Cooling for the building is provided by groundwater pumped round the building from bore holes sunk to the level of London's water table. The water is further used to fill the lavatory cisterns before being flushed out and represents a considerable saving in energy use.
Natural shade from direct sunlight is provided by the distinctive stepped façade and any internally generated heat is recycled, obviating the need for chilling units.
The shape of the building, which is a modified sphere, is angled to ensure minimal heat gain in summer and minimal heat loss in winter and uses only 25 percent of the energy consumption when compared to a conventional four-square building of similar volume.
Directly to the west lies an amphitheatre fashioned from limestone owned by More London which, as a public venue, can accommodate up to 1,000 people and is known as 'the Scoop'.
The building's spiral ramp is 0.5 km (0.31 miles) long.
The building comprises public facilities, committee rooms and a meeting chamber which can accommodate up to 250 members of the public.
Every one of City Hall's glass panels is unique and is cut by laser.
City Hall was opened by Queen Elizabeth II in July 2002.
The top storey is referred to as 'London's living room' and leads out onto a balcony providing a fine 360˚ panorama of the city.
The building's floor space has the flexibility to be arranged from open-plan to cellular offices.
City Hall is clad with 3,844 glass panels (7,300 square meters) of triple-glazed, low E glass incorporating shading devices.
In 2007, solar panels were installed on the roof to further increase the building's environmental sustainability.
The building is one of the most energy efficient in London.
Although City Hall is owned by More London, the Greater London Authority has a 25-year lease on the building at an annual rent of £393 per square meter (£36.50 per square foot), whilst the British taxpayer paid for an internal fit-out.
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