A Methodological Framework for Life Cycle Sustainability Assessment of Construction Projects Incorporating TBL and Decoupling Principles

Abstract

The triple bottom line (TBL) principle encompasses the idea of continued economic and social well-being with minimal or reduced environmental pressure. However, in construction projects, the integration of social, economic, and environmental dimensions from the TBL perspective remains challenging. Green building rating tools/schemes, such as Green Rating for Integrated Habitat Assessment (GRIHA), Leadership in Energy and Environment Design (LEED), Building Research Establishment Environment Assessment (BREEAM), and their criteria, which serve as a yardstick in ensuring sustainability based practices and outcomes, are also left wanting. These green building rating tools/schemes not only fail to comprehensively evaluate the three dimensions (social, economic, and environment) and interaction therewith, but also lack in capturing a life cycle approach towards sustainability. Therefore, this study intends to address the aforementioned challenges. The first part of this study presents the concept of sustainable construction as a system of well-being decoupling and impact decoupling. Findings in the first part of this study provide a rationale for developing a methodological framework that not only encapsulates a TBL based life cycle approach to sustainability assessment in construction, but also evaluates interactions among social and economic well-being, and environmental pressure. In methodological framework development, two decoupling indices were developed, namely, the phase well-being decoupling index (PWBDI_K) and phase impact decoupling index (PIDI_K). PWBDI_K and PIDI_K support the evaluation of interdependence among social and economic well-being, and the environmental pressure associated with construction projects in different life cycle phases. The calculation underpinning the proposed framework was illustrated using three hypothetical cases by adopting criteria from GRIHA Precertification and GRIHA v.2019 schemes. The results of these cases depict how the interactions among different dimensions (social, economic, and environment) vary as they move from one phase to another phase in a life cycle. The methodological framework developed in this study can be tailored to suit the sustainability assessment requirements for different phases and typologies of construction in the future.

1. Introduction

Sustainability considerations in the building and construction (B&C) sector are becoming more important due to increasing international pressure to address the UN’s Sustainable Development Goals (SDGs), a universal framework for sustainable development that revolves around people, planet, and prosperity [1]. The building and construction sector impacts all three dimensions of sustainability; namely, social, environmental, and economic, also known as the triple bottom line (TBL). Social impact by creating spaces to live and work in, economic impact by contributing to gross domestic product (GDP) and creating jobs, and environmental impact due to the usage of resources and raw materials and the generation of construction and demolition (C&D) waste during the processes of construction [2,3,4]. C&D is the industry term for end of life determination of building and construction materials, although increasingly from a circular economy perspective, this term may considered as deconstruction instead. Buildings/constructed facilities may last 80–100 years or more, and they need to be maintained throughout their life cycle. The operation, maintenance, and decommissioning phases of a constructed facility also have social impact, through the wellbeing of spaces and improvement in productivity, etc.; economic impact through procurement costs, operational costs, job opportunities, etc.; and environmental impact through the use of energy, water, waste generation, etc. However, the pace of the B&C sector in adopting life cycle cum TBL based sustainability practices is slow [5].

In delivering TBL based sustainability outcomes, the implementation of green/sustainable building and construction assessment tools/schemes may be helpful [3,6]. Green Rating for Integrated Habitat Assessment (GRIHA-India), Leadership in Energy and Environment Design-Indian Green Building Council (LEED-IGBC-India), Green Star-Australia, Building and Construction Authority Green Mark (BCA Green Mark-Singapore), Deutsche Gesellschaft für Nachhaltiges Bauen (DGNB-Germany), Comprehensive Assessment System for Built Environment Efficiency (CASBEE-Japan), Building Research Establishment Environment Assessment (BREEAM-UK), Green Globes-Canada, Green Building Index (GBI-Malaysia), Global Sustainability Assessment System (GSAS-Gulf countries), and others are some of the popular assessment tools/schemes in different regions and countries of the world. These rating tools/schemes serve as a reference guide to assess the building/constructed facility’s sustainability performance. The tools have been developed so as to include a set of parameters that pertain to the design, construction, operation, and maintenance phases of buildings/constructed facilities [7]. However, to ensure continuous delivery of sustainability outcomes, current sustainability assessment tools/schemes need to continuously improve to overcome their various limitations, such as lack of life cycle assessment considerations, a holistic approach, performance orientation, effective communications, continuity, participation, a specific vision, adequate scope, a clear framework and indicators, and others [8,9,10,11,12,13]. Most of the current assessment tools/schemes award certification to buildings/construction based on a single compiled score, in which the environmental aspect of sustainability dominates the social and economic aspects of sustainability. Within these certification tools/schemes, the life cycle approach should be consistently considered, rather than individual measurements for evaluating the overall performance of construction projects [13]. These assessment systems should be transparent, tailor made, and flexible enough for assessing the sustainability requirements of preconstruction, construction, operation and maintenance, and the decommissioning/deconstruction phases of construction.

Growing acceptance of the life cycle based sustainability approach and its evaluation requires comprehending the relationships and interactions of different dimensions of sustainability by tactically bringing them together. Decoupling analysis is one such tool, which evaluates the quality of economic growth by measuring the coupling between economic growth, and environmental impact and resource use. Decoupling evaluation is at the core of the sustainability framework [14]. Current sustainability assessment frameworks for buildings/construction lacks decoupling evaluation. The majority of previous studies for evaluating decoupling in the B&C sector were at an aggregated industrial level, and evaluated decoupling between two dimensions of sustainability only, i.e., between economic and environment [15,16,17].

At present, there is no sustainability assessment rating tool/scheme for buildings/construction that explicitly focuses on measuring sustainability from the TBL perspective incorporating decoupling evaluation. Hence, a conceptual sustainability assessment framework needs to be developed, not just for the rating of the constructed facility, but also because of the life cycle of a building. A framework that focuses on a life cycle cum TBL based sustainability approach and, at the same time, ensuring the transition from linear (less sustainable) to circular (more sustainable) systems is critical. Therefore, this research focuses on developing TBL based sustainability assessment framework cutting across different life cycle phases, simultaneously evaluating the transition of linear systems to circular systems using scores obtained from TBL based sustainability assessment at each phase of construction.

The objectives of the current study are as follows:

• To identify different TBL based sustainability, i.e., social, economic, and environmental, assessment parameters and indicators for the different life cycle phases of a construction.
• To propose a methodological framework and classification system by integrating TBL based life cycle sustainability parameters and decoupling indices.

Following this introduction, Section 2 critical reviews the current literature on the interaction among different aspects of sustainability, current sustainability assessment frameworks and presents a comparison of ten rating tools from the TBL perspective. In Section 3, the research method is presented. This section offers analysis of the extracted TBL based life cycle sustainability assessment parameters and presents the methodological framework for calculating TBL scores for life cycle phases and decoupling indices. Section 4 focuses on the hypothetical cases, taking GRIHA criteria to illustrate the calculation procedure of decoupling indices developed in the framework. Section 5 provides the conclusion related to this research.

