Emerging Trends in Lifecycle Assessment of Building Construction for Greenhouse Gas Control: Implications for Capacity Building

 

Abstract

This mini-review addresses the critical problem of significant greenhouse gas (GHG) emissions from the global construction industry, which accounts for 37% of energy-related carbon emissions. With global building areas expected to double by 2060, this paper aims to analyze carbon emission characteristics and control strategies throughout the buildings' entire life cycle, emphasizing the urgent need for effective life cycle carbon management. We introduce and contextualize life cycle assessment (LCA) methods, focusing particularly on Scope 1, 2, and 3 emissions across different life cycle stages of buildings—from design through demolition. Our key findings highlight the potential of intelligent grid energy management systems (EMS) to optimize carbon efficiency in real-time, a pioneering approach that has yet to be widely implemented. The review synthesizes global advancements in green building practices, particularly in regions like Europe, America, and China, and discusses the varied success of these regions in integrating comprehensive carbon management strategies throughout the building life cycle. We conclude with strategic recommendations for future research directions, policy-making, and international cooperation to enhance the sustainability of the construction industry. This study ultimately aims to contribute robust evidence supporting the adoption of advanced LCA methodologies and intelligent EMS in reducing the construction sector's carbon footprint.

Keywords: Greenhouse Gas Measurement, Life Cycle Assessment (LCA), Building Sustainability, Carbon Emission Control, Intelligent Energy Management Systems

Graphical Abstract

Highlights:

1.     Identifies significant carbon footprints in both the construction and operational phases of buildings.

2.     Highlights advancements in life cycle assessment (LCA) techniques to optimize carbon management.

3.     Emphasizes the role of technological innovation in reducing greenhouse gas emissions effectively.

1. Introduction

The global urgency to address climate change is underscored by increasing greenhouse gas (GHG) emissions, with the construction industry playing a pivotal role due to its substantial environmental impact. According to the Emissions Gap Report 2024, buildings account for 6% of the total GHG emissions in 2023, primarily from fossil fuel combustion used to generate on-site electricity and heat in commercial and residential settings (IPCC 2006 categories: 1A4) [1]. Considering the broader construction industry, it contributes to 37% of global energy-related carbon emissions [2-3], a figure that is expected to escalate as global building areas are projected to double by 2060 [4]. This anticipated expansion presents significant challenges to environmental sustainability, highlighting a critical research gap in effective carbon management strategies within the sector. Life cycle carbon emission management offers a methodical approach to curbing these impacts, advocating for a comprehensive analysis of environmental effects at all stages of a building's life cycle, from production to disposal [5]. This approach not only addresses direct emissions but also targets embedded carbon emissions from material extraction, manufacturing, transportation, and construction, thereby offering a robust framework to reduce the construction industry’s overall carbon footprint [6]. However, despite the acknowledged effectiveness of life cycle carbon emission management, its integration into practical decision-making remains limited, largely due to the absence of standardized implementation frameworks and varying levels of technological adoption across regions. Recent advancements in green building practices and carbon management strategies have been observed globally, yet significant discrepancies persist. Regions such as Europe, the US, and China have made notable strides, each implementing systems like the EU's Building Life Cycle Carbon Roadmap, the LEED system, and various green building certifications, respectively [7-8]. These systems have propelled a shift towards low-carbon buildings and fostered sustainable development, particularly in emerging markets that are increasingly adopting innovative technologies and policy measures to mitigate building emissions [9].

Despite these advancements, the comprehensive management of carbon emissions across the entire life cycle of buildings remains a critical gap. Most policies and research focus predominantly on managing operational carbon—emissions generated during a building's use phase—while embedded carbon receives comparatively less attention despite its significant contribution to the sector's carbon footprint [10]. This paper aims to address these issues by providing a comprehensive analysis of carbon management strategies across the building life cycle, highlighting both the progress and challenges of current practices, and underscoring the need for an integrated approach that encompasses both embedded and operational carbon emissions. By exploring real cases and data, this study will not only shed light on effective strategies but also pave the way for future research directions and policy formulations necessary for sustainable global development.

2. Comparative Analysis of Green Building Policy Impacts

2.1 Green Buildings Development

The global construction industry's efforts to curb carbon emissions have intensified, with countries adopting diverse strategies to address both operational and embedded carbon. The 2022 Global Status Report for Buildings and Construction highlights the potential for global raw material consumption to nearly double by 2060, emphasizing the urgent need for effective carbon management strategies [11-13]. Table 1 provides a snapshot of the key regulations and standards in different regions, reflecting their unique approaches to reducing carbon emissions in the building sector.

Table 1. Comparative overview of building standards and regulations.

Country/Region	Regulation/Standard	Context Description	Source Citations
European Union	Energy Performance of Buildings Directive (EPBD)	Mandates nearly zero-energy buildings by 2020, focusing on energy efficiency and renewable energy integration	European Commission
United States	Leadership in Energy and Environmental Design (LEED)	Promotes sustainable building design, focusing on energy efficiency and reduced carbon footprint	U.S. Green Building Council
China	Green Building Evaluation Standard (GBES)	Encourages energy-saving and environmentally friendly practices, with a performance rating system	China Green Building Council
United Kingdom	Future Homes Standard	Targets new homes to produce 75-80% less carbon emissions by 2025, aiming for net-zero by 2050	UK Government
Australia	National Construction Code (NCC)	Incorporates energy efficiency measures to reduce GHG emissions	Australian Building Codes Board
Brazil	Brazilian Labeling of Buildings Program (PBE Edifica)	Incentivizes energy efficiency in buildings through labeling and certification	Brazilian Ministry of Mines and Energy
South Africa	Green Building Council South Africa’s Green Star Rating	A system that evaluates environmental building practices and impacts	Green Building Council South Africa

The effectiveness of building standards and regulations in reducing carbon emissions exhibits substantial variability across global regions, reflecting disparities in technological access, regulatory rigor, and economic conditions. Developed nations, with their robust policy frameworks, typically incorporate advanced technologies and strict regulations that are regularly updated to reflect new environmental challenges and scientific insights. These regions benefit from comprehensive strategies that integrate life cycle assessments more deeply into building practices, effectively managing both operational and embedded carbon [14]. In contrast, developing countries often demonstrate a patchwork of progress and challenges. While some are advancing rapidly, adopting green building practices and enhancing regulatory frameworks, others lag due to limited access to cutting-edge technologies and less stringent environmental regulations. This uneven landscape not only highlights the disparities in global environmental policy effectiveness but also underscores the critical need for international cooperation and support to elevate building standards globally [15]. Moreover, the focus on operational energy efficiency in building regulations, which has dominated the landscape for decades, is now shifting towards a more holistic view that encompasses the entire life cycle of building materials and construction processes. This shift is crucial as it addresses a significant gap in the management of embedded carbon emissions — emissions that are often overlooked despite their substantial contributions to the sector's overall carbon footprint. However, the transition to life cycle thinking is not without its challenges. It requires a paradigm shift in both regulatory approaches and the building sector's operational practices, demanding new knowledge, skills, and technologies [16].

Additionally, the lack of standardized implementation frameworks for life cycle assessment (LCA) methods poses a significant barrier to their widespread adoption. Without uniform standards, the effectiveness of LCA methodologies varies dramatically, complicating efforts to compare or harmonize approaches across borders. This variability can impede the global construction industry's progress toward sustainability goals, as differing methodologies may lead to inconsistencies in data reporting and environmental impact assessments. To truly enhance the global construction industry's sustainability practices, a concerted effort is needed to develop and disseminate standardized, accessible LCA frameworks [17]. Such efforts should be supported by international bodies and involve a collaborative approach among nations to share best practices, innovations, and technological advancements. This collaborative approach could ensure that even less developed regions can adopt effective carbon management strategies, reducing global disparities in building sustainability practices [18].

2.2 Progress in Carbon Management in the Construction Industry Across Different Regions

Table 2 provides a regional comparison of carbon management strategies, which expands on each entry with more detailed critical insights into how these strategies are implemented, their effectiveness, and specific regional challenges [19]. This approach will provide a clearer understanding of the intricacies and impacts of these strategies across different regions.

Table 2. Regional comparison of carbon management strategies.

