Embodied carbon: Nearing net-zero buildings

Until recently, the main focus of architects, building services engineers and clients has been on minimising operational carbon emissions – the amount of carbon emitted during the in-use phase of a building – while emissions relating to the rest of a building’s lifecycle have been largely ignored.

With enhanced regulations and improvements in energy efficiency, the amount of energy used in the operation of buildings has declined. Correspondingly, this has increased the significance of the energy used to build them in the first place, particularly if we are to deliver zero-carbon buildings.

A building’s whole life carbon emissions refers to both its operational and embodied carbon emissions, including those of the materials, transportation of materials, the construction, repair, maintenance and even the deconstruction of a building.

Unlike operational energy, embodied energy savings have an immediate impact on a building’s whole-life carbon and they are independent of the occupant’s behaviour.

The choice of materials and construction methods can significantly impact the amount of energy embodied in a building. Most obvious, perhaps, is the embodied energy of materials such as concrete. But, just as important as the energy embodied in a building’s fabric is the energy embodied in its building services, the equipment used to heat, cool, ventilate and light a space.

There is a huge amount of building services equipment installed in a typical office. If this is not well designed and operated, and disposed of prudently, the life-cycle emissions associated with these elements can dwarf emissions embodied in the structural elements.

According to some researchers, the building services can be responsible for as much as 25% of the total embodied carbon in a fully serviced typical office building, which can be equivalent to its operational emissions over many years of use.

Building services systems and components are often assembled from metals and metal alloys, materials with high embodied carbon. In addition, their manufacture may involve complex assemblies of components, many of which are transported over long distances.

Environmental product declarations (EPDs) are the accepted way of establishing a product’s embodied carbon. However, the complexity of building services supply chains mean that, as yet, very few manufacturers of plant and equipment have produced EPDs.

To enable engineers to consider the carbon embodied in a scheme’s building services systems the Chartered Institution of Building Services Engineers (CIBSE) has published the building services industry’s first embodied carbon toolkit, known as Technical Memoranda 65.  This industry-leading document was put together by a collaborative group of engineers from CIBSE, Elementa and Integral Group.

CIBSE TM65: Embodied carbon in building services: A calculation methodology is not aiming to replace EPDs, but it will allow embodied carbon estimations to be made for building services products when no EPD is available.

Importantly, TM65 provides a consistent approach to the way embodied carbon calculations for building services products are carried out and reported.

The CIBSE guidance is increasingly being applied to MEP (mechanical, electrical and plumbing) products manufactured and installed all over the world.

An indication of the growing importance of embodied carbon to corporations is that CIBSE is now working with multinationals to apply the methodology to embodied carbon in their UK estate.

The information generated by this document is further being used to help in the development of an embodied carbon database for building services products. This will make it easier to accelerate progress towards achieving net zero-carbon buildings.

The publication of TM65 serves to highlight how CIBSE is leading the way in finding practical solutions to tackle this issue of embodied carbon in building services globally which encapsulates CIBSE’s philosophy of “it’s down to all of us to make a difference”.