Classification of Key Construction Materials in Life Cycle Assessment for Achieving Carbon-Neutral Buildings: A Meta-Analysis of 100 G-SEED Certified Projects

1. Introduction

The building sector is responsible for nearly 37% of global greenhouse gas (GHG) emissions, with a significant portion originating from the production, transportation, and installation of construction materials—commonly referred to as embodied carbon [1]. As operational carbon emissions decline due to high-performance insulation and energy-efficient systems, embodied carbon has become a critical focus in the pursuit of carbon-neutral buildings [2].

Life Cycle Assessment (LCA) is widely recognized as a robust methodology for evaluating the environmental performance of buildings across their entire life cycles. Numerous studies have shown that a small number of materials—such as concrete, steel, and insulation—account for the majority of a building’s embodied carbon [3,4]. Despite this, current LCA practices typically require exhaustive material inventories, many of which have minimal impact on the overall environmental footprint.

International certification systems such as LEED, BREEAM, and DGNB have incorporated LCA into their frameworks, and countries like France and the Netherlands have mandated LCA submissions for new buildings [5,6]. However, the lack of practical guidance on which materials to prioritize in carbon assessments limits both the efficiency and applicability of LCA in design and policy contexts.

In South Korea, the G-SEED certification system currently includes LCA as part of its evaluation criteria and plans to strengthen these requirements after 2025. Yet, no studies have systematically analyzed LCA data submitted under G-SEED to identify material contribution patterns. This evidence gap hampers efforts to streamline LCA practices and integrate embodied carbon considerations into routine design workflows.

To address this gap, this study analyzed 100 LCA reports submitted for G-SEED certification to identify the construction materials that collectively represent over 99% of the total material mass. Based on this analysis, we developed a simplified classification framework comprising 12 core material categories, organized by functional role and carbon impact. The aim is to support practical LCA simplification by focusing on essential components while preserving sufficient accuracy for carbon assessment and certification purposes.

2. Materials and Methods

2.1. Literature Review

An extensive literature review was conducted to establish a conceptual foundation for material classification in building LCA, focusing on the following four domains.

• Global trends in embodied carbon and life cycle assessment methodologies;
• Material-level impact studies (e.g., concrete, steel, insulation);
• Prior approaches to material ranking, classification, and prioritization;
• The integration of LCA into green building certifications and policy mechanisms.

2.2. Data Collection and Analysis

The primary dataset comprised 100 LCA reports submitted for G-SEED certification in the Republic of Korea between 2017 and 2024. These reports covered diverse building typologies (residential, office, school, and retail) and structural systems (reinforced concrete, composite, and steel-reinforced concrete).

The analysis proceeded as follows:

• Bill of Quantities (BoQ) Review: Each report’s BoQ was examined to determine the total number of materials listed.
• Mass Contribution Calculation: For material group, the percentage contribution to the total mass was computed.
• Material Ranking: Materials were ranked based on their frequency of occurrence across projects, cumulative mass contribution, and relative carbon impact potential.
• Classification Framework: Materials were grouped into 12 categories based on their functional roles and potential integration into certification systems.

3. Literature Review

3.1. Overview of LCA in Buildings

LCA has become a standardized methodology for evaluating the environmental impacts of buildings across their entire life cycle—from the extraction of raw materials to end-of-life disposal [7,8]. In highly energy-efficient buildings, embodied carbon—emissions resulting from the production and construction of materials—can account for 30–70% of total greenhouse gas (GHG) emissions [2,3]. As such, emissions from the material phase have become increasingly central to achieving carbon neutrality in the built environment.

Figure 1. Importance of material-phase emissions has become increase [2].

Figure 1. Importance of material-phase emissions has become increase [2].

3.2. Embodied Carbon and Material Contributions

Embodied carbon refers to the GHG emissions associated with all life cycle stages of construction materials, including raw material extraction, manufacturing, transportation, and installation. International standards such as ISO 14040/14044 and EN 15978 provide methodological frameworks for conducting building LCAs, defining system boundaries and modules [9].

Figure 2. Building’s LCA stages according to EN 15978.

Figure 2. Building’s LCA stages according to EN 15978.

