Mark of rudiments

  • 30/08/2007

Building materials have ecological footprints

The construction material in buildings have evolved from mud to sun-dried bricks to burnt bricks, then to lime, glass, iron products, lime-pozzolana cement, aluminium, portland cement and plastics. Production of building materials has moved from highly decentralised and labour-intensive processes to centralised, machine-dependent industry mode. This needs hauling of raw materials and transportation of finished products over a large distance, resulting in fossil fuel consumption and carbon emissions.

The choices of materials and construction methods can significantly change the amount of energy embodied in the structure of a building.

The answers are not blowing in the wind. Each choice of building material has its trade-off. For instance, all products like mud, stone, cement, steel, etc have an embodied energy, which varies according to local conditions.The point then is whose embodied energy is smaller and whose footprint is sustainable in a given geographical area. Canadian Architect, a monthly architecture magazine, has calculated embodied energy of about 30 construction materials and found synthetic carpets and aluminium to have the highest embodied energy of 148 megajoules (MJ) per kg and 227 MJ per kg respectively. As against this the embodied energy of stone (local) as 0.79 MJ per kg; brick as 2.5 MJ per kg; plywood 10.4 MJ per kg; glass 15.9 MJ per kg; steel 32 MJ per kg; zinc 51 MJ per kg; pvc 70 MJ per kg; and paint as 93.3 MJ per kg. It would be interesting to estimate the ecological footprint of buildings to see if architects actually use more or less than one square metre of available ecological carrying capacity to deliver one square metre of building area.

iisc has done some comparative assessment of buildings using different construction material. It found that a reinforced concrete multi-storey building consumes highest amount of energy at 4.21 gj per square m (gj/sq m) of built up area, whereas the energy consumed by the load bearing conventional two-storey brickwork building is 2.92 gj/sq m, which is 30 per cent less than the former. In sharp contrast, a two-storey building using alternative building material like stabilised mud blocks (smb) walls, smb filler slab roofs, is highly energy efficient and consumes only 1.61 gj /sq m of energy.

Anil Laul, principal architect of Faridabad-based Anangpur Building Centre (abc) has implemented the principles of utilising local building materials at his centre while constructing it in 1992. abc is constructed on an abandoned quarry at a cost of mere Rs 208 per sq ft [1992 cost, which is now Rs about 500 sq ft] as against the cost of Rs 2,300 for per sq ft for modern green buildings.

According to V Suresh, former managing director of hudco, "35 per cent of the cost in constructing a building is labour costs while 65 per cent goes into raw material; and within latter, cement and steel alone account for 30 per cent of the cost. For instance, one tonne of cement costs Rs 5,000 and a tonne of steel costs Rs 35,000; and price of both the raw materials is on a rise, not to forget their environmental costs