Wednesday, May 25, 2011

CONSTRUCTION - The best architects? Termites

At the heart of the African savannah stands a city that is a model of sustainable development. Its towers are built entirely from natural biodegradable materials. Its inhabitants live and work in air-conditioned spaces and moistened, without consuming a single watt of electricity. The water comes from deep wells and the residents support themselves by growing food gardens within the city.

This metropolis is not only environmentally friendly, with its curved walls and elegant arches, it also has a certain beauty. This is not a human city, of course. It is a termite mound. Unlike termites and other insects that build nests, we humans are concerned about some designing buildings in harmony with our environment.

"We can apply absurd architectural ideas without incurring the penalty of Natural Selection," observes architect Juhani Pallasmaa, University of Technology Helsinki, Finland. But now that we are aware of climate change and depletion of resources, how insects manage their habitat creates renewed interest.

For it seems we have much to learn from them. "We do not understand very well the processes of construction and design principles of insect nests," says Guy Théraulaz, Research Centre on Animal Cognition CNRS in Toulouse. This is not for want of trying. Research on the mounds built by termites began in the 1960s, when the Swiss entomologist Martin Lüscher conducted a series of groundbreaking studies on nests shaped by termites in the genus Macrotermes plains of southern Africa.

It was he who advanced the idea that these mounds are in fact chaotic appearance of green buildings beautifully designed. He has demonstrated a strong link between type of building mounds and feeding termites. The species of Macrotermes feeds on cellulose, a component of plants that humans can not digest either termites, indeed.

But these insects have solved the problem by growing mushrooms for turning wood into digestible nutrient. These crops must be well ventilated, and temperature as their carefully controlled humidity, which is no small matter in tropical climates where termites live. To maintain the temperature and humidity at constant levels while removing carbon dioxide (CO2), we need a gas exchange process very efficient.

A mound type, which has 2 million termites must "breathe" a thousand liters per day of fresh air. To determine the conditions for such an exchange, Scott Turner, a termite specialist at the University of the State of New York at Syracuse, and Rupert Soar, the architecture firm Freedom Engineering, Nottingham, studied the principles Design of Macrotermes mounds in Namibia.

They found that the walls were warmer than the center of the nest. According to them, the aeration is done by the turbulence generated by winds that sweep the hills. A simple breath contains small eddies and current speeds and direction of propagation varied frequencies of rotations ranging from very fast to very slow.

But the outer walls of the mounds are constructed so that only the slowly rotating vortices can penetrate inside. The range of frequencies ranging from wind gust to another, stale air of the nest and the fresh outdoor air moving inside the mound, which ensures the exchange of two streams.

In other words, the mound works like a giant lung. This mode of ventilation differs radically from that of modern humans buildings where fresh air is pumped through pipes to reject the stale air outside. Scott Turner is convinced that there are lessons to be learned from the construction method for termite mounds.

We should not design the walls as barriers to prevent outside air from getting inside, but rather as flexible and permeable interfaces that govern the exchange of heat and air between the inside and outside. "Instead of opening a window to let in fresh air, what are the walls that play this role, but by careful filtering the air as in the mounds," he said.

The ideas of the expert - and many others - were discussed during a workshop on the architecture of insects held in Venice in 2009 by Guy Théraulaz. The purpose of this meeting was to gather knowledge from various professions, the entomologist to the architect. "Common features began to emerge, said Scott Turner.

Many biologists believed that architects had to learn a lot from us. I think the reverse is also true. "One of the topics of discussion was the ability of termites to adapt their structures to local conditions. In very hot climates, for example, termite mound bury them deeply in this vast heat sink that is the ground, a very effective way to control the temperature.

Other species maintain moisture by depositing a mixture of wood and grass chewed on the mound this mixture acts like a giant sponge, able to release or absorb up to 80 liters of water to offset changes humidity inside the nest. Such a method could be used to moisten the buildings in hot and dry areas by placing water tanks in their foundations.

"Now that we better understand this regulatory process, new horizons open before us to develop biological design principles", welcomes Scott Turner. One could also draw on methods of construction employed by insects. The paper wasp, so named because of the fibrous material it uses to shape its rays, is one of the insects that nest building has been most studied.

The spokes are made of tubular cells and hexagonal sections, even though their designs are extremely varied, their configuration is not a coincidence. To understand the mode of construction beams, Guy Theraulaz and his colleagues gave chewing wasps paper of different colors for each stage of nest building.

It showed that the wasps observe building regulations based on the configuration of neighboring cells. "For example, they prefer to add cells to a corner rather than start a new row," said French researcher. None of the wasps have a clue what will be the final structure, but by following a set of rules - shaped by evolution and maximizing the chances of survival of insects - the group manages to build a nest very well designed .

Termites arrive at a similarly satisfactory using chemical signals called pheromones. Chewing pellets ground to form a kind of cement, workers release a chemical that, for a few minutes, may be perceived by those who are in their immediate vicinity. It follows a chain reaction in which more pillar rises, it becomes a major source of pheromones and more termites are encouraged to add more mud.

This process is contrary to the idea of design and control of human and make a plan by an architect and stick scrupulously. But Scott Turner believes that if technological advances allow us, we could adopt more similar to those of these insects. "There are huge opportunities," says he, for robotics, which could create networks of agents connected by a decentralized information that can reshape the structure of the building depending on local conditions.

"Such an assumption may seem fanciful but it's just a return to old practices of human organic construction and design of habitat, in which additions and modifications were made piecemeal in response to circumstances. Termites are often faced with similar problems of housing and we respond more effectively and sustainably.

"A mound is in many respects as alive as the termites that build it", said Scott Turner. Perhaps the buildings of the human will they too in the near future.

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