The construction and development sector is a critical supporter of greenhouse gas emissions. They are transmitted when building materials are manufactured, buildings are constructed and energy is utilized in structures during their operations. According to the 2019 Global Status Report for Buildings and Construction, the buildings and construction sector accounts for over 40% of energy-related greenhouse gas emissions. Many of the naturally available and local building materials may not be sustainable in the long run. As a result, many of the building materials may become scarce. Hence, it is high time we begin looking for more sustainable building materials. However, we don't need to go out and find new materials; instead, we need to go back and reintroduce traditional building materials and procedures. Kerala traditional architecture is one such example that still largely uses sustainable building materials. This blog investigates some of these sustainability lessons we can learn from the building materials, and the vernacular architecture of Kerala.
List of Contents
1. Traditional Architecture of Kerala
Traditional Kerala architecture, as elsewhere, evolved in response to the climate, local materials, and socio-economic conditions. The traditional architecture of Kerala is modest. Houses never acquired the grandeur of North Indian palaces or bungalows; they were simple, small and refined. The most prominent feature of traditional buildings is the sloping roof with ‘eaves’ (roof ears). It hangs low, shielding the walls from rain and harsh sunlight, thus, keeping the interiors cool. The carpenters also considered the roof design as one of the most important and difficult parts of constructing a house.
The Padmanabhapuram Palace shown below is an example of the traditional Kerala Architecture with noteworthy roofs. Consequently, the rich lived in houses made of laterite blocks, lime, timber and clay tiles while poorly constructed houses used less permanent building materials such as earth, bamboo and coconut leaves. However, the predominant features of the sloping roof are visible in all the houses, irrespective of their economic status.
2. Natural Materials Vs Local Materials
Gandhi Ji suggested in a conversation with Sri Laurie Baker that the ideal home should be built with materials that are available within a five-mile radius of the site. There is a difference between local materials and natural materials. Natural materials may not be available locally, so they might not be completely sustainable. But local materials can be both natural, and sustainable. For example, natural materials such as marble may not be available locally, and as a result, they may not be sustainable because of the extra energy used for their transportation. Having said that, traditional Kerala architecture uses local materials, that are also sustainable. Bamboo, earth, lime, timber, leaves etc., are some of the commonly used building materials in Kerala. In addition to being sustainable building materials, they are available locally and are suitable for the hot humid climate of the state.
3. Traditional Building Materials in Kerala
In earlier times, several large buildings were built using earth or mud. The sun-dried mud bricks may be used for the second storey of a two-storey building, with the ground floor made of laterite. They may also be used for the less important parts of buildings. The use of earth blocks (without ramming or sun-dried bricks) was popular among the poorer sections of society. Many buildings constructed with laterite also use earth as mortar, to save the cost of construction. The general impression of the public is that a building with earth blocks is sustainable. But in many cases, it need not be true.
The cost of the superstructure of a building is only 15-20 % of the overall cost of construction, meaning the rest of the building units need not be sustainable at all. When the earth from the building site is utilised, it becomes very sustainable. But if the material has to be transported over a distance, then the embodied energy will go up, reducing the sustainability factor. Strengthening of earth blocks by cement will also reduce the sustainability aspect. On the other hand, if interlocking earth blocks are used, then the sustainable character will be more since no cement mortar is involved.
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In Kerala, the foundations were usually built with laterite blocks. Laterite is a hardened earth layer formed due to the weathering of acid rocks. It is dug out from the earth and its compressive strength can be higher than that of burnt bricks. It is very non-porous and cannot hold water. Usually, it is found 3 to 15 metres below the ground. The top one to two metres will be soft and the bottom merges with the clay layer. Laterite can be called the “Blessing of Kerala” since 80% of the state is covered with it. When my father constructed a house in my village, the laterite was quarried from the site itself.
Laterite has been widely used for constructing the superstructure. The use of burnt bricks for construction was rare except in the case of a few palaces. Nowadays, the laterite can be machine cut. The advantage of this is that the blocks have much higher compressive strength. The disadvantage is that these are transported over a long distance, ergo the process involves more energy.
Lime obtained from shells was burnt in kilns and used as mortar for the buildings. Lime was produced by beating it vigorously with a stiff bristle brush, after adding water. Lime was beaten with a special wooden tool in tanks specifically made for this purpose. This process helped in increasing its strength and workability, thereby reducing the amount of water to be added. This is beneficial as the strength of lime further improves when less water is used, and when it is air-dried. Many organic items were also added to increase the strength of the lime mortar.
In our textbooks, we learn more about the disadvantages of lime such as it is slow setting, not having enough strength etc. But lime is very sustainable as a binding material as numerous studies show that it is much less energy-consuming when compared with cement. Cement is a high energy-consuming material with limestone as one of the main ingredients for its manufacture. When cement is used as mortar in a wall, the bricks cannot be recovered for re-use, if the building is demolished later. Conversely, if lime is used, the bricks can be reused, which ultimately makes lime mortar more sustainable.
