Eco friendly Building Materials and Techniques

Housing is one of the basic needs of human society. In India, in the year 2005, there were one hundred and fourty million houses and around two hundred million households. The shortage of dwellings was sixty million - a huge number which is ever increasing. Indian construction industry is among one of the biggest industry in terms of employment generation, volume of material produced and annual expenditure. However the Indian building industry is highly decentralized, involving diverse stakeholders engaged in design, construction, equipment provision, installation and renovation of buildings. Conventional building materials like burnt bricks, steel and cement are high in cost, utilize large amount of non-renewable natural resources like energy, minerals, top soil and forest cover. The desirable materials and techniques must be sustainable in addition to functional efficiency.   

Current annual consumption of bricks alone is estimated as 170 billion. The estimated consumption by the year 2020 is expected to be about 260 billion. Presently the consumption of the cement and structural steel is to the tune of 110 mega tons and 12 mega tons respectively. Indian cement industry is growing at the rate of 8 %. All these activities are creating lot of ecological imbalances. The building industry is contributing 22 % of total carbon dioxide emissions. Brick making is robbing top fertile soil (300 mm depth) at the rate of thousand square kilometer per year. Brick industry consumes more than 20 million tonnes of coal as well as large amount of biomass. Moreover the burnt clay bricks are not recyclable in the sense that clay is lost for- ever. Eco friendly brick would have low embodied energy, will be locally processed, would require less of energy in processing, and would be recyclable.

In vernacular architecture adobe (althaub in Arabic meaning mud or earth) was used extensively. Traditional mud wall construction varied enormously with topography, climatic conditions and need of different regions. The common methods of earth construction are adobe, cob, wattle and daub, rammed earth, earth berming, and cut blocks. One of the important benefits of earth structures is its better thermal insulation. Wattle and daub is a building material used for making walls, in which a woven lattice of wooden strips called wattle is daubed with a sticky material usually made of some combination of wet soil clay, sand, animal dung and straw. Wattle and daub has been used for at least 6,000 years, and is still an important technique in many parts of the world. Many historic buildings include wattle and daub. Adobe bricks are usually made with tightly compacted sand, clay and straw or dung. The blocks these days are made using soil, lime, sand and cement in recommended proportion, depending on the quality of the available mud. Intelligent use of mud blocks in various elements of the house like lintels and roof can reduce the use of cement and concrete. Vaulted roofs and domes reduce the use of cement and concrete in the building. The brick arch in the wall can replace concrete lintel and beam. However, scarcity of good soil, experienced labour and quality supervisors and lack of awareness of this technology have discouraged architects from designing adobe homes these days. Adobe houses are "alternative construction technology" with many advantages. They are cost-effective as these houses need little or no maintenance. The cost can be further brought down with the use of clay flooring , Jaali windows and recycled doors. Mud blocks need no plaster and paint. The flip side is that adobe walls usually never rise above two stories because of low load bearing and low structural strength. Moreover, to secure the house from termite and rodents, anti-termite chemicals must be used in the manufacture of the blocks. Suitable compaction will deter the rodents.  Exposed mud blocks absorb water. A coat of water-retardant chemical must also be applied to protect the walls from dampness. A lengthy roof overhang may be another option to give protection from rain.

Cob is a building material consisting of clay, sand, straw, water, and earth, similar to adobe. Cob is fireproof, resistant to seismic activity, and inexpensive. It can be used to create artistic, sculptural forms and has been revived in recent years by the natural building and sustainability movements.

Soil cement block or stabilized mud block is a modern eco-friendly option. For stabilized mud blocks the raw material could be anything from soil or  fines, fly ash, mine tailings, mine waste, lime stone waste, red mud, lime sludge, kiln dust etc. With the help of stabilizers like lime or cement they can be compacted to a high density block and cured. Stabilised mud blocks consume only 23 % of the energy of a burnt clay brick. Moreover fly ash bricks are thermally more insulating. The energy used in transporting one cubic metre of burnt clay brick is 200 MJ per 100 km. Thus use of locally available raw material and local processing of bricks makes more environmental sense.

The alternative materials for roofing could be precast RCC joist with prefab brick panels, RC plank, funicular shell, precast Jackarch panel, concrete panel, ferrocement panel etc. Pine needle board may be used for flooring, walling, structural membrane, boxes and interior finishing on walls. Fabrication of pine needle boards promotes local entrepreneurship and utilization of forestry residue.       

 Architects and builders interested in sustainable building materials and techniques may browse the websites of Building Materials and Technology Promotion Council and National Council of Cement and Building Materials.