Whole Building LCA in 2028Move Beyond Calculation and Drive Decarbonization

in Japanese

(originally published in Japanese on 15 January 2026)

The national government in Japan is considering launching a policy scheme to encourage the calculation of building LCA (life cycle assessment) focused primarily on carbon emissions, targeting buildings with a total floor area of 5,000 m² or more in 2028. According to the publicly available roadmap, the direction is to mainstream LCA calculation and introduce reduction measures in the 2030s, followed by strengthening those measures in the 2040s.¹

To date, decarbonization in the building sector in Japan has largely focused on improving energy performance and reducing operational energy use. However, meaningful decarbonization cannot be achieved unless we also address whole-life carbon, including emissions from material production through construction, renovation, and demolition. Whole Building LCA (WBLCA) is an attempt to make this “previously invisible carbon” visible and incorporate it into design and construction decision-making.

At the same time, feedback from design and construction practitioners have not been uniformly positive. Concerns such as “Will this simply add another submission requirement?” or “Will this only increase the workload?” are not uncommon. For many practitioners, WBLCA remains a relatively unfamiliar concept, and the perceived burden often comes first.

What we should reaffirm here is that the fundamental purpose of WBLCA is to improve the quality of decision-making across the building sector as a whole—and, through the accumulation of better decisions, to accelerate decarbonization across the industry. From a policy perspective, it is not sufficient to simply mandate calculation. There are many issues that must be addressed at the policy design stage, including mechanisms for data interoperability, integration with design workflows, and standardization of tools. Building on this recognition of the challenge, this column explores how WBLCA can be used effectively without exhausting practitioners. From a perspective that connects design practice, policy design, and industrial decarbonization, this column aims to offer proposals to ensure that 2028 becomes not simply “the year submission becomes mandatory,” but the starting line for transformation.

Implementation of WBLCA in Europe and the United States

In Europe, building LCA has already become institutionalized in many countries, and practice has entered a phase of operational implementation and refinement. In numerous jurisdictions, whole-life carbon assessments are mandatory for new buildings, and their results extend beyond compliance documentation to actively inform discussions on design and material selection. The scope of calculation and evaluation methodologies has been updated incrementally in response to issues identified through practical application.

In the United States, progress has been driven both by federal green procurement policies for public buildings under the Biden administration’s Inflation Reduction Act (IRA) and by proactive initiatives at the state and local levels.² Mandatory WBLCA calculations are being introduced for buildings above a specified size, alongside embodied-carbon disclosure requirements and maximum thresholds for key materials in public procurement for buildings and infrastructure. To remain competitive in these markets, companies must develop LCA data and supply low-carbon products, directly affecting materials manufacturers. In this way, market mechanisms within the building materials industry are stimulating investment in decarbonization. WBLCA therefore functions not only as a tool for designers and contractors, but also as a mechanism that engages the entire supply chain.

What Europe and the United States share is a clear recognition of WBLCA not merely as a calculation exercise, but as a strategic instrument for achieving decarbonization objectives. To enable stakeholders across the industry to work toward a shared goal, it is essential to present a clear and forward-looking policy roadmap.

2. Clarifying the Roadmap

The experience of Europe and the United States demonstrates that building LCA can drive industrial decarbonization when embedded within a clear and forward-looking policy framework. Beyond the mandate itself, a shared sense of long-term direction has played a crucial role in advancing decarbonization efforts and shaping investment decisions.

In Europe, mandatory WBLCA calculations have been introduced alongside a phased/gradual tightening of future performance requirements and expansion of scope (Figure 1). Because the policy framework is designed to evolve through practical implementation, both designers and manufacturers can plan mid- to long-term responses. As a result, investment in low-carbon building materials is framed not merely as regulatory compliance, but as strategic preparation for emerging markets.

A similar approach can be seen in the United States, where California has led the introduction of WBLCA through public procurement. The state requires LCA calculations for buildings exceeding a specified size and sets maximum embodied-carbon limits for key materials, with provisions for revising these thresholds every three years (Figure 2). In other states and municipalities, announcements of EPD submission requirements and LCA mandates frequently signal the likelihood of future threshold tightening. Although initial thresholds are set at levels that most manufacturers can meet, they nonetheless encourage major materials industries—such as steel and cement—to invest in LCA data development and low-carbon product innovation.

These examples illustrate that the effectiveness of an LCA regulatory framework depends not only on current obligations, but also on the clarity of its future trajectory. When the long-term direction remains uncertain, companies are less inclined to commit to large-scale capital investments or technological transitions. Conversely, when a staged regulatory roadmap is clearly articulated, voluntary action can advance even ahead of formal regulatory revisions.

Japan, too, must move beyond its current framework. The 2028 mandate should be positioned as an initial milestone, accompanied by the early presentation of a clear and predictable policy roadmap backcast from the 2050 carbon-neutral target. Clarity about the long-term trajectory will enable manufacturers, designers, and contractors to align their planning horizons and make informed investments in decarbonization.