According to EN 15978, the building life cycle is typically segmented into Modules A (product and construction stages), B (use stage), C (end-of-life stage), and D (benefits beyond the system boundary). Within this framework, Modules A1–A3 (Product Stage: raw material supply, transport, and manufacturing) are considered critical, as they account for the majority of embodied carbon in buildings [10]. Numerous studies have confirmed that emissions from these stages dominate the overall environmental impact of construction materials, particularly for structural components [2,3].

Figure 3. System boundary of building materials [10].

Figure 3. System boundary of building materials [10].

Furthermore, A persistent challenge in LCA implementation lies in the exhaustive material inventories traditionally required by standards. While typical Bills of Quantities (BoQs) may include hundreds of material entries, research indicates that a small subset of materials—such as concrete, steel, and insulation—often represents over 90–95% of the total mass and carbon impact [12,13]. To improve LCA efficiency without compromising accuracy, recent approaches have proposed a cumulative mass-based threshold—commonly set at 99%—to limit detailed assessments to high-impact materials [13,14]. This method aligns with the Pareto principle, ensuring that the most significant contributors are fully captured while omitting negligible components. Meta-analyses have further validated that materials with high production volumes or energy-intensive manufacturing processes—such as cement, rebar, and aluminum—are primary contributors to environmental impacts [15,16].

In practice, calculating cumulative mass contributions and excluding the bottom 1% of materials enables substantial reductions in data entry and modeling complexity while maintaining robust carbon estimates for Modules A1–A3. This approach is increasingly recognized as a viable strategy for simplifying LCA processes in certification systems and early-stage design decision-making [12,17].

3.3. Material Classification and Prioritization

Despite growing awareness of the importance of embodied carbon at the material level, standardized frameworks for classifying and prioritizing construction materials remain underdeveloped [13,18]. Discrepancies in classification criteria—such as functional roles (e.g., structural vs. non-structural), spatial location (e.g., envelope vs. interior), or database conventions—undermine consistency and comparability across LCA studies.

In response, researchers have proposed various data-driven classification models, including impact clustering and material ranking [14,19], while others have recommended using Environmental Product Declaration (EPD)-based weighting schemes to support more objective material selection [12,17].

3.4. Role of LCA in Certification and Policy

Leading international green building certification systems—such as LEED, BREEAM, and DGNB—have formally incorporated LCA as an evaluation criterion and offer credits for reducing life cycle environmental impacts [20,21]. In Europe, countries such as Denmark, France, and the Netherlands have gone further by mandating LCA submissions as part of the permitting process for new buildings [6].

However, research shows that despite LCA’s institutionalization, the absence of practical tools for material prioritization continues to hinder its effective integration into design and assessment workflows [22,23,24,25].

3.5. Practical Challenges in LCA implementation

Although LCA is widely recognized as a robust and standardized methodology, its implementation in design workflows remains challenging. Studies have identified three key barriers that limit the broader adoption of LCA beyond specialized expert groups.

First, LCA is heavily dependent on expert knowledge and specialized tools, posing high entry barriers for general practitioners—especially during the early design stage [13,18]. Expertise is required to define system boundaries, interpret results, and apply complex databases, leading to the concentration of LCA tasks within consultancy firms and reducing its accessibility to architects and engineers.

Second, uncertainty in input data and variability across databases (e.g., emission factors, EPDs) pose significant challenges [12,17]. Inconsistent data quality and the lack of region-specific values compromise both comparability and reliability, reducing confidence in LCA outputs for design decision-making.

Third, there is a lack of clear, actionable guidance for material selection based on environmental impact—particularly in early design phases. While standards such as EN 15978 and ISO 14040 provide methodological structures, they do not specify how to prioritize materials within practical time and budget constraints [14,25].

Finally, while cumulative mass-based thresholds (e.g., 99%) offer conceptual simplicity, their application in practice can be burdensome. Calculating and verifying cumulative contributions requires detailed quantity take-offs and reliable inventory data—information often unavailable during early design stages [13]. As a result, the intended simplification may become impractical without digital integration (e.g., BIM-LCA automation) or standardized material grouping.

These limitations highlight the need for user-friendly, streamlined frameworks that enable practitioners to focus on high-impact materials without requiring exhaustive analysis or exclusive reliance on expert workflows.

3.6. National Context and Research Contribution

In the Republic of Korea, the G-SEED certification system incorporates LCA reporting and is set to strengthen these requirements after 2025. However, little effort has been made to synthesize accumulated LCA data to identify consistent material contribution patterns. This lack of analysis hampers the development of a context-specific framework for classifying materials by environmental impact and limits the practical use of LCA in Korean design practice.

