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An internationally-applicable methodology for the calculation of embodied carbon in building services engineering

CIBSE's embodied carbon methodology began in 2021:

Embodied carbon in building services: A calculation methodology (TM65)

TM65 itself is versatile, but UK-specific.

Now, we'd like to make it globally valid and globally consistent. (If you'd like to help, see the FAQ further down).

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

Because we like to make your job easier, here's a digital tool

(for use in the UK)...

Embodied Carbon Calculator: United Kingdom (beta v1.2)

... and here's one for Australia and New Zealand.

Embodied Carbon Calculator: Australia and New Zealand (beta v1)

If you'd like to help us gather data

and create rule of thumb guidance, submit one of these:

Embodied Carbon Reporting Form (beta v2)

If you'd like us to create an embodied carbon database,

encourage manufacturers to submit one of these:

Embodied Carbon Manufacturer Form (beta v2)

We're also producing system-specific publications,

including this one:

Embodied carbon in building services: Residential heating (TM65.1)

Coming soon: publications to address HVAC and logistics,

and local addenda for North America, the United Arab Emirates, the Middle East and North Africa.

To learn more, see our #GrowYourKnowledge webinars:

Creating a local addendum to TM65: Frequently-asked questions

An addendum can be developed by a local group, institution or professional body (we will refer to this body as the ‘proposing institution’ below).   

The roles coordinated by the proposing institution may be carried out in a voluntary capacity, may become a part of an existing role, or may be paid. Covering necessary costs will be the responsibility of the proposing institution. To discuss specifics, email [email protected]. 

The proposing institution should discuss this with CIBSE. The local addendum must be read in conjunction with Embodied carbon in building services: A calculation methodology (TM65), which can be purchased at, but may also be made available for sale by the proposing institution. 

CIBSE Training offers sessions on TM65, but training is not mandatory.  

Some roles should be coordinated by the proposing institution: 

  • Working Group members (individuals representing a mix of disciplines) to discuss and agree local assumptions  
  • Chair (and possibly vice-chair) of the working group, who will liaise with CIBSE and coordinate the working group workshops  
  • Author or authors of the addendum, to develop content for the working group sessions, liaise with the CIBSE Embodied Carbon Steering Group and liaise with the CIBSE Knowledge team during the peer review, editing and production phase.  

Some roles will be coordinated by CIBSE: 

  • CIBSE Embodied Carbon Steering Group 
  • CIBSE Knowledge Project Manager 
  • CIBSE Knowledge (editor, typesetter) 

This will vary according to locality, so is for the proposing institution to decide. Previous experience suggests that a minimum of four working group sessions will be required, which would equate to around 10-14 hours of time from each working group member. However, this will increase if a large number of stakeholders are involved or if the situation is complex.  

A possible plan for a straightforward locality might look like this: 

  • Prepare for session one: read Embodied carbon in building services: A calculation methodology (TM65) and Embodied carbon in building services: Using the TM65 methodology outside the UK (TM65LA) (roughly one hour)  
    • Session 1 (90 minutes): What is the TM65 methodology? 
  • Preparation work to develop the assumptions (one to two hours) 
    • Session 2 (90 minutes): What assumptions need to change for our locality? 
  • Preparation work to further develop the assumptions (one to two hours) 
    • Session 3 (90 minutes): Review and agree revised assumptions 
  • Review and comment the addendum draft (one to two hours) 
    • Session 4 (90 minutes): Presentation of the final output. 

All manufacturer forms and reporting forms must be emailed to [email protected]. This information will be used by CIBSE to develop a generic database of building services equipment.

If you would like to collaborate on the development of a database, please contact CIBSE. 

CIBSE Certification is working with selected manufacturers on an Embodied Carbon verification scheme based on the TM65 methodology, and the number of participants will be expanded in due course.

In the meantime if you would like to take part in the scheme, or have any questions, then feel free to email us at [email protected]

Creating a local addendum to TM65: The process

The steps below are fully explained within Embodied carbon in building services: using the TM65 methodology outside the UK. Information not contained within the publication is highlighted in bold below. 

1. Go/ No go

Define the locality; assess the need for an addendum; assess the suitability of the TM65 methodology in the locality.  

2. Contact CIBSE

Email [email protected] and explain your answers to the questions in step 1. CIBSE will advise whether or not there is an addendum underway in your locality or a locality nearby, and will put you in touch with the CIBSE Embodied Carbon Steering Group, which will assess your answers to Step 1.  

3. Set up a working group in the defined locality

4. Clarify how the TM65 methodology should be adapted 

5. Agree material embodied carbon coefficients 

6. Agree assumptions specific to the locality 

7. Conduct a sensitivity analysis

8. Draft the addendum 

  • Ensure that the draft reflects a consensus of working group views.
  • Agree a schedule of progress meetings with CIBSE Knowledge; meetings once a fortnight usually work very well, but this is up to you to decide along with the Knowledge team.  
  • Submit completed drafts to [email protected] to be reviewed by the CIBSE Embodied Carbon Steering Group. The steering group will work collaboratively with your working group/ drafting team, and may suggest some revisions to ensure alignment with CIBSE TM65. 
  • Once the drafting team and steering group have created a final draft, submit it to [email protected] for peer review. The Knowledge team will then arrange a peer review of at least three objective reviewers, in line with CIBSE’s quality assurance process. Your working group/ drafting team is welcome to make suggestions as to who may be appropriate peer reviewers, but must then ensure that these individuals are not involved with authoring. Once the review is complete – normally in four to eight weeks – CIBSE Knowledge will return the draft to you for incorporation of peer review comments.  
  • Please note that it is not necessary for authors to incorporate all peer review comments; however if they choose not to incorporate certain comments, they must be able to justify their reasoning.  
  • Submit the draft to [email protected] for editing, layout and publication.    

9. Implement the TM65 methodology locally

Once the addendum is published, all relevant groups and organisations should be made aware of the addendum and should be encouraged to understand the benefits of a consistent approach to generating data.  

  • The CIBSE Marketing team will liaise with you about promoting the guidance in your locality, and help you to encourage those who use the guidance to submit embodied carbon manufacturer forms and reporting forms, and embodied carbon data, to CIBSE.  
  • Work with CIBSE to collect and make use of the resulting data. 

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The CIBSE embodied carbon methodology is the result of a partnership between CIBSE Research and Introba, a deep green engineering and consulting firm located across Australia, Europe, and North America.

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