Comparing Differences in Building Life Cycle Assessment Methodologies

This article discusses the significant variances in Life Cycle Assessment (LCA) methodologies across different geographical regions, focusing on their impact on the comparability and accuracy of environmental assessments in the building sector.

Key Points:

• LCAs are crucial for evaluating a building’s environmental footprint but vary widely in methodology, especially in Europe, complicating benchmark comparisons.
• The study highlights methodological discrepancies in system boundaries, building element groups, floor area definitions, reference study periods, and impact categories.
• It addresses other uncertainties affecting LCA reliability, such as LCA practitioner skills, standardised values, and software differences.
• A comparison between Danish and Swedish LCA regulations reveals significant outcome differences due to methodological variances.
• Initiatives for harmonisation and a common format for presenting carbon assessment findings are underway to improve LCA accuracy and comparability.

In the realm of sustainable construction, Life Cycle Assessments (LCAs) have emerged as a critical tool for systematically evaluating a building’s environmental footprint and guiding informed decision-making. Despite their significance, the application of LCA methodologies in the building sector is marked by significant variances across different geographical regions. This disparity in methodologies leads to considerable differences in the results and performance of buildings, complicating the process of benchmarking and comparing LCA outcomes. Additionally, the inherent flexibility within each methodology introduces further uncertainties, rarely disclosed in LCA reports.

This article delves into the methodological discrepancies observed in prominent building LCA methodologies in Europe, particularly focusing on the scope differences as defined by the European Committee for Standardisation’s EN15978:2011 standard, based off a report published by Ramboll in July of 2023 .

The study also sheds light on other factors influencing LCA accuracy and comparability, presenting the findings through straightforward visuals for easy industry stakeholder comprehension.

The construction sector significantly influences society and the natural environment. Life Cycle Assessments, widely adopted to gauge the environmental impact of buildings, differ substantially in their adoption and implementation across different regions, leading to varied outcomes. This inconsistency poses challenges in making informed decisions regarding environmental performance and crafting effective building regulations and policies.

To address these challenges, Ramboll developed a building benchmarking database for carbon footprints, accommodating variations in LCA methodologies. This article aims to illuminate the discrepancies in LCA methodologies in the built environment by examining factors contributing to these variances and suggesting ways to enhance the effectiveness of LCAs in promoting sustainable building design and construction practices.

System Boundary

The system boundary defines the processes included in the building’s assessment. While there is consensus on reporting the product stage as a grouped value, discrepancies in the inclusion and grouping of other life cycle stages limit the comparability of LCA results. Notably, the calculation and inclusion of operational emissions (modules B6 and B8) vary significantly, often misrepresenting building performance when compared internationally.

Building element groups, crucial in organising the assessed building model, show discrepancies in mandatory and voluntary inclusion across different LCA methodologies. The chosen elements and the level of detail significantly influence the impact assessment, underscoring the need for clear communication of the LCA scope.

Comparing LCAs often involves presenting results per unit floor area. However, the definition of a building’s floor area, which impacts the floor area metric, varies across different countries and methodologies. This variation poses challenges in ensuring accurate comparisons.

The temporal boundary for an assessment, or the Reference Study Period (RSP), significantly influences the LCA outcomes. Differences in RSP can lead to ambiguous comparisons, necessitating careful consideration and adjustment for accurate evaluation.

While Global Warming Potential (GWP) is a universally recognised metric and required by all LCA methodologies, the inclusion of other impact categories varies. This variability underscores the need for a broader understanding of LCAs beyond merely measuring carbon dioxide emissions.

Several other factors contribute to the reliability and comparability of LCAs, including the design stage of the LCA, the skills and experience of LCA practitioners, the availability and use of standardised GWP values and Environmental Product Declarations (EPDs), differences in calculation software, treatment of biogenic carbon, and the inclusion of decarbonisation pathways.

A theoretical comparison of identical office buildings on either side of the Danish-Swedish border, assessed using Danish and Swedish regulations, highlights the potential distortion in LCA outcomes due to methodological differences. Even when reduced to common life cycle stages and building element groups, significant discrepancies persist due to differing data sets and the application of penalty values to generic data in the Swedish methodology.

The long-term solution lies in enhancing the harmonisation of methodologies and the use of common scope definitions. Current initiatives, like the European Commission’s update to the Energy Performance of Buildings Directive and Ramboll’s development of a common format for presenting carbon assessment findings, aim to improve accuracy, consistency, and transparency in LCAs. Ramboll’s benchmarking database, designed to accommodate a wide range of LCA methodologies through sufficient data granularity, represents a step towards enabling more consistent benchmarks and comparisons.

Life cycle assessments are pivotal in evaluating and guiding sustainable building design. However, the myriad of methodologies, assessment elements, and interpretations create substantial inconsistencies in reported carbon values. Achieving greater harmonisation, enhancing rigor, and ensuring robust compliance are crucial steps towards addressing these challenges. Recognising and delineating life cycle scopes and boundaries is essential in assessing performance and making meaningful comparisons. Ramboll’s benchmarking database exemplifies an approach towards collecting and comparing building carbon data, driving the industry towards more accurate, consistent, and transparent LCAs, and ultimately contributing to the decarbonization of the built environment.

If you are interested in further regulation updates check our regulation category which we constantly update and take a look at our updated embodied carbon optimizer tool for a simplified LCA in your early design phases.

Ramboll — Comparing differences in building life cycle methodologies