Region	Key Standards or Policies	Focus Areas	Challenges	Advances Noted
Europe	EU Building Life Cycle Carbon Roadmap	Comprehensive lifecycle management of building projects from inception to demolition.	Difficulties in harmonizing standards across diverse member states with varying local regulations and building practices.	Strong governmental support and integration of advanced technology facilitate thorough implementation of lifecycle assessments.
United States	LEED Certification System	Promotes sustainable design and energy efficiency through stringent certification criteria.	High costs and complex certification process can deter smaller projects and developers from participating.	Broad adoption across commercial and residential projects leading to significant reductions in energy use and GHG emissions.
United Kingdom	PAS 2080 Standard	Focuses on lifecycle assessment and the use of low-carbon materials throughout the building process.	Challenges in integrating the standard across different sectors and aligning it with existing building regulations.	Comprehensive approach has set a benchmark in detailed lifecycle management, influencing global standards.
China	Four Saves and One Environmental Protection	Targets energy and material efficiency to minimize environmental impact during construction and operation.	Scaling these practices to the vast number of ongoing construction projects is challenging.	Notable rapid advancements in green building practices, with a significant push towards achieving national carbon neutrality goals.
Emerging Markets	Various regional initiatives	Generally focuses on the adoption of sustainable technologies and the development of local green building standards.	Often limited by financial and technical constraints, which hinder widespread adoption of advanced sustainable practices.	Increasing international investment and growing governmental support are enhancing the capability to implement sustainable solutions.

European and American Progress: Europe and the United States have set benchmarks in the implementation of comprehensive carbon management strategies within the construction industry [20]. Europe's approach is characterized by a holistic view of the building lifecycle, as evidenced by the EU's Building Life Cycle Carbon Roadmap, which mandates significant carbon management from material extraction through to disposal. This roadmap emphasizes a cradle-to-grave approach and integrates strict measures to ensure that every stage of the building process contributes to carbon reduction [21]. Similarly, the U.S. leverages the LEED certification system extensively, focusing on sustainable design and construction to minimize both embedded and operational carbon emissions. The system encourages the use of energy-efficient materials and technologies, significantly reducing carbon footprints of new buildings and renovations [22].

Distinctive UK Framework: The UK has differentiated itself with the PAS 2080 standard, a guideline that uniquely addresses carbon management throughout a project's lifecycle, from inception to deconstruction. This standard advocates for a strategic emphasis on life cycle carbon assessment from the demand stage, pushing for the adoption of low-carbon materials and energy systems right from the design phase [23]. It facilitates meticulous planning and resource optimization throughout the building's life, making the UK a leader in sustainable building practices [24].

Innovations in China: China’s rapid urbanization and construction growth have propelled it to advance aggressively in green building practices. Through initiatives like the "Four Saves and One Environmental Protection," China focuses on enhancing energy and material efficiency at all stages of construction and operation [25-26]. The country’s emphasis on the adoption of green building certifications and low-carbon design has been pivotal in promoting sustainable urban development. China’s approach highlights a significant commitment to reducing its construction sector's carbon footprint, aligning with its broader environmental goals of achieving carbon neutrality.

Emerging Markets: Emerging markets face unique challenges in implementing robust carbon management strategies due to varying economic conditions and technological accessibility [27]. However, these regions recognize the critical importance of sustainable construction practices in mitigating climate change impacts. Efforts to adopt existing technologies and develop new policies are evident, with a significant focus on improving energy efficiency and reducing reliance on high-carbon materials. The adaptation of international best practices and the increasing availability of investment for green projects are helping these markets progress toward more sustainable construction practices [28].

2.3  Critical Analysis of Building Standards and Regulations

While all regions have developed robust frameworks to encourage sustainable building, the adaptation and full implementation of these standards vary significantly. Challenges such as cost, technological availability, and regulatory support play critical roles [29]. For example, in the United States, the high cost of LEED certification can deter smaller developers, whereas in China, the challenge lies in enforcing standards across its massive construction industry [30]. Regions like the EU and Australia have effectively integrated new technologies through these standards, driving innovation in building materials and construction techniques [14-16.30]. However, the pace of updating these standards to incorporate the latest technologies can be a limiting factor, as seen with the Australian NCC.Incentives such as those provided by Brazil's PBE Edifica have shown to be effective in promoting energy efficiency but require greater public awareness and integration into broader regulatory frameworks to be fully effective. In contrast, South Africa's Green Star rating system has become a market differentiator, yet its impact is limited by high costs associated with certification [31].

3. Enhanced Life Cycle Assessment Framework for Building Sustainability

3.1 Introduction to Life Cycle Assessment for Buildings

Life Cycle Assessment (LCA) in Table 3 is an indispensable tool for quantifying the carbon footprint of buildings from inception through to demolition, providing an exhaustive evaluation of both direct and embedded carbon emissions. This method facilitates the pinpointing of emission hotspots and enables the formulation of specific strategies for carbon reduction. The framework established by the EN 15978:2011 standard is pivotal for this analysis, categorizing the building lifecycle into distinct stages, each representing critical phases in the environmental impact of the structure [32].

Table 3. Stages of building life cycle according to EN 15978:2011.

Stage	Description	Impact Areas
Product Stage (A1–A3)	·       A1 (Raw Material Supply): Emissions from extracting raw materials like mining or harvesting. ·       A2 (Transport): Transportation of raw materials to manufacturing facilities. ·       A3 (Manufacturing): Emissions from the production of building materials, such as steel or concrete.	Significant embedded carbon emissions, critical for high-energy-intensive materials.
Construction Stage (A4–A5)	·       A4 (Transport): Transportation of building materials to the construction site. ·       A5 (Construction/Installation Process): Emissions from on-site construction activities, including machinery use and material waste.	Optimization opportunities through the use of local materials and energy-efficient equipment.
Use Stage (B1–B7)	·       B1 (Use): This stage accounts for the emissions directly associated with the building's operations but excludes energy consumption. It includes the base level of emissions from operational processes essential for building functionality. ·       B2 (Maintenance): Includes emissions from routine maintenance activities required to keep the building operational. This can involve cleaning, minor repairs, or servicing of systems like HVAC, which do not involve major material replacements. ·       B3 (Repair): This involves corrective actions that are necessary to fix damages or deterioration that occur during the building's use phase. Repairs can vary in scale and often involve replacing or fixing parts of the building fabric or systems to restore them to working condition. ·       B4 (Replacement): Refers to the process of substituting significant components of the building that have reached the end of their useful life, such as replacing entire HVAC systems, roofing, or glazing units. This stage is critical as it often involves substantial emissions due to the production and transportation of new materials. ·       B5 (Refurbishment): Entails more extensive restoration or improvement of existing building sections, potentially including aesthetic updates and energy efficiency upgrades. Refurbishments can lead to significant reductions in operational emissions if they incorporate energy-saving technologies and materials. ·       B6 (Operational Energy Use): Represents emissions from energy consumed for heating, cooling, lighting, and other electrical uses during the building’s operational phase. It is typically the most significant source of emissions in the building's life cycle and thus a primary target for reduction strategies. ·       B7 (Operational Water Use): Encompasses emissions related to water supply and treatment within the building. This includes the energy used in heating water, pumping, and managing wastewater, which can also contribute to the building's carbon footprint.	Operational emissions often dominate life cycle emissions; focus on energy efficiency can reduce impact.
End-of-Life Stage (C1–C4)	·       C1 (Deconstruction/Demolition): Represents emissions from the demolition process itself. This stage involves the dismantling or destruction of the building structure, requiring heavy machinery that emits substantial amounts of CO2. ·       C2 (Transport): Includes emissions from transporting waste materials from the demolition site to recycling centers or landfills. The efficiency of the transport logistics can significantly impact the overall emissions from this stage. ·       C3 (Waste Processing): Covers emissions from sorting, processing, or recycling building materials. Effective waste processing can significantly reduce the environmental impact by diverting materials from landfills and reducing the need for new raw materials. ·       C4 (Disposal): Refers to emissions associated with the final disposal of materials, particularly in landfills or through incineration. This stage can be minimized through effective recycling and reuse strategies, which prevent significant amounts of greenhouse gas emissions.	Emphasis on recycling and material recovery to reduce environmental impacts.
Benefits Beyond the System Boundary (D)	D (Reuse, Recovery, Recycling Potential): Benefits of recycling or reusing materials to reduce future environmental burdens.	Supports circular economy practices by offsetting emissions in future production cycles.

