In this blog post, we introduce the principle of natural cooling utilising the unique ventilation structure of termite mounds and examples of energy-saving architecture that imitate this principle.
Mick Pearce, an environmental architect from Zimbabwe, built the East Gate Shopping Centre, a naturally air-conditioned building without air conditioners, in Harare, the capital of Zimbabwe, which maintains an indoor temperature of 24°C and saves 90% of energy costs. How is this possible in Africa, where the average annual temperature reaches 40°C? Architect Mick Pearce found the answer in African termites, which live undisturbed in their nests even when the temperature difference between day and night reaches 30°C. Termites regulate the temperature and humidity inside their nests using natural ventilation without any external energy supply.
Even when the temperature in the African savannah reaches 38°C at midday, the temperature inside a termite mound remains at a constant 30°C. The ventilation method that makes this possible is called the ‘termite mound principle.’ So, what is the termite mound principle? Termite mounds rise high into the sky, and their outer walls act as mortar (a mixture of cement and sand mixed with water).
Ventilation holes are made at the top to release hot air and at the bottom to let in cool air, and the holes are opened and closed as needed to maintain the indoor temperature. During the day, fresh air enters through the lower holes and is cooled by the cool air inside. The cooled air passes through the internal passageways and rooms, where its temperature rises, and then escapes through the upper holes. At night, when the air temperature drops, the air is discharged directly to the outside through passageways near the outer walls without passing through the rooms, cooling the heat accumulated during the day and regulating the indoor temperature.
The reason why the internal temperature can be maintained at 30°C even though the temperature of the outer walls is higher than 38°C is as follows. First, the outer walls of termite nests have excellent insulation properties. These insulated outer walls act as a primary barrier against changes in the outside temperature. Second, the scientific structure of the internal ventilation passages. During the day, fresh air passes through the lower passages and cools down, and this cooled air lowers the temperature in every corner of the rooms. When this air becomes warm, it is discharged to the upper part. The cool night air cools the heat accumulated inside through the passages near the outer walls. This is similar to the way houses in Stuttgart are arranged so that the wind can flow evenly throughout the village, and the termites arrange the air passages inside their nests to allow air to flow freely and open and close the air holes to control the direction of the air flow. In conclusion, termite mounds are energy-efficient structures that utilise passive design, using the difference in temperature between day and night to cool the interior, which is heated by the heat of the day, with cool air at night.
Passive design refers to a design method that avoids the use of mechanical heating and cooling systems and considers energy conservation. Through this, it can be seen that not only natural ventilation during the day but also night ventilation, which is natural ventilation at night, is a very effective passive system for saving cooling energy in summer in areas with large temperature differences.
Architect Mick Pearce’s East Gate Shopping Centre is a naturally cooled building without air conditioning that utilises night ventilation based on the principle of termite mounds. It is a nearly zero-energy building with almost no air conditioning costs, and it is desirable that it does not even use renewable energy, which requires high initial costs. In Korea, too, a lot of energy could be saved in building design if night ventilation could be utilised. Of course, it is not easy to apply this principle to all buildings in Korea, where the temperature difference between day and night is not large in summer. In particular, concrete apartments with high heat capacity do not cool down easily at night due to the night breeze, which does not differ greatly from the daytime temperature. However, in areas surrounded by rivers, forests, and mountains, the river and mountain breezes make the summer cooler than in other areas. The natural ventilation effect based on the termite mound principle can be partially applied to buildings in areas with these characteristics.
