CIBSE TM65, Embodied carbon in building services: A calculation methodology, provides guidance on calculating the embodied carbon emissions of mechanical, electrical and plumbing engineering products used in buildings. Since its 2021 inception, the Technical Memorandum has spawned several significant addenda. This CPD will provide a reminder of the scope of TM65, and explore the regional- and sector-specific addenda that have been published to support and encourage the adoption and application of TM65 as a route to predicting the life-cycle global warming impact of a product.
TM65 and Environmental Product Declarations (EPDs) are standardised ways to assess and report embodied carbon. They each play a distinct role in fostering transparency and driving the reduction of embodied carbon in the building services industry.
EPDs are independently verified and registered documents that communicate transparent information about the life-cycle environmental impact of a product. They are considered the most reliable source of information about the environmental impacts of a product and are a standardised way of declaring carbon emissions associated with a product throughout its life-cycle, using a global warming potential (GWP) indicator. They provide a comprehensive and independently verified assessment of a product’s life-cycle environmental impacts, going beyond just GWP emissions. EPDs are developed from Product Category Rules (PCRs), which provide sets of rules, requirements and guidelines that have been developed following existing standards, such as BS EN ISO 140251 and BS EN 15804.2
TM65, and the various additions, serve as a valuable interim methodology for approximating embodied carbon emissions when EPDs are not available. TM65 is specifically relevant when assessing the environmental impact of MEP systems, particularly as it notes that they can constitute a significant portion of a building’s embodied carbon. This is considered to be in the order of at least 30% in new buildings (excluding refrigerant leakage), and potentially up to 75% in retrofit projects. The methodology provided in the TM emphasises the importance of considering the entire life-cycle of these products, including manufacturing, installation, maintenance and end-of-life disposal. While carbon is a primary focus, the document also highlights the importance of considering other environmental and social impacts when specifying products.
TM65 stresses that requesting EPDs created by manufacturers should be the first step in determining the embodied carbon of MEP products. However, owing to the limited availability of EPDs for MEP products, TM65 provides two interim calculation methods that deliver an ersatz alternative to an EPD:
- The ‘basic’ calculation method that requires less information from manufacturers, primarily relying on product weight and material composition breakdown. It uses a scale-up factor to account for life-cycle stages beyond material extraction.
- The ‘mid-level’ calculation method demands more detailed information, including energy consumption during final factory assembly, transport distances and refrigerant leakage rates. It offers a more comprehensive assessment of embodied carbon compared with the basic method.
See boxout panel for more detail on the two methods.
Basic calculation: Requires fundamental product information, including: the product weight; material composition breakdown (at least 95%); refrigerant type and charge (if applicable); and the expected product service life. Mid-level calculation: Demands all the data used in the basic method, plus the estimated proportion of factory energy use by fuel type attributed to the product, and the final assembly location. A more granular assessment that includes: The mid-level calculation method is considered more robust, as it incorporates more detailed information about the manufacturing process and transportationTM65 methods
Both calculation methods use a standardised life-cycle stage framework based on BS EN 15978:2011,3 categorising emissions into modules (cross-referenced to the life-cycle modules of BS EN 15978). For example, TM65 currently includes A1-A4 (product and transport), B3 (repair), C2-C4 (end-of life processes) and, in terms of refrigerant leakage, B1 (use) and C1 (deconstruction). B4 (replacement) is aimed at being calculated at a system level. This consistent approach allows for comparisons between products, and contributes to building a broader understanding of embodied carbon in MEP systems.
Regional adaptations of TM65 are crucial for improving the consistency and relevance of these assessments in different geographical contexts. Since the original publication of TM65 in 2021, there have been further publications that focus on specific sectors and regions. The significance of the addenda is emphasised by the very significant financial and technical input provided by organisations, as acknowledged at the start of each publication.
TM65LA, Embodied carbon in building services: Using the TM65 methodology outside the UK, provides a toolkit that defines the process for adapting the TM65 methodology for use outside the UK by offering a step-by-step approach for creating local addenda. It emphasises the importance of considering regional variations in factors such as transport distances and carbon intensities. It also provides guidance on how to use the TM65 methodology for individual projects in regions lacking local addenda, and aims to promote the consistent assessment of embodied carbon emissions in building services globally. Localised addenda have been produced, and co-funded, with local experts, companies and organisations (as acknowledged in each publication).
TM65ANZ, a local addendum that focuses on Australia and New Zealand, provides alternative assumptions tailored to these regions. Key adjustments include local transport scenarios; refrigerant leakage rates; and a specific carbon factor for landfill. This revises the refrigerant leakage rates to align with Australian and New Zealand standards and practices – this is significant, as refrigerant leakage can have a substantial impact on a product’s overall embodied carbon footprint.