The Product Stage, encompassing raw material supply, transport, and manufacturing, is notable for its significant contribution to embedded carbon emissions, particularly in materials that are energy-intensive to produce, such as steel and concrete. This stage requires meticulous attention to the sources of raw materials and the energy efficiency of manufacturing processes [33]. Following this, the Construction Stage involves the transportation and installation of building materials, where strategic optimization, such as the utilization of local materials and energy-efficient construction practices, can substantially mitigate carbon emissions. During the Use Stage, which includes maintenance, repair, replacement, refurbishments, and operational energy use, emissions associated with the building's operations often constitute the majority of its lifecycle emissions. This phase highlights the importance of designing buildings that are energy-efficient and easy to maintain. The End-of-Life Stage, covering deconstruction, demolition, waste processing, and disposal, presents opportunities for reducing environmental impact through focused efforts on material recovery and recycling, thereby supporting circular economy initiatives. Additionally, the Benefits Beyond the System Boundary, such as the potential for reuse, recovery, and recycling of materials, play a crucial role in offsetting emissions in future production cycles and underline the importance of designing buildings with their eventual end-of-life in mind [34].

By structuring the LCA in accordance with the EN 15978:2011 guidelines, stakeholders can systematically identify carbon hotspots and develop targeted strategies to reduce emissions across all life cycle stages. This standard provides a consistent methodology that facilitates comparability and enhances the reliability of LCA results, making it a critical tool for sustainable building design and decision-making as summarized in Figure 1. Despite the structured approach provided by the EN 15978:2011 standard, several methodological challenges persist. The complexity and resource intensity of conducting a comprehensive LCA can be prohibitive, particularly in contexts where data is scarce or the technological capacity for detailed environmental assessment is lacking [33,35]. Moreover, the standard's rigidity may not adequately accommodate the diverse range of building types and may fail to reflect local environmental conditions or innovative construction practices. Recent literature, including works by Zujian et al. and Masoud et al., calls attention to the need for LCA methodologies to adapt to temporal variations in grid and material emission factors. These variations can significantly influence the accuracy of long-term decarbonization predictions, particularly in rapidly evolving markets or in regions where renewable energy integration is accelerating [36]. These studies advocate for the integration of real-time data and the development of more dynamic and flexible LCA frameworks that can better capture the complexities of modern building environments.

To improve the utility and accuracy of LCA in building assessments, it is recommended that LCA frameworks be developed to be more adaptable, capable of integrating a broader array of building types and environmental conditions (Figure 1). Enhancing data collection methods to capture detailed, real-time information on material properties, construction techniques, and building operations is also critical [37]. Such improvements could facilitate more precise evaluations of environmental impacts and foster more effective carbon management strategies. Furthermore, fostering collaboration among academia, industry, and policymakers can synergize efforts and ensure that advancements in LCA methodologies are effectively translated into practice (Table S1). Sharing knowledge and aligning strategies across these sectors can significantly enhance the capacity of the construction industry to meet sustainability goals [31,38].

Figure 1. Carbon management in infrastructure and qualified management framework.

3.2  Incorporating Scope 1, 2, and 3 Emissions in Building Life Cycle Assessment (LCA)

Life Cycle Assessment (LCA) categorizes carbon emissions into three distinct scopes, each representing different sources within the building life cycle. A typical strategic analysis of Scope 1, 2, and 3 emissions enables a nuanced understanding of a building's comprehensive carbon footprint [39]. This approach not only identifies the primary sources of emissions throughout the building life cycle but also aids in developing targeted carbon reduction strategies tailored for each stage. By systematically addressing each scope, stakeholders can implement more effective sustainability measures, ensuring that all potential environmental impacts are considered and mitigated:

• Scope 1 Emissions: Direct emissions arise from activities controlled or owned by the entity, such as the combustion of fuels in construction machinery and emissions from on-site manufacturing processes. These emissions are immediate and visible, occurring at the construction sites and production facilities, making them critical targets for direct management strategies.

• Scope 2 Emissions: Indirect emissions result from the consumption of purchased electricity, steam, heating, and cooling. These emissions are consequential to the building’s energy use and typically originate from the utility providers’ energy production processes. Scope 2 emissions are integral to assessing the energy efficiency of building operations, encompassing all phases from construction to end-use stages, including heating, cooling, and lighting.

• Scope 3 Emissions: These encompass all other indirect emissions not covered under Scope 2. Scope 3 emissions are the most extensive category, including both upstream and downstream emissions. Upstream emissions involve activities from the production of purchased goods, transportation of raw materials, and other preliminary activities leading to the construction phase. Downstream emissions involve post-construction processes like the use phase and maintenance, encompassing emissions from building operations and end-of-life stages.

3.3 Comprehensive Management of Raw Materials and Lifecycle Carbon Emissions

Life Cycle Assessment (LCA) serves as a critical methodology for quantifying and managing the carbon emissions of buildings throughout their entire lifecycle [40]. This detailed analysis is indispensable for achieving an accurate and holistic understanding of a building’s carbon footprint. The carbon footprint encompasses both embedded and operational carbon emissions, which are integral to assessing the overall environmental impact of building projects [41-43]. Embedded Carbon Emissions are generated during the initial phases of a building's life, including material extraction, manufacturing, transportation, and construction activities on site. These emissions also arise during the demolition or potential reuse of materials at the end of the building's life cycle. Such emissions are significant as they cover a wide range of processes that contribute to the building's total carbon footprint, necessitating meticulous management and reduction strategies [49\4].  Operational Carbon Emissions, on the other hand, are associated with the energy consumed to maintain comfortable indoor environments through heating, cooling, lighting, and the operation of appliances. These emissions typically occur throughout the life of the building, starting from its completion to its eventual end of use. Operational emissions are critical as they often constitute the largest share of a building’s total emissions over its lifetime [43].

Figure 2. Life Cycle Assessment Scopes – Embodied and Operational Carbon.

In assessing the carbon footprint of various building types, it is evident that the contribution of embodied and operational carbon varies significantly. For instance, standard residential buildings typically exhibit an embodied carbon contribution ranging between 20–40%, whereas operational carbon can account for 60–80% of the total emissions [16]. This contrast is even more pronounced in low-energy residential buildings, where embodied carbon makes up 50–70% of emissions, reflecting more sustainable construction practices that lower operational carbon to 30–50%. In commercial office buildings, the split is approximately 30–50% for embodied carbon and 50–70% for operational carbon, underscoring the ongoing energy demands of such structures. Infrastructure projects like bridges present the highest levels of embodied carbon, ranging from 80–90%, with operational carbon constituting a smaller fraction of 10–20%. These figures, sourced from robust studies by RMI in 2021, Pomponi & Moncaster in 2016, and the UNEP 2020 Global Status Report, highlight the critical need for targeted carbon management strategies that address both the initial construction phase and the building’s operational life to enhance overall sustainability in the built environment [23].

3.3.1 Raw Material Sourcing and Impact

The sourcing of raw materials is a pivotal initial stage in the life cycle of any building project, presenting significant environmental impacts that permeate all subsequent phases—from construction and use to eventual demolition. The process typically begins with the extraction of materials, utilizing heavy machinery for activities such as mining and logging [44]. Embedded carbon emissions and primary emissions from the extraction phase are largely due to the use of heavy machinery in activities such as mining and logging, as well as the transportation of these materials to manufacturing sites. Accurately assessing the carbon footprint at this stage is crucial because the initial choice of materials can significantly influence the overall sustainability of a building. For example, selecting materials with lower embedded carbon or sourcing materials from locations that minimize transportation emissions can lead to substantial reductions in the greenhouse gas (GHG) emissions associated with the construction phase [24,46]. This early decision-making process is pivotal in setting the stage for a building's long-term environmental impact.

Moreover, the control and measurement of GHG emissions are not solely about reducing emissions; they are also about establishing accountability throughout the entire life cycle of a building [47]. By integrating rigorous emissions tracking from the raw material extraction phase, stakeholders can make more informed decisions that align with environmental targets. This comprehensive approach encourages the construction industry to adopt more sustainable practices by identifying areas where carbon efficiency can be improved, ranging from material selection to end-of-life recycling or disposal (Figure 2). Incorporating advanced technologies and strategies in raw material management can significantly enhance sustainability [48]. For instance, using renewable energy sources to power extraction equipment can reduce the carbon footprint associated with material extraction. Additionally, optimizing material usage to minimize waste and improving logistical routes to cut down on transportation emissions are critical steps that can contribute to reducing the overall environmental impact of buildings [17,49]. This life cycle perspective not only helps in achieving compliance with environmental regulations—such as those aimed at reducing carbon tax liabilities—but also fosters a more sustainable construction industry that contributes to broader climate change mitigation efforts [50].

