Due to increased environmental concern all over the world, practice of sustainable buildings or Green Buildings is being encouraged. The practice of green building can lead to benefits including reduced operating costs by increasing productivity, using less energy and water, improved public and occupant health due to improved indoor air quality, and reduced environmental impacts. Besides various other requirements, one of the essential requirements of the green building is to use enivrionment–friendly building materials – Green Materials. At present, there seems to be lot of confusion in defining green materials and manufaturers will have claims qualifying their products as green materials. There is a need to have evaluation criteria for qualifying materials as green materials. An attempt has been made in this paper to propose a scale for evaluation of building materials considering various factors that are essential for sustainable development, based on which classification of materials can be made in to different categories of green materials.
Paresh H. Shah, Professor and Head, Civil Engineering Department, Institute of Technology, Nirma University, Ahmedabad
Due to industrialization process over a period of last 200 years and utilization of fossil fuels such as coal and petroleum, the concentration of green house gases (such as carbon dioxide and methane) in the atmosphere is increasing quite rapidly. This has resulted in increasing global average temperature (global warming) which is the major point of concern all over the world. The Kyoto Protocol has been agreed to by several nations, committing to specified, legally binding reductions in emissions of six “greenhouse gases.” Approximately 30-40% of total energy consumption is accounted for building sector. It is hence essential to explore energy efficient building alternatives in order to help in mitigation efforts to the effects of global warming. Green building or environmental sustainable building technologies are gaining the attention of all the stakeholders of the construction industry. Factors considered for green building designs include appropriate site selection, use of environment–friendly building materials (Green Materials), energy efficient building practices such as passive cooling. Other factors including the use of maximum day lighting, use of energy efficient building materials, appropriate use of lighting fixtures, etc., use of water efficient technologies, rain water harvesting, use of renewable energy sources, recycling of waste water, through efficient solid waste management, etc. Currently, there are number of rating agencies encouraging green building movement and bench marking/standardizing green building technologies. As one of the criteria is use of green materials and there seems to be a lot of confusion about designating any material as green material. There is a need to have some evaluation criteria for the same. Currently, efforts are on to develop a scale which can help in classifying building materials as green materials.
Evaluation Criteria for Green Materials
Due to phenomenal growth in the construction industry, there is tremendous pressure on depletable earth resources such as soil, sand, stones, wood, etc. Production of building materials leads to irreversible environmental impacts. Using environment–friendly building materials is the best way to build an eco-friendly building. Following criteria can be used to identify the green materials.
- Local availability of materials
- Embodied energy of materials
- % of recycled/waste materials used
- Rapidly renewable materials
- Contribution in Energy Efficiency of buildings
- Recyclability of materials
- Environmental Impact
Using above mentioned criteria and assigning certain rating (R1-R8) to each of the criteria, overall evaluation of the material can be made by summation of score obtained by any material in these ratings. Guidelines for assigning rating to each criteria is discussed in following text.
i) Local availability of materials
As far as possible locally available materials are to be preferred so as to minimize the energy spent in transportation of the building materials. Energy consumed in transportation should be considered as total energy spent on transporting materials starting from the place of manufacturing. Depending upon distance from the place of manufacturing of the material, points for rating R1 can be allotted to the materials, based on following guidelines.
ii) Embodied energy of materials
Embodied energy is an assessment of the energy required to manufacture any building material. This include energy required to extract raw materials from nature, energy used to transport raw materials to manufacturing unit and the energy used in manufacturing activities to provide a finished product. Every building is a complex combination of many processed materials, each of which contributes to the building’s total embodied energy. Embodied energy is a reasonable indicator of the overall environmental impact of building materials, assemblies or systems. Embodied energy of some building materials is mentioned in Table-2. Depending upon embodied energy of the materials, points for rating R2
can be allotted based on guidelines given in Table-3.
(iii) Percentage of recycled/waste materials used
Building materials can be manufactured using recycled materials or using waste materials. Use of recycled materials helps the environment and the economy in several ways. A significant effect is that of lessening the need for manufacture with virgin, non-renewable resources, which saves precious resources, energy and cost. Waste materials that would have ended in landfills after its useful life, instead can be reprocessed for use in other products. Use of various type waste materials such as fly ash, blast furnace slag, red mud, waste glass, marble dust, cinder, rice husk, coconut husk, banana leaves, jute fibers, rubber from automobile tires, etc. is demonstrated by research. Table-4 specifies guidelines for rating R3
for this criterion.
(iv) Use of renewable resources
Materials manufactured with resources that are renewable (i.e. wood or solar power) rather than non-renewable (i.e. fossil fuels) shall be preferred. Depletion of the earth’s resources is occurring at an alarming rate. Entire ecosystem is affected due to continuous extraction of raw materials from the earth. As stock of fossil fuel is limited, it may get exhausted very soon. By utilizing renewable energies, such as wind, solar, tidal, as well as renewable materials, such as wood (certain certified species which are rapidly renewable), grasses or sand, impact on biodiversity and ecosystems can be lessen.
