Biomythology: Eastgate-gate 1 (or How the Eastgate Centre, Harare, is not like a termite mound)

December 11, 2012 by DaveParr 18 Comments

The Eastgate Centre, Harare, Zimbabwe, is a very famous building to environmental construction. Designed by Mick Pearce in conjunction with ARUP, the mixed office complex and shopping mall utilises thermal mass and a specific air change schedule, using high rates of mechanical night cooling, supplemented by smaller rates of passive ventilation during the day to keep air fresh and at the correct temperature. In addition fan power requirements are reduced by stack effect ventilation through the building, and the buoyancy effect generated by the occupants’ metabolic activities. The ventilation costs one tenth of that of a comparable building, saving $3.5 million in energy costs in the first 5 years.

What follows is a reworking of part my dissertation. Plagiarism is not encouraged. This work is protected through creative commons licences. The suggested academic reference is:

Parr,D., 2012, Biomimicry Lessons for Building Ventilation, Submitted for qualification of Environmental Design of Buildings MSc, at Cardiff University – Welsh School of Architecture. Treatment available at biomimicron.wordpress.com

UPDATE 23/04/2013: Since this set of articles was published, I have had the good fortune to get to talk to both Rupert Soar and Mick Pearce extensively about their work, and recieved information from Dan Phillips. In being able to get EVEN MORE information from all these people, I now feel that this series of articles is still only part of the discussion. There is nothing in these articles which is outright untrue, however they miss a significant proportion of Mick, Dan and Arups good work. Look out for Eastgate Now: Redux coming soon…

This is all very good design, which Pearce should rightly be very proud of. He uses building science and knowledge of the building function and occupant activity to create a thermally comfortable space with understanding of the local climate, using very little energy. He credits inspiration for this building to the termite mounds all across this region of Africa. The termites utilise wind driven and thermosiphon flow powered by the termites own bodies to accelerate ventilation through the nest. These methods lead to an extremely stable nest temperature, never varying more than 1 ^oC.

Pearce’s structure is built around a central chimney, with the hot air generated by his occupants being naturally drawn through convection out of the chimney, and the radiant heat being transmitted into the thermal mass, which further enhances the convection. At night electrical fans suck in cold air, which passes through the building, cooling the thermal mass and expelling heat out of the chimney again. The termites techniques have been clearly applied to the form of this building leading to reduced reliance on external power generation and so less external energy consumption from the wider national grid. The use of stack ventilation, electrical fans, thermal mass and buoyant air all mimic the processes of a termite nest.

In nature termites obviously don’t have a ‘power grid’ though and so bridge this energy deficit through micro-generation strategies. The fungus combs they cultivate are harvested locally, and transported to the base of the nest. Here a ‘delta primitive’ cast, subservient to the blue skinned Kree, load the terrigen crystals into the Nega-bomb enabling a  Cthulu Universe to enter through the tear in space and….

This picture is satirical

Wait a second. That’s the plot of Realm of Kings. Termites don’t have a method to ‘make up the deficit’ and power tiny fans, so what IS going on here?

1)    Termites have entirely passive structure

2)    Man makes building inspired by science based on termite nests

3)    Man’s building requires extra energy to function

Therefore there are two opportunities for a mistake here. Either:

a)    Man has misapplied correct science

b)    Man has applied incorrect science

The Inhabitat link above has got so much wrong (I’ve noticed Jill Fehrenbacher’s work is particularly prone to bad science) but they are by NO MEANS the only ones. Stick your guess as to which mistake, a) or b) it is in the comments. Part 2 next…

Biomythology: Eastgate-gate (or How the Eastgate Centre, Harare, is not like a termite mound) by Biomimicron: Parr, D is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.