3.3.2 Manufacturing and Production Processe

The manufacturing and production phase in the life cycle assessment (LCA) of building materials is a significant source of greenhouse gas (GHG) emissions, especially for energy-intensive materials like steel and cement. This stage involves the conversion of raw materials into finished products and is marked by substantial energy requirements. System boundaries for this phase include the sourcing of raw materials, their transportation to manufacturing sites, and the actual production processes, all of which contribute to both direct and indirect emissions [26]. Direct emissions occur onsite at manufacturing facilities, primarily from the use of energy in production processes. Indirect emissions are associated with the generation of electricity and heat needed for manufacturing. Typically, these processes are heavily dependent on fossil fuels, which are significant contributors to carbon dioxide emissions. For instance, the production of cement involves a calcination process that alone produces approximately 0.93 kg of CO₂ per kg of cement, highlighting the high energy consumption and emissions intensity of such materials [51].

Emissions from the manufacturing phase are substantial, making it one of the most significant sources of CO₂ emissions within the entire building life cycle. This is particularly true in regions where the energy grid relies heavily on coal or natural gas. Transitioning to renewable energy sources, such as solar, wind, or biomass, is therefore crucial for reducing emissions. This shift not only aligns with broader sustainable development goals but also helps mitigate the environmental impact of the building sector. For example, the integration of solar energy systems in manufacturing can drastically reduce reliance on fossil fuels [52]. Adopting more energy-efficient manufacturing technologies also plays a critical role. High-efficiency kilns in cement production and electric arc furnaces in steelmaking can significantly lower emissions [53]. Additionally, the use of prominent databases like ecoinvent allows for accurate tracking and reporting of emissions throughout these processes, ensuring that the functional unit of LCA—typically one kilogram of manufactured material—accurately reflects the environmental impact [54-56]. Furthermore, improving the efficiency of logistical operations to reduce transportation emissions and optimizing material usage to minimize waste are essential steps in enhancing the sustainability of manufacturing processes. These strategies are part of a comprehensive approach to managing life cycle greenhouse gas emissions, from raw material extraction to the end-of-life stage of the building materials [57-58].

3.3.3 Construction Phase

The construction phase is pivotal within the lifecycle of a building, marked by diverse activities that cumulatively shape the project's carbon footprint. This stage is characterized by the operation of construction machinery, transportation of materials, and various on-site processes such as lifting, cutting, and assembling building components [43]. The prevalent use of diesel-powered machinery and vehicles is a primary source of carbon emissions, resulting in significant direct and indirect emissions released into the atmosphere. The transportation of materials to construction sites notably amplifies the carbon emissions during this phase, with the extent of emissions heavily influenced by the distance traveled and the transportation methods employed [18]. Fuel consumption by construction machinery accounts for the bulk of direct emissions, further exacerbated by the transportation of materials ranging from minor components to substantial structural elements. Additional on-site emissions, including those from power generators and temporary heating systems, contribute to the project's environmental burden.

Strategically reducing these emissions is crucial and involves optimizing material transportation logistics to shorten travel distances and switching to lower-emission transport methods. Moreover, integrating energy-efficient and cleaner technologies in construction machinery can dramatically decrease fuel consumption and associated emissions. Where practical, utilizing prefabricated components, produced in energy-efficient facilities, serves to minimize emissions further on-site [35,54]. Effective greenhouse gas control during the construction phase thus involves not only the adoption of new technologies but also careful planning and management of construction practices to minimize environmental impact. This phase represents a critical opportunity for emission reduction within the building's entire life cycle, supporting broader goals of sustainability and environmental responsibility in the construction industry. The construction phase includes emissions from specific activities: (a) Brickwork: 50 – 100 kg CO₂/m³, considering machinery and material transportation; (c) Reinforced Cement Concrete (RCC) Work: Emissions are higher at 300–500 kg CO₂/m³, primarily due to cement and steel usage; (c) Plastering and Painting: Plastering generates approximately 8 – 12 kg CO₂/m², while painting can emit around 1 – 3 kg CO₂/m², depending on the type of paint. Quantifying these emissions allows project planners to adopt lower-emission construction techniques and materials [55].

3.3.4 Building Operation and Maintenance

The operation and maintenance phase of a building is critical due to its prolonged duration and sustained energy demands, which significantly contribute to the building's overall carbon footprint. Operational carbon, which includes energy consumed for heating, cooling, lighting, and running appliances, is a major contributor throughout the building’s lifecycle: (a) Electricity Use: Produces 0.5 – 1.2 kg CO₂/kWh, depending on the energy grid’s mix of fossil fuels versus renewables; (b) HVAC Systems: Heating and cooling systems account for 25 – 40% of operational emissions, translating to approximately 100–200 kg CO₂/m² per year in typical office buildings; (c) Lighting: Emits around 10–20 kg CO₂/m² per year with conventional lighting. This phase continuously generates substantial carbon emissions, emphasizing the need for targeted emission reduction strategies [9]. Operational carbon dynamics are driven by the building’s energy requirements to maintain optimal environmental conditions for occupant comfort. HVAC systems are notable for their substantial energy use, heavily influencing the building's energy profile. Similarly, lighting and various electrical appliances contribute significantly to the energy demand. The source of this energy—whether from fossil fuels or renewable resources—critically impacts the resultant carbon emissions. For instance, HVAC systems operating on electricity from coal-fired plants will have a higher carbon footprint compared to those utilizing renewable energy sources [56-57]. Incorporating renewable energy technologies such as solar panels or wind turbines dramatically reduces reliance on fossil fuels, thereby minimizing carbon emissions. For example, the use of photovoltaic systems to harness solar energy can significantly offset the consumption of grid electricity, especially in regions like Australia, where solar potential is high. Back to basis, another example via incorporating advanced energy simulation tools such as EnergyPlus is also crucial for precisely measuring and managing the energy performance of buildings during the operation phase. EnergyPlus can simulate heating, cooling, lighting, ventilating, and other energy flows, offering detailed insights into the building’s energy dynamics. Features of EnergyPlus include detailed thermal comfort models that help optimize HVAC system performance to reduce unnecessary energy use while maintaining comfort levels.

The Maintenance and Repairs phase is a crucial aspect of a building’s life cycle, encompassing activities necessary to maintain the functionality, safety, and comfort of the building over time [12,58]. This phase contributes to both embedded and operational carbon emissions, as it requires the use of new materials and energy to carry out repairs and ongoing maintenance. Effectively addressing these emissions is essential to minimizing the building’s environmental impact throughout its entire lifespan. Embedded carbon in this phase arises from the production of new materials needed for upkeep, such as replacement parts, structural components, or finishes [59]. These materials often involve energy-intensive manufacturing processes similar to those used during the building’s initial construction, contributing to the overall carbon footprint each time maintenance or repairs are conducted. The frequency and scale of these activities directly influence the cumulative embedded carbon throughout the building’s life cycle [57]. Each of these activities adds to the building’s total operational carbon emissions, further contributing to its ongoing environmental impact. Primary emissions in this phase are primarily associated with the production and transportation of materials needed for maintenance. The production process for these materials, typically involving significant energy consumption from fossil fuels, leads to carbon dioxide emissions. Additionally, transporting these materials to the building site often involves the use of vehicles that emit greenhouse gases, especially when long distances or heavy materials are involved. To mitigate emissions associated with maintenance and repairs, several strategies can be employed. Using durable, high-quality materials that require less frequent replacement can reduce the need for repairs, thereby minimizing embedded carbon. Selecting materials with lower embodied carbon, such as those made from recycled or sustainably sourced components, can also help reduce the overall environmental impact [47,60]. Optimizing logistics to reduce transportation distances and employing more efficient, lower-emission vehicles can further cut down on transportation-related emissions. Energy-efficient maintenance practices, including the use of energy-efficient tools and machinery, can also contribute to reducing operational carbon. Furthermore, incorporating smart maintenance technologies that predict and address issues before they become significant problems can improve efficiency and reduce the need for extensive repairs. GHG emissions during maintenance and repairs depend on the materials and scope: (a) Minor Repairs: For example, replacing a single drywall panel generates around 20–40 kg CO₂, including material production and installation; (b) Roof Repairs: Can emit up to 500–700 kg CO₂, depending on materials like asphalt shingles or metal sheets; (c) Complete Refurbishments: Major renovations, such as replacing flooring, windows, and insulation, may generate 100–300 kg CO₂/m². These figures highlight the importance of durable materials and predictive maintenance to reduce carbon impacts.

