Green building refers to the process of designing, constructing, maintaining, deconstructing and renewing a building or locality keeping in mind the positive and harmful repercussions that each decision taken in these steps have both on the environment and also on the internal quality of living in these buildings. Apart from the goal of achieving better conditions both outside and inside the building, another important aspect of green building is to make the life-span of a building resource efficient.

The concept of green building or sustainable building was born because of the fact that buildings are one of the major consumers of natural resources as well as one of the major contributors of pollutants to the environment. Buildings also influence the health and working capacity of human beings. Green building generally involves consideration of the following major elements during the development.

• Designing and Planning
• Material selection
• Construction
• Maintenance
• Generation of wastes
• Quality of living standards
• Renewal and deconstruction

Although there are various interpretations of green building, it is essentially through the above-said points that it achieves improvement over traditional construction techniques. Since, green building is a process which promises high performance and resource efficiency through the above stated elements, it is also necessary that oneshould evaluate the amount of effectiveness of a proposed green building project. Accordingly, a number of assessment systems have been developed by different countries so that they can evaluate the effectiveness which a green building proposal will have according to their country’s need and standard.

Need & Benefits of Green Building
The construction sector poses a great threat to the environment as it utilises a lot of natural resources and produces a lot of wastes. Globally, buildings account for at least 40 per cent of energy use according to World Business Council for Sustainable Development. An estimated 42 per cent of global water consumption and 50 per cent of global consumption of raw materials are used during the manufacture, construction and operational periods of the buildings. In addition, building activities contribute an estimated 50 per cent of the world’s air pollution, 42 per cent of greenhouse gas emissions, 50 per cent of all water pollution, 48 per cent of all solid wastes and 50 per cent of all CFC addition to the environment.

The growing technological advancements in engineering led a lot of global organisations and analysts to believe that the construction sector is a major industry where improvements can be made to construct high efficiency buildings. These projections pointed towards the reduction in wastes generation and addition to the environment by the buildings and also their impacts on the overall environmental health over the years. An estimate of how much energy could be saved from buildings was also made which took into account the steady advancement of technology along with its implementation on buildings. It has been reported that the emissions savings potential is as much as 84 gigatons of CO2 by 2050, through direct measures in buildings such as energy efficiency, fuel switching and the use of renewable energy. Also, the building sector has the potential to make energy savings of 50 per cent or more in 2050, insupport of limiting global temperature rises to 2C above the pre-industrial level. It is because of the inability of traditional construction to keep up with the modern times and also due to the massive potential available in this sector, the concept of green building was born.

After its birth green building quickly became very popular among researchers due to its wide undiscovered potential as well as among industries because of the better results it was providing in terms of the following factors:
• Reduced capital cost
• Reduced maintenance cost
• Business benefits
• Health and productivity gains
• Lower emission of harmful wastes and greenhouse gases
• Reusability and retrofitting of green buildings and reusability of residential land.

Assessment Systems of Green Buildings
As described before, different countries have come up with different assessment systems to evaluate how ‘green’ a building is according to their country’s standards. The common thing in all of these assessment systems is that they all try toachieve high-performance buildings while maintaining good internal and environmental conditions. If this was the case then why a universal system is not employed for the evaluation process if all the goals are the same? One of the reasons for this difference is that different countries have different geographical locations. Geographical location of a country influences a lot of the factors for the country like its climate, weather, economy, resources and so on. Hence, if for example, a standard temperature range for comfort inside the buildings is mentioned universally then, different countries will have to use different amounts of resources to achieve it and in doing so the outcome of the process may not be resource efficient. This not only shows the resource picture of the hypothetical standard assessment system; also due to the difference in climate of different regions the amount of resources used will differ and hence, the amount of wastes produced will be different. In a similar manner, a lot of other important green building elements can and will differ drastically based upon geography alone. In short, if a universal assessment system is prescribed for all countries to follow then the achievement of any one of the objectives laid by the system will make it near impossible to achieve. This conclusion is based upon the fact that there is a delicate and critical constraint between all the green building elements and hence, a change in the value of any one of them disrupts the others.

The major elements of green building where the process strives to achieve excellence has already been mentioned.Now an attempt will be made to show some of the many assessment systems and their credit structure to give an idea of which major elements are more important than the others. But before that a brief discussion on the classification of the assessment systems is in the order. All therating system may be classified into two following groups:
• Single Attribute Rating System (Example: ENERGY STAR) It deals with only one aspect or one major element of green building and evaluate only one feature of the building.
• Multiple Attribute Rating System (Example: LEED)

In this system, multiple elements of green building are considered and the efficiency of the whole building is evaluated.