Figure 1: Nordic roadmap　

Figure 2: Embodied-carbon thresholds for building materials published by California DGS 

3. A Phased Approach to Calculation Scope and Target Materials

Building LCA entails numerous uncertainties, including variability in material data, assumptions about service life, and projections of future renovation scenarios. Eliminating all uncertainty is unrealistic, as building LCA is fundamentally an assumption-based assessment. The objective is not to pursue absolute precision, but to clarify the relative differences in carbon performance among design and material options. In this sense, LCA should function as a practical decision-support tool, enabling progress even when uncertainty cannot be fully resolved.

For this reason, a phased approach is particularly important in the initial stage, allowing practitioners to gradually build familiarity with LCA. This is closely related to when and how calculations are conducted. By the detailed design stage, structural systems and key material choices are largely fixed, leaving limited opportunity for meaningful improvement if LCA is applied only retrospectively.

By contrast, during the planning and schematic design stages, decisions that significantly influence whole-life carbon remain flexible, and the potential impact of LCA is greatest. Early-stage LCA should therefore prioritize speed, simplicity, and comparability rather than strict precision. At the launch of the policy scheme, it would be effective to begin with simplified calculations, for example, by limiting the scope to structure and envelope components and focusing on major emission sources such as cement/concrete and steel. This would allow practitioners to become familiar with building LCA and integrate it more naturally into early design decisions. After several years of implementation, the scope could be expanded step by step to include MEP systems, replacements, and end-of-life stages such as demolition.

For major emission sources, clearer evaluation methods and supportive policy measures are essential. In the cement and concrete sector, it will be important to establish clear evaluation approaches—such as accounting for manufacturing CO₂ emissions, transport distances, supplementary cementitious material ratios, and strength-class–based threshold setting—while strengthening support measures for the development of Environmental Product Declarations (EPDs)³. In the steel sector, even if transitional approaches that allocate aggregated emissions reductions (such as the Japan Iron and Steel Federation’s “GX Steel”⁴ ) are accepted, it remains essential to set clear time limits and articulate future targets for traceability, physical segregation, and the transition to more stringent verification methods. Establishing practical guidelines on where low-carbon steel, such as EAF steel, can be applied is also crucial to support its adoption by designers.

In addition, evaluation criteria should incorporate incentive-oriented elements that extend beyond numerical results alone. By recognizing design strategies that enhance circularity, such as reusability, reversible connections, and modularization, and promoting measures such as reuse-rate metrics and the use of material banks to expand future reuse potential, LCA can serve as a gateway to a circular economy.

Prioritizing key materials, maintaining a streamlined calculation scope, and enabling LCA use from the earliest design stages—this phased and selective approach is essential to developing building LCA into an effective policy framework that supports decision-making across both design practice and the broader industry.

4. From Supporting EPD Expansion to Building Market Infrastructure

To make building LCA function as an effective policy framework, expanding EPDs is an essential foundation. From the perspective of international alignment, Japan’s development of EPDs remains significantly behind that of Europe and the United States. The number of EPDs for Japanese building materials is still limited: not because domestic manufacturers lack environmental awareness, but because institutional barriers have accumulated, including high preparation costs, complex application procedures, and uncertainty about how EPDs will ultimately be used.

For SMEs in particular, preparing an EPD represents a substantial burden, and many remain in a position where they understand the necessity but are unable to take the first step.

However, as examples from Europe and the United States demonstrate, EPDs are not merely disclosure tools. When linked to building LCA policy schemes, public procurement, and the establishment of thresholds and targets, EPDs function as market infrastructure that supports investment in low-carbon products. In international building and real estate markets, the presence or absence of an EPD is increasingly becoming a factor that directly influences product selection and competitiveness.

In Japan, therefore, EPD expansion should be positioned not as an aspirational goal, but as a strategic measure that underpins the building LCA policy framework. As a first step, stronger support measures for EPD development are needed—such as subsidies for preparation costs and ongoing technical assistance—alongside improvements to existing programs to create an environment in which SMEs can participate more easily.

At the same time, simplifying and accelerating application procedures is critical. By developing standardized templates, enabling the use of default or standardized emission factors where appropriate, and introducing more efficient review processes, the barriers to EPD creation can be lowered.

An important milestone will be reaching a point where market-level benchmarks for each material become visible. As more EPDs are published, the embodied-carbon performance of each material category becomes clearer, and a market “average level” emerges. Manufacturers can then objectively assess where their products stand and develop a concrete vision of the performance level they should aim to achieve.

Only when the current situation is quantified can improvements to manufacturing processes and decarbonization investments be addressed as strategic management decisions. Without a visible target level, it is difficult to commit to mid- to long-term investments. EPDs should therefore be positioned as a starting point for building materials manufacturers,making their current performance transparent and enabling the next steps, such as process improvements and low-carbon investment. Furthermore, if the policy roadmap can clarify in advance the schedule for future threshold-setting, manufacturers’ planning and decision-making will become even more realistic and forward-looking.

Figure 3: Increase in the number of EU EPDs
—approximately 40,000 EN15804-based EPDs as of January 2025

5. The Need to Develop Building LCA tools that can be Integrated into Practical Workflows

To embed building LCA in practice, it is essential to establish calculation methods that can be smoothly integrated into real-world workflows from design through construction and procurement.