3.3.5 End-of-Life Management

The End-of-Life and Demolition phase marks the final stage in a building’s life cycle, where the structure is dismantled and materials are either disposed of or recycled [20]. This phase is critical in terms of both embedded and operational carbon emissions, as the activities involved are energy-intensive and generate significant waste. Proper management of this phase is essential to minimizing the building’s overall environmental impact. Embedded carbon in the end-of-life and demolition phase is inherent in the materials being dismantled. The embodied energy from the original construction and any subsequent maintenance and repairs is released back into the environment if the materials are not properly recycled or reused [60]. This embedded carbon represents the cumulative impact of all the materials used throughout the building's life cycle, highlighting the importance of sustainable material choices and practices from the outset. Primary emissions during the demolition process primarily arise from the fuel consumption of demolition equipment. Heavy machinery such as excavators, bulldozers, and cranes, which are essential for safely and efficiently dismantling buildings, typically run on diesel or other fossil fuels, resulting in substantial direct carbon dioxide emissions. Additionally, the process of handling and transporting waste materials also contributes to primary emissions. Improper disposal of waste materials, such as sending them to landfills or incineration, can lead to further emissions, exacerbating the environmental impact [61]. Mitigating the environmental impact of the end-of-life and demolition phase involves several strategic approaches. Implementing deconstruction practices instead of traditional demolition can significantly reduce emissions. Deconstruction involves carefully dismantling buildings to salvage materials for reuse or recycling, thereby reducing the embedded carbon released during the process [56]. This approach not only minimizes waste but also promotes the circular economy by extending the lifecycle of building materials. Optimizing the use of demolition equipment to enhance efficiency and reduce fuel consumption is also crucial. This can be achieved through regular maintenance of machinery, employing more energy-efficient models, and exploring alternative fuels or electric-powered equipment where feasible.

Effective waste management strategies are essential in this phase. Separating materials on-site to facilitate recycling can greatly reduce the amount of waste sent to landfills, thus minimizing emissions from waste handling and disposal [61]. Additionally, using local recycling facilities can reduce transportation emissions, further contributing to emission reduction efforts. Incorporating lifecycle analysis and planning from the early stages of a building project ensures that end-of-life considerations are integrated into the design and construction phases. This foresight allows for the selection of materials and construction methods that facilitate easier deconstruction and recycling, ultimately reducing the building’s overall environmental footprint. Demolition generates GHG emissions through fuel use and material handling: (a) Demolition Activities: Excavators, bulldozers, and related machinery emit 20 – 30 kg CO₂/hour of operation; (b) Waste Transportation: Adds 0.1 – 0.3 kg CO₂ per ton per km, depending on the distance to recycling or landfill sites; (c) Landfilling: Non-recycled materials may contribute an additional 30 – 40 kg CO₂/ton through methane emissions during decomposition. Planning for material reuse and recycling can significantly mitigate these emissions [62].

3.3.7 Material Reuse and Recycling

The Material Reuse and Recycling phase is crucial in reducing the environmental impact of buildings by extending the lifecycle of materials and minimizing the need for new resources. This phase involves repurposing materials from demolished buildings or excess materials from construction sites, significantly reducing both embedded carbon and primary emissions. Effective strategies for reuse and recycling are essential to managing greenhouse gases across all stages of a building's lifecycle. Reusing materials curtails the demand for new material extraction and production, thereby reducing the carbon footprint associated with the initial stages of raw material processing and transportation [63]. For instance, utilizing reclaimed wood, steel, or concrete not only circumvents the energy-intensive production processes required for new materials but also offers considerable carbon savings. Similarly, recycled materials typically require less energy to process than manufacturing from virgin resources, aiding further in the reduction of embedded carbon [21]. Energy consumption during this phase, although necessary for recycling and reprocessing, is generally less intensive than the initial production of new materials. Recycling processes like those for aluminum and steel are notably less energy-consuming than their extraction and initial refining. Reprocessing activities such as crushing and reusing concrete also consume less energy compared to new cement production, which is notably energy-intensive.

To enhance the effectiveness of material reuse and recycling, several strategies can be implemented. First, establishing comprehensive recycling programs at construction and demolition sites ensures that materials are systematically sorted and diverted from landfills. This involves creating facilities and processes for collecting, sorting, and storing reusable materials. Second, promoting the use of recycled materials in new construction projects can drive demand for recycled products and create a market for reclaimed materials. This can be supported by policies and incentives that favour the use of recycled content in building materials. Additionally, technological advancements in recycling processes can further reduce the energy consumption associated with material reprocessing. Innovations such as advanced sorting technologies, more efficient crushing and grinding equipment, and improved reprocessing methods can enhance the efficiency of recycling operations. Investing in research and development in this area is crucial for continuous improvement [64]. While material reuse and recycling can offset emissions, the process still generates GHGs: (a) Metal Recycling: Recycling steel emits 0.5 – 0.7 kg CO₂/kg, significantly lower than producing virgin steel (1.85 kg CO₂/kg); (b) Concrete Recycling: Crushing and reusing concrete emits 5 – 10 kg CO₂/ton, far less than new production; (c) Timber Reuse: Salvaged wood emits 0.05 – 0.1 kg CO₂/kg, considering transportation and minor processing. By prioritizing material reuse and recycling, stakeholders can contribute to a more sustainable and resilient construction industry. By thoroughly analysing carbon emissions at each stage, life cycle assessment (LCA) provides crucial insights into the carbon footprint of a building and helps in the development of effective carbon reduction strategies. This method not only aids in understanding the overall carbon footprint of a building but also offers a scientific basis for formulating and implementing effective carbon reduction measures.

4. Carbon Management in Building Life Cycle

4.1 Embedded Carbon Management in Construction: A PAS 2080 Approach

Embedded carbon management is an integral part of sustainable construction, aimed at reducing carbon emissions across all phases of a building's lifecycle [65]. The strategy encompasses several critical stages, each offering distinct opportunities to minimize carbon outputs and thereby lessen the overall environmental footprint of the project. Figure 3 illustrates the integration of carbon management into every decision-making step as prescribed by PAS 2080, ensuring that every phase, from inception through to demolition, is aligned with sustainable practices. The strategy encompasses several critical stages, each offering distinct opportunities to minimize carbon outputs and thereby lessen the overall environmental footprint of the project.

·       Demand Stage: This initial phase involves critical assessments to justify the project's need while considering its carbon implications. Evaluative measures are employed to estimate the carbon emissions from various site and design options, prioritizing those with the least environmental impact. This stage is pivotal for setting a sustainable precedent that guides all subsequent phases.

·       Option Assessment Stage: Here, the focus shifts to rigorously analyzing the carbon impact of different design proposals. Utilizing benchmarks in the absence of comprehensive data helps in comparing potential material choices, such as the use of wood versus reinforced concrete, facilitating decisions that favor lower carbon emissions.

·       Design Stage: The design process is refined to incorporate strategies that significantly cut carbon emissions. This involves a thorough analysis of potential emission sources and exploring mitigation strategies. The integration of low-carbon materials and sustainable energy solutions, such as recycled components and renewable energy technologies, is crucial during this phase.

·       Delivery Stage: Effective carbon management continues through the construction phase, where real-time monitoring of emissions is crucial. This stage ensures that the adopted low-carbon solutions are implemented effectively, and resource utilization is optimized. Practices such as the maximization of material recycling help in further diminishing the carbon footprint.

·       Termination Stage: Finally, the focus turns to the end of the building’s lifecycle. Strategies are implemented to assess and manage emissions associated with demolition, repurposing, or reuse. The goal is to develop comprehensive plans that minimize environmental impacts during these final phases.

Figure 3. Integrating carbon into decision-making for every work stage of the building and infrastructure according to PAS 2080 clause.

