Lessons from Tradition
As a geographic entity that experiences sub-tropical climatic conditions, India has developed some very efficient building construction techniques that actively mitigates this. Before the advent of modern building techniques which subsequently made all buildings look the same irrespective of their geographical location, we had numerous traditionally developed construction methods and technology that were not only effective but also sustainable. Now, these techniques and methods are nearing extinction with higher population demands and growing industrialization.
Barring a few hands-on workshops here or there such methods are often forgotten. These methods worked in tandem with our diversity in culture, temperate variations, vegetation, and even natural calamities specific to each location. The prime utility of any structure is to give shelter and protect its inhabitants from the effects of the climate outside and provide comfort. As we hear of the rise in global temperature, the necessity to be more sustainable in every aspect of life is as high as ever. These locally sourced materials would respond to the localities very hot summers, humid rainy season, and mild winters.
Here, we discuss a few traditional roofing practices that were prevalent. As diverse as our terrain is, so are the various techniques employed at every unique location.
1. Timber, Bamboo & Thatch
Mostly found in the northeastern states of India this type of system is employed to withstand severe temperature variations as well as frequent rains. Bamboo and timber are used to constitute the form while the roof is thatched. Locally available and simple materials like cow dung, mud, and indigenously produced mortar made of paddy is used. These materials apart from being climate positive are also extremely effective in thermal insulation and strength.
A similar system traditionally used in parts of Rajasthan is Kuccha Thatch made of mud, grass, reed, thatch, leaves etc. Because of the raw materials used, this type of construction is not only cost-effective but also provides excellent insulation. It helps regulate the internal temperature when it's extremely cold or hot. But because of the limited strength, these are often easily destroyed during calamities.
2. Clay tiled Roofs of Kerala
Clay tiled roofs offer excellent thermal insulation. In traditional Kerala homes, there is an air gap between the tile layer and the roof which considerably reduces the heat transfer beneath the roof. The high-pitched roof of traditional Kerala structures maximize pressure differences to optimize airflow. The attic space acts as an insulating layer. The gables also aid in constant air flow via convection. It is provided with fenestration to let the hot air discharge to maintain the second roof cooler.
3. Madras Terrace Roofs
A traditional roofing technique that is primarily found in South India for spanning flat roofs. It involves the construction of a roof by diagonally laying the bricks (aachikkal – bricks of smaller thickness) over wooden rafters with lime plaster. Observable in flat roof structures of Karnataka and Tamil Nadu, these are used to span smaller rooms. The main components of the roof are clay tiles, lime mortar and timber. All these components have very low conductivity and hence keep the internal temperature maintained all the time.
These materials absorb the incident heat as well as has a high heat transfer time which means the heat is transferred through conduction over a longer period of time. Although a bit expensive in terms of construction costs, studies show that there is almost a 3–4-degree difference in internal and external temperatures. The Bengal roof is another regional variation of this type of roofing method.
4. Filler Slab
The filler slab is a common feature observed in homes in Kerala, thanks to Laurie Baker who extensively used it in his designs and popularized it among the public. In filler slabs, the concrete in the tension zone is replaced with other materials. The filler material, thus, is not a structural part of the slab.
The most popular filler material is the roofing tile. Mangalore tiles are used make a filler slab. The air pocket formed by the contours of the tiles makes an excellent thermal insulation layer. Apart from being low cost, the tiles also formed a unique pattern on the ceiling rendering an aesthetic value.
5. Earthen pots Insulation systems is a traditional method used in India where the roofs are covered with upside-down earthen pots and then cemented in place. This traps air between the original roof and the top surface, thus providing insulation following the same principle as filler slabs. It follows the simple principle of air cavities through earthen pots on the roof surface, to achieve thermal comfort. The use of cavities is similar to the use of any insulating material. If air space is left between two layers it acts as a barrier to heat transfer. Using earthen pots to keep roofs cool has been traditionally practiced but the method suffers from practical difficulties and the roof is rendered unusable after installation. This method helps keep the building cool in summers and warm in winters.
6. Guna tumbler roof
A variant of filler slab, guna roof is an excellent alternative for conventional roof systems. They provide excellent insulation as they form a vault and each tumbler acts as an arch are arranged in a series by being inserted into each other consecutively. This helps the interiors remain cool during summers and warm during winters due to air cavity formed inside each tumbler. Studies show that there is almost a 10 degree difference between the inside and outside temperatures in such structures. Such structures can also being widely constructed in Auroville as well as at the Centre for Science at Wardha, where such sustainable practices are widely encouraged.
7. Brick Domed and vaulted roof
A feature that can be observed extensively in ancient structures like the domes enhance thermal insulation while also promoting optimum air circulation since they are corner-less. They reduce the heat interaction between the indoors and outdoors, as the surface area to volume ratio is low, when compared to flat roof structures these receive 25-30% less solar radiation. They also reduce solar heat gain due to self-shading. Brick domes and vaults have existed in India for centuries and are even standing tall in many structures like the Gol Gumbaz of Bijapur, the largest in India.
This is not an exhaustive list by any means. There are innumerable indigenous practices across the country that were practiced extensively since times immemorial. This blog post is just a slight reminder that sustainable and traditional methodologies are complementary to each other. Ancient constructions have lasted for centuries in India, constructions that respected its climate and geography. There are ample opportunities in documenting and studying these methods so as to improvise them to fit our changing needs for a sensitive and sustainable tomorrow.