2. Building and Construction Sustainability

2.1. Rethinking Sustainability as a System of Well-Being Decoupling and Impact Decoupling

Construction is critical to the sustainable development framework, as it affects three dimensions of sustainability: social well-being, economic well-being, and environmental pressure [18,19,20]. Construction has traditionally operated as a “take, make, waste” process, taking raw material from nature, using it in construction and then either abandoning the facility after use or dumping the debris into a landfill. This approach to construction is known as the linear approach to construction. Critical evaluation of current construction processes reveals that they are high on the consumption of resources and pollution creation [21,22]. The net result of this is the increasing scarcity of construction materials and reduction in available natural resources at an alarming rate. Growing concern for the environment, especially in the last few decades, has resulted in several agreements and efforts to define a framework for sustainable development, with an emphasis on concepts such as reduce, recycle, and reuse; more use of green buildings; renewable energy; zero waste; and other such related concepts.

Construction, especially in developing countries, is modelled on a linear approach [23]. The linear approach to construction is characterized by an increase in demand for extracting virgin materials for production and the subsequent construction, operation and maintenance of a project. However, even during/after the construction, operation and maintenance of a project, it continues to impact other aspects of sustainability, i.e., the economic and social. On the economic side, focus is usually on the increase in production profits. With increased production profits, further investment in the economy leads to better job opportunities. In addition, with better job opportunities and economic activities, the socioeconomic gap decreases.

On the contrary, this linear approach further intensifies the extraction of virgin materials and, as a result, sustaining economic and social well-being in the long run is not certain. In a linear approach, social well-being and its improvement are largely dependent on the use of resources from nature and, with an ever increasing population, the use of resources is bound to increase and, as a result, environmental pressure will increase. Economic well-being and growth are also associated with the ever increasing use of resources, resulting in environmental degradation. If continued in the same way, these impacts will lead to disruptions in ecosystem services that are vital to social well-being [14].

To ensure sustainability in the longer run, the vision should not be only aimed at minimizing resource use/resource optimization as this may result in slowing down economic growth [24]. The new systems that enable resource optimization, reduce environmental impacts, and provide alternative economic returns and the social well-being of stakeholders associated with construction, need to be developed [25].

Seeing the nature of the resource intensive construction industry, developing tools for estimating well-being decoupling and impact decoupling and incorporating them in sustainable assessment has become critical to realize the true picture of sustainability (Figure 1). In other words, construction needs assessment models to ensure the decoupling of social and economic well-being from environmental pressures created in different phases of a construction.

2.2. Current Sustainability Assessment Frameworks in Construction

To assess the extent of sustainability compliance, a framework encapsulating sustainability assessment principles and sustainability procedures is required. According to Sala et al., (2015) [8], a framework for sustainability assessment should be based on certain principles, such as: guiding vision (progress towards the goal of delivering well-being should be within planetary limits and ensured for current as well as future generations), essential considerations (incorporating social, economic and environment components and their interactions), adequate scope (progress towards sustainable development should adopt certain timeline, to address both short and long term effects, and it should also capture local as well as global effects), framework and indicators (based on a certain conceptual framework that is to be linked with identified core indicators and reliable data), transparency (the transparency of data and data sources for indicators should be considered), effective communication (clearly communicating with a wide audience and the proper dissemination of results), continuity and capacity (should be continuously monitored and scored), and broad participation (it should encourage legitimacy and relevance by the way of interaction among stakeholders right from the initial stages of the project).

The construction industry, too, has a long history of developing and using such sustainability assessment frameworks [26,27]. Green building councils of different countries are actively involved in developing such frameworks for sustainability assessment schemes. Typically, assessment schemes have been devised using a yardstick for delivering sustainability outcomes through constructed facilities. GRIHA (India), LEED-IGBC (India), Green Star (Australia), BCA Green Mark (Singapore), DGNB (Germany), CASBEE (Japan), BREEAM (UK), Green Globes (Canada), GBI (Malaysia), GSAS (Gulf countries), and others are some of the prevalent assessment tools/schemes. As already mentioned, green rating tools/schemes include a set of parameters and indicators to assess the level of sustainability [7]. Illankoon et al. (2017) [28], after reviewing and comparing eight international green building tools, established seven key criteria in these rating tools as follows: site, energy, water, indoor environment quality, materials, waste and pollution, and management. Other than these key criteria, criteria such as triple bottom line (TBL) reporting, education and awareness, the economic aspects of various costs, sustainable design and planning, and stakeholder engagement can be used to develop new rating tools in the future, as these are missing from the rating tools but illustrated in literature [28].

2.2.1. Critique of Current Sustainability Assessment Frameworks in Construction

Often, the terms green and sustainable construction are used synonymously, but they do have slightly different meanings. As per the US EPA, green building is also referred to as green construction, a structure with an application of processes that are environmentally friendly and resource efficient throughout their life cycle, i.e., during planning, construction, operation, maintenance, renovation, and end of life phases. However, a sustainable building or construction is not only about environmental protection and promoting resource optimization, but should also encompass social well-being factors—such as: (1) security, safety, satisfaction, comfort, and human contributions such as skills, health, knowledge, and motivation [29,30]; (2) people’s social–cultural spiritual needs [31]; and (3) education and skill development, equality, health and safety, community engagement and benefits [32]—and economic sustainability parameters, such as: (1) monetary gains to the stakeholders from the project [33]; (2) growth, efficiency and stability [34]; and (3) employment and economic opportunities [35]. A sustainability framework in construction should be based on the fact that construction activities should be socially, economically, and environmentally safe [28].

Critical evaluation of ten rating tools/schemes reveals that most of them deliver a single rating to construction projects after evaluating them against a predetermined set of sustainability parameters that are mostly dominated by environmental parameters. Most of these rating tools/schemes are biased towards evaluating environmental sustainability, whereas economic and social aspects are partially neglected [28]. Though most of the rating tools/schemes consider social dimensions by allocating 25% of the credit points on average, economic sustainability is rarely evaluated. The DGNB (Germany) rating system gives substantial weightage to economic sustainability by allocating 30% of the credit points, in comparison to other tools (

Table 1. Weights of TBL (social, economic, and environment) credits in different rating tools/schemes.

Building Assessment Tools	Social	Economic	Environment
GRIHA (India)	24	5	71
LEED-IGBC (India)	18	---	82
Green Star (Australia)	31	---	69
Green Mark (Singapore)	18.8	---	81.2
DGNB (Germany)	30	30	40
* CASBEE (Japan)	28.8	6.2	65
BREEAM (UK)	26	12	62
Green Globes (Canada)	22	---	78
GBI (Malaysia)	28	1	71
GSAS (Gulf)	28	3	69

* Refer to Appendix A for methodology and detailed division of credits from TBL considerations in different rating tools/schemes. * CASBEE (Japan): It does not allocate any credit points; it calculates built environment efficiency (BEE) as the ratio of environmental quality of a building to an environmental load of a building.

).

The rationale for focusing more on environmental sustainability is that once environmental sustainability criteria are satisfied then social and economic aspects will be taken care of [36]. Moreover, some of the researchers claim that most rating tools/schemes fail to capture a TBL based perspective on sustainability [10]. The lack of consideration of social and economic dimensions in building performance during its life cycle leads to a deviation from the true meaning of sustainability. Most of the assessment tools and respective criteria (credits) are concerned with the design, construction, and operation and maintenance phases of a project; conception and demolition/decommissioning are not explicitly considered [37].