The operation stage of a building's life cycle is the primary source of carbon emissions, mainly due to energy use for heating, lighting, and air conditioning [38,66]. Effective operational carbon management is essential to reduce these emissions and involves optimizing energy consumption and refining maintenance strategies. Key actions include continuous monitoring of carbon emissions, optimizing energy use, and using operational data to improve future carbon management benchmarks. By making data-driven decisions, building managers can enhance efficiency and reduce the overall carbon footprint, contributing to long-term sustainability goals.

4.2 Intelligent Grid Energy Management System (EMS)

Intelligent grid energy management systems (EMS) are pivotal in enhancing the energy efficiency of commercial buildings and significantly reducing carbon emissions. Unlike conventional energy systems, intelligent grid EMS employs real-time data monitoring, adaptive analysis, and automated controls to optimize energy usage effectively. This advanced technology not only boosts operational efficiency but also supports comprehensive sustainability initiatives.

4.2.1 Stage 1: Demand Assessment and System Design

The initial stage of deploying an intelligent grid EMS entails a detailed demand assessment, tailoring the system to meet the specific requirements of the building. This process encompasses evaluating the building's energy needs and designing an integrated system to address these demands efficiently. The system design incorporates various components, each critical to the building's overall energy management strategy. Table 4 illustrates the integration of these components into the system design, which covers:

• Building Description: Specifications such as Window to Wall Ratio (WWR), glass U-Value, and the solar reflectivity of wall paint are meticulously assessed to ensure optimal energy use.

• System Description: The efficiency of air-conditioning systems, mechanical ventilation fan systems, and lighting systems are evaluated to enhance overall energy performance.

• Other Operational Configurations: Factors like air conditioning system type, lighting efficacy, and the use of energy-efficient technologies are critically analyzed to maximize energy savings.

Table 4. Key activities and details in demand assessment and system design for intelligent grid EMS in commercial buildings.

S/N	Component	Baseline Standard and Assumptions
1	Building Description
1.1	Building Envelop Design	·       Window to Wall Ratio (WWR): 0.4 ·       Glass U-Value (W/m²·K): 2.8 ·       Glass SHGC: 0.36 ·       Window Frame U-Value (W/m²·K): 1.5 ·       Solar Window Film U-Value (W/m²·K): NA (No Solar Window Film) ·       Solar Window Film SHGC: NA (No Solar Window Film) ·       Wall U-Value (W/m²·K): 1.6 ·       Solar Reflectivity of Wall Paint: 0.2 ·       Shading Coefficient: 1 (No Shading Devices) ·       Roof U-Value (W/m²·K): 1.6
1.2	Building Size and Configuration	·       Building GFA: Reference Model to be the same as Proposed Model ·       Percentage of Air-Conditioned Area (%): Reference Model to be the same as Proposed Model ·       Percentage of naturally ventilated area converted from air-conditioned area (%): 0 ·       Total Mechanically Ventilated Area Including Carpark (m²): Reference Model to be the same as Proposed Model ·       Building Storey: Reference Model to be the same as Proposed Model
2	System Description
2.1	Air-conditioning System and Air-distribution System	·       Air Conditioning System Type: Reference Model to be the same as Proposed Model ·       Air Conditioning System Efficiency (kW/RT): Based on air-conditioning system components’ efficiency below ·       Chiller Efficiency (kW/RT): 0.91 (water-cooled chiller),1.52 (air-cooled chiller) ·       Chilled Water Pump Efficiency (kW/m³/s): 470 ·       Condensing Water Pump Efficiency (kW/m³/s): 400 ·       Cooling Tower Efficiency (L/s/kW): 1.3 ·       Unitary Air-Conditioning System Efficiency (kW/RT): 1.44 ·       Air Distribution System Type: AHU-CAV (if proposed model uses AHU), FCU-CAV (if proposed model uses FCU) ·       Air Distribution System Efficiency (kW/RT): Based on air-distribution system components’ efficiency below ·       Air Conditioning System Optimisation: Not Applied ·       Use of Variable Speed Drive (VSD) in AHU/FCU: Not Applied ·       Use of Alternative Cooling Technologies: Not Applied ·       Air Distribution Fan Efficiency (W/CMH): 0.56 (AHU-CAV), 0.23 (FCU-CAV) ·       Demand-Controlled Ventilation of AC Area: Not Applied ·       Use of Energy Recovery Ventilation System: Not Applied ·       Use of Fans to Offset Cooling Load: Not Applied ·       Fresh Air Intake Rate (L/s/m2): 0.94 (Office Building, Hotel, Healthcare Facility, Industrial Building, Residential Building), 1.89 (Retail Building), 3.15 (Educational Institution), 1.18 (Others)
2.2	Mechanical Ventilation Fan Systems	·       Mechanical Ventilation Fan Efficiency (W/CMH): 0.31 ·       Demand-Controlled Ventilation of MV Area: Not Applied ·       Average Floor Height of Ventilated Area (m): 3.5 ·       Average Ventilation Rate (ACH): 6
2.3	Lighting Systems	·       Use of Energy Efficient LED Lights: Not Applied ·       Light Efficacy (lm/W): 31 ·       Lux Level: 500 (Office Building, Healthcare Facility, Industrial Building, Others), 600 (Retail Building), 300 (Educational Institution, Hotel, Residential Building) ·       Use of Smart Lighting Control: Not Applied ·       Use of Daylighting: Not Applied
2.4	Hot Water System	·       Hot Water System COP: 2.215 ·       Use of Solar Hot Water Collectors: Not Applied ·       Hot Water Usage (L/person/day): 0 (Office Building, Industrial Building, Retail Building, Educational Institution, Others), 80 (Residential Building), 125 (Hotel), 160 (Healthcare Facility)
2.5	Lift & Escalator	·       Use of Energy Efficient Lift: Not Applied ·       Use of Energy Efficient Escalator: Not Applied ·       Lift Power Density (W/m2): 2 (Office Building), 1 (Retail Building), 1.5 (Hotel), 0.9 (Educational Institution), 1.5 (Healthcare Facility), 0.6 (Industrial Building), 0.5 (Others), 0.2 (Residential Building) ·       Escalator Power Density (W/m2): 0.3 (Office Building), 2.5 (Retail Building), 0.5 (Hotel), 0.1 (Educational Institution), 2 (Healthcare Facility), 0.1 (Industrial Building), 0.5 (Others), 0 (Residential Building)
3	Other Operational Configurations
3.1	Receptacle Loads	·       Use of Smart Plug Load Control: Not Applied ·       Use of Energy Efficient Appliance: Not Applied ·       Receptacle Load Density (W/m2): 6 (Retail Building), 8 (Industrial Building, Residential Building, Others), 10 (Office Building, Educational Institution), 12 (Hotel), 21 (Healthcare Facility)
3.2	Building Energy Management System (BEMS)	·       Implementation of Building Energy Management System: Not Applied
3.3	Renewable Energy System	·       Installation of Rooftop Photovoltaic (PV) : Not Applied ·       Installation of Building Integrated Photovoltaic (BIPV): Not Applied ·       Full-sun Hour for Rooftop PV (hour): 3.5
3.4	Operation Schedules	·       Operation Schedule (hr/week): Reference Model to be the same as Proposed Model
3.5	Occupancy Load	·       Occupancy Density (m2/person): 10 (Office Building, Hotel, Healthcare Facility, Industrial Building), 5 (Retail Building), 3 (Educational Institution), 29 (Residential Building), 8 (Others)

4.2.2 Stage 2: Implementation and Integration

This phase transitions from theoretical system design to practical implementation, integrating the EMS within the building's existing energy framework [66]. The key activities during this stage include (Table 5):

• Energy Efficient System Installations: Implementing high-performance systems such as energy-efficient chillers, optimized air conditioning, and advanced lighting systems to reduce energy consumption significantly.

• Renewable Energy Solutions: Installing rooftop photovoltaic (PV) systems and building-integrated photovoltaics (BIPV) to harness solar energy, thereby reducing reliance on non-renewable energy sources.

• Advanced Building Controls: Employing smart lighting controls and energy management systems to regulate energy use meticulously, ensuring operational efficiency and substantial energy savings.

Table 5. Key activities and details in the implementation and integration of intelligent grid EMS in commercial buildings.

