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

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 -

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, 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.

Eastgate is emulated by London's Portcullis House (2001), opposite the Palace of Westminster. The distinctive giant chimneys on which the system relies are clearly visible.”

 http://en.wikipedia.org/wiki/Eastgate_Centre,_Harare

“Architect Mick Pearce collaborated with engineers at Arup Associates to build a mid-rise building in Harare, Zimbabwe that has no air-conditioning, yet stays cool thanks to a termite-inspired ventilation system. The Eastgate building is modeled on the self-cooling mounds of Macrotermes michaelseni, termites that maintain the temperature inside their nest to within one degree of 31 °C, day and night, - while the external temperature varies between 3 °C and 42 °C. Eastgate uses only 10 percent of the energy of a conventional building its size, saved 3.5 million in air conditioning costs in the first five years, and has rents that are 20% lower than a newer building next door”

http://www.biomimicryinstitute.org/case-studies/case-studies/termite-inspired-air-conditioning.html