So, for example, it replaces Table 4.4 in TM65 with Table 2.1, providing updated annual leakage rates for the ‘use’ phase (B1) and end-of-life leakage rates for the ‘deconstruction’ phase (C1). These revised rates are based on the Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH) guidelines that were originally outlined in Methods of Calculating Total Equivalent Warming Impact.4
The GWP values for refrigerants are aligned with those used in the Green Star rating system, a prominent sustainability benchmark in Australia and New Zealand. As such, Table 2.2 in TM65ANZ supersedes Table 2.2 in TM65, offering updated GWP values sourced from various bodies, including the California Air Resources Board, the Institute of Refrigeration, and the Intergovernmental Panel on Climate Change’s (IPCC’s) AR5 report.5
TM65ANZ acknowledges the unique geographical characteristics of Australia and New Zealand by modifying the transport assumptions. Table 2.8 in TM65ANZ introduces region-specific transport distances, distinguishing between products manufactured within Australia, within New Zealand, or globally (Asia). These revised distances better reflect typical supply chains in the region, which can make a significant impact on the final carbon footprint. For example, products manufactured nationally in Australia are assumed to travel 2,000km by heavy goods vehicle (HGV), whereas products manufactured globally (Asia) are estimated to travel 10,000km by ship and 300km by HGV.
TM65ANZ provides more granular carbon factors for electricity, accounting for variations across Australian states and New Zealand regions. Consequently, Table 2.6 in TM65ANZ supersedes Table 4.10 in TM65, offering region-specific values based on data from the Australian government’s then Department of Industry, Science, Energy and Resources (DISER – now Department of Industry, Science and Resources), and the New Zealand Ministry for the Environment.
Adjustments are made for the carbon factor for landfill emissions (C4) to reflect local waste management practices, by using a value of 0.2kgCO2e per kg waste that has been sourced from the Australian government’s DISER (and compares with 0.0089kgCO2e per kg waste in TM65). While TM65ANZ retains the same embodied carbon coefficients for materials (A1) as the original TM65, it emphasises that using locally-sourced EPDs is preferable whenever they are available, and TM65ANZ serves as a valuable interim methodology until EPDs become more widely available in the region.
The most recent addendum to TM65, TM65NA, published in conjunction with ASHRAE, relates to North America (United States, Canada and Mexico). As with TM65ANZ, it incorporates regional factors such as electricity and gas carbon factors based on location, specific transport scenarios, and updated refrigerant leakage rates derived from US regulations. Just as with TM65ANZ, this is not designed as a standalone document; it is intended to be used in conjunction with the core TM65 methodology.
TM65NA introduces North American-specific embodied carbon coefficients for materials such as fibreglass, rockwool and general insulation, sourced from the Embodied Carbon in Construction Calculator (EC3) database.6 TM65NA updates the refrigerant leakage rates to align with North American standards and practices. It replaces Table 4.4 in TM65 with Table 2.2, providing updated annual leakage rates for the ‘use’ phase (B1) and end-of-life leakage rates for the ‘deconstruction’ phase (C1). These rates are sourced from ASHRAE Standard 34.7 The GWPs for common refrigerants are based on the IPCC’s AR5 and AR68 reports. TM65NA recommends the use of AR6 values (published after the original TM65), as they represent the latest scientific estimates, and Table 2.3 in TM65NA replaces Table 2.2 in TM65.
The geographical scale of North America and the diversity of its supply chains have necessitated revised transport assumptions. Table 2.5 in TM65NA replaces Table 4.9 in TM65, introducing new transport distances based on product complexity, and distinguishing between transport by HGV, rail and sea. This includes assuming that nationally manufactured products (high complexity) travel 6,000km by truck. Additionally, more detailed information is provided in Table 2.11 ‘Default transportation scenarios for North America (A4)’, including common North American scenarios such as ‘partial cross country’ (with 50km HGV and 4,800km by train). This also includes estimates that products sourced from Asia to the West Coast travel 10,000km by sea, and European manufacturing (to the east coast) 5,600km by sea.
Recognising the variability in electricity generation mixes across North America, TM65NA provides more relevant carbon factors for electricity. Table 2.6 includes specific values for various US grid regions, while Table 2.7 offers values for different Canadian provinces. TM65NA emphasises the importance of understanding how the location of manufacturing can affect embodied carbon results, especially in the mid-level calculation method.
The carbon factors for landfill emissions (C4) are aligned with waste management practices in North America. Table 2.12 in TM65NA replaces Table 4.15 in TM65, using a value of 0.052kgCO2e per kg waste sourced from the US Environmental Protection Agency (EPA). TM65NA acknowledges the need for consistent documentation and calculation methodologies, and highlights ongoing efforts by organisations such as ASHRAE, CIBSE, the International Living Future Institute (ILFI)9 and US Green Building Council (USGBC)10 to improve alignment in North America. It also references initiatives such as the MEP 2040 Challenge,11 which aims to reduce the carbon footprint of building systems.
There are localised worked examples (in both TM65NA and TM65ANZ) for both the basic and mid-level calculation methods. These examples demonstrate how to apply the methodology step by step, and offer insights into data requirements and interpretation of results. A sensitivity analysis is crucial in embodied carbon calculations, particularly when using methodologies such as TM65, to understand the influence of various factors and assumptions on the results.