Energy Efficiency Measure	Affected System	Energy Saving Calculation Method for the Impacted System
Design of Natural Ventilation	Air-conditioning and Air-distribution System	Eliminated all air-conditioning and air-distribution energy consumption for areas converted from air-conditioned to naturally ventilated spaces.
Reduced Window to Wall Ratio	Air-conditioning and Air-distribution System	Resulted in a reduced ETTV (Envelope Thermal Transfer Value) based on the ETTV formula, leading to a decreased cooling load as predicted by the Machine Learning model.
Insulation of Roof
Insulation of External Walls
Use of High Performance Glass
Use of Solar Window Film
Use of Thermally Broken Window Frames
Use of Reflective Paint/Cool Paint
Installation of External Shading Devices
Energy-Efficient Unitary Air-Conditioning System	Air-conditioning and Air-distribution System	The reduced air-conditioning system energy consumption is calculated based on improved unitary air-conditioning system efficiency over baseline and cooling loads of proposed model and baseline, respectively.
Energy-Efficient Chiller	Air-conditioning System	Resulted in improved air-conditioning system efficiency over baseline which is predicted by Machine Learning model.
Energy-Efficient Chilled Water Pump
Energy Efficient Condensing Water Pump
Energy-Efficient Cooling Tower
Air Conditioning System Optimisation	Air-conditioning System	The reduction in air-conditioning system energy consumption is estimated based on an assumption of 15% energy savings compared to the scenario without the application of this EEM.
Use of Variable Speed Drive (VSD) in AHU/FCU	Air-distribution System	Resulted in improved air-distribution system efficiency compared to the scenario without the application of this EEM, which is predicted by Machine Learning model.
Use of Alternative Cooling Technologies	Air-conditioning and Air-distribution System	The reduction in air-conditioning and air-distribution system energy consumption is estimated based on an assumption of 30% energy savings compared to the scenario without the application of this EEM.
Energy Efficient Air Distribution Fan	Air-distribution System	Resulted in improved air-distribution system efficiency over baseline which is predicted by Machine Learning model.
Demand-Controlled Ventilation of AC Area	Air-conditioning and Air-distribution System	The reduction in air-conditioning and air-distribution system energy consumption is estimated based on an assumption of 15% energy savings compared to the scenario without the application of this EEM.
Use of Energy Recovery Ventilation System	Air-conditioning System	Resulted in reduced cooling load which is calculated based on estimated Fresh Air Cooling Load Ratio according to building type and proposed Energy Recovery System Efficiency
Use of Fans to Offset Cooling Load	Air-conditioning System	The reduction in air-conditioning system energy consumption is estimated based on an assumption of 10% energy savings on the applied space compared to the scenario without the application of this EEM.
Use of Energy Efficient LED Lights	Lighting System	Resulted in reduced light power density in the applied space, which is calculated based on the assumed lux level according to building type and efficacy of light.
Use of Smart Lighting Control	Lighting System	The reduction in lighting system energy consumption is estimated based on an assumption of 30% energy savings on the applied space compared to the scenario without the application of this EEM.
Use of Daylighting	Lighting System	The reduction in lighting system energy consumption is estimated based on an assumption of 30% energy savings on the applied space compared to the scenario without the application of this EEM.
Energy-Efficient Mechanical Ventilation Fan	Mechanical Ventilation System	The reduction in mechanical ventilation system energy consumption is calculated based on the improved fan efficiency and estimated mechanical ventilation rate.
Demand-Controlled Ventilation of MV Area	Mechanical Ventilation System	The reduction in mechanical ventilation system energy consumption is estimated based on an assumption of 20% energy savings on the applied space compared to the scenario without the application of this EEM.
Use of Smart Plug Load Control	Receptacle Loads	The reduction in receptacle load energy consumption is estimated based on an assumption of 15% energy savings compared to the scenario without the application of this EEM.
Use of Energy Efficient Appliance	Receptacle Loads	The reduction in receptacle load energy consumption is estimated based on an assumption of 20% energy savings compared to the scenario without the application of this EEM.
Use of Energy Efficient Hot Water System	Hot Water System	The reduction in hot water system energy consumption is calculated based on the improved hot water system efficiency, hot water heating temperature and estimated hot water consumption according to building type.
Use of Solar Hot Water Collectors	Hot Water System	Eliminated hot water energy consumption for the proportion of hot water supplied by solar hot water collectors.
Use of Energy Efficient Lift	Lift & Escalator	The reduction in lift energy consumption is estimated based on an assumption of 18% energy savings compared to the scenario without the application of this EEM.
Use of Energy Efficient Escalator	Lift & Escalator	The reduction in escalator energy consumption is estimated based on an assumption of 30% energy savings compared to the scenario without the application of this EEM.
Implementation of Building Energy Management System	All Building Systems	The reduction in the overall building energy consumption is estimated based on an assumption of 10% energy savings compared to the scenario without the application of this EEM.
Installation of Rooftop Photovoltaic (PV)	Renewable Energy System	The rooftop renewable energy generation is estimated based on rooftop solar panel area, rooftop solar panel efficiency and the assumed full-sun hour per day according to the building location.
Installation of Building Integrated Photovoltaic (BIPV)	Renewable Energy System	The BIPV renewable energy generation is estimated based on BIPV solar panel area, BIPV solar panel efficiency and the assumed full-sun hour per day according to the building location.

4.2.3 Stage 3: Monitoring and Verification

The final stage involves setting up robust monitoring systems to ensure the EMS operates as designed [47]. Continuous data collection from smart meters and IoT devices enables real-time tracking of energy consumption. Regular system assessments help verify energy savings against projections, ensuring the EMS's effectiveness as summarized in Table 6. This stage is crucial for:

• Validating Energy Savings: Continuous comparison of expected savings with actual energy data to confirm the EMS's efficiency.

• Optimizing System Performance: Using collected data to refine and adjust the EMS, enhancing its effectiveness and ensuring sustained energy savings.

Table 6. Key activities and details in the monitoring and verification of intelligent grid EMS in commercial buildings.

Key Activities	Details
Real-time Data Collection	Continuous collection of energy consumption data using smart meters and IoT devices for accurate monitoring.
Continuous Verification of Energy Savings	Ongoing verification of energy savings by comparing predicted savings with real-time data to ensure system accuracy and efficiency.
Emission Reduction Calculation	Calculation of emission reductions by applying energy savings data to predefined emission factors, providing measurable environmental impact.
Data-driven System Optimization	Continuous optimization of the EMS based on collected performance data, aimed at achieving maximum energy efficiency and reducing carbon emissions.

Through systematic implementation and management of an intelligent grid EMS, commercial buildings can achieve significant energy savings and carbon emission reductions, meeting global sustainability goals and bringing notable economic and environmental benefits to enterprises.

4.3  Economic and Regulatory Benefits of Energy Strategies in Building Operations

Improving energy efficiency in commercial buildings offers substantial benefits beyond environmental protection, delivering significant economic advantages and facilitating regulatory compliance [4]. As demonstrated by the energy consumption distribution in commercial buildings, clear trends indicate reductions in energy use, greenhouse gas emissions, and carbon tax liabilities, which translate into decreased operational costs and reduced financial burden of carbon taxes.

4.3.1 Intelligent Grid Energy Management Systems (EMS)

Intelligent Grid Energy Management Systems play a crucial role in achieving these efficiencies. By providing precise data on energy consumption and detailed reports on carbon reductions, EMS helps businesses meet stringent regulatory requirements, manage carbon taxes more effectively, and verify emission reduction outcomes accurately [52]. This ensures smoother regulatory compliance and optimizes energy efficiency and demand response capabilities. For example, the Empire State Building's retrofit utilized advanced EMS technologies, achieving a 38% reduction in energy consumption and annual savings of $4.4 million, showcasing the dual economic and environmental benefits achievable through intelligent energy management. Furthermore, achieving energy savings and carbon reduction goals not only supports global sustainability objectives but also provides competitive advantages to businesses [15]. By reducing energy costs and ensuring compliance with regulations, companies can improve their bottom line while enhancing their reputation as environmentally responsible organizations. In today’s eco-conscious market, these achievements contribute to stronger customer loyalty, attract investment, and set businesses apart from their competitors.

