As we move ever closer to the net-zero deadline of 2050, reducing CO2 throughout the design, construction and operation phases of our new buildings and infrastructure is key. With engineers and construction professionals still adjusting to this sustainable movement, there can be the potential for confusion with many new phrases and terms flying around. Embodied carbon and operational carbon, ECFs and EPDs are just a few examples. Here, we try to take some of the mystery away.
Operational vs. embodied carbon
A crucial aspect of planning and designing using green alternatives is understanding operational vs. embodied carbon. While both contribute to global carbon emissions, embodied carbon can be defined as the carbon output produced during the construction of a building. It is the result of specific processes and design decisions, rather than a continuous emission of CO2. This includes the manufacture and extraction of materials used to construct the building and the transportation of these materials to the construction site.
In contrast, operational carbon is the CO2 emitted during the ongoing operation of the building, which of course can fluctuate depending on the technology and level of use over time. Services, appliances and other infrastructure, such as automatic doors, contribute to operational carbon.
To put this in real terms, an airplane flying from the UK to Germany would be classified as operational carbon, while the CO2 generated from the original construction of the airplane would be embodied carbon.
In recent years, significant steps have been taken to reduce operational carbon, with substantial improvements in technology and energy-efficient appliances. Inventions such as LED lighting, smart heating and innovative technologies in the home are just a few examples of the progress made to reduce operational carbon. These products should be standard in newly constructed buildings, and will be vital in the drive towards net-zero.
In comparison, we are still using carbon-intensive methods to manufacture our building materials and construct our buildings. As such, it is crucial that we address the levels of embodied carbon and work to reduce this within the built environment.
One way to do this is to calculate embodied carbon during the initial design and engineering stages and monitor it throughout the process. By calculating embodied carbon in these early design stages, engineers can make better, more informed decisions, with more time to make changes based on embodied carbon output.
Estimating the embodied carbon of each structural component, such as a steel beam or concrete slab, is typically calculated by multiplying the quantity of the material by a carbon factor, usually measured in kgCO2e per kg of material for each part of the life cycle, which looks like this: Quantity of Material x Carbon Factor = Embodied Carbon
Construction life cycle
The construction life cycle includes suggested embodied carbon factors (ECFs) in each section, making the calculation and monitoring of embodied carbon much more manageable at each stage. As you can see in the graphic below, the life cycle is divided into four stages and several modules for more accurate calculations.
Stages A1 to A5 refer to the product and construction phase and, in turn, incorporated carbon generation. While the modules within stages B relate to the lifetime use of the building or structure, classified under operational carbon. In addition to the four life cycle stages, a separate section covers some miscellaneous carbon outputs that should be considered. These are known as "Beyond Life" and cover the carbon benefit or burden for recycling materials, energy recovered from materials and reuse of materials. It is clear that recycling or reusing products at the end of their lives contributes to a circular economy that will go a long way in the UK's journey to net-zero.
ECFs vs. EPDs
Environmental Product Declarations (EPDs), often confused with ECFs, are product-specific reports that document the environmental impact and performance of a product or building material. Essentially, an EPD is a tool that helps manufacturers and specifiers opt for more environmentally conscious materials for production, thus lowering the overall carbon impact.
While an EPD is specific to a particular product, ECFs take this view further by considering the other stages of the life cycle - including transportation to the building site and assembly on site - to provide a more rounded view of its overall carbon value. The engineering industry will use ECFs when modeling the building or structure and providing a report on its embodied carbon emissions.
A vital issue with embodied carbon monitoring and calculation is the current lack of a strict code around it. While EPDs are standardized and regulated, ECFs are not - a clear sign of how new the industry is to the issue of embodied carbon calculations. As such, embodied carbon results can vary widely between engineers, despite using the same materials in the same way. Of course, embodied carbon is an emerging topic in construction, and in due course, standards will probably be set for everyone to work to.
Found within Trimble's Tekla Structural Designer, the Embedded Carbon Calculator works collaboratively with the 3D engineering modeling and analysis software. Designed for these early planning stages at A1-A3 level, the tool enables an automatic view and understanding of the carbon impact of materials and plans, allowing engineers to make more informed choices in the early stages of construction and understand the embodied carbon output of each structure.