Life cycle sustainability assessment (LCSA) is defined as the evaluation of environmental, social, and economic negative impacts and benefits that occur through decision-making processes, towards more sustainable projects/products throughout the life cycle of projects/products [38] (Equation (1)).

$$\mathit{LCSA}=f(\mathit{Soc-LCA}+\mathit{Eco-LCA}+\mathit{Env-LCA})$$

(1)

where,

• Soc-LCA = f (social assessment parameters, conceptual planning and feasibility study, design and engineering, construction, operation and maintenance, and end-of-life);
• Eco-LCA = f (economic assessment parameters, conceptual planning and feasibility study, design and engineering, construction, operation and maintenance, and end-of-life); and
• Env-LCA = f (environment assessment parameters, conceptual planning and feasibility study, design and engineering, construction, operation and maintenance, and end-of-life)

Life cycle sustainability assessment/management is missing from such tools/schemes. In a review paper, Wulf et al. (2019) [39] found that, in recent years, with respect to LCSA, the focus has been more on case studies and less on developing methodological frameworks. Sala et al. (2013) [40], in their study, advocate the development of a methodology that adopts a holistic approach and has the capacity to address general or complex system theory. Critical topics that need to be addressed in developing an LCSA based methodological framework should include the development of quantitative and practical indicators for Soc-LCA, approaches to assess the scenarios from a life cycle perspective, standardizing methods to include uncertainties, synergies, and tradeoffs between different dimensions of sustainability [41,42]. Although the literature shows TBL perspectives have been gradually adopted, in-depth investigation of environmental, economic, and social holistically is still missing [4].

Any kind of sustainable assessment and management of construction requires close coordination and interactions among internal and external stakeholders that are associated with the construction project life cycle phases, otherwise, the assessment becomes too theoretical [43,44,45].

Another aspect that is critical for LCSA is decoupling analysis. “Decoupling” as a term was first advanced by the OECD in 2001; it highlights the concept of continued socio-economic growth with diminishing environmental impacts. Decoupling and its evaluation, which is at the core of the sustainability framework [14], is missing from such rating tools/schemes, though the underlining principles of sustainability assessment overlap with decoupling. Central to the UN SDGs/Agenda 2030, decoupling serves as a foundation for materializing the overarching framework of sustainable development; without decoupling the UN SDGs will not be achievable [46].

Current research challenging existing LCSA frameworks call for (1) adopting a holistic approach towards understanding the dynamic interactions between different dimensions of sustainability, (2) shifting from multidisciplinary to transdisciplinary approaches, (3) capability of moving forward through visions and goals, (4) continuous social learning for the stakeholders, and (5) probabilistic approach for dealing with uncertainties [8].

Based on the above critiques, at present, the current rating tools/schemes for supporting sustainability outcomes are left wanting, as they do not deal with all the aspects of TBL and interactions thereof. Moreover, real world, i.e., industry practices, have also not presented as a way forward in supporting TBL based sustainability outcomes. Hence, the current study puts forward a methodological LCSA framework that focuses on TBL based sustainability outcomes and, at the same time, ensures the transition from less sustainable (coupled) systems to more sustainable (decoupled) systems.

3. Research Method

This research is designed in three parts, as shown in Figure 2. In part 1, the study commences with a review of the current green/sustainability rating tools/schemes from the TBL perspective by examining each of the assessment parameters of these rating tools/schemes and classifying them under environment, social or economic categories. It presents a critique of current sustainability assessment frameworks in construction and then establishes the need for the present study.

In part 2, the extraction, integration, and identification of potential TBL based sustainability assessment parameters from different sources, cutting across different life cycle phases (conceptual planning and feasibility, design and engineering, construction, operation and maintenance, end of life) of a construction project, are presented. In addition, a new methodological framework for the LCSA of construction, incorporating TBL and decoupling principles, is presented in this part. This part also presents the key steps involved in computing TBL scores and decoupling indices for different phases, and a classification system for mapping construction projects using computed TBL scores and decoupling indices.

In part 3, the application of the proposed methodological framework using the sustainability assessment criteria of GRIHA Precertification and GRIHA v.2019 schemes are presented, and calculations are shown for computing decoupling indices (well-being and impact decoupling indices) using three hypothetical cases, followed by conclusions and limitations of this research.

3.1. Extraction of Life Cycle Based TBL Sustainability Assessment Parameters

TBL based sustainability parameters and their potential indicators were extracted from previous works. Sustainability parameters and their indicators are prerequisites for any sustainability assessment, as they are critical for setting/translating into sustainability targets [8] (Sala et al., 2015). Based on this argument, the sustainability assessment parameters for different construction phases, along with their description and potential indicators, were identified through a sequential literature review (SLR). A similar approach was used by Stanitsas et al. (2020) [47], to identify the sustainability indicators for the management of construction projects. These identified parameters are knowingly put at a higher level with fewer details about their indicators, as there can be numerous potential indicators under each of the sustainability assessment parameters. The selection of indicators depends on various factors based on regional context, and may not be globally accepted.

Table 2. Pool of relevant social based sustainability assessment parameters for different phases of construction.

Social Sustainability Parameters (Phase 1. Conceptual Planning and Feasibility Study)
Parameters	Description	Indicators	References
Stakeholders’ consultation and engagement	Consultation and engagement with stakeholders/affected communities to identify and monitor their concerns and opportunities in different phases of construction	Consultation/engagement report based on parameters such as: expectations, project constraints, partnership, safety, employment, training, accessibility, and others *	[48,49,50,51,52,53,54,55,56,57,58]
Health and safety considerations	Planning for health and safety issues related to workers (including female workers), users, and other stakeholders	Considerations of guidelines related to health and safety of the stakeholders, which can be documented in the form of Health Impact Assessment (HIA) *	[52,53,57,59,60,61]
Ethical considerations	Planning to promote and ensure professional ethics, avoiding ethical dilemmas, dealing with conflicts of interest, and others	Adopting a framework for monitoring and ensuring compliance to ethical practices *	[62,63,64,65,66,67]
Social Sustainability Parameters (Phase 2. Design and Engineering)
Parameters	Description	Indicators	References
Decent work and economic growth	Incorporate policies for creating job opportunities in neighborhood communities, maintaining social and demographic equity in the design team, construction workers, and others involved in different life cycle phases	Adopting/implementing framework for assessing the trends in the stocks of natural resources, emissions, and discharges in the environment resulting from economic activities; accounting of environmental preservation cost and conservation cost	[1,68,69]
Health, well-being, and the environment	Design for better health, outdoor/indoor environments that promotes better lifestyle practices, nutrition, social connectivity, minimized infectious disease transmission, and others	Adopting design considerations such as: universal accessibility and sustainable transportation, resilient buildings and infrastructure, high quality public and green spaces, good mental health, and others *	[68,69,70]
Design with socioeconomic consideration	Design for promoting culture of occupational health (physical and mental), safety, social inclusion of workers, and include labor provisions in tendering process and supplier contracts	Adopting design considerations such as: design for safety and sanitation for construction workers, design for dedicated facilities for service staff, design for the positive social impact, which include provisions for promoting gender equality, protecting labour rights, and others	[68,71]
Long term value to the society and enhancing local quality of life	Designs considering physical and environmental impacts on the local area, taking community input for improving community’s health	Adopting a framework for evaluating social value to the society	[68,69]
Prioritizing occupant’s comfort	Designs with considerations for environment that is comfortable to occupant	Adopting guidelines of ASHRAE standards for the design of high performance green buildings, which include: thermal comfort, natural and energy efficient lighting, acoustic comfort, olafactory, ergonomics, and visual comforts in designs	[68,72]
Social Sustainability Parameters (Phase 3. Construction)
Parameters	Description	Indicators	References
Socioeconomic strategies for workers	Avoidance of unsafe acts/conditions, promoting gender equality, labor rights, habitable living conditions, grievance redressal mechanism, sustainability awareness, training, skills, and others for workers during construction	Adopting a framework for defining and delivering socioeconomic benefits to the construction workforce *	[68,73,74,75,76,77]
Long term value to the society and local quality of life	Environmental practices at construction sites	Adopting guidelines for mitigation of air pollution, noise pollution, traffic, congestion, waste, and other pollution created on site and in surrounding areas	[68,78,79]
Social Sustainability Parameters (Phase 4. Operation and Maintenance)
Parameters	Description	Indicators	References
Prioritizing occupant’s comfort	Creating an environment that enhances occupant’s comfort during operational phase	Adopting a framework for measuring and enhancing occupant’s comfort *	[68,80,81,82,83]
Operations for protecting and improving health	Support and enhancement of physical/mental health, minimization of infectious disease transmission, accessibility to public transport, space for physical activities, healthy food options, access to clean water, and others	Conducting postoccupancy evaluation survey results and adopting mitigation measures for infectious disease and improving health in a built environment	[68,84,85,86]
Socioeconomic strategies during the operational phase	Creating wider social and economic benefits to relevant stakeholders	Adopting a framework for assessing and promoting diversity, equity, and inclusions among stakeholders	[68,87,88]
Social Sustainability Parameters (Phase 5. End of life)
Parameters	Description	Indicators	References
Effective project communication	Disclosure/digital dissemination of information to the public about dismantling process, and other related issues	Evaluate the level of communication among stakeholders *	[89,90]
Security	Work and safety plan for the contaminated/noncontaminated area, and other related issues	Considerations of guidelines related to health, safety, and security of the stakeholders *	[90,91,92]