To address this gap, the present study analyzed 100 LCA reports submitted under G-SEED to identify 12 key materials that accounted for the majority of total material mass. Based on their functional roles, this study proposes a systematic classification framework aimed at improving embodied carbon management in both domestic and international contexts.

4. Data Collection and Analysis Result

4.1. Status of Green Building Certification and Life Cycle Assessment Reports in Korea

Similar to international green building certification systems such as LEED, BREEAM, and DGNB, South Korea has implemented its own green building certification program—G-SEED—in operation since 2002. G-SEED certification is mandatory for public buildings and is promoted in the private sector through incentives such as acquisition tax reductions and building regulation relaxations. As a result, the system has been widely adopted, with approximately 25,000 buildings certified as of 2024.

A major revision of the G-SEED framework took place in 2016, during which Life Cycle Assessment (LCA) was introduced as a formal evaluation criterion. Since then, the use of LCA in certification has gradually expanded. Table 1 presents the number of LCA reports submitted annually since the criterion’s introduction.

In the first three years, LCA adoption was limited to around 2% of certified buildings. However, this uptake has steadily increased, reaching 24% by 2024—reflecting the growing emphasis on embodied carbon assessments within Korean green building practices.

Figure 4. Comparative certified and LCA reported buildings ratio.

Figure 4. Comparative certified and LCA reported buildings ratio.

As LCA reporting becomes more prevalent, a foundation for comprehensive life-cycle carbon management in buildings is being established. However, G-SEED still has several limitations inherent to LCA, including the complexity of conducting a 99% cumulative mass analysis, limited integration with LCI databases and EPDs, and insufficient verification of data completeness and consistency.

To address one of these critical limitations, this study proposes an alternative approach by identifying key construction materials using existing LCA reports. The objective is to provide a practical basis for material selection that could substitute for full cumulative mass analysis during LCA implementation. The dataset analyzed consisted of 100 LCA reports submitted under G-SEED certification (Appendix A). As shown in Table 2, the building typologies included residential, office, school, hotel, retail, and other non-residential types such as research centers, warehouses, and data centers. The structural systems are categorized as reinforced concrete(RC), RC+steel composites (RC + S), and steel-reinforced concrete (SRC).

4.2. LCA Data Analysis

A review of the BoQs for the 100 buildings was conducted. The number of BoQ items ranged from 110 to 6,259, while the number of materials actually used in the LCA reports varied from 38 to 2,473. On average, each BoQ contained 990 items, whereas the average number of materials included in the LCA was 319, representing 35.24% of total BoQ items.

However, the correlation between the total number of BoQ items and the number of LCA-selected materials was relatively weak (R² = 0.4673), indicating that variations are largely influenced by BoQ composition and the level of detail applied by LCA practitioners during material selection.

As Typically, preparing an LCA report involves: (1) An initial quantity analysis of around 990 BoQ items; (2) Selection of approximately 319 materials that cumulatively account for 99% of total material mass;(3) Collection of environmental data for each selected material.

This cumulative mass analysis presents a significant initial hurdle, which likely contributes to the limited practical adoption of LCA in design and certification workflows.

To address this challenge, this study aims to classify essential materials from the BoQ that should be prioritized in LCA, providing a more practical alternative to full cumulative mass calculations. Figure 5 illustrates the proposed simplified approach.

4.3. Quantity Breakdown in LCA

All 100 LCA reports performed a 99% cumulative mass analysis to identify which materials were assessed (Appendix B). The number of selected materials ranged from 38 to 2,473, with an average of 319 items. Collecting and linking environmental data for each material—potentially over 2,473 data points per project—is impractical. Therefore, it is common practice to group similar materials into representative categories and assign shared environmental data.

In the analyzed reports, materials were typically grouped into 5 to 12 categories, with an average of eight material groups. These groupings are outlined in Table 3.

An analysis was conducted on the frequency of use of 12 major construction material categories across 100 LCA reports (Table 4). The results indicated that Concrete and Structural Steel were included in all 100 reports. Cement and Insulation were used in 98 reports, whereas Sand and Gravel were used in 95. Stone and gypsum boards were included in 63 reports, whereas Glass Products were included in 57 reports. Metal Finishes were reported in 45 cases, tiles in 35 cases, and Paints and Wall Coverings and Wood were the least frequently included, appearing in five and four reports, respectively (Figure 6).