By leveraging BIM⁵, LCA can be linked to quantity updates and recalculations as design changes occur, making it easier to use LCA as a decision-support tool within the design process. However, during the construction and procurement phases, it is often more realistic to conduct calculations based on cost estimates and quantity information. Implementing LCA therefore requires a flexible perspective that accommodates different approaches depending on the project phase.

In this context, the development of J-CAT⁶ in Japan is significant. At present, J-CAT is used primarily in processes that rely on estimates and quantity data. Because it does not directly integrate with BIM, it is difficult to incorporate into early-stage design studies. However, it provides calculation tools for both non-residential and residential buildings and is available free of charge as a nationally supported tool, an important advantage at a time when rising soft costs are a concern for practitioners.

At the same time, estimate-based LCA tools such as J-CAT have inherent limitations. Estimates often include lump-sum descriptions, and material breakdowns and quantities are not always explicit. As a result, outcomes can be sensitive to assumptions, and discrepancies may arise between practitioners.

For this reason, it is important to apply methods appropriately according to the project phase, paying close attention to both the timing and scope of LCA. By the detailed design stage, structural systems and major materials are largely fixed, and retrospective LCA offers limited opportunity for improvement. In such cases, LCA risks becoming merely a “confirmation exercise” rather than a decision-support tool.

In contrast, during planning and schematic design, key decisions that significantly influence whole-life carbon—such as structural system, span, and material direction—remain flexible. If an LCA tool can deliver rapid results at this stage, it becomes possible to compare multiple options and incorporate “low-carbon” as a design concept within the design process. At this stage, LCA functions not as a post hoc calculation task, but as a tool that supports decision-making, where its impact is greatest.

Designers’ efforts can be made visible through BIM-based calculations, while general contractors’ contributions can be reflected through estimate-based calculations, leading to improved material selection and greater quantity accuracy. Only when mechanisms exist to make each party’s efforts visible can LCA take root in practice.

Ultimately, what matters is that the efforts of designers, general contractors, and manufacturers connect naturally with BIM and estimation workflows. Only then can LCA become truly effective.

6. Promoting implementation through incentives and accumulation of experience

To establish building LCA as an effective policy framework, it is essential not only to design the policy itself, but also to intentionally develop mechanisms for accumulating and sharing practical knowledge.

A central element is the positioning of pilot cases. In Japan, LCCO₂ calculations have been conducted under certain components of the Ministry of the Environment’s ZEB subsidy program. However, if practical methodologies and innovations—such as how workloads were reduced and which approaches proved effective—are systematically documented and shared, these experiences can serve as valuable references for practitioners.

In coordination with subsidy programs, it would be desirable to systematically collect and organize case studies, including projects that applied LCA from the early design stages, projects that incorporated EPDs at an early phase, and projects that achieved significant reductions through structural choices. These cases should be compiled into an open casebook. Doing so would enable practitioners to understand concretely “what can be done” and “where the challenges lie,” thereby helping LCA evolve from an abstract policy requirement into a practical design tool.

It is also necessary not only to present calculation methods and underlying assumptions, but to organize and publish representative reduction measures and to provide evaluation criteria that consider the overall balance of environmental impacts. Discussions often focus on reducing the quantity of a single material or adopting low-carbon alternatives; however, mechanisms that provide additional incentives for projects achieving substantial reductions across whole-life carbon should also be considered.

Conclusion

The building LCA calculation mandate beginning in 2028 represents a structural policy shift intended to reframe buildings not only in terms of “operational energy,” but also through the lens of “carbon”, and to transform decision-making across design, procurement, and manufacturing. Its success will depend not on whether calculation is mandated, but on how it is implemented.

In Europe and the United States, policy frameworks were launched early—accompanied by roadmaps even when still incomplete—revised through practical application, and linked to industrial policy and public procurement, thereby inducing investment in low-carbon building materials. In these contexts, LCA functions as a framework that encourages action in anticipation of future markets.

If 2028 is viewed as the starting point, three elements are particularly important.

First, Japan must present a concrete and predictable policy roadmap backcast from the 2050 carbon-neutral goal. With clear long-term visibility, manufacturers, designers, and contractors will be better positioned to make mid- to long-term investment decisions.

Second, Japan must expand the use of EPDs. Beyond strengthening support for EPD development and simplifying application procedures, it is important to establish benchmark “average levels” derived from accumulated EPD data and to provide visibility into future threshold-setting aligned with the roadmap.

Third, Japan must establish mechanisms that enable practical workflows to operate in coordination with BIM and cost-estimation tools. To ensure that LCA is not merely a retrospective confirmation exercise but part of the “first conversation” in planning and schematic design, Japan needs rules and evaluation methods for early-stage LCA application and comparison, standardized calculation processes, and institutional frameworks that clarify roles and facilitate knowledge sharing. It is essential to define the decisions key stakeholders make at each phase—planning, design, procurement, and construction—and to demonstrate how those decisions contribute to improved LCA outcomes.

Building LCA is a tool to enhance the quality of design, reshape industrial behavior, and, through accumulated progress, advance decarbonization across society. We hope that 2028 will become the starting line from which such transformation begins.