(v) Contribution in Energy Efficiency of buildings
Construction and operation of buildings utilizing major portion of total energy produced. With little careful efforts, designers and builders can reduce energy loads on structures, reducing energy requirements and the strain on natural resources. With proper orientation of building with reference to solar radiation to receive maximum day lighting, operable windows for natural cross-ventilation, use of passive cooling techniques, (eliminating or lessening the need for air conditioning), walling unit with lower U values, roof insulation, water-saving devices and more efficient appliances can all work to lessen energy needs. Consideration of alternate energy source use, such as wind, solar and tidal power, can help alleviate reliance on traditional fossil fuel sources. Bureau of Energy Efficiency (BEE) has been set up by Govt. of India, who has formulated Energy Conservation Building Code (ECBC),
which is defining certain minimum energy performance standard for buildings. ECBC specifies minimum values for U-factor (U-factor is thermal transmittance which is the rate of transfer of heat through unit area of a structure for unit difference in temperature across the structure., unit is W/m2
C), Solar Heat Gain Coefficient (SHGC - the ratio of the solar heat gain entering the space through the fenestration area to the incident solar radiation. Solar heat gain includes directly transmitted solar heat and absorbed solar radiation, which is then reradiated, conducted, or convected into the space) and Visual Transmittance (VT – it indicates percentage of visible portion of solar spectrum that is transmitted though a given glass) with guidelines to be Table 6 specifies guidelines for rating R5
for this criterion.
(vi) Recyclability of materials
The recyclability of the materials can be judged from quantity of materials recovered for re-use after the useful life of materials/products or after demolition of the building. Table - 7 specifies guidelines for rating R6
for this criterion.
Materials which are long lasting and needing little maintenance are preferred. Material replacement puts a strain on the earth, its resources and inhabitants. In making materials more durable and easy to maintain, manufacturers can help in eliminating a costly, damaging and time-consuming process of replacement. Rating R7
for this criterion can be considered as mentioned in Table-8.
(viii) Environmental Impact
All materials used for construction of buildings must not harm the environment, pollute air or water, or cause damage to the earth, its inhabitants and its ecosystems during manufacturing process, and also during use or disposal after end of life. Material should be non-toxic and contribute to good indoor air quality. Worldwide industrial production uses billions of tons of raw materials every year. Pollution caused in excavation, manufacturing, use or disposal of a product can have far reaching consequences on the Earth’s ecosystem. Poor indoor air quality caused by VOC emission costs billions in medical bills and lost productivity to companies every year. The manufacturing, use, and disposal of PVC pose substantial and unique environmental and human health hazards because of its uniquely wide and potent range of chemical emissions throughout its life cycle. It is virtually the only material that requires phthalate plasticizers, frequently includes heavy metals and emits large numbers of VOCs. In addition, during manufacture it is responsible for the production of a large number of highly toxic chemicals including dioxins (the most potent carcinogens measured by man), vinyl chloride, ethylene dichloride, etc. When burned at the end of life, whether in an incinerator, structural fire or landfill fire, it releases hydrochloric acid and more dioxins. Products made with PVC may be avoided as far as possible. Following points should be considered for evaluating environmental impact of the building materials, allocating rating R8
Classification of materials based on scale
After evaluating the material for above mentioned criteria and allocating points for rating R1
, totaling maximum to 100 points, materials can be classified based on total points scored, as per following guidelines.
Using the criteria some of the materials are classified assuming certain data as mentioned in Table-11.
There is a need for standardized procedure for evaluting the green materials. A scale has been suggested for this purpose. However, a lot of standardized data to be generated for the parameters such as emodied energy of some traditional building materials, U-factor of the materials, VOC content of some of the materials like paints, wood based productes, carpets, etc., to use the scale effectively.
- Alternate Building Materials and Technologies by K. S. Jagdish, B. V. Ventkarama Reddy & K. S. Nanjunda Rao, New Age International Publishers
- Draft Eenergy Conservation Building Code, published by Bureau of Energy Efficiency.
- Embodied Energy Computations in Buildings by Krishnakedar. S. Gumaste, Journal of Advances in Energy Research (AER – 2006).
- Embodied Energy of Building Envelopes and its Influence on Cooling Load in Typical Indonesian Middle Class Houses by Agya Utama and Shabbir H. Gheewala, 2nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)” 21-23 November 2006, Bangkok, Thailand.
The article has been reproduced from the proceeding of "National Seminar on Green Structures for Sustainability" with the kind permission from the event organisers.