Embodied Carbon Calculation (CIBSE TM65): A Closer Look
As we set our sights on the construction of net-zero buildings, the conversation has started to shift from operational carbon emissions to the broader scope of whole-life carbon emissions – a notoriously difficult thing to measure.
Join Mehul Chhowala, our Sustainability Consultant, as he examines how the CIBSE TM65 (CIBSE technical memorandum 65, TM65:2021) can help us measure the embodied carbon of MEP (Mechanical, Electrical and Plumbing) products.
The importance of embodied carbon in building services
For many years, MEP consultants like us have been dedicated to reducing operational carbon, during both the design stage and product selection, in aid of helping to reduce the overall emissions of a building. While these well-designed services may help to reduce operational carbon, the products themselves can have a significant impact on the overall embodied carbon associated with the project.
At product stage, embodied carbon emissions are associated with the extraction, transportation, and processing of raw materials - and the energy consumption used to manufacture the product itself. The environmental effect of the use stage is estimated by refrigerant leakage, repair and product replacement. Decommissioning and processing at the end of the product's life cycle also contributes to the total effect. Because MEP products have a shorter service life than the rest of the building, the emissions associated with system replacement are higher.
Recent studies emphasise the substantial impact of MEP systems on whole life carbon emissions, constituting 5–25% of embodied carbon in new constructions and up to a staggering 75% in retrofits.
The only way to effectively measure whole life carbon emissions of a building is with a clear understanding of the environmental performance of products and materials. Environmental Product Declarations (EPDs) certificates that provide the environmental impacts of MEP equipment in terms of their embodied carbon are one of the most useful tools to achieve this, yet are not always readily available from manufacturers.
CPW Sustainability Consultants have been calculating the embodied carbon associated with MEP systems for over 10 years, often working in the absence of any real industry guidance, to demonstrate how such systems can make a significant contribution to the overall embodied carbon content of a building project.
What is TM65:2021?
In January 2021, the construction industry received a pivotal guide to support calculations. ‘TM65 Embodied carbon in building services: A calculation methodology (2021)’ is a guide which helps the industry to evaluate embodied carbon emissions in building services design.
Guidance is provided on how to use EPDs to assess the embodied carbon of equipment, and also to estimate the embodied carbon where EPDs are not available. TM65's framework covers product-level embodied carbon calculations, considering stages from manufacturing to disposal. It introduces two calculation methods: the ‘basic’ and 'mid-level,' with the latter being more robust, requiring extensive manufacturer information.
The basic calculation approach simply requires material composition and information on refrigerants used, but the mid-level calculation method includes additional information such as energy used in manufacturing and industrial location, yielding a more robust conclusion.
In future, the aim is to develop an embodied carbon product database, which will enable MEP engineers to efficiently assess the whole life carbon emissions of their designs.
Embodied carbon calculations in action
Recognising the role MEP services play, our work on a recent project focused on minimising the embodied carbon impact - with the TM65 mid-level methodology being implemented during the design stage. This was essential as EPDs for the building services products were not widely available.
We focused initially on the major mechanical and electrical equipment that was crucial to the project, such as chillers, heat pumps, air handling units, VRF multi-split units, fan coil units, heat interface units, radiators, water heaters, lighting fixtures, and PV panels.
To obtain all the information required for the TM65 mid-level calculation, product manufacturers were approached. Some of the larger manufacturers had already completed TM65 mid-level calculations and had the information readily available, while others were happy to share the information we required. The journey towards net-zero buildings demands a meticulous approach from all partners and suppliers. As small-scale manufacturers do not have EPDs for their products, a CIBSE-standardised form must be filled out with the essential information to compete the TM65, which takes additional time. Following receipt of the necessary information from manufacturers, the TM65 mid-level calculation methodology was applied to the respective products, resulting in specific embodied carbon figures.
Adopting the TM65 mid-level methodology for our client, helped us to quantify and produce a more accurate representation of the embodied carbon emissions associated with MEP products for the project. Based on the results obtained, product selection might be altered to reduce the embodied carbon against industry benchmarks. The TM65 methodology promotes a long-term approach to building design that considers the embodied carbon over the lifespan of the MEP systems.
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