Why Part Z references the RICS Professional Statement

Every calculation relies on assumptions, and carbon is no different. The importance of making sensible and consistent assumptions is therefore paramount to reach a robust and defensible design. This is no different for whole life carbon, which involves many material-, market-, location- and time-dependent factors, and future scenarios.

The Royal Institution of Chartered Surveyors’ Professional Statement (RICS PS) ‘Whole life carbon assessment for the built environment’ (2017) - guidance for UK industry professionals undertaking whole life carbon assessments (WLCA) in accordance with EN 15978.

European Standards already exist for the assessment of the sustainability of the built environment, both in terms of carbon and other environmental impact metrics. EN 15978 ‘Sustainability of Construction Works’, published in 2011, presents the methodology for conducting life cycle assessments (LCAs), defining key concepts such as modules, reference study period, boundaries and scenarios. One important step in the calculation process is selecting the appropriate emission factors for each material or product, particularly for the product stage (A1-A3 modules). This data is obtained from Environmental Product Declarations (EPD), whose structure is set out in EN 15804 (2012, with 2020 addendum).

However, EN 15978 lacks the detailed interpretation and implementation guidance needed by those calculating WLC. This could lead to variance in results for similar projects, which in could in turn hinder comparison and benchmarking.

Enter the Royal Institution of Chartered Surveyors’ Professional Statement (RICS PS) ‘Whole life carbon assessment for the built environment’ (2017), the reference of choice for most, if not all, UK industry professionals undertaking whole life carbon assessments (WLCA). The RICS PS is in fact the only UK-based WLCA guidance available for the interpretation and implementation of the framework put forward by EN 15978. Since it was first published in 2017, verified WLCA tools in the UK claim compliance with RICS as a carbon calculation credential and the Greater London Authority’s WLCA guidance to support the requirements of the New London Plan heavily relies on compliance with the RICS PS.

In light of this, Part Z references the RICS PS throughout and the Part Z authors recommend that the UK Government standardise the use of the PS.

Much has changed since the 1st edition of the PS in 2017, and in recognition of this, a project to update the PS has recently commenced. The purpose of the project is to add clarification rather than change any fundamentals. The revision of the PS will respond to the following key areas of further development identified over the years by practitioners:

• Definition of calculation scope – The key uncertainty here relates to external works and below-ground infrastructure, which on some projects may be a significant part of total upfront carbon but could be easily separated out in calculations and reporting so that consistent comparisons can be made. 

• Selection of data sources – While the PS sets out a hierarchy for the selection of EPD types, the recommended use for each is not included. An update to the PS could helpfully contain further guidance on when to use different EPD types and what to do if no EPD are available. As a starting point, this could build on the recommendations of PAS 2080. 

• Consideration of relevant assumptions and scenarios – There is currently limited guidance on the assumptions and scenarios underpinning in-use and end-of-life stages. The PS revision intends to set out additional baseline assumptions (e.g. replacement periods, maintenance and repair proportions, etc.) and end-of-life scenarios for typical building components. This has already started to happen within industry bodies, such as the Institution of Structural Engineers’s ‘How to calculate embodied carbon’ (2nd ed., 2022), the Centre for Window and Cladding Technology’s ‘An introduction to sustainability in facades’ (2021), and the Chartered Institution of Building Services Engineers’s TM65 for building services (2021).

Additionally, the build-up of default emissions factors for construction installation processes (A5 module) and deconstruction and demolition processes (C1 module) could be further clarified and potentially revisited to better reflect current construction practice.

Simon Sturgis, a co-author of Part Z, is the lead author of the RICS PS and deems these development areas could be completed and implemented in a new edition of the PS within a year. The PS could then be referred to directly within Building Regulations as the standard to which all WLC calculations must comply - and calculation tools could be verified for compliance with the updated PS to simplify the submission to Building Control and the subsequent approval process.