The Eastgate Centre is a shopping centre and office block in central Harare

Harare

Harare before 1982 known as Salisbury) is the largest city and capital of Zimbabwe. It has an estimated population of 1,600,000, with 2,800,000 in its metropolitan area . Administratively, Harare is an independent city equivalent to a province. It is Zimbabwe's largest city and its...

, Zimbabwe

Zimbabwe

Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...

 whose architect is 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

Temperate

In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...

 climate despite being in the tropics, and the typical daily temperature swing is 10 or 40 °C. This makes a mechanical or passive cooling system a viable alternative to artificial air-conditioning.

Passive cooling

Passive cooling

Passive cooling

Passive cooling refers to technologies or design features used to cool buildings without power consumption, such as those technologies discussed in the Passive house project.-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
  Heat capacity , or thermal capacity, is the measurable physical quantity that characterizes the amount of heat required to change a substance's temperature by a given amount...
  
  , 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.

Eastgate is emulated by London's Portcullis House

Portcullis House

Portcullis House is an office building in Westminster, London, UK, that was commissioned in 1992 and opened in 2001 to provide offices for 213 Members of Parliament and their staff, augmenting limited space in the Palace of Westminster and surroundings....

 (2001), opposite the Palace of Westminster

Palace of Westminster

The Palace of Westminster, also known as the Houses of Parliament or Westminster Palace, is the meeting place of the two houses of the Parliament of the United Kingdom—the House of Lords and the House of Commons...

. 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

Arup

Arup is a global professional services firm headquartered in London, United Kingdom which provides engineering, design, planning, project management and consulting services for all aspects of the built environment. The firm is present in Africa, the Americas, Australasia, East Asia, Europe and the...

, gave Pearce a set of rules.

They said that no direct sunlight must fall on the external walls at all and the north façade [direction of summer sun] window-to-wall area must not exceed 25%. They asked for a balance between artificial and external light to minimize 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

Termite

Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...

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.

Pearce's practice is in Harare, and he specialises in buildings which are low cost, low maintenance, and have low environmental impact. His projects try to make best use of locally available resources, and include Harare International School Arts Centre, Harare Hindoo Temple and Chinhoyi

Chinhoyi

Chinhoyi is a large provincial town and is the capital of Mashonaland West province in Zimbabwe. Sinoia was established in 1906 as a group settlement scheme by a wealthy Italian called Lieutenant Margherito Guidotti who encouraged 10 Italian families to settle there.- Overview :Chinhoyi is located...

 Provincial Hospital, Zimbabwe. In 2003 Pearce was awarded the Prince Claus Award for culture and development, for his work on Eastgate.

External links

• ArchNet Digital Library Photographs and diagrams of the Eastgate Centre.

See also

• Biomimetics
  Biomimetics
  Biomimetics is the study of the structure and function of biological systems as models for the design and engineering of materials and machines. It is widely regarded as being synonymous with biomimicry, biomimesis, biognosis and similar to biologically inspired design.-History:The term biomimetics...
  
  
• Energy conservation
  Energy conservation
  Energy conservation refers to efforts made to reduce energy consumption. Energy conservation can be achieved through increased efficient energy use, in conjunction with decreased energy consumption and/or reduced consumption from conventional energy sources...
  
  
• Passive solar
• Solar chimney
  Solar chimney
  A solar chimney — often referred to as a thermal chimney — is a way of improving the natural ventilation of buildings by using convection of air heated by passive solar energy...
  
  
• Architecture of Africa
  Architecture of Africa
  The architecture of Africa, like other aspects of the culture of Africa, is exceptionally diverse. Many ethno-linguistic groups throughout the history of Africa have had their own architectural traditions...
  
  

Further reading

• "Sustainable Architecture", The Architectural Review, UK, Sep 1996.
• Baird, George (2001). The Architectural Expression of Environmental Control Systems. Spon Press. ISBN 0-419-24430-1
• Gissen, David (2003). "Big and Green: Toward Sustainable Architecture in the 21st Century. Princeton Architectural Press. ISBN 1-56898-361-1