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Tuesday, November 26, 2019

Materials Selection for Green Buildings

The selection of green building materials and products represents one important strategy in the design of a green building. Green building materials offer specific benefits to the building owner and building occupants and are follows:
  • Reduced maintenance/replacement costs over the life of the building.
  • Energy conservation.
  • Improved occupant health and productivity.
  • Lower costs associated with changing space configurations.
  • Greater design flexibility.
Building and construction activities worldwide consume 3 billion tons of raw materials each year or 40 per cent of total global use. Using green building materials and products promotes the conservation of dwindling nonrenewable resources internationally.
In addition, integrating green building materials into building projects can help reduce the environmental impacts associated with the extraction, transport, processing, fabrication, installation, reuse, recycling and disposal of these building industry source materials.

Selection criteria for green material

A) Resource efficiency:
  1. Recycled Content: Products with identifiable recycled content, including post-industrial content with a preference for post-consumer content.
  2. Natural and renewable: Materials harvested from sustainably managed sourced and preferably have an independent certification (e. g. certified wood) and are certified by an independent third party.
  3. Resource-efficient manufacturing process: Products manufactured with resource-efficient processes including reducing energy consumption, minimizing waste (recycled, recyclable and or source reduced product packaging), and reducing greenhouse gases.
  4. Locally available: Building materials, components, and system found locally or regionally saving energy and resources in transportation to the project site.
  5. Salvaged, refurbished, or remanufactured: Includes saving material from disposal and renovating, repairing, restoring, or generally improving the appearance, performance, quality, functionality, or value of a product.
6) Reusable or recyclable: Select materials that can be easily dismantled and reused or recycled at the end of their useful life.
7) Durable: Materials that are longer lasting or are comparable to conventional products with long life expectancies.

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.
  1. Local availability of materials
  2. The embodied energy of materials
  3. % of recycled/waste materials used
  4. Rapidly renewable materials
  5. Contribution in Energy Efficiency of buildings
  6. Recyclability of materials
  7. Durability
  8. Environmental Impact
Using the above-mentioned criteria and assigning a 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 a rating to each criterion is discussed in the following the 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 the 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) The embodied energy of materials

Embodied energy is an assessment of the energy required to manufacture any building material. This includes the energy required to extract raw materials from nature, energy used to transport raw materials to the 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. The 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 fibres, 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. The entire ecosystem is affected due to the continuous extraction of raw materials from the earth. As a 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 lessened.
(v) Contribution in Energy Efficiency of buildings

Construction and operation of buildings utilizing a major portion of the 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 daylighting, 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/m2-0C), 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 through 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 the number of materials recovered for re-use after the useful life of materials/products or after the demolition of the building. Table - 7 specifies guidelines for rating R6 for this criterion.
(vii) Durability

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 the construction of buildings must not 
harm the environment, pollute air or water, or cause damage to the earth, its inhabitants and its ecosystems during the manufacturing process, and also during use or disposal after end of life. The 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 the environmental impact of the building materials, allocating rating R8.

Classification of materials based on a scale

After evaluating the material for the above-mentioned criteria and allocating points for rating R1-R8, totalling maximum to 100 points, materials can be classified based on total points scored, as per the following guidelines.

Using the criteria some of the materials are classified assuming certain data as mentioned in Table-11.
B) Indoor Air Quality (IAQ):
  1. Low or non -toxic: Materials that emit few or no CFC’s, reproductive toxicants, or irritants as demonstrated by the manufacturer through appropriate testing.
  2. Minimal chemical emissions: Products that have minimal emission of Volatile Organic Compounds (VOCs). Products that also maximize resources and energy efficiency while reducing chemical emissions.
  3. Moisture resistant: Product and systems that resist moisture or inhibit the growth of biological contaminants in building.
  4. Healthfully maintained: Materials, components, and systems that require only simple, non-toxic, or low-VOC methods of cleaning.
  5. Systems or equipment: Products that promote IAQ by identifying indoor air pollutants or enhancing air quality.
C) Energy Efficiency:
Material, components, and systems that help reduce energy consumption in building and facilities.
D) Water Conservation:
Products and systems that help reduce water consumption in building and conserve water in landscaped areas.
E) Affordability:
Building product life-cycle costs are comparable to conventional materials and are within a project-defined percentage of the overall budget.

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