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Greener materials: imperative need for the sector

The building and construction sector contributes to about one third of global CO2 emissions and over a third of all energy and material resources are used to build and operate buildings and over a third of the total waste results from construction and demolition activities (UNEP, Green Economy report Report, 2011). The total material extraction globally increased by a factor of 8 from 1900-2005 and the strongest increase can be observed for construction minerals that grew by a factor of 34. India, being a developing economy, the construction sector contributes to about 10% of the GDP annually.

With over 70% of commercial spaces yet to be built, the volume of building and construction activity is going to see phenomenal increase in the years to come. A look at the existing and upcoming policy dialogues around energy and resource saving options in the sector reveals that there is considerable focus on end use energy, water and resource savings. Materiality and embodied energy content in a building is ignored in the current dialogue of energy saving options in a building. While it is important to save energy through improved air-conditioning and lighting, it is equally important to reduce embodied energy content of buildings by reducing quantum of cement, steel, glass, aluminium and other materials that have high embodied energy and that require huge amount of energy to produce them.

Alternative technologies and materials that required less energy for production are not mainstreamed adequately. To give an example, use of fly ash based cement is recommended by Indian Codes and can replace between 25-30% of cement in concrete, but it is not always a preferred option.

Structural engineers often cite reasons, for example , longer curing time required for achieving adequate strength particularly in higher grade concrete (question to structural engineers: Is that a valid reason?), amongst other. There is mixed opinion in the community of structural engineers on use of fly ash and I think there is a need for mandatory norm to promote use of industrial waste /fly ash to enable cope with diminishing mineral base to support cement production . The main raw material used for the production of cement is limestone. Limestone in particular for cement production is usually seen as an abundantly available resource in India. Reserves amount up to 14,926 million tonnes.

If research studies are to be relied upon, the yearly demand of limestone will increase up to between 1000 million tonnes (low-demand case) and 1400 million tonnes (high-demand case) in 2030, in India. Cumulating the yearly required limestone for cement production in both scenarios and comparing it with the known Indian reserves of limestone show that the known reserves may last until 2028 in the high-demand case or until 2031 in the low-demand case.Once exhausted, we have to depend on imported minerals that shall impact our economy. GRIHA, green rating for integrated habitat assessment, the green building rating framework developed by TERI and adopted by Government of India gives considerable weightage to use of materials that have recycled content or use of local materials that require less energy for production and transportation. Usage of flyash /industrial waste based cement for construction is one of them.

Material use for construction and buildings can be broadly classified under three categories namely natural materials (e.g river sand, stone) , processed materials e.g dressed and processed stone) and manufactured materials (e.g steel, tiles etc) , listed in an ascending order of embodied energy content. Green buildings promote use of materials that are naturally and abundantly available (this saves on transportation energy in addition to embodied energy), followed by materials that require less processing (e.g unprocessed stones, dressed and unpolished stone finishes), and lower use of manufactured materials that have high manufacturing energy (lesser use of cement, steel or aluminium etc). Use of recycled content or recyclability of a material is also preferred.

Another area of concern is overdesign of structures and systems. Meeting safety norms is sacrosanct, but there is no uniformity in factor of safety that is assumed for structural and mechanical/electrical design. Over design leads to over use of materials. Sustainable consumption and production of resources is actively been pursued in several regions of the world and there's an urgent need to look at material consumption cycle in the construction sector and ways and means to optimize their use. Use of light weight aerated concrete blocks with fly ash replacement can reduce used of burnt clay bricks produced from fertile top soil and also reduce weight of structural systems.

Recycling of steel, aluminium, glass is technically feasible and should be adopted as industry best practice. Construction and demolition waste has huge potential of being reused and reconstituted into usable products such as aggregates for concrete, or for paver blocks etc. The waste generated by construction and demolition is also substantial in India. In India, on an average about 12-14 million tonnes of construction and demolition waste is generated annually. The construction and demolition waste accounts for a substantial share (about 1/3rd) in the total solid waste being generated in the country. The waste from soil, bricks and concrete accounts for a substantial amount of the total construction and demolition waste generated and most of it goes to landfill. There is urgent action required for better utilization of solid wastes generated from construction and demolition.

Organisations such as Building Materials and Technology Promotion Council (BMTPC) have a wealth of low energy construction technologies and products, yet to be mainstreamed. While Government of India has an ambitious programme on housing for all, it is important that sustainability should be an inbuilt parameter in all upcoming and existing government programmes on housing and construction. Otherwise, we shall be constructing millions of square metres that shall lock in inefficiencies in form of unsustainable material use.

Materials used for interior finishes also need to be chosen after careful consideration. Unfortunately, there are no standards or parameters for defining green quotient or sustainability of materials and there is fair bit of green washing that happens in the sector. GRIHA has launched a product catalogue wherein it reviews various parameters in a material prior to enrolment as a green product into its database. The parameters that form part of product review and enrolment include the manufacturing/processing energy, recycled content/recyclability, thermo-physical properties, content of harmful pollutants/emissions from the materials, performance efficiency etc. It was an interesting find, that while ceramic tiles have potential for including recycled material content, there is minimal recycled content in a vitrified tile. Also, light colored vitrified tiles have lower recycled content than dark colored ones. This poses a dilemma in use of these tiles in a sustainable /green building. Light colored flooring would have higher light reflection (and hence desirable, in order to save lighting energy consumption) but have low recycled material content. The light reflection properly wins over recycled content in this case as operational energy is considered to be much higher than embodied energy in a building. There are many questions such as above in the discussion on green material use in sustainable and green buildings and hence need for research and deeper understanding.

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