Eastgate Centre, Harare
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The Eastgate Centre is a shopping centre and office block in central
Harare Harare (; formerly Salisbury ) is the capital and most populous city of Zimbabwe. The city proper has an area of 940 km2 (371 mi2) and a population of 2.12 million in the 2012 census and an estimated 3.12 million in its metropolitan ...
,
Zimbabwe Zimbabwe (), officially the Republic of Zimbabwe, is a landlocked country located in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Botswana to the south-west, Zambia to the north, and Mozam ...
, designed by Mick Pearce. Designed to be ventilated and cooled by entirely natural means, it was probably the first building in the world to use natural cooling to this level of sophistication. It opened in 1996 on Robert Mugabe Avenue and Second Street, and provides 5,600 m² of retail space, 26,000 m² of office space and parking for 450 cars.


Designing for thermal control

The Eastgate Centre's design is a deliberate move away from the "big glass block". Glass office blocks are typically expensive to maintain at a comfortable temperature, needing substantial heating in the winter and cooling in the summer. They tend to recycle air, in an attempt to keep the expensively conditioned atmosphere inside, leading to high levels of air pollution in the building. Artificial air-conditioning systems are high-maintenance, and Zimbabwe has the additional problem that the original system and most spare parts have to be imported, squandering foreign exchange reserves. Mick Pearce, the architect, therefore took an alternative approach. Because of its altitude, Harare has a
temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...
climate despite being in the tropics, and the typical daily temperature swing is 10 to 14 °C. This makes a mechanical or passive cooling system a viable alternative to artificial air-conditioning.


Passive cooling

Passive cooling works by storing heat in the day and venting it at night as temperatures drop. * Start of day: the building is cool. * During day: machines and people generate heat, and the sun shines. Heat is absorbed by the fabric of the building, which has a high
heat capacity Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin (J/K). Heat capacity i ...
, so that the temperature inside increases but not greatly. * Evening: temperatures outside drop. The warm internal air is vented through chimneys, assisted by fans but also rising naturally because it is less dense, and drawing in denser cool air at the bottom of the building. * Night: this process continues, cold air flowing through cavities in the floor slabs until the building's fabric has reached the ideal temperature to start the next day. Passively cooled, Eastgate uses only 10% of the energy needed by a similar conventionally cooled building.Architects for Peace. Profile and excerpt from th
jury report
of the 2003 Prince Claus Award, presented to Mick Pearce on 10 December 2003.
When actively cooled, the Centre consumes 35% less energy to maintain the same temperature as a conventionally cooled building.Video, National Geographic. Eastgate is emulated by London's
Portcullis House Portcullis House (PCH) is an office building in Westminster, London, United Kingdom, that was commissioned in 1992 and opened in 2001 to provide offices for 213 members of parliament and their staff. The public entrance is on the Embankment. Part ...
(2001), opposite the
Palace of Westminster The Palace of Westminster serves as the meeting place for both the House of Commons of the United Kingdom, House of Commons and the House of Lords, the two houses of the Parliament of the United Kingdom. Informally known as the Houses of Parli ...
. The distinctive giant chimneys on which the system relies are clearly visible.


Modern use of traditional solutions

To work well, the building must be very carefully designed. After computer simulation and analysis, the engineering firm
Ove Arup Sir Ove Nyquist Arup, CBE, MICE, MIStructE, FCIOB (16 April 1895 – 5 February 1988) was an English engineer who founded Arup Group Limited, a multinational corporation that offers engineering, design, planning, project management, and ...
, gave Pearce a set of rules.
They said that no direct sunlight must fall on the external walls at all and the north façade irection of summer sunwindow-to-wall area must not exceed 25%. They asked for a balance between artificial and external light to minimise energy consumption and heat gain. They said all windows must be sealed because of noise pollution and unpredictable wind pressures and temperatures, relying on ducted ventilation. Above all, windows must be light filters, controlling glare, noise and security.
To help with this last, the windows have adjustable blinds, but Pearce also used deep overhangs to keep direct sun off windows and walls. Deep eaves are a traditional solution in Africa, shading the walls completely from the high summer sun, while allowing the lower winter sun to warm the building in the morning. Further, passive cooling systems are particularly appropriate for this part of Africa because, long before humans thought of it, passive cooling was being used by the local
termite Termites are small insects that live in colonies and have distinct castes (eusocial) and feed on wood or other dead plant matter. Termites comprise the infraorder Isoptera, or alternatively the epifamily Termitoidae, within the order Blattode ...
s. Termite mounds include flues which vent through the top and sides, and the mound itself is designed to catch the breeze. As the wind blows, hot air from the main chambers below ground is drawn out of the structure, helped by termites opening or blocking tunnels to control air flow.


See also

* Biomimetics * Energy conservation *
Passive solar In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unli ...
*
Solar chimney :''This article refers to a device for ventilation. For the power generation technology, see Solar updraft tower.'' A solar chimney often referred to as a thermal chimney is a way of improving the natural ventilation of buildings by using convect ...
*
Architecture of Africa Like other aspects of the culture of Africa, the architecture of Africa is exceptionally diverse. Throughout the history of Africa, Africans have developed their own local architectural traditions. In some cases, broader regional styles can be id ...


Notes


Further reading

* "Sustainable Architecture", ''The Architectural Review'', UK, Sep 1996. * Baird, George (2001). ''The Architectural Expression of Environmental Control Systems''. Spon Press. * Gissen, David (2003). "Big and Green: Toward Sustainable Architecture in the 21st Century''. Princeton Architectural Press.


External links

* Retrieved 31 January 2006. Full text available to subscribers only.
"Learning from Termites"
AIArchitect. Retrieved 1 February 2006.
ArchNet Digital Library
Photographs and diagrams of the Eastgate Centre. {{Coord, 17.831, S, 31.053, E, display=title, source:dewiki Buildings and structures completed in 1996 Shopping malls in Zimbabwe Low-energy building Shopping malls established in 1996 Buildings and structures in Harare Tourist attractions in Harare