* For further explanation refer to Appendix B.

,

Table 3. Pool of relevant economic based sustainability assessment parameters for different phases of construction.

Economic Sustainability Parameters (Phase 1. Conceptual Planning and Feasibility Study)
Parameters	Description	Indicators	References
System of environmental–economic accounting	Integrating economic and environmental data for analysing the interrelationship between economy and environmental stock changes	Adopting/implementing framework for assessing the trends in the stocks of natural resources, emissions, and discharges in the environment resulting from economic activities; accounting of environmental preservation cost and conservation cost	[93,94]
Financial and economic feasibility	Estimating the return on investment, creditworthiness, viability, and cash flow during the entire life cycle of a project	Financial and economic feasibility assessment report of construction projects	[76,95,96]
Cost management plan	Concerning different processes and planning for controlling the cost of resources and other costs of the construction	Adopting framework to avoid time and cost overrun during different phases of a construction	[96,97,98,99]
Human resource planning	Concerning the capacities and capabilities of an individual worker in contributing towards sustainability	Adopting a framework for human resource management (HRM), focusing on aspects such as defined task domain of an employee, recruitment, remuneration, working conditions, training of the workforce, etc.	[100,101,102,103,104]
Supply chain collaboration	Strategies for collaborative practices, ensuring selection of order winners for improved business case	Measuring level of collaboration in the supply chain, i.e., collaboration index	[105,106,107,108,109,110]
Targeted incentives	Strategies for incentivizing to increase worker’s motivation and improving work productivity	Adopting a framework for targeted incentive schemes during different project phases	[111,112,113]
Ability to pay and affordability	Cost bearing ability of users during construction, operation, and maintenance of a project	Adopting framework to evaluate/facilitate the cost reduction of the constructed facility	[47,114]
Economic Sustainability Parameters (Phase 2. Design and Engineering)
Parameters	Description	Indicators	References
Design for quality of service	Design with considerations and promoting resource efficiency by adopting principle shift from linearity to circularity in construction	Adopting design principles such as: functionality and usability, durability and reliability, design for maintenance consideration, flexibility and adaptability for future changes, design for assembly and disassembly (DfD), design for extended life, and reuse/remanufacturing/recycling, specifying reclaimed/recycled materials, and others	[6,23,115]
Life cycle costing for alternative designs	Estimate the costing of the entire life cycle of the construction project, which includes acquisition cost, facility management (operational) cost, and disposal cost	Adopting framework that assists in different design/specifications alternatives with different cash flows over life cycle of construction project	[70,116,117]
Economic Sustainability Parameters (Phase 3. Construction)
Parameters	Description	Indicators	References
Cost, quality, and schedule management	Ensure reduction in the cost of poor quality work and avoid time–cost overruns in building/construction projects	Adopting a framework for performance management in construction projects	[118,119,120,121,122]
Innovation and productivity	Enhance growth through innovation and productivity in building/construction projects	Adopting a framework for promoting innovation and productivity in construction processes	[123,124,125]
Economic Sustainability Parameters (Phase 4. Operation and Maintenance)
Parameters	Description	Indicators	References
Operational costs	Estimating operational and maintenance cost of built nvironment	Adopting models for predicting life cycle costing that includes the cost for periodic inspections, facility’s operational cost, preventive maintenance cost, replacement and repairs cost, and reactive maintenance cost	[126,127,128]
Risk management and long term asset value	Ensure resilience of the built assets by managing risks proactively	Adopting a framework for built asset management with indicators such as responsible building operations, maintenance of built assets, managing environmental risks, analysing potential risks, and preparation for climate action	[128,129]
Sustainable operations and procurement	Ensure sustainable conscious operations and procurement with acknowledged social and environmental standards	Adopting guidelines for sustainable building operations, selecting suppliers and service providers, technical monitoring, maintenance, and construction measures	[128,130,131]
Economic Sustainability Parameters (Phase 5. End-of-life)
Parameters	Description	Indicators	References
Risk assessment and cost security	To assess and mitigate the economic/financial risks associated with decommissioning of project	Adopting a framework for risk management, which includes: estimating cost of the dismantling process, assessing the uncertainties and financial risks with the estimates of dismantling cost	[90,132,133]
Values of expandable resources	Devise strategies for estimating the flow of building stocks	Maintaining account of building stocks that are potential expandable components *	[90,134]
Separation, recycling, and disposal	Prudent and circular use of materials and products	Adopting framework for circular use of C&D waste *	[90,135,136,137]
Tendering Process	Contract award based on parameters such as separate collection rate, sorting rate, recycling rate, hazardous substance plan, site equipment plan, and others	Adopting a conceptual framework for assessing the contractor’s eligibility and performance	[90,138]

* For further explanation refer to Appendix B.

and

Table 4. Pool of relevant environmental based sustainability assessment parameters for different phases of construction.

