Understanding Embodied Carbon in Architecture – Part 1

In sustainable architecture, discussions often revolve around the operational energy use of buildings and the incorporation of renewable resources. Operational energy pertains to the energy required for heating, cooling, lighting, and running appliances, which is meticulously optimised in designs adhering to Passivhaus standards. By focusing on superior insulation, airtight construction, and energy-efficient systems, Passivhaus buildings significantly reduce energy consumption and enhance indoor comfort. This approach ensures that buildings are energy-efficient and cost-effective over their lifespan and is an approach we consistently strive to implement

However, another critical aspect of a building's environmental impact is often overlooked: embodied carbon. Embodied carbon refers to the emissions produced during the entire lifecycle of building materials, including extraction, manufacturing, transportation, and assembly. While operational energy addresses the energy consumed during the building's use, embodied carbon accounts for the emissions generated before the building even opens its doors. Addressing embodied carbon is essential for a comprehensive approach to sustainability, as it highlights the need for responsible material selection, efficient construction practices, and innovative design solutions to minimise the carbon footprint from the very beginning. 

So, what is Embodied Carbon?

Embodied carbon is all the CO2 emitted when producing materials. It's calculated from the energy used to extract and transport raw materials as well as emissions from manufacturing processes. The embodied carbon of a building can include all the emissions from the construction materials, the building process, all the fixtures and fittings inside, as well as from deconstructing and disposing of it at the end of its lifetime. (UCL Engineering)

This concept highlights that a building's environmental impact extends beyond its operational phase. It accounts for the carbon emissions embedded within the physical structure, from the foundation to the finishes. By quantifying a building's embodied carbon, architects and designers can better understand its contribution to climate change and identify opportunities for mitigation.

For example, according to Timber Development UK, using a timber frame instead of masonry could reduce the embodied carbon of a building by 20%.

Why Does Embodied Carbon Matter?

While operational energy use is significant, the embodied carbon of a building can represent a substantial portion of its total emissions, especially in structures with long lifespans and their long-term impacts. Ignoring embodied carbon means neglecting a significant portion of a building's environmental impact.

Considering embodied carbon encourages a holistic view of sustainability in architecture. It prompts architects to assess not only a building's energy efficiency and performance but also the environmental consequences of its materials and construction processes.

Reducing embodied carbon is crucial for combating climate change. As the construction industry is one of the largest contributors to global carbon emissions, addressing embodied carbon offers an opportunity to make significant strides towards carbon neutrality and sustainability.

Minimising embodied carbon often entails using fewer materials, opting for low-carbon alternatives, and prioritising recycled or reclaimed materials. This promotes resource efficiency and encourages the adoption of circular economy principles within the construction sector.

How can we reduce embodied carbon?

Fabric First Material Selection.

Choose materials with lower carbon footprints, such as sustainably sourced timber, recycled metals, or low-carbon concrete alternatives like fly ash or screw pile foundations. Biogenic materials like timber and straw will have a lower embodied carbon than intensively produced materials like aluminium. Its also worth noting the sequestration that occurs whilst these biogenic materials are growing, in effect locking up carbon in a buildings materials.

Think about a building in layers.

Design with building layers in mind i.e. where elements that need to last a long time like structure it might use higher carbon materials like glulam, steel or concrete whereas the layers which have a lower lifespan like internal finishes say 5-10 years, lower embodied carbon materials can have a huge impact.

Design Optimisation.

Optimise building designs to reduce material use without compromising structural integrity or functionality. Employ efficient construction methods and modular construction techniques to minimise waste.

Lifecycle Analysis.

Conduct lifecycle assessments to evaluate the embodied carbon of different design options and make informed decisions based on environmental impact.

Adaptive Reuse and Deconstruction.

When renovating or decommissioning buildings, prioritise adaptive reuse and deconstruction over demolition. Salvaging and repurposing materials can significantly reduce embodied carbon.

Carbon Offset.

Remaining emissions can be offset through carbon sequestration initiatives, such as afforestation projects or investing in renewable energy.

Embodied carbon represents a critical aspect of sustainable architecture that demands attention from architects, designers, builders, and policymakers alike. By accounting for the environmental impact of building materials and construction processes, we can create structures that not only minimise carbon emissions but also contribute to a healthier and more sustainable built environment. Embracing the principles of embodied carbon reduction is essential for shaping a greener, more resilient future for generations to come.