The Efficient Thermal Properties of Yurts and Tongkonens

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Yurt is a type of dwelling that originated in Mongolia, in Central Asia. It is a dwelling that the Nomads used years ago and which is still being built to date. The nomads were communities that travel from one place to another consistently, with their respective livestock. Yurts are mainly located on deserted lands such as steppes and tundra.

Yurts were built in such a manner that they can be easily dismantled, built and carried around. An approximate of thirty minutes to three hours is required to assemble and dismantle such yurts. These are self-supported structures with a strong framework. In strong winds it is likely that such structures remain firm to the ground due to the way the structural elements act as a whole. The structure consists of a conical roof system with a crown on top which exerts a force on the walls beneath it. These walls are tied to the door frame so as to create a complete circle. The external top layer provides extra rigidity and firmness to the structure which help in keeping the yurt attached to the ground. The materials used can be obtained locally and from their own livestock. This is due to the fact that willow branches and felt are used. The felt will act as insulation and as a water proofing. Covers of around 6 meters in diameter can be produced with an approximate number of 180 fleeces each. The preparing of these fleeces was generally done by the women of the communities; rubbing, rolling and watering are some of the techniques applied to obtain the final product.

The average temperature in Mongolia varies from -400C in winter up to +400C in extreme summer days. Thus, the yurt had to be designed in such a way that thermal comfort is present in both extreme cases. To cater for this, a crown, situated at the top and in the centre of the roof was used so that air circulation is achieved by allowing fresh air to circulate regularly. This is attained by having cold air sinking downwards and hot air rinsing upwards. This system provides fresh air being distributed evenly throughout the internal layout.

Yurts have a shape that provides a very thermal efficient temperature on its own. Thermal comfort is achieved by the way it is constructed and is good for both the long, dry and cold winters and the warm summer days. In winter, smoke from stoves using wood can be used to keep the internal plan warm without further insulation when the temperature goes down to -50C. When temperatures get below -400C, thicker felts are used to help in keeping the internal layouts warm. On the other hand in hot weather, sides are lifted slightly upwards with belts increasing air flow to create a pleasing environment. Moreover, a cover is placed on top on the crown so as to prevent warmth from sun radiating through it. With regards to rain periods, this cover will also be used to keep the internal layout of the yurt dry.

Tongkonen is the traditional house of the Toraja People who live in the Sulawesi Province in Indonesia. These are houses situated in a Tropical climate zone where relative air humidity is high, 60 to 100%, it is subjected to precipitation and the average temperature is around 300C with low fluctuations between night and day. Hurricanes and typhoons are common in such climate conditions. Tongkonen houses not only serve as a dwelling for domestic purposes but it is also an informative centre, ritual centre, and the legend of families. Thus only rich noble families and custom leaders can erect such structures.

‘Tongkonen’ is always facing towards the North, since the Toraja people believe that North symbolizes life. The rice barns also referred to as ‘alang’ are then placed in front of these buildings facing south. The space created in the middle is known as parampa and it is the place where crops are left to dry, children play, women work and men arrange cock fights. Some rooms that are found in the tongkonen are called tangdo, Sali and sumburg. Stairs and sleeping areas for in-married girls are found in the first room. On the other hand, sali is the main living area for the whole family which also serves as a sleeping quarter to unmarried men of the family and the servants. A rectangular shaped box known as the hearth, is also found in this room, and is used both for cooking and for heating purposes. Finally there is the sumburg room which is the room dedicated to the master of the house and his wife.

The structure is then divided into two parts; the space structure, which is also divided into two, and the building structure. The space structure consists of the user and the type of activities done by different users. This is illustrated on the latter sketch.

On the other hand each element of the building structure is named accordingly. It has got a square base with a large saddleback roof. The front and rear sides of the roof are over hanging known as longa. ‘Tulak somba’, are columns that are used to support the longa on either side. Stone, wood and rushes are materials used to construct such a building. Stone was used for the foundations of the building while the columns, walls and roofs were done by local timber and the roof was covered with bamboo as the construction was generally found in native forests and nature. Carpentry tools and wood carvers were also used by the Toraja people to build their homes and they also managed to construct scaffolding made out of bamboo to finalise their work.

Tulou Buildings are found in the Wuyi Mountains of Fujian situated in the South East of China. They are found in the subtropics which are classified as an area that is subject to humid, hot summer and mild to cold winters.

The Hakka people were considered to be the first ethnic group to build such Tulou. However, evidence shows that these buildings were built way before their arrival. This ethnic group migrated from the North of China to the Southern part between the fourteenth and the fifteenth century. Therefore they had to settle in the mountains and in less fertile lands due to their late arrival. Different ethnic groups had various conflicts and family feuds. Thus, the Tulou had to serve as fortification that separated the groups accordingly. This is the reason why Tulous are surrounded by walls of clay up to 1.5 meters in depth and 18 meters in height with an iron clad portal and also with places for weapons.

There are two types of Tulou; one is circular in shape while the other is rectangular in shape. The construction of such Tulou was done by peasants, and skilled workers were only assigned to build complex masonry and carpentry works. The outer wall in both cases separates the village pathways from the uniform small rooms overlooking a common courtyard. The walls’ thickness reduces with height and they are also inclined inwards as the height increases. The majority were built out of a composite material known as ‘sanhetu’; this consists of a mixture of earth, lime and sand compacted together. Stamping is required to erect the wall requested; thus, a two metre wooden mould is needed to compact the material evenly. To be successful maximum strength is required and also each layer should be left to dry completely between layers respectively. The walls are reinforced by split bamboo canes between layers and L-shaped cedar branches for the corners in order to minimize erosion. Whitewash was applied to facades acting as waterproofing and also it helps in reflecting solar heat reducing indoor temperatures.

Xiao Sun, Quindi Li and Xudong Yang studied the indoor thermal environment in three of the Nanjing Tulou Buildings together with thermal comfort and the energy consumption for both summer and winter. The results were as follows:

  • Typical Summer Day : maximum outdoor temperature was 350C while the maximum indoor temperatures were 280C, 28.60C, 28.90C respectively
  • Typical Winter Dar: minimum outdoor temperature reached 9.90C while minimum indoor temperatures were 15.80C, 14.40C, 13.80C respectively.

Results showed that when comparing Tulou buildings with rural buildings the thermal comfort in Tulou buildings was higher than those of the rural and average consumption per household was lower as well. Moreover, a Tulou building model was done to study these results and in the end it was concluded that ventilation in summer and air tightness in winter together with thick walls help in creating suitable thermal comfort for different climates accordingly.

The three case studies mentioned above are different and distinct from one another. Yurts and Tongkonen are still being built today with only few material changes. This shows how important their construction was back in old times. A rounded shape is common in both the yurt’s case study and the Tulou one. However, they are constructed in a completely different manner. One is lightweight and can be portable and the other is permanent and monumental respectively. They also serve in their own ways good thermal environment throughout the year under different climate conditions. The thick walls used in the third case study and the fabric used in the first one, both help in keeping a constant air temperature inside. Comparing the two together, one will notice that people tried to build their residents according to their needs. The nomads had to travel a lot so they used lightweight structures while the hakka people had to defend themselves from their rivals and built huge houses to house large groups. Moreover, for Tongkonen dwellings large roofs had to be built to protect residents from their constant hot climates. With respect to nomads, they had an opening in the middle to allow for sunlight in cold days to warm up the inside which could then be closed during hot days. . However, all dwellings were built for one reason that is to house individuals from different climates with different materials found in respective regions.