Granite is the most common stone used for construction in Kerala. The state does not have deposits of limestone or sandstone. Granite is very hard and is used in the foundations. It has been rarely used for the superstructure, until recently. There was a time when I thought of granite as a sustainable building material, but things are quite different now. In the olden days, it was very much a local material, but now big quarries have come up in the western ghats, many of whom are present in vulnerable and fragile areas. Granite that is being quarried from these places is not sustainable, because of the harmful effects it causes on our environment in the form of landslides and other natural disasters.
Timber is one of the foremost building materials in Kerala. It was widely available with many varieties being highly durable as well. Teak, jack wood, anjili wood and thembavu were commonly used. Buildings with timber walls were built in Travancore till about 100 years ago. The traditional architecture of Kerala extensively uses timber for walls, doors, windows, intermediate floors and roofs. Timber resources were in short supply towards the end of the 19th century, as a result of the advent of the development of the railways. Although there were many private forests, in due course of time, the Government wanted to have the monopoly on the kinds of timber that were generally used for house construction. Therefore, laterite began to be used for walls, instead of timber.
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Because of the prominence of timber in the traditional architecture of Kerala, the carpenters were the head craftsmen. Since there was little masonry work, masons were of negligible importance. (Arayum Nirayum). According to me, timber is going to be the future building material. Unlike earth, burnt bricks, granite etc., this is a material that can be renewed and recycled. The biggest advantage of timber is that by using them in our buildings, the carbon gets locked. Trees are the only things that can convert carbon dioxide in the atmosphere into oxygen. If timber is allowed to decay or used as firewood, then the carbon is released back into the atmosphere, thereby completing the carbon cycle. If more lumber is used in construction, the amount of carbon in the atmosphere will decrease. Thus, more and more trees will be grown, reversing global warming.
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3.6 Examples of Timber Construction From Around the World
We have to be aware of what is happening across the world. The West has committed many mistakes and it is important that we do not commit the same. Timber and its by-products will become common as a building material in the coming years. For instance, I have seen many buildings with cross-laminated timber in London. They are made by employing a non-toxic adhesive to glue layers of timber plank together, at right angles to one another. Generally, there will be 3, 5 or 7 layers of timber each one approximately 22mm thick. Ho Ho Tower is a 24 storied building in Vienna. Once completed, it will be the tallest timber building in the world. As much as 76% of the building uses timber. Protective coating has been given on top of the exposed timber elements.
4. Lessons of Sustainability
4.1 Social and Economic Sustainability
Every timber that we use in our buildings need not be sustainable. If the source of the timber is from cutting down a virgin forest, then it is less sustainable. Is the process of cutting the timber sustainable in the long run? In the processing of timber, if there is an exploitation of labour, then it is to be questioned. The best is to use recycled timber (from demolished buildings). The prices are also cheap for recycled timber. But the usage of recycled timber is much less nowadays. I use them in my buildings and the price is less than half. We have to also look at the manufacturing process of plywoods. If the processing involves the use of the chemical formaldehyde, then it is not sustainable. Formaldehyde is used in resins that are used as glue between different layers. Research has shown that formaldehyde is a carcinogen that causes cancer. In the west, formaldehyde-free plywoods are available.
4.2 Adaptive Reuse of Old Buildings is the Best Sustainable Design Strategy
A study done by the US Energy Information Agency says that buildings constructed before 1920 are more energy-efficient than those put up between 1920 and 2000. Reusing an existing building is a very green and valuable way to conserve energy as conservation uses 40% fewer materials than new construction.
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Moreover, rehabilitating housing stock ensures a steady stream of work in the construction industry. Infrastructure investment is reduced and the greenery is also preserved. Even if more eco-friendly technology is adopted, it still influences the environment. The most eco-friendly structure is one that already exists.
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The whole world is thinking about ecological balance and sustainability. Earlier, ecology used to be primarily associated with forests, dams and lakes. But, now it is understood that it has to do with architecture as well. When we look at ecology in a broader context, two things become very important. Firstly, reducing the number of materials to be used. This is what Laurie Baker said more than 40 years ago- “If it is not necessary, then don’t use it.” The second thing is to reuse old materials so that we conserve the resources. We have to think about architecture in a holistic way. I am not talking about getting designs inspired by nature. I am not talking about having some greenery in our buildings, but of course, it should be there. I mean a much larger relationship with multiple dimensions. That is what will make architecture and design more sustainable.
It is time that we do not use any building material as such; we have to look at the process and the transportation when talking about sustainable building materials. It is important that we ask all questions before using them. In India, it is very difficult to know some details, but it is time that we start demanding it. We have to look beyond the life cycle assessment to find out what is sustainable and what is not. We should explore this symbiotic relationship between architecture and ecology to find an equilibrium. The design of the built environment should cause less harm to the environment, so that future generations can live more comfortably.