Eco-friendly Habitats to Combat Climate Vicissitudes

India has a number of historical buildings, palaces, mausoleums memorials etc. One factor is common amongst all of them. They are cool in summers and remain warm during winters. The houses of the yore were constructed with climate in mind. For example Lucknow's Imambara constructed by Nawab Asif-ud-daula (1775), it is said that it has empty pitchers placed over- turned on the roof under the layer of lime and coarse sand. The air space of the pitchers acted as an insulator. The walls of small 'lakhauri' bricks are almost three feet thick and keep the building insulated from the vagaries of weather.The advent of the British added European grandeur and style to Moghul Architecture of the yesteryears with innovations. For example, Claude Martin, a Frenchman who combined the functions of trader, military adventurer and architect was recommended to Nawab Asif-ud-daula in 1776 by the Resident John Bristow, writes Rosie Llewelyn-Jones in her book, 'A Fatal Friendship'. Martin erected a residential building for himself in 1781. Located on the right bank of Gomti River, the building had Martin's living rooms at three different levels. During the summers when the water level in the river went down Martin lived in the basement which was at level with the river surface. During the rains as the river level rose Martin ascended another story and when the weather cooled down he shifted to the bedroom on the top floor which had a huge terrace part of which was erected on piers sunk in the river. It seems the arrangement of natural 'air-conditioning' kept Martin's house cool in the summers and warm in the winters! After his death in 1800 the house was taken over by Nawab Saadat Ali Khan and named 'Kothi Farhad Baksh'. Later the building came to be known as 'Chattar Manzil' and presently houses the famous Central Drug Research Institute.Cost was no consideration to these builders and owners it was the climate that mattered for them.In the post colonial era the styles of architecture changed. The rising cost of land, housing materials and population explosion forced people to consider smaller houses with thinner brick walls. Climate is once again in the saddle now and the architects are coming forward with eco-friendly, cost effective housing techniques to meet the challenge of global climate change. Nilanjan Sengupta of the forum of scientists, Engineers and Technologists, Kolkata, quoting the report of the Intergovernmental Panel on Climate Change (IPCC) says in his recent paper published on the issue in the Current Science 'WARMING of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level'. As Green House Gases (GHGs) keep accumulating in the atmosphere the phenomenon of global warming will keep going. Global cooling and warming has been going on since the earth came in to being. At present we are in a warming phase. Whether we want it or not the nature is at work to keep the atmosphere warm. But as inhabitants of this Globe our contribution towards GHGs has been more than positive. It is something like hacking the branch of the tree on which you are sitting! In every filed of technology there is a rush to check the emission of GHGs. At least on paper everything is trying to become green they say.The population boom on the other hand has caused a boom in the construction activity. With the availability of wood getting scarcer there is demand for bricks, cement and mortar, steel etc. for construction of dwellings. That is why the construction industry is one of the major sources of pollution says Nilanjan. Modern buildings consume energy in a number of ways, he says. The manufacture of construction material itself is a great polluter. Construction related activities account for a large chunk of carbon dioxide emission in the atmosphere. Energy consumed in the construction activity like in the manufacture of construction materials, transportation of these materials from plants to sites, energy used in the actual construction work, running of the building after occupation and later even the demolition of a building consumes energy.
Nilanjan claims that at the Forum they have developed techniques to reduce the quantity of construction materials and also substituted them with low-energy consuming materials thereby making the buildings cost effective and eco-friendly. The manner in which the urban habitats are becoming a concrete jungle, technologies tried by Nilanjan's forum appear to be the need of the time.Knowing the actual quantity of carbon dioxide emissions in the manufacture of construction materials is important says Nilanjan. The ingredients for a 'pucca' building are steel, cement and brick. Production of one ton of crude steel emits about 2.75 ton of carbon dioxide. It is natural that conversion of crude steel to processed steel emits higher quantities of carbon. Similarly cement manufacture releases about 0.9 ton of carbon dioxide for each ton of cement produced.Nilanjan has not taken the environmental degradation due to extraction of sand in his paper because sand is a natural product obtained from the river beds. However, one must remember that despite being freely available, removal of vast quantities of sand leads to degradation of river banks causing water-logging in the post monsoon periods and indiscriminate extraction causes extensive bank erosion. Similarly in the large cities like Chennai and Bangalore the thickness of sand available is very little and it is a major source of ground water. The author had reported extraction of sand from tube-wells which had stopped yielding water. Such extractions cause large scale sinking. Even over-exploitation of tube-wells leads to 'caving in' and the sand grains after losing the film of water, just collapse. Due to this reason, in Agra in U.P. reports of houses collapsing due to sinking of ground were in the news two years ago. Therefore despite sand being naturally available ingredient for construction activities, it needs to be mined with caution. It may not add to carbon dioxide in the atmosphere but haphazard mining does leads to land degradation and misery for the common man. The most important unit of a building is the brick. Nilanjan says that brick production is carried out in a big way and the kilns guzzle large quantities of coal. He records that 38 tons of carbon dioxide is released in the atmosphere for every 100,000 bricks manufactured. Brick manufacture has another serious implication which Nilanjan has not taken in to account as his discourse is mainly about carbon emission and ways to control it. Brick manufacture needs lots of clay. On the outskirts of any township in the alluvial planes of north India one can find innumerable brick kilns dotting the landscape. Well these planes as we know have been formed by the painstaking efforts of the rivers which have deposited all the sands the richest vaults of ground water. In addition there are layers of clays, which are now the source of the bricks. One can see degraded land around the brick kilns where the clays have been removed and converted to bricks. These depressions lead to water stagnation and alkalinization of the soil. Finally even the area surrounding the brick kiln becomes infertile. Very few people realize that it will take another 1000 years for the nature to get back what has been removed.Nilanjan recommends use of various cost saving technologies like Rat-trap bond in wall construction, which involves laying bricks on their sides with a cavity of 4" in between. The plain surfaces of bricks make the outer surfaces of the walls. This bond has strength equal to a 250 mm solid brick wall yet consumes 20% less bricks. Total cost of 26% is saved by this technique. The air gap of 4" provides a good insulation to keep the rooms cool during summers and warm during the winters. The plain surfaces of brick walls need no plaster hence save the cost of cement and sand, labor and are aesthetically pleasing. This technique was popular in England for buildings up to three stories till the turn of the 20th century. Laurie Baker (1917-2007) an English architect came to India in 1945 as a missionary and settled here in Thiruvananthapuram. Houses constructed by him using this technique stand firmly even today after more than 40 years. The other techniques that cut costs of material and construction are Brick arches in lieu of traditional RCC lintels. These cost about 30-40% less than the lintels. Similarly Filler slab in roof composed of bricks, tiles etc consumes much less steel as the roof becomes lighter in weight. Costs of such roofs are reduced by about 23%. Additional 40% saving is obtained by this technique as it needs less steel and cement says Nilanjan. Yet another technique is use of compressed earth blocks made of a mixture of cement, gypsum and lime. Because of uniform shape bonding them is faster and construction is naturally faster. It is overall cost efficient technique. However, in high rainfall areas such blocks need a layer of plaster.