Understanding Key LCA Terminologies: A Guide for Professionals

Life Cycle Assessment (LCA) is becoming increasingly central to how we evaluate the environmental performance of buildings and materials. From industry tools and environmental declarations to design reports and compliance documentation, the terminology used in LCA can vary widely and is often inconsistently applied.

This article clarifies essential terms and scope definitions associated with building LCAs, including how to interpret key metrics such as embodied carbon, operational carbon, and whole-of-life emissions. It is tailored for practitioners in Australia and New Zealand and offers a structured reference for navigating LCA results more confidently and critically.

Core LCA Terminology

Life Cycle Assessment (LCA)

LCA is a method for assessing the environmental impacts associated with all stages of a product or system’s life cycle. For buildings, this typically includes the extraction and processing of raw materials, manufacturing, transportation, construction, use, maintenance, and end-of-life treatment.

LCAs are used to support sustainable design, procurement decisions, and regulatory compliance. In the context of the built environment, LCA is most commonly applied to estimate greenhouse gas (GHG) emissions, expressed in carbon dioxide equivalents (CO₂-e), but can also address other impact categories such as resource use, water consumption, and acidification.

Standardised methodologies for building LCAs are defined in ISO 14040/44 and EN 15978. Both New Zealand and Australia commonly use EN 15978 to structure assessments, especially where integration with tools like Green Star or NABERS is required.

Embodied Carbon

Embodied carbon refers to the GHG emissions that occur during the production, transportation, construction, maintenance, and end-of-life of building materials. This includes emissions from the extraction of raw materials, manufacturing processes, distribution, and eventual demolition or disposal.

Embodied carbon is fixed at the point of practical completion, making early design decisions particularly influential. For many buildings, it represents a substantial portion of total emissions, particularly in regions with decarbonised energy grids, such as Aotearoa New Zealand.

Over recent years, construction material industries, including the cement and steel sectors, have made substantial progress in reducing the carbon intensity of their products through efficiency improvements, use of supplementary materials, and implementation of cleaner technologies. Consequently, LCA studies increasingly rely on up-to-date Environmental Product Declarations (EPDs) to reflect these improvements accurately.

Operational Carbon

Operational carbon encompasses the emissions associated with the use phase of the building, primarily from energy (B6) and water use (B7). It includes energy for heating, cooling, lighting, ventilation, and appliances.

In many existing buildings, operational emissions dominate total life cycle impacts. However, as buildings become more energy efficient and power grids transition to renewable sources, the proportion of embodied carbon is increasing. For new developments aiming for net-zero targets, operational carbon must be minimised through passive design, efficient systems, and renewable energy generation.

Whole Building Life Cycle Assessment (WBLCA)

A Whole Building Life Cycle Assessment considers the environmental impacts of the entire building over a defined lifespan. This includes all structural and envelope systems, internal linings, services, finishes, and fittings, as well as operational energy and water use where relevant.

A WBLCA is typically conducted to inform early design decisions, compare alternatives, or demonstrate compliance with rating tools such as Green Star (in Australia and New Zealand) or the National Construction Code’s Performance Solutions pathway. It provides a more complete picture of a building’s emissions profile compared to isolated product-based assessments.

Scope Definition: Interpreting Modules and Life Cycle Stages

LCA scope is structured using life cycle modules defined by EN 15978. These modules represent different stages of a building’s life and are grouped as follows:

A1–A3: Product Stage (Cradle-to-Gate)

This includes raw material extraction (A1), transport to the manufacturer (A2), and manufacturing processes (A3). These are the modules typically covered in EPDs.

Assessing A1–A3 allows for early-stage material comparisons and is often used to identify high-impact products. However, it is not sufficient for capturing transport to site, installation, maintenance, or end-of-life processes.

A1–A5: Upfront Carbon (Cradle to Practical Completion)

Upfront carbon refers to the emissions that occur before a building is occupied. This includes the product stage (A1–A3), transportation to site (A4), and construction/installation processes (A5).

This boundary is increasingly used in policy settings and design rating tools. For example, New Zealand’s Building for Climate Change programme and Australia’s Green Star Buildings framework both reference upfront carbon as a key reporting metric. It represents a practical minimum for conducting meaningful assessments of new construction projects.

A1–C4: Whole-of-Life Embodied Carbon (Cradle-to-Grave)

This includes the entire life cycle of materials, from extraction through to end-of-life (A1–A5), use-phase maintenance and replacements (B1–B5), and end-of-life processes such as deconstruction, transport, waste processing, and disposal (C1–C4). Operational energy and water use (B6–B7) are excluded.

This boundary provides a comprehensive measure of embodied carbon over a building’s assumed lifespan and is essential for understanding long-term impacts beyond initial construction.

A–C + B6–B7: Whole-of-Life Carbon (Cradle-to-Cradle)

Whole-of-life carbon includes all embodied and operational emissions, modules A through C, plus energy and water use (B6–B7). It is the most complete assessment boundary, accounting for both materials and building operations.

This scope is recommended for net-zero carbon strategies, integrated sustainability reporting, and long-term policy evaluation. Some assessments may optionally include Module D, which reflects benefits from material recovery, reuse, or recycling beyond the system boundary.

Interpreting Reports: Additional Contextual Considerations

In addition to understanding the modules included, practitioners should critically assess the following elements when reviewing or conducting an LCA:

Life Expectancy of the Building

Most building LCAs in New Zealand assume a 50-year life span, in line with local regulatory and rating frameworks. However, if a building is expected to last longer or undergo significant refurbishments, this will influence replacement cycles (B4) and maintenance schedules (B2–B3), potentially affecting total life cycle impacts.

Biogenic Carbon

Biogenic carbon refers to the carbon sequestered in renewable biological materials (e.g., timber). Depending on the reporting methodology, this carbon may be shown as stored temporarily (A1), released at end-of-life (C4), or both. Transparency in how biogenic carbon is accounted for, and whether net sequestration is claimed, is critical for interpreting results responsibly.

Module D Reporting

Module D estimates the potential emissions avoided through recycling, reuse, or energy recovery beyond the system boundary. While useful for illustrating circular economy benefits, it should be reported separately and not combined with A–C impacts. Including Module D without clear separation can lead to misleading conclusions.

Data Quality

The accuracy of an LCA depends heavily on the quality and relevance of the data used. High-quality LCAs use specific EPDs and regionally representative datasets. When older or generic datasets are used — particularly those not reflective of Australian or New Zealand conditions, the results should be interpreted with caution. Reports should disclose data sources, dataset ages, and any assumptions or limitations.

System Boundaries and Exclusions

Every LCA has defined boundaries. Common exclusions may include site works, landscaping, furniture, building services (e.g., lifts, solar panels), or refrigerants. The rationale for any exclusions should be stated clearly. These elements can represent significant emissions and their omission may underestimate total impacts.

Conclusion

Understanding and correctly applying LCA terminology is essential for interpreting carbon reports, informing sustainable design, and supporting policy development. Clear communication of scope, boundaries, and assumptions is fundamental to ensuring that LCA results are meaningful and actionable.

As the use of LCA continues to expand in the built environment across Australia and New Zealand, a shared understanding of these terms will support more consistent and transparent decision-making across projects and teams.

To learn more about how life cycle modules work and how to apply them effectively, refer to our detailed article :Understanding the Life Cycle Stages in Construction.