Country Specific Assessment Systems
Previously, it was explained why assessment systems are specific to countries and why it is near about impossible to develop a universal assessment system applicable for every country. The different assessment systems and the specific countries where these are used are listed below:
• Leadership in Energy and Environmental Design (LEED) used in USA
• BRE Environment Assessment Method (BREEAM) used in United Kingdom
• Green Building Council of Australia (GBCA) used in Australia
• Green Mark Scheme used in Singapore
• Hong Kong Building Environmental Assessment System (HKBEAM) used in Hong Kong
• Pearl Rating System for Estidama used in Abu Dhabi
• Deutsche Gesellschaft für Nachhaltiges Bauen(DGNB) used in Germany
• Comprehensive Assessment System for Built Environment Efficiency (CASBEE) used in Japan
• Green Rating for Integrated Habitat Assessment (GRIHA) used in India.
The logos of different green building assessment systems used in various countries have been shown in Fig.1.

Some Green Buildings in the World
In this section, some of the popular green buildings already constructed throughout the world have been mentioned along with their major salient features.

Bloomberg’s New European Headquarters, London, UK
High sustainability standards are the philosophy of every aspect of the building design. Sustainable design features of this building are integrated ceiling panels, combined air supply, cooling, light and acoustic functions in a petal leaf like design. It is rated outstanding by BREEAM with a design phase score of 98.5 per cent and a final stage score of 99.1 per cent. The interior and exterior views of the building are shown in Figure 2.

U.S Green Buillding Council Head Quarters, Washington, USA
This building aimed at achieving all the credits available for every category under a particular LEED scorecard. Highlights of the building include rapidly renewable bamboo flooring, reused granite countertops, non-toxic paint, abundant natural daylight, daylight sensors, high efficiency lighting and renewable sources of green energy to run and maintain the building. It has LEED Platinum certification for commercial interiors.The inside and outside views of this building are shown in Figure 3.

Vodacom New Innovation Centre, South Africa
This center is created to serve as an international hub where new ideas and technology converge together. As a way of projecting this convergence of ideas, the building is aimed at being at harmony with the physical environment. Employing a number of sustainable techniques, this building is truly an engineering marvel. It israted 6-star green star by the GBCSA, first building in South Africa to achieve such status and is shown in Figure 4.

Hysan Place, Causeway Bay, Hong Kong
Developed by Hysan Development Company Limited and designed by international architect Kohn Pedersen Fox, Hysan Place is a mixed-use office and vertical mall complex located at 500 Hennessey Road, Causeway Bay, Hong Kong. Notable sustainable or green features of this building include urban windows at lower floors and green roofs at various levels. It has a Platinum certification from BEAM plus and a LEED Platinum certification in Core and Shell scorecard.The photographic view of this building has been shown in Figure 5.

Suzlon One Earth, Pune, India   
This building occupying an area of 10 acres is located in Pune and is completely eco-friendly and self-sufficient utilising renewable energy, including hybrid wind turbines, solar panels and photovoltaic cells. It is divided into five interconnected individual buildings as shown in Figure 6.

Suzlon One Earth has successfully reduced its operating cost by 35 per cent. This benefit is then passed on by the company to its customers through increased investment in technology. It has GRIHA 5 Star certification and also a LEED Platinum certification.

Future of Green Building
One of the important aspects of green building is the improvement provided by these buildings as opposed to the overall costs of these buildings. Overall cost includes designing cost, construction cost and maintenance cost. Green building takes a step in the right direction over the years of operation. It is seen that the cost of maintenance and also of retro-fitting the building is considerably less as compared to the conventional buildings as illustrated in Table 1 and Table 2.

Apart from decrement in maintenance and operational cost, green building also achieves better conditions of living inside the buildings which directly results in higher productivity of the residents or employees. These have been presented in Figure.7

Green building achieves considerable excellence as opposed to conventional buildings in every element as discussed before. Despite its obvious benefits, it has still not gained widespread popularity as there is no general awareness about these types of buildings. In addition, there is a lack of trained individuals in this field also lack of demand in the market. But the main factor is its initial high cost. No doubt the green building is economically cheaper in the long run, but the most firms cannot sustain the high initial cost of these buildings when there is a lack of a market. Data related to the main barriers to green building for the year 2012, 2015 and 2018 have been presented in Figure 8.

It can be observed from the above figure that higher initial cost has improved considerably, but the other factors are still remaining almost at the same level.

Arunava Mukherjee,
Mechanical Engineering Graduate,
Indian Institute of Engineering Science
and Technology,

Arpit Singh,
Mechanical Engineering Graduate,
Indian Institute of
Engineering Science
and Technology,

Arcot Prasanna Abhinay,
Mechanical Engineering Graduate,
Indian Institute of
Engineering Science
and Technology,

Dr. Bijan Kumar Mandal,
Professor and Former
Head Department of
Mechanical Engineering,
Indian Institute of
Engineering Science
and Technology, Shibpur

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