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CIBSE expands building services embodied carbon calculation methodology to support engineers internationally

CIBSE is launching an addendum to TM65, the embodied carbon calculation methodology published in 2021. TM65 Embodied carbon in building services: Using the TM65 methodology outside the UK (TM65LA) is designed to create global consistency on how the embodied carbon of building services equipment can be assessed.

TM65 provides a methodology to estimate the life cycle embodied carbon of products used in building services engineering where no environmental product declaration (EPD) is available. Many of the methodology’s inherent assumptions in the 2021 publication are specific to the UK.

This addendum aims to complement TM65 by defining how local addenda can be developed. As such, it sets out how the methodology can be adapted to be used outside of the UK. It is not a standalone document and cannot be applied without first understanding TM65.

To ensure that the CIBSE TM65 methodology is globally valid and globally consistent, CIBSE supports the creation of local addenda to TM65 that are specific to localities outside of the UK. This document aims to assist in the creation of these local addenda.

Primary authors, Louise Hamot and Clara Bagenal George (Integral Group) said: “The aim is to create global consistency with relevance locally. The TM65 methodology inherently relies on a set of assumptions that might differ in different countries for supply chain or geographical reasons. This guide sets the rules for creating consistent local addenda. A local addendum can be developed for a continent, a country, a state, a city or a region. The overarching methodology would be the same but applied with local assumptions and local carbon factors.”

CIBSE TM65LA was authored by Louise Hamot and Clara Bagenal George (Integral Group), with contributions from Dr Joe Jack Williams (Feilden Clegg Bradley Studios); Dr Julie Godefroy (CIBSE); Leonardo Poli (Integral Group); Louise Wilkinson (Integral Group); and Simon Wyatt (Cundall).

If you are interested in creating an addendum for your region (or to assist in its creation), first get in touch with CIBSE at

For full details on the drafting and submissions process, how to get started, and the full TM65 suite of publications see 

Access TM65 Embodied carbon in building services: Using the TM65 methodology outside the UK (TM65LA) via


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