Environmental Sustainability Parameters (Phase 1. Conceptual Planning and Feasibility Study)
Parameters	Description	Indicators	References
System of environmental–economic accounting	Integrating economic and environmental data for analysing the interrelationship between economy and environmental stock changes	Adopting/implementing framework for assessing the trends in the stocks of natural resources, emissions, and discharges in the environment resulting from economic activities; accounting of environmental preservation cost and conservation cost	[93,94]
Environmental feasibility report/environmental impact assessment	Potentials benefits and ecological risks associated with the proposed project	Evaluating air, water, noise, land, and other pollution monitoring, prevention, and control strategies	[76,139,140,141]
Environmental management plan	Plan for controlling the environmental cost associated with the life cycle phases of a construction	Adopting a framework for environmental cost management accounting	[47,142]
Environmental Sustainability Parameters (Phase 2. Design and Engineering)
Parameters	Description	Indicators	References
Design with safe, healthy, and circular building materials	Promoting the use of materials that can be salvaged and reused aimed at sustainable consumption and production	Adopting/implementing framework for assessing the trends in the stocks of natural resources, emissions, and discharges in the environment resulting from economic activities; accounting of environmental preservation cost and conservation cost	[37,68,70,143,144,145]
Design for harmony between nature and the built environment	Design with considerations such as access to nature, biophilic benefit to people, occupants’ access to nature outdoors, and encouraging biodiversity within site footprints and surroundings	Adopting assessment framework for assessing the value of habitat that includes estimating the quantity and quality of biodiversity gained or lost, comparing pre- and postconstruction phases	[68,146,147,148]
Design for protecting and improving health	Design for maintaining/improving indoor air quality, water quality in order to minimize health risks	Adopting WHO Air Quality Guidelines, ASHRAE set benchmarks and WHO Guidelines for drinking water quality	[68,149,150,151,152]
Design for tackling climate change	Design with a commitment to water efficiency, net zero life cycle emissions, resilience against climate change and extreme weather events across all life cycle phases	Adopting guidelines for net zero emissions and climate resilience with design strategies aimed at mitigation and adaptation	[153,154]
Environmental Sustainability Parameters (Phase 3. Construction)
Parameters	Description	Indicators	References
Water use efficiency and managing local shortage crisis	Commitment towards water reduction in material production and different construction phases	Adopting a strategic framework for adopting and promoting water saving across life cycle phases of a construction	[68,155,156,157,158,159]
Safe, healthy, and circular use of building materials	Avoid usage of hazardous building materials, promote recycling and circular use of building materials	Adopting monitoring framework towards material loop closing in construction processes with focus on: designing out the waste, using circular building products preferring refurbished, recycle, and remanufactured products	[160,161,162,163,164]
Environmental Sustainability Parameters (Phase 4. Operation and Maintenance)
Parameters	Description	Indicators	References
Water use efficiency and managing local shortage crisis	Ensure commitment towards water demand reduction, wastewater treatment, rainwater management, and preserving water qualities for minimizing health risks	Adopting a strategic framework for promoting water saving across life cycle phases of a construction	[68,165,166,167]
Solid waste management	Ensure waste management systems are in place aimed at waste elimination, waste minimization, and material reuse	Adopting decision support framework for solid waste management postoccupancy	[68,70,168,169,170]
Air quality management	Ensure ambient air quality indoors and outdoors by real time monitoring	Adopting a framework for integrating air quality impacts in life cycle assessment	[68,171,172]
Environmental Sustainability Parameters (Phase 5. End of life)
Parameters	Description	Indicators	References
Material flow balance	C&D waste generated during demolition/decommissioning phase	Adopting a framework for acounting of masses arising in demolition/dismantling process, maintaining inventory of massess incurred, estimationg the distance, and others	[90,173,174]
Life cycle assessment of material flows	Environmental impacts/risks because of output flows, waste generated, emissions, and others	Adopting a framework for estimating/preventinng environmental impact arising from demolition of the constructed facility	[90,175]
Hazardous substance remediation	Hazardous substances generated during demolition/decommissioning phase	Adopting hazardous substance remediation guidelines and accounting of hazardous substances separately	[90,176]

present the holistic view of TBL based sustainability assessment parameters that are relevant to different phases of a construction project. This set of identified parameters form the rationale for developing an integrated framework and classification system for sustainable construction, incorporating TBL and decoupling principles.

3.2. A Methodological Framework for Calculating TBL Scores and Decoupling Indices for Life Cycle Phases

Methodological frameworks provide the structure to guide users by using stages or a step by step approach. They help in improving the consistency, robustness, and reporting of the activity, the quality of the research, the standardization of approaches, and maximizing the trustworthiness of the results [177]. Figure 3 illustrates the proposed LCSA framework in six steps.

3.2.1. Identification of Potential Sustainability Parameters/Indicators for Life Cycle Phases of Construction and Weight Determination for Assessment Phases, Categories, and Parameters

Based on common consensus, the assessment parameters and corresponding indicators for construction phases are to be identified using suitable multicriteria decision analysis (MCDA) techniques. After finalizing assessment parameters and corresponding indicators (Table 2, Table 3 and Table 4), the weights that are to be allocated for project phases (W_k, k = 1 i.e., Conceptual Planning and Feasibility Study, k = 2 i.e., Design and Engineering, k = 3 i.e., Construction, k = 4 i.e., Operation and Maintenance, and k = 5 i.e., End of life), assessment categories (W_l, l = 1 i.e., social, l = 2 i.e., economic, l = 3 i.e., environment), and assessment parameters (W_m, m = 1…. n, where n is a number of assessment parameters). Yu et al. (2018) [13] follow a similar approach in their study.

3.2.2. Benchmark/Baseline Score Matrix of Sustainability Assessment

Setting a benchmark score or target score under each of the sustainability assessment parameters (Table 1) is a key feature in most sustainability assessment rating tools/schemes. A benchmark/baseline score is a product of the phase weight (W_k), category weight (W_l) and parameter weight (W_m) (Equation (2)).

$$\mathit{Benchmark}/\mathit{Baseline} \mathit{score}=Wk\ast Wl\ast {{\displaystyle \sum }}_{m=1}^{n}Wm$$

(2)

Similarly,

Table 5. Benchmark/baseline score matrix.

Project Phase	Conceptual Planning and Feasibility Study	Design and Engineering	Construction	Operation and Maintenance	End of Life	Life Cycle Benchmark TBL Score (LCBTS)
Sustainability Pillars
Social	$\mathrm{W}1\ast \mathrm{W}1\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}2\ast \mathrm{W}1\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}3\ast \mathrm{W}1\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}4\ast \mathrm{W}1\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}5\ast \mathrm{W}1\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}1\ast {\displaystyle {\displaystyle \sum }_{k=1}^5}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wk}\ast \mathrm{Wm}$
Economic	$\mathrm{W}1\ast \mathrm{W}2\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}2\ast \mathrm{W}2\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}3\ast \mathrm{W}2\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}4\ast \mathrm{W}2\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}5\ast \mathrm{W}2\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}2\ast {\displaystyle {\displaystyle \sum }_{k=1}^5}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wk}\ast \mathrm{Wm}$
Environment	$\mathrm{W}1\ast \mathrm{W}3\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}2\ast \mathrm{W}3\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}3\ast \mathrm{W}3\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}4\ast \mathrm{W}3\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}5\ast \mathrm{W}3\ast {\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wm}$	$\mathrm{W}3\ast {\displaystyle {\displaystyle \sum }_{k=1}^5}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wk}\ast \mathrm{Wm}$
Project Phase Benchmark Sustainability Score (PPBSS)	$\mathrm{W}1\ast {\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wl}\ast \mathrm{Wm}$	$\mathrm{W}2\ast {\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wl}\ast \mathrm{Wm}$	$\mathrm{W}3\ast {\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wl}\ast \mathrm{Wm}$	$\mathrm{W}4\ast {\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wl}\ast \mathrm{Wm}$	$\mathrm{W}5\ast {\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{Wl}\ast \mathrm{Wm}$	${\displaystyle {\displaystyle \sum }_{\mathrm{K}=1}^5}{\displaystyle {\displaystyle \sum }_{\mathrm{l}=1}^3}{\displaystyle {\displaystyle \sum }_{\mathrm{m}=1}^{\mathrm{n}}}\mathrm{Wk}\ast \mathrm{Wl}\ast \mathrm{Wm}$
						Cumulative Benchmark Sustainability Score (CBSS)

represents the benchmark or baseline score matrix. In simple words, each cell represents the maximum performance under the corresponding phase and sustainability pillar.

