There remains significant inconsistency with respect to the basic definitions in use with reference to carbon and net zero carbon terminologies over the life cycle of buildings and infrastructure. This document provides a common set of definitions for the built environment sector. It has been put together initially by a working group within the Whole Life Carbon Network (WLCN, a group of some 90 built environment professionals) and including detailed discussions between WLCN, LETI, CIBSE, RIBA, RICS, IStructE, ICE, and UKGBC. The ‘Definitions’ are structured around CEN TC 350 life cycle modules, (e.g. BS EN 15978:2011 for buildings, BS EN 17472: 2022, PAS 2080:2016 for Infrastructure, BS EN 15643 2021.)

There are currently many variations in the terminology used to define carbon emissions (operational, embodied, whole life etc.) which leads to confusion amongst stakeholders. The definitions in this document build on the work of others but have been altered and developed as a ‘family’ of definitions that work together, with the intention of achieving greater consistency across the built environment industry. The ‘net zero carbon’ definitions in the document are based on the ‘Paris Proof’ approach which dictates that the Built Environment Industry should only use the limited amount of carbon – including energy and material resources – apportioned to it, in order for the UK economy as a whole to reach net zero emissions by 2050 and ensure best efforts to limit global warming to 1.5 degrees Celsius, a trajectory supported by the Science Based Targets Initiative. This requires reducing global built environment emissions by 50% by 2030, required by reducing global built environment emissions as a priority measure, and a decreasing reliance on offsets over time to achieve a net zero carbon balance.