4.3.2 Feed-in Tariffs and Economic Evaluation

Improving energy efficiency in commercial buildings offers substantial benefits that extend beyond environmental protection, delivering significant economic advantages and facilitating regulatory compliance. As energy consumption is a major contributor to operational costs, effective strategies that reduce energy usage not only lower utility bills but also minimize carbon tax liabilities. Enhanced energy efficiency directly impacts these operational costs by decreasing energy consumption, thereby reducing financial burdens associated with energy expenditure and environmental regulations [27]. The integration of feed-in tariffs (FiTs) significantly enhances the economic evaluation of renewable energy technologies in commercial buildings. By allowing businesses to sell excess energy back to the grid at a premium rate, FiTs offer a reliable financial incentive, boosting the adoption of renewable technologies such as solar and wind. This mechanism not only supports initial investment in green technologies but also ensures continued operational savings and environmental benefits, aligning economic incentives with sustainability goals. Germany's feed-in tariff system, established as part of the Renewable Energy Sources Act (EEG), has been pivotal in promoting the adoption of renewable energy technologies across the country [51]. By guaranteeing fixed payments for the electricity generated from renewable sources, the system has spurred significant investment in solar and wind projects. As of 2021, renewable energy accounts for about 40% of Germany's electricity consumption. However, the success of feed-in tariffs in Germany has not been without its trade-offs. The costs associated with the EEG surcharge to finance the tariffs have been passed on to consumers, leading to some of the highest electricity prices in Europe. This raises questions about the long-term sustainability of such subsidies, especially in economic downturns [18]. Furthermore, the reliance on subsidies might stifle innovation in more cost-effective technologies and market-driven solutions.

4.3.3 Trade-offs Between Operational and Embodied Carbon

Understanding the differences between operational and embodied carbon is critical in formulating comprehensive carbon reduction strategies. Operational carbon refers to emissions from the building during its use phase, primarily due to energy consumption for heating, cooling, and lighting. Strategies to mitigate operational carbon focus on enhancing energy efficiency and integrating renewable energy sources, where FiTs can play a transformative role by offsetting costs and encouraging broader adoption of such technologies. Conversely, embodied carbon encompasses emissions from the materials and construction processes used throughout the building's lifecycle, from extraction and manufacturing to transportation and installation [37]. Reducing embodied carbon involves selecting low-carbon materials, optimizing design for minimal resource use, and maximizing material reuse and recycling. The trade-offs between focusing on reducing operational versus embodied carbon often depend on the building's lifecycle stage and the specific environmental goals of a project. For example, new constructions might benefit more from embodied carbon strategies, whereas operational carbon strategies are typically more relevant for existing buildings looking to improve efficiency and reduce energy costs. The effectiveness of carbon reduction strategies, including FiTs, can vary significantly by region due to differences in climatic conditions, available technologies, regulatory environments, and energy resource availability [45]. For instance, regions with abundant sunlight and supportive governmental policies may find solar energy investments more beneficial, enhanced by FiTs that make these options financially viable. In contrast, areas with less solar exposure but strong winds might focus on wind energy strategies, although the economic benefits would heavily depend on local FiT policies and market demand. Moreover, the limitations of these strategies in certain regions can be attributed to factors such as lack of infrastructure, economic constraints, and regulatory hurdles. For example, in less developed regions, the high upfront costs and lack of technical expertise can limit the adoption of advanced energy-efficient technologies and renewable energy systems, despite potential long-term savings and environmental benefits [17].

5. Conclusions

This study has provided a comprehensive analysis of global advancements in green building practices, with a particular focus on the detailed application of life cycle assessment (LCA) methods tailored for individual buildings. Our review has identified significant innovations in policies and technologies across regions including Europe, America, Britain, China, and emerging markets. These regions’ efforts in adopting sustainable practices are not only enhancing their local environments but also setting benchmarks for global construction standards. A key contribution of this research is the introduction and detailed explanation of LCA methods that encompass Scope 1, Scope 2, and Scope 3 emissions. This approach ensures a holistic view of environmental impacts across all stages of a building’s lifecycle—from demand assessment through to end-of-life management, providing a theoretical and practical framework crucial for the green transformation of the construction industry . Moreover, this study emphasizes the importance of effective carbon management strategies at each lifecycle stage of a building, proposing practical approaches to integrating these strategies into everyday construction practices.

The breadth of LCA’s application as discussed herein does reveal certain limitations, particularly in capturing the dynamic regional particularities and the rapid adoption of new construction methodologies and materials. Furthermore, the variability in the enforcement of policies and the adoption rate of technological innovations may limit the applicability of our findings across different global contexts. To address these challenges and enhance the robustness of building assessments, this study proposes the following policy recommendations:

·       Promoting International Collaboration: There is a critical need to enhance the sharing of best practices and sustainable technologies internationally to ensure equitable advancements in green building practices.

·       Advocating for Standardization in LCA Application: Proposing the development of standardized LCA methodologies at the international level could facilitate more consistent environmental impact assessments and reporting.

·       Encouraging Support for Emerging Technologies: It is essential for governmental bodies to incentivize research into and the deployment of innovative materials and building technologies that have the potential to minimize environmental impacts.

Looking forward, the trajectory of green building heavily relies on the continuous integration of state-of-the-art practices and global cooperation. The ongoing adoption of innovative technologies and the collaboration across borders will be pivotal in minimizing the ecological footprints of construction projects (Figure 5). Future research should focus on the integration of real-time data into LCA to enhance its accuracy, explore the impact of occupant behaviors on energy efficiency, and apply sustainable construction principles across different sectors. These areas promise to significantly advance the sustainability and efficiency of buildings globally, fostering a comprehensive approach to environmental stewardship in the construction industry.

Figure 5. Relationships between value chain members across assets, networks and systems.

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In conclusion, this study underscores the critical role of LCA in advancing sustainable construction practices worldwide. By incorporating comprehensive lifecycle analyses into the planning and development phases of building projects, the construction industry can significantly mitigate its environmental impact. Adopting the strategies outlined in this study will not only aid in achieving carbon neutrality but also enhance the sustainability of the built environment on a global scale. Our findings and recommendations provide a roadmap for future initiatives, aiming to foster a more sustainable and resilient global construction industry.

Consent to Publish Declaration: Not applicable.

Ethics and Consent to Participate Declaration: Not applicable.

Data Availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Funding Declaration

This research was funded by 2025 Hangzhou Huaxin Testing Technology Co., Ltd. Nanjing Tech University Joint Corporate Postdoctoral Research Program and Enerstay Sustainability Pte Ltd (Singapore) Grant Call (Call 1/2022) _SUST (Project ID BS-2022), Singapore.

Competing Interests

The authors declare no conflict of interest.

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Appendix

Table S1. GHG emissions across building materials, activities, and life cycle stages.

Category	Activity/Material	GHG Emissions (CO2Equivalent)	Source/Reference
Material Manufacturing	Cement	0.93 kg CO2 /kg	IPCC, UNEP Reports
Steel	1.85 kg CO2 /kg	World Steel Association
Brickwork	0.17-0.45 kg CO2 /brick	LCA Studies
Timber	0.15-0.25 kg CO2 /kg	Forestry and Construction Research
Construction Activities	Brickwork	50-100 kg CO2 /m3	LCA and Industry Benchmarks
RCC Work	300-500 kg CO2 /m3	LCA and Construction Studies
Plastering	8-12 kg CO2 /m2	LCA Studies
Painting	1-3 kg CO2 /m2	LCA Studies
Building Operation	Electricity Use	0.5-1.2 kg CO2/kWh	IEA, Regional Energy Mix Data
HVAC Systems	100-200 kg CO2/m2 per year	Energy Modeling and LCA Studies
Lighting	10-20 kg CO2 /m2 per year	LCA for Traditional vs LED Lighting
Maintenance and Repairs	Minor Repairs	20-40 kg CO2	LCA of Common Materials
Roof Repairs	500-700 kg CO2	Roofing LCA Studies
Complete Refurbishments	100-300 kg CO2 /m2	Major Renovation Studies
Demolition	Demolition Activities(Machinery Use)	20-30 kg CO2/hour	Diesel Machinery Emission Factors
Waste Transportation	0.1-0.3 kg CO2 /ton/km	Vehicle Emissions Standards
Landfilling	30-40 kg CO2/ton	IPCC Waste Management Guidelines
Material Reuse/Recycling	Steel Recycling	0.5-0.7 kg CO2/kg	World Steel Association
Concrete Recycling	5-10 kg CO2/ton	Waste Recycling Studies
Timber Reuse	0.05-0.1 kg CO2/kg	Salvaged Wood Research