When analyzed by quantity contribution, concrete accounted for 85.6% of the total mass, followed by cement and brick (5.5%), Structural Steel (4.6%), and Sand and Gravel (2.4%), whereas all other material categories represented less than 1% each (Figure 7).

Figure 8. Number of LCA reports using the material category .

Figure 8. Number of LCA reports using the material category .

Figure 9. Mass balance average Ratio by material category.

Figure 9. Mass balance average Ratio by material category.

5. Discussion

The findings of this study underscore the practical challenges and potential opportunities associated with implementing Life Cycle Assessment (LCA) within South Korea’s building sector under the G-SEED certification framework. Although LCA adoption has grown significantly—from just 2% of certifications in 2016 to 24% by 2024—its effective application remains constrained by complex data requirements and methodological hurdles.

5.1. Practical Barriers to LCA Implementation

The analysis highlights major barriers to LCA adoption in Korean building projects. While a typical BoQ includes nearly 990 items, the average LCA report includes only 319 items, accounting for roughly 35% of the BoQ. This illustrates the resource-intensive and time-consuming nature of conducting a comprehensive 99% cumulative mass analysis.

The weak correlation between BoQ size and LCA material count (R² = 0.4673) suggests a lack of standardization in material selection, often relying on practitioner discretion rather than objective criteria—echoing findings from international literature [13,14]. This complexity, especially during early design phases when detailed take-offs and environmental datasets are unavailable, discourages broader adoption of LCA. Similar limitations have been observed in LEED and BREEAM systems, where early-stage tools lack guidance for practical material prioritization [27,28].

5.2. Dominance of Key Material Categories

The frequency analysis confirms a strong Pareto effect: a small number of materials accounts for the majority of environmental impacts. Concrete alone contributes 85.6% of total mass, followed by cement and bricks (5.5%), structural steel (4.6%), and aggregates (2.4%). Other materials—such as glass, insulation, and finishes—each contribute less than 1% by mass, although they may exhibit high environmental intensity per unit mass. These results are consistent with international studies on embodied carbon distributions [10,14].

5.3. Implication for G-SEED and Global Certification Frameworks

The current G-SEED requirement for a 99% cumulative mass analysis could be effectively replaced by assessing 12 predefined material categories. This simplification would significantly reduce data demands, supporting wider adoption of LCA in both certification workflows and early design phases.

This approach is aligned with international trends promoting streamlined LCA protocols, as advocated by recent European initiatives and ISO-based guidelines. For instance, EN 15978 permits scenario-based assessments when detailed data are unavailable, while LEED v5 emphasizes early-stage carbon considerations via predefined assemblies. By incorporating similar principles, G-SEED could improve comparability with global standards while maintaining methodological robustness.

5.4. Policy and Industry Recommendations

The analysis highlights the significant barriers to LCA adoption within the Korean building sector. A typical BoQ includes approximately 990 items, whereas an LCA report averages 319 items, reflecting an approximate

6. Conclusions

This study analyzed 100 LCA reports submitted under the G-SEED certification system to identify patterns in material contributions and develop a simplified classification framework to support LCA implementation. The results revealed that 12 material categories, dominated by concrete, structural steel, and cement, consistently represented over 99% of the total material mass.

By predefining these categories, the proposed framework reduces the complexity of cumulative mass analysis and facilitates broader adoption of LCA across the industry. Beyond improving methodological efficiency, this framework enables more targeted applications of low-carbon materials across both structural and non-structural components, including building envelopes and finishes.

Such targeted material strategies are essential for achieving national and global carbon neutrality goals, especially as embodied emissions increasingly dominate the life cycle impacts of high-performance buildings.

However, a key limitation remains: current LCA practices in Korea are largely confined to building structures, excluding civil engineering works and MEP (Mechanical, Electrical, and Plumbing) systems. Future efforts should focus on integrating these components into a comprehensive sector-wide assessment to realize full life cycle carbon reductions.

By combining empirical evidence with a practical classification model, this study contributes to the advancement of LCA as a strategic tool supporting policy development, certification system enhancement, and industry-wide adoption of sustainable, low-carbon materials.