As TM65 was initially developed for the UK context, it relies on assumptions that may not accurately represent other regions – TM65LA stresses the need for local addenda to address these regional differences. Sensitivity analysis helps in quantifying the impact of variations, such as: transport distances; electricity grid carbon factors; end-of-life processes (recycling rates and disposal methods); and refrigerant choices and leakage rates. This aids more informed decision-making about material choices that might include considering alternative sources of steel (which often determines a large part of a manufactured item’s embodied carbon), such as the lower-carbon steel explored in the panel ‘Reducing steel’s environmental impact’.
Other areas that may be highlighted are manufacturing locations, system suppositions and areas where more data collection – or refinement of assumptions – are needed. Such analysis may be employed to compare the results obtained from basic and mid-level calculation methods, assessing the potential for overestimation or underestimation in the basic method. This comparison helps identify potential discrepancies – such as where the basic method might not adequately capture the embodied carbon impacts – that can prompt further investigation or refinement of the methodology.
The practical examples on sensitivity analysis in both TM65NA and TM65ANZ reveal potentially significant differences in embodied carbon depending not only on the manufacturing location, but also between the two geographic zones, highlighting the importance of regional variations.
Reducing steel’s environmental impact
The quest for reduced embodied carbon has encouraged steel producers to develop processes that reduce emissions in manufacturing. By drawing on renewable sources of electricity to heat electric arc furnaces, and incorporating significant proportions of recycled scrap metal, substantial CO₂ reductions can be delivered, compared with traditional methods.
For example, an international steel manufacturer12 claims that CO₂ emissions can be as low as 0.3kgCO2e per kg of finished steel when the source material is 100% recycled scrap steel. (This compares with traditional steel production methods, especially those using blast furnaces, that typically emit around 2-3kgCO2e per kg of steel.) The air handling unit (AHU) in Figure 1 is an example of how this might make a practical impact on the embodied carbon of MEP products while maintaining function and performance.
So far, there have been three addenda produced to address the needs of particular industry sectors, to understand system-level impact. All three have extensive discussion, applications and worked examples of employing the TM65 methods, and have been developed and co-funded by experts in the respective sectors, as acknowledged in each addenda. In brief, TM65.1 specifically examines the embodied carbon impact of space heating and hot-water systems for residential new-build developments in a UK context, following the same calculation methodology as TM65 at the product level.
A lighting-specific perspective on embodied carbon assessment is provided by TM65.2; it offers guidance on material selection, system boundaries, and reporting specific to lighting equipment. The third sector-related addendum, TM65.3, addresses the embodied carbon in logistics centres, encompassing both MEP and material handling equipment (MHE). It analyses the impact of different building types and systems commonly found in logistics facilities.
TM65 is not intended to replace EPDs, but rather to bridge the gap until EPDs become widely available for all building services equipment, supporting decision-making related to embodied carbon. However, those who apply TM65 are encouraged to request EPDs from manufacturers to signal that there is industry demand, and so encourage manufacturers to invest in EPD development. At the same time, TM65 encourages users to share their embodied carbon calculations with CIBSE to help develop a comprehensive database and refine the methodology further.
A primary aim of TM65 remains to provide an understanding of whole-life carbon and embodied carbon in building services, moving towards a future where EPDs become widely available.
All TM65 resources, including calculation tools, can be accessed at cibse.org/tm65. Upcoming addenda will include guidance tailored to heating, ventilation and air conditioning (HVAC) systems for office environments, and adaptations specific to the United Arab Emirates region.
- Withs thank to Louise Hamot of Introba for her valuable expertise and contributions to this article.
© Tim Dwyer 2024.
References:
- BS EN ISO 14025:2010 Environmental labels and declarations. Type III environmental declarations. Principles and procedures, BSI 2010.
- BS EN 15804:2012+A2:2019 Sustainability of construction works – Environmental product declarations — Core rules for the product category of construction products, BSI 2019.
- BS EN 15978:2011 Sustainability of construction works – Assessment of environmental performance of buildings – Calculation method, BSI 2011.
- Methods of calculating Total Equivalent Warming Impact (TEWI), AIRAH 2012 – bit.ly/CJDec24CPD1 – accessed 26 October 2024.
- IPCC AR5 report – bit.ly/CJDec24CPD2.
- Building Transparency Embodied Carbon in Construction calculator (EC3) Database –bit.ly/CJDec24CPD3 – accessed 26 October 2024.
- ASHRAE Standard 34-2019 Designation and Safety Classification of Refrigerants, ASHRAE 2019.
- IPCC AR6 report – bit.ly/CJDec24CPD4.
- Embodied Carbon Guidance, International Living Future Institute (ILFI) – bit.ly/CJDec24CPD5 – accessed 26 October 2024.
- Driving Action on Embodied Carbon in Buildings, USGBC, 2023 – bit.ly/CJDec24CPD6 – accessed 26 October 2024.
- MEP 2040 Challenge – bit.ly/CJDec24CPD7 – accessed 26 October 2024.
- bit.ly/CJDec24CPD8 – accessed 26 October 2024.