EN 15978

EN 15978 is a European standard that defines the calculation method for assessing the environmental performance of buildings using a life cycle assessment (LCA) approach. Published in 2011 (with a revised EN 15978-1 under development), it sets out how to describe the building, define system boundaries, structure the life cycle into modules (A–D), collect inventory data, calculate indicators (e.g. global warming potential, resource use, waste), and report results for both new and existing buildings, including refurbishments.

EN 15978 exists to harmonise building-level environmental assessment across Europe. Before its publication, different tools and schemes used incompatible boundaries and indicators, making results hard to compare. The standard provides a common “grammar” for building LCAs within the wider CEN/TC 350 sustainability framework (linked to EN 15643 and EN 15804 for product-level EPDs). Its role is to ensure that, regardless of the software or rating scheme used, the underlying life-cycle structure and calculations are consistent.

The RICS WLCA standard is effectively an applied, more detailed implementation of EN 15978 (plus related standards) for the built environment, particularly in the UK but with global ambitions. WLCA adopts the EN 15978 life-cycle stages and system boundaries, then adds prescriptive guidance on practical issues that EN 15978 intentionally leaves open: typical data sources, default assumptions, national factors and reporting formats, as well as integration with cost classification (ICMS3) and local databases such as the Built Environment Carbon Database.

In short, EN 15978 provides the high-level, technology-neutral framework for building environmental performance assessment; the RICS WLCA standard takes that framework and turns it into a concrete, project-ready methodology for whole life carbon assessments that can support design choices, benchmarking, regulation and net-zero roadmaps.