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Green building rating systems in India

A green building rating system is a tool that evaluates the performance of a building and its impact on the environment. It comprises a predefined set of criteria relating to the design, construction, and operations of green buildings.

In India, there are predominantly three rating systems – Leadership in Energy and Environmental Design (LEED), the rating systems from Indian Green Building Council (IGBC) and the Green Rating for Integrated Habitat Assessment (GRIHA). In addition, there is also the Energy Consumption Building Code (ECBC) and the National Building Code (NBC), which provide guidelines on energy consumption. All buildings in India need to comply with these prescribed guidelines.

Role of glass in green rating

LEED and glass

LEED, or Leadership in Energy and Environmental Design, is a green building certification program that recognizes top-notch building strategies and practices. Glass plays an important role in LEED certification and can significantly impact a building’s rating. LEED certified buildings save money and resources, and have a positive impact on the health of occupants, while promoting renewable energy.

GRIHA and glass

GRIHA, or Green Rating for Integrated Habitat Assessment, is a rating tool that assesses the performance of a building against certain nationally acceptable benchmarks. Developed by TERI and adopted by the Indian Government in 2007, it serves to carry out a qualitative and quantitative assessment and accordingly rate a building on its level of ‘greenness’.

Understanding glass specifications

A good solar control glass for a green building must deliver effectively on energy efficiency. The glass must take care of heat gain from direct sunlight and heat gain due to the difference in heat between the inside and outside of a building.

Measuring heat gain of a green building glass:
  • Solar factor

    This is a measure of how much direct heat from the sun is filtered while entering a building.

    Green tip: A low solar factor is considered ideal for tropical countries to construct buildings without glare.

  • U-value

    This is a measure of how much heat is transferred from the outside of a building to the inside due to temperature differences.

    Green tip: Low U-Values have been known to maximize energy efficiency while reducing energy consumption by as much as 40%.

  • Relative heat gain

    A term that describes the amount of heat energy entering through the glass due to direct solar radiation incident and heat transfer due to temperature differences.

    Green tip: Lower the relative heat gain, better the energy efficiency.

The relative heat gain for different kinds of glass:

IGBC and LEED

The United States Green Building Council (USGBC) is best known for its initiative called LEED (Leadership in Energy and Environmental Design) – a globally acclaimed green building rating system.

LEED provides third-party verification that a building or community has been designed and built using strategies aimed at improving performance across all metrics: energy savings, water efficiency, CO2 emissions reduction, improved indoor environmental quality, and stewardship of resources.

The Indian Green Building Council, which had adopted the LEED system, has now launched nine new rating systems of its own.

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GRIHA rating system

GRIHA, or Green Rating for Integrated Habitat Assessment, is a rating tool that assesses the performance of a building against certain nationally acceptable benchmarks. Developed by TERI and adopted by the Indian Government in 2007, it serves to carry out a qualitative and quantitative assessment and accordingly rate a building on its level of ‘greenness’.

GRIHA currently operates under ADARSH (Association for Development and Research on Sustainable Habitats) and is supported by the National Advisory Council (NAC) and Technical Advisory Committee (TAC).

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What you need to know about ECBC guidelines

ECBC of India, or Energy Conservation Building Code, has laid down norms for the technical specifications of glass, depending on the geographical location of the building and the glazing area.

Choosing your glass based on ECBC requirements:

Step 1: Determine the Window Wall Ratio (WWR) for the building
Step 2: Determine your climatic zone
Step 3: Determine the performance values of the glazing like solar factor, U-Value and light transmission, and prescriptive requirements specific to the climatic zones and WWR

In case of external shadings, determine the M-Factor for the trade-off of solar factor requirement in case of use of external shading device like overhangs, vertical fins protecting the fenestration. Adjust the SHGC based on the M-Factor.

  • What is window wall ratio (WWR)?

    Window wall ratio is the ratio of the building's total window area, measured from the outside of the frame to the gross exterior wall area.

  • How do I know which climatic zone I fall into?
  • I use external shadings. Do I still have to follow the SHGC requirements?

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