The term embodied carbon is appearing more and more in conversations among professionals in the building industry. But what is it exactly, and how does it relate to a building’s lifecycle? What are the impacts we are trying to capture from embodied carbon of materials versus embodied carbon of the whole building?
This article will bring more clarity on embodied carbon and whole life carbon, the phases of a building’s lifecycle and their impact on the environment, and the opportunities for lowering these emissions.
As we produce increasingly energy efficient buildings - that use less energy to run and rely more and more on renewable energy, the attention is shifting towards lowering another large source of energy consumption: the building’s embodied carbon. This is the amount of carbon “locked” into the building structures, and includes the energy used in production of materials, transport, construction and all processes involved to build the building.
Let’s get some clarity on the terminology.
Embodied carbon and whole life carbon
In the building life cycle, embodied carbon is the carbon dioxide equivalent (or greenhouse gas) emissions associated with the non-operational phase of the project. This includes emissions caused by extraction, manufacture, transportation, assembly, maintenance, replacement, deconstruction, disposal and end of life aspects of the materials and systems that make up a building.
The whole life carbon of the building is both the embodied carbon and the carbon associated with its operation (heating, cooling, powering, providing water
etc.).
This means that a significant proportion of a building’s lifetime carbon is locked into the fabric and systems. Addressing the embodied carbon can provide cost-effective potential for carbon and cost savings over and above those traditionally targeted through operational savings.
Embodied carbon calculations are often associated to single materials or building components. Remember that these are the impacts associated to the components only, and the sum of the embodied carbon of all the building materials is NOT the embodied carbon of the building. At the building level, always consider the phases of the building lifecycle, such as construction, fit out etc.
How do we assess the impacts of a building’s lifecycle?
We can think of the building lifecycle as a process broken down into the following phases, with each phase having impacts to the whole sustainability spectrum:
Raw materials extraction and components/materials production;
Design;
Materials procurement;
Construction;
Operation;
Demolition/ disposal.
The major focus of the industry and regulations currently sits on operational energy efficiency (phase 5). This is where normally the greatest amount of energy is spent with consequences on greenhouse gas emissions. However, the other phases have significant impacts too, and in some building types embodied carbon accounts up to 50% of the total lifecycle carbon!
If we take operational energy out of the equation for the purpose of this discussion, we can easily understand how the main focus becomes materials, structures and building products, and processes of construction/demolition.
The discipline that historically provides an environmental assessment of a life cycle of a product, process or complex structure like a building, is called Life Cycle Assessment (LCA).
The main outputs of an LCA study, which correspond to environmental impacts, can be categorised in the following list:
Global Warming Potential or GWP (contribution to climate change)
Eutrophication (excessive amounts of water nutrients)
Ozone layer depletion
Human toxicity
Acidification (of oceans)
Material depletion
Please bear in mind that embodied carbon calculations only take into account energy, carbon emissions and their impacts, therefore do not include a 360 degrees evaluation of all the environmental impacts of the process.
What are the opportunities for lowering embodied carbon?
Brief stage
The greatest opportunity for impact on embodied carbon comes at the project brief stage, where low embodied carbon targets can be set up for the project team.
Design stage
At the design stage, the greatest challenge sits in assessing potential embodied carbon impacts of the main structure and selecting low embodied carbon alternatives. By looking at the structures and materials with the highest quantities, it is possible to identify “easy wins” for the project; selecting materials which are recyclable and with high recycled content helps lower the embodied carbon.
Material procurement and construction
At material procurement and construction phase, using locally sourced materials reduces transport cost and associated carbon emissions. Selecting responsibly and sustainably sourced materials encourages best practice throughout the supply chain.
Generic embodied energy/LCA data are an average accounting of the impact for a particular product typology (e.g. concrete frame)
Product certifications such as Environmental Product Declarations (EPDs) give data for specific products made by a specific manufacturer.
Handover
During handover, there are opportunities relative to the choice of fit-out elements, again responsibly sourced, with low embodied impacts and possibly with high standard of durability and recyclability.
What is the business case for low embodied carbon buildings?
Embodied carbon, circular economy and energy saving are all connected to the embodied carbon and lowering environmental impacts in the building lifecycle. As discussed in previous course mails, all these savings for the environment also have financial benefits.
The economic case for considering embodied carbon as a priority has also been studied; results indicated that embodied carbon solutions are relatively low cost when compared to many operational carbon saving solutions, it encourages lean design and drives resource efficiency and an assist in achieving credits in some building assessment sustainability rating schemes.