold ground water from the Thames water table is brought up through bore holes where it flows through beams on each floor to chill the office spaces, thereby reducing electricity consumption from air conditioning systems, and is then used to flush toilets. The building is also naturally ventilated, with user-operated vents beneath every window.
Despite claiming to 'demonstrate the potential for a sustainable, virtually non-polluting public building', its energy use measurements were initially shown to be fairly inefficient; at one time achieving a 2012 Display Energy Performance Certificate rating of 'D'. Improvements have been made since construction was completed, and in 2014/15, City Hall emitted 1,985 tonnes of carbon dioxide, which it claims is 'better than the average amount for similar buildings'.
Some of these improvements are as follows:
- Solar photovoltaic panels installed in 2007.
- 'Voltage optimisation' technology was installed to reduce the voltage used to the minimum required.
- Changing from 75 watt bulbs to 16 watt LEDS where possible, with movement sensors on all floors.
- 'Boiler optimisation' to ensure that no more heat is generated than required.
- Smart meters that allow energy use to be measured on a floor-by-floor basis.
 Project data
- Address: Southwark, London.
- Architect: Norman Foster.
- Structural engineer: Arup.
- Construction manager: MACE.
- Height: 45 m.
- Construction start: 1998.
- Construction completed: 2002.
- Tenants: Greater London Authority.
- Owner: More London Development Ltd.
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