1. 0°C is probably warm enough:
Figure 1: One of the world’s great achievement in the harshest environment on Earth (Wikipedia)
When the “brief” is to survive and avoid freezing to death in an environment where temperature averages at -45°C, there really is no room for excessive decorations or aesthetic considerations. Its inhabitants and creators – the Inuit people (or ‘Eskimo”) – as a result possess an acute awareness and understanding of where they live. From the Bering Straits of Alaska to Greenland, they, over thousands of years, have mastered the skills of catching fishes, seals, as well as navigation & spatial cognition, and the ability to make everything from harpoons, net gauges, vessels to clothing with the minimum amount of resources. Their snow house, also known as Igloo, is among the most spectacular engineering works. The dome is the only possible shape that suits the intent since it mathematically requires the least amount of material to encase the maximum volume possible. Each block of snow is placed in spiral sequence upward, hence no formwork is required. In applied mechanic, the shape used in igloo is known as catenoid which offers optimal balance between height and diameter without the risk of collapsing under the weight of compacted snow. As a result, thicker walls can be used for better insulation without the fear of additional weight. The material must be snow, not ice since snow is constantly at O°C, while ice can be much colder. Snow block, as ironic as it sounds, has great thermal performance due to the air pocket inside acting as a great insulation. The blocks selected have to be strong, easily cut without breaking and stackable.
Figure 2-4 (left to right): Section through the igloo; spiral construction of the snow blocks, principles of ventilation and cold air sink (picture link)
The area excavated for snow block is also used as the lower half of the shelter which is sometimes connected to a short tunnel to reduce wind and heat loss. Because ‘cold air sinks and hot air rises’ this act as a cold trap, while the sleeping area is raised to take advantage of the heat from stove, lamp, etc. Moreover, the dome shape ensure that there is no internal corners to avoid condensation. The inside surface is slightly melted for better bondage and sealant between blocks. This is also one of the reason that snow must be used instead of ice, since the nature of snow can allow melting on the surface and refreeze afterward, whereas ice will melt continuously throughout. Consideration must also be paid to air ventilation large enough for the escape of carbon dioxide emitted from the inhabitants, without losing too much heat. Inuit people can further improve the thermal performance by lining the inside surface with animal skin, to help them through a long winter. Igloo is the highest form of passive housing in extreme cold climate. All of this genius understanding of material and construction technique resulted in the internal temperature of about -7°C-16°C. That is a 50°-60°C different achieved compared to the outside temperature, with no assisting mechanical system whatsoever. Since the 1950’s, Inuit have lived in permanent communities, with homes, supermarkets, and very few still use igloos.
2. Hot N Cold:
Disclaimer: This is not about Katy Perry’s hit song!
Figure 5-6 (left to right): Urban fabric of Yazd, Iran (picture link); Shibam – “the Manhattan on the desert” (Wikipedia)
Let’s now go to the other extreme. In areas with desert climate like Yazd in Iran, temperature between day and night can fluctuate between 46°C to -20°C. To battle such harsh environment, sun-dried mud brick & rammed earth have been predominantly used as building materials due to its large thermal lag property. During the day, these earth structures insulate well against high temperature. At night, the absorbed heat is slowly released to keep the inside warm. At an urban scale, villages & towns follow a compact layout so that walkways, streets and corridors are shaded as much as possible by buildings, reducing heat absorption during summer as well as avoiding heat loss and wind during winter. The design strategy also considers : the use of plants, ponds, bright colours painting, small windows & vents in order to further improve the overall thermal performance.
Figure 9-10 (left to right): Plan and section of the ice house (picture link)
It works so well that not only the internal temperature are kept reasonably cool but even ice can also be made and maintained without any assisting mechanical systems. The structure comprises of an egg-shaped cistern with underground chamber and a long shallow channel which is shaded by a great wall as high as 12m made from excavated earth that form the channel itself. Due to the constant shading and the freezing temperature at night, water in the channel turns to ice which is then collected and stored in the underground chambers. With the help of straw and sawdust as insulation, ice can remain frozen for many months. Another feature that characterises desert vernacular architecture is the windcatcher. Depending on wind directions, windcatcher can have one, four or eight openings and functions in three ways:
1. catching cooler breezes into the building
2. dragging hot air through an underground canal (qanat) where it gets cooled down and travels through the building
3. dragging hot air out due to pressure gradient
Figure 11-13 (left to right): Windcatcher and how they works (Wikipedia)
To sum up, what can be taken from such marvels of construction is not an advocacy to return to these vernacular structures (igloo is very inconvenient and uncomfortable, regardless of how great they perform), but to admire and learn from these truly amazing feat of architectures and their ability to blend science with native traditions.
1. Kazemi, A. G. & Shirvani, A. H., “An Overview of some vernacular techniques in Iranian Sustainable Architecture in reference to cistern and ice houses”, Journal of Sustainable Development, Vol.4 No.1, February 2011
2. Saraydar, M. & Arabi, R., “Climate Effect on Architecture: A comparative study between climate-responsive architecture of Iran and Egypt “, Current World Environment, Vol.10 Issue 01, 2015