3.2.3. Computation of Normalized Performance Score Matrix of Sustainability Assessment

In sustainability assessment, the rationale underpinning the normalization of scores is to transform the measurement of different assessment parameters/indicators to a common unit, and to ease out the inclusion for aggregate sustainability assessment scores. For example, if the benchmark (maximum) score/credit points for an assessment category (social) is 24 and, during the assessment process, a project obtains 15 credit points out of 24 maximum available points, then the normalized social score is (15/24 = 0.625) (Equation (3)).

Normalized performance score (P_nor) = Performance assessment score/Performance benchmark score

(3)

where,

Performance assessment score is the score obtained by a project in a particular assessment parameter and Performance benchmark score (Equation (2)) is the maximum score that can be obtained in a particular assessment parameter. It may be noted that other approaches towards normalization can also be adopted and the present method has been used in the absence of more definitive and universally acceptable methodology.

Similarly,

Table 6. Normalized performance score matrix.

Project Phase	Conceptual Planning and Feasibility Study	Design and Engineering	Construction	Operation and Maintenance	End of Life	Life Cycle TBL Score (LCTS)
Sustainability Pillars
Social	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}1,1, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}2,1, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}3,1, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}4,1, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}5,1, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{k=1}^5}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nork},1,\mathrm{m}$
Economic	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}1,2, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}2,2, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}3,2, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}4,2, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}5,2, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{k=1}^5}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nork},2,\mathrm{m}$
Environment	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}1,3, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}2,3, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}3,3, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}4,3, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}5,3, \mathrm{m}$	${\displaystyle {\displaystyle \sum }_{k=1}^5}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nork},2,\mathrm{m}$
Project Phase Sustainability Score (PPSS)	${\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}1,\mathrm{l},\mathrm{m}$	${\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}2,\mathrm{l},\mathrm{m}$	${\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}2,\mathrm{l},\mathrm{m}$	${\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}2,\mathrm{l},\mathrm{m}$	${\displaystyle {\displaystyle \sum }_{l=1}^3}{\displaystyle {\displaystyle \sum }_{m=1}^n}\mathrm{P} \mathrm{nor}2,\mathrm{l},\mathrm{m}$	${\displaystyle {\displaystyle \sum }_{\mathrm{K}=1}^5}{\displaystyle {\displaystyle \sum }_{\mathrm{l}=1}^3}{\displaystyle {\displaystyle \sum }_{\mathrm{m}=1}^{\mathrm{n}}}\mathrm{P} \mathrm{nork},\mathrm{l},\mathrm{m}$
						Cumulative Sustainability Score (CSS)

represents the normalized performance score matrix; each cell represents performance under the corresponding phase and sustainability pillar.

3.2.4. Chain Numbers of Performance Score Matrix of Sustainability Assessment

The chain number method is commonly employed in econometric analysis, in which value of any given period is related to its immediate predecessor value (values expressed as against preceding value = 100 or 1) [178]. Similarly, chain numbers for social well-being, environmental well-being, and environmental pressure (1-normalized environmental score) (Equation (4)) can be calculated by using a simple aggregative method, representing the sustainability performance of a particular phase of construction with respect to the preceding phase of construction. For example, in Table 9, Case-1, if the normalized social score in the preconstruction phase, as expressed, is 15/24 = 0.625 and the normalized social score in the construction phase, as expressed, is (14/24 = 0.583) then the chain index (SOPn) for the preconstruction and construction phases will be (0.625/0.625 = 1) and (0.583/0.625 = 0.93), respectively (Equation (5)).

Environmental pressure = 1 − Normalized environment score

(4)

Chain Index = Normalized performance score of current phase/Normalized performance score of base phase

(5)

3.2.5. Computation of Phase Well-Being Decoupling Index and Phase Impact Decoupling Index

Examining the importance of decoupling analysis in sustainability assessment and based on decoupling theory, this step involves the development of two decoupling indices, namely: (1) phase well-being decoupling index (2) phase impact decoupling index. The phase well-being decoupling index estimates if there is an increase in social well-being corresponding to the environmental pressure (1-normalized environmental score) for different phases (Equation (6)). The phase impact decoupling index estimates if there is an increase in economic performance corresponding to the environmental pressure (1-normalized environmental score) for different phases (Equation (7)).

Phase well-being decoupling index of stage K (PWBDI_K) = SOPn/ENPn

(6)

Phase impact decoupling index of stage K (PIDI_K) = ECPn/ENPn

(7)

where,

SOPn is the chain index of the normalized social performance score of one phase to the next phase;

ECPn is the chain index of the normalized economic performance score of one phase to the next phase;

ENPn is the chain index of the normalized environmental pressure score of one phase to the next phase;

PWBDI_K is the ratio of the change in social well-being performance to the change in environmental pressure upon moving from one phase to the next phase;

PIDI_K is the ratio of the change in social well-being performance to the change in environmental pressure upon moving from one phase to the next phase.

3.2.6. Classification System Based on TBL Scores and Decoupling Indices for Different Life Cycle Phases

Table 7. Description of different types of coupling/decoupling based on PWBDI_K and PIDI_K.

Type of Coupling/Decoupling		Possible Cases	Remark	State of Sustainability
PWBDI k > 1	Absolute well-being decoupling	SOPn > 1, ENPn < 1	Increase in social well-being but decrease in environmental pressure	Ideal state
	Relative well-being decoupling	SOPn > 1, ENPn > 1	Increase in social well-being exceeds increase in environmental pressure
	Contract well-being decoupling	SOPn < 1, ENPn < 1	Decrease in social well-being is less than the decrease in environmental pressure	Permitted state
PWBDI k < 1	Expansive well-being recoupling	SOPn > 1, ENPn > 1	An increase in social well-being is coupled with increasing environmental pressure	Prohibited state
	Absolute well-being recoupling	SOPn < 1, ENPn > 1	Decrease in social well-being with increase in environmental pressure
	Relative well-being recoupling	SOPn < 1, ENPn < 1	Decrease in social well-being is more than the decrease in environmental pressure
PIDI k > 1	Absolute impact decoupling	ECPn > 1, ENPn < 1	An increase in economic well-being but decrease in environmental pressure	Ideal state
	Relative impact decoupling	ECPn > 1, ENPn > 1	An increase in economic well-being exceeds increase in environmental pressure
	Contract impact decoupling	ECPn < 1, ENPn < 1	Decrease in economic well-being is less than the decrease in environmental pressure	Permitted state
PIDI k < 1	Expansive impact recoupling	ECPn > 1, ENPn > 1	An increase in economic well-being is coupled with increasing environmental pressure	Prohibited state
	Absolute impact recoupling	ECPn < 1, ENPn > 1	Decrease in economic well-being with increase in environmental pressure
	Relative impact recoupling	ECPn < 1, ENPn < 1	Decrease in economic well-being is less than the decrease in environmental pressure

presents the description of the different cases of coupling and decoupling that are possible after computation of the phase well-being and impact decoupling indices. Li et al. (2019) [179] provide a similar kind of cut off values of decoupling degrees. Figure 4 is a graphical representation of the state of sustainability (ideal, permitted, and prohibited) that arise from different combinations of PWBDI_K and PIDI_K, as given in Table 7.

4. Applicability of Proposed Methodological Framework

This section presents the details of applying a TBL based sustainability assessment criteria, as given in

Table 8. Benchmark score and performance score matrix of the three cases.

Sustainability Assessment Parameters	Pre-Construction Phase				Construction Phase
Assessment Criteria	Benchmark Score	Performance Score			Benchmark Score	Performance Score
		Case-1	Case-2	Case-3		Case-1	Case-2	Case-3
So-1: Sustainable Site Planning—Green Infrastructure	3	2	3	3	3	2	3	2
So-2: Occupant Comfort—Visual Comfort	4	3	3	4	4	3	2	2
So-3: Occupant Comfort—Thermal and Acoustic Comfort	2	1	0	2	2	1	1	2
So-4: Occupant Comfort—Indoor Air Quality	6	4	2	5	6	4	3	3
So-5: Socio-Economic Strategies—Safety and Sanitation for Construction Workers	1	1	1	1	1	1	1	1
So-5: Socioeconomic Strategies—Universal Accessibility	2	1	1	2	2	1	1	2
So-6: Socioeconomic Strategies—Dedicated Facilities for Service Staff	2	1	1	2	2	1	1	2
So-7: Socioeconomic Strategies—Positive Social Impact	4	2	3	3	4	2	3	3
Ec-1: Life Cycle Costing—Life Cycle Costing Analysis	5	3	4	5	5	2	4	3
En-1: Sustainable Site Planning—Green Infrastructure	2	2	1	2	2	2	2	1
En-2: Sustainable Site Planning—Low-Impact Design Strategies	5	3	2	4	5	3	3	4
En-3: Sustainable Site Planning—Low-Impact Design Strategies	2	1	1	2	2	1	1	1
En-4: Construction Management—Air and Soil Pollution Control	1	1	1	1	1	1	0	1
En-5: Construction Management—Topsoil Preservation	1	0	1	1	1	1	0	1
En-6: Construction Management—Construction Management Practices	2	1	2	2	2	1	1	2
En-7: Energy Optimization—Energy Optimization	12	8	10	10	12	7	8	4
Energy Optimization—Renewable Energy Utilization	5	4	3	4	5	2	2	3
En-8: Energy Optimization—Low ODP and GWP Materials	1	0	0	1	1	0	1	1
En-9: Water Management—Water Demand Reduction	3	2	2	3	3	2	3	2
En-10: Water Management—Wastewater Treatment	3	1	2	3	3	2	2	2
En-11: Water Management—Rainwater Management	5	4	3	3	5	2	4	3
En-12: Water Management—Water Quality and Self-sufficiency	5	3	2	2	5	1	3	2
En-13: Solid Waste Management—Waste Management-Post Occupancy	4	4	3	3	4	3	4	4
En-14: Solid Waste Management—Organic Waste Treatment On-site	2	2	2	2	2	1	2	2
En-15: Sustainable Building Materials—Utilization of Alternative Materials in Building	5	3	4	4	5	3	4	3
En-16: Sustainable Building Materials—eduction in GWP through Life Cycle Assessment	5	3	2	3	5	3	2	3
En-17: Sustainable Building Materials—Alternative Materials for External Site Development	2	1	0	1	2	1	1	1
En-18: Performance Metering and Monitoring—Commissioning for Final Rating	0	0	0	0	0	0	0	0
En-19: Performance Metering and Monitoring—Smart Metering and Monitoring	6	4	3	5	6	4	4	4
En-20: Performance Metering and Monitoring—Operation and Maintenance Protocol	0	0	0	0	0	0	0	0

, for three hypothetical cases and the related computations for the phase well-being decoupling index (PWBDI_K) and phase impact decoupling index (PIDI_K), as given in

Table 9. Computation of phase well-being decoupling index and phase impact decoupling index for the three cases.

	Case-1		Case-2		Case-3
	Pre-Construction Phase	Construction Phase	Pre-Construction Phase	Construction Phase	Pre-Construction Phase	Construction Phase
Social Score	15	14	22	15	15	17
Economic Score	3	4	5	2	4	3
Environment Score	47	44	56	38	47	44
Normalized Social Score	0.625	0.583	0.92	0.625	0.625	0.71
Chain Index (SOPn)	1.00	0.93	1.00	0.68	1.00	1.14
Normalized Economic Score	0.60	0.80	1.00	0.40	0.80	0.60
Chain Index (ECPn)	1.00	1.33	1.00	0.40	1.00	0.75
Normalized Environment Score	0.66	0.62	0.79	0.54	0.66	0.62
Normalized Environmental Pressure Score	0.34	0.38	0.21	0.46	0.34	0.38
Chain Index (ENPn)	1.00	1.12	1.00	2.19	1.00	1.12
Cumulative Score	65	62	83	55	66	64
# GRIHA rating	***	***	****	**	***	***
Chain Number	1.00	0.95	1.00	0.66	1.00	0.64
PWBDI	0.83		0.31		1.02
Remark	Decrease in social well-being with the increase in environmental pressure		Decrease in social well-being with the increase in environmental pressure		An increase in social well-being exceeds the increase in environmental pressure
PIDI	1.19		0.18		0.67
Remark	An increase in economic well-being exceeds the increase in environmental pressure		Decrease in economic well-being with the increase in environmental pressure		Decrease in economic well-being with the increase in environmental pressure
Categorization	Acceptable region		Prohibited region		Acceptable region

^# “*” in the different columns refers to the rating as per GRIHA. For example, “***” is three star which is given as “***”.

. The criteria chosen in the present formulation are based on the GRIHA Precertification scheme and GRIHA v.2019, a justification for which is also included for completeness.

Apart from the authors’ regional context and understanding of the industry, some of the other important reasons for selecting the GRIHA’s criteria for use in the proposed framework are explained in the following paragraphs:

• According to the latest report of IPCC (2021) [180], we are already on a trajectory towards a 1.2 degrees Centigrade increase and we must act immediately to meet the 1.5 degrees Centigrade target, highlighting the urgency of this issue. The solutions are clear but the willingness to implement solutions is still lacking. These solutions should focus on long term outcomes and impacts, focusing on inclusive and green economies, prosperity, cleaner air, and better health.
• At present, more than 50% of the population live in cities and this is expected to grow to 70% by 2050. The urban population of India (17.7% of the world’s population) has been rising sharply over the past decades and is projected to reach 9.9 billion by 2050 [181]. Rapid urbanization aimed at economic growth in developing regions of the world (mostly in Africa, Latin America, and Asia) creates unprecedented challenges on environmental and socio-economic fronts. As stated by the GRIHA Council, “as per international commitments, India plans to reduce its energy intensity by 33%–35% by 2030 [182]. Green building design, construction and operation will play a critical role as they are synonymous to both sustainable construction and assured high performance”.
• Further, the GRIHA Council also stated that, “GRIHA—with its commitment towards Intended Nationally Determined Contributions (INDCs) has been instrumental in recent years for good practices and innovative solution for enhancing resource efficiency in the building sector. GRIHA’s large scale adoption will have enormous potential in addressing challenges”. However, like any other assessment tools/schemes, GRIHA, too, has scope for improvement in its assessment framework (as discussed in Section 2.2.1). The endeavor to create large scale impact by proposing a new assessment framework with modifications in the existing assessment framework and mapping projects using well-being and impact decoupling indices (Figure 3) will be instrumental in progressing towards true sense of sustainability.
• The GRIHA rating tool has separate schemes for assessing the sustainability performance of the preconstruction (planning, feasibility, design and engineering) and construction (new construction) phases. Though the assessment parameters are defined from a TBL perspective, the weights allocated to different dimensions are not transparent, and are not based on a clear logical set of parameters.
• In addition, to test the proposed life cycle assessment framework incorporating TBL and decoupling indices (phase well-being and impact well-being), TBL based sustainability scores for at least two phases are required. As GRIHA allows the same projects to be rated against its Pre-certification and New-Construction schemes, providing the TBL based assessment scores for the same project in different life cycle phases. This presents a good opportunity for testing the proposed framework with slight modifications in the assessment scores obtained by the projects in their different life cycle phases.

The GRIHA Precertification scheme represents the sustainability assessment of pre-construction phase, i.e., conceptual planning and feasibility study and design and engineering, clubbed together. The GRIHA v.2019 scheme represents the sustainability assessment of the construction phase. The benchmark scores for the different assessment criteria (Table 8) in these schemes have been developed based on the analytical hierarchical process (AHP) (GRIHA v.2019 Abridged Manual, 2019) [70]. Table 8 also shows the assumed performance score for three hypothetical cases in the preconstruction and construction phases. As mentioned above, the computations using these assumed values for the different indices, as defined in Equations (6) and (7), have been shown in Table 9.

5. Conclusions

Construction assessment schemes and tools have been widely criticized for ignoring the life cycle assessment of social and economic dimensions in their sustainability frameworks. Moreover, decoupling and its assessment, which is acknowledged as a core of sustainability frameworks, is also not captured by any of these sustainability assessment tools/schemes. This study is an attempt to answer the above limitations of current sustainability assessment tools/schemes by developing a methodological framework for the life cycle sustainability assessment of construction, incorporating TBL and decoupling principles. The main conclusions/findings from this study can be summarized as follows:

• Construction, especially in the developing world, still operates on take, make, waste (linear/coupled) systems. Life cycle sustainability assessment (LCSA) frameworks that ensure continued economic and social well-being, but with reduced environmental pressures, are missing, i.e., decoupled systems have a clear role to play.
• Comparative analysis of GRIHA (India), LEED-IGBC (India), Green Star (Australia), BCA Green Mark (Singapore), DGNB (Germany), CASBEE (Japan), BREEAM (UK), Green Globes (Canada), BEAM Plus (Hong Kong), and GSAS (Gulf countries) from a TBL perspective shows that most of these assessment tools are biased towards environmental sustainability evaluation and have allocated 69 percent of total credit points, on average. Although most of these assessment tools try to evaluate social sustainability by allocating 25 percent of the total credit points, on average, economic sustainability has been mostly neglected in the sustainability assessment.
• Only the DGNB (Germany) system was observed to have a balance in their approach for allocating credit points across the three dimensions of sustainability. It allocated 30, 30, and 40 percent of total credit points towards evaluating social, economic, and environmental dimensions of sustainability, respectively (Table 1). However, irrespective of initial weights across TBL dimensions, these rating tools provide classification systems based on an aggregate scoring system (except CASBEE) and, therefore, they lack in evaluating interactions among different pillars of sustainability.
• Credit criteria, such as: ethical considerations, a system of environmental–economic accounting, targeted incentives, long term value to the society, design for harmony with nature and the built environment, and design for tackling climate change, are some of the key criteria that are not explicitly included in rating tools/schemes but are found in the literature. For optimized sustainability evaluation, these criteria should be included in the current sustainability rating tools/schemes (Table 2, Table 3 and Table 4).
• DGNB (Germany) is the only rating tool that has a sustainability assessment scheme for rating the decommissioning/deconstruction phase of a building project (pilot mode). Considering the importance of the decommissioning phase in the building life cycle, TBL based sustainability assessment criteria for the decommissioning phase needs to be considered. Green building councils (GBCs) should focus on developing assessment schemes/tools and respective criteria for the decommissioning phase, taking account of the regional context.
• The current study proposes a methodological framework for calculating life cycle based TBL scores and decoupling indices. Two decoupling indices are proposed, i.e., phase well-being decoupling index (PWBDI_K) (Equation (6) and phase impact decoupling index (PIDI_K) (Equation (7), for supporting TBL-based life cycle assessment. These developed decoupling indices specifically estimate the interdependence of human well-being, economic growth, and environmental pressure associated with construction projects. Construction projects in their different life cycle phases can be mapped using computed PWBDI_K and PIDI_K by referring to Table 7 and Figure 4 of this study.
• The sustainability assessment criteria from the GRIHA Precertification and GRIHA v.2019 schemes, representing assessment criteria of pre-construction and construction phase, respectively, were used to illustrate the calculations in the proposed LCSA framework. For three hypothetical cases, PWBDI_K and PIDI_K were computed representing projects moving from the preconstruction phase to the construction phase. It was highlighted that for case-1 and case-3, their GRIHA rating (***) was maintained after sustainability evaluation of the preconstruction and construction phases. It can be seen from Table 8 and Table 9 that the performance of case-2 changed from (****) to (**) when moving from the preconstruction phase to the construction phase. This can be taken to be an example of how the proposed framework can be used to ensure that projects do not lose track when moving from one phase to another.
• The PWBDI value for case-1 indicates that there is a decrease in social well-being with an increase in environmental pressure, and the PIDI value for case-1 indicates that there is an increase in economic well-being that exceeds the increase in environmental pressure. The PWBDI value for case-2 indicates that there is a decrease in social well-being with an increase in environmental pressure and the PIDI value for case-2 indicates that there is a decrease in economic well-being with an increase in environmental pressure. The PWBDI value for case-3 indicates that there is an increase in social well-being that exceeds the increase in environmental pressure and the PIDI value for case-3 indicates that there is a decrease in economic well-being with an increase in environmental pressure (Table 7 and Table 9). However, based on aggregate scores, different scenarios are possible and, moreover, when these projects move from one phase to another phase, they can behave differently, irrespective of their base phase performance, as illustrated by the PWBDI and PIDI for GRIHA cases. For a better understanding of the proposed PWBDI/PIDI approach an illustrative example has been included in Appendix C.

The proposed methodological framework not only encapsulates a TBL based life cycle sustainability approach in construction, but also ensures a monitoring mechanism for the same using decoupling indices. Given the fact that the parameters involved in the operation and decommissioning phases could be quite different from those in the preconstruction and construction phases (as illustrated in Table 2, Table 3 and Table 4), the present study is confined to the preconstruction and construction phases only. It is agreed that scores derived from a “real” project would be more valuable and convincing. However, in the absence of such (real) data, the present study only presents the methodological framework and includes a “proof of concept” verification or validation on the basis of assumed (but “reasonable”) values. The authors continue to strive to collect/access real data in their future works.