Making sense of embodied carbon

Calculating a building or structure’s embodied carbon often falls to surveyors, architects and structural engineers at the design stage of a project but what exactly is it and why does it matter.

Embodied carbon may just be one piece of the sustainability puzzle, however, embodied carbon assessment helps to compare the environmental impacts of different building materials, designs and construction methods by highlighting those elements that are carbon-intensive. This means other lower carbon options can be sourced and considered early on. A low carbon building is one that optimises the use of resources both to build it and to use it over its lifetime.

What is the embodied carbon of a building?

The embodied carbon of a building relates to all the greenhouse gas emissions (GHG) from the construction lifecycle of a building.

This includes the carbon emissions for materials, products and systems. From raw material extraction, manufacturing and transportation, the construction process itself, right through the building’s lifespan. It also accounts for any refurbishment or maintenance required and ultimately its end of life including demolition and material disposal or processing.

To help describe the environmental impact of a built asset, its life cycle, typically taken as 60 years, is split into stages and modules as defined by BS EN 15804 in the diagram below.

Diagram showing environmental impact of a built asset, its life cycle, typically taken as 60 years, is split into stages and modules as defined by BS EN 15804

(Ref: How to calculate embodied carbon - The Institution of Structural Engineers (istructe.org))

Embodied carbon is measured using carbon dioxide equivalent emissions (kgCO2e). This unit of measurement is based on the relative impact of a given gas on global warming or its Global Warming Potential (GWP). Often, embodied carbon and GWP are used interchangeably.

The UK government’s ‘Guidance on how to measure and report your greenhouse gas emissions’ includes embodied carbon emissions within its Scope 3 category. The RIBA ‘Embodied and whole life carbon assessment for architects’ expands on this, in that construction materials specified by architects are produced by other parties and would be counted as their scope 1 or 2 emissions. Whole life carbon in relation to a building covers scope 1, 2 and 3 emissions. But, how has the concept of embodied carbon evolved?

A closer look at why carbon emissions have become an important construction consideration

The level of carbon dioxide has been rising dramatically since the industrial revolution, especially over the last hundred years, with fossil fuels being burned to create energy and heat. This releases more carbon into the atmosphere each year than the plants and sea life of the world can absorb, making carbon dioxide the biggest greenhouse gas culprit - carbon has a lifetime of anywhere between 20 and 200 years.

As you will no doubt be aware, the ‘cost’ is climate change and its harmful effects on the world including increased levels of extreme weather events, such as flooding, droughts, storms and fires.

A global temperature increase of 1.5°C is the estimated “tipping point”, which is only 0.5°C away from where we are now. Carbon emissions need to be cut in half by 2030.

Climate Action Timeline

1988 - The UN Intergovernmental Panel on Climate Change (IPCC) was set up.

2008 - UK passes the Climate Change Act

UK Government committed to an 80% reduction of greenhouse gas emissions by 2050, compared to 1990 levels.

Driving progress, the Act introduced a system of carbon budgets. These provided legally binding limits on the amount of emissions that may be produced in successive five-year periods.

2010 - Cancun Agreement

The first UN Framework Convention on Climate Change (UNFCCC) document to mention a limit to global warming of 1.5°C was the Cancun Agreement, adopted at the sixteenth COP (COP16) in 2010.

It established a process to review the long-term global goal (LTGG) and the overall progress made towards achieving the LTGG, which was ‘to hold the increase in global average temperature below 2°C above pre-industrial levels’. It also recognised the need to consider ‘strengthening the long-term global goal on the basis of the best available scientific knowledge…to a global average temperature rise of 1.5°C’.

2015 - UN 2030 Agenda for Sustainable Development and the Paris Agreement

The United Nations General Assembly adopted the 2030 Agenda for Sustainable Development with 17 Sustainable Development Goals. Goal 13 relates to Climate Action.

Building on the UN Framework Convention on Climate Change (UNFCCC), later that year at the 21st Conference of the Parties (COP21) in December 2015, 195 nations adopted the Paris Agreement - the first-ever universal, legally binding global climate change agreement.

It set out a global framework to avoid dangerous climate change by limiting global warming to well below 2°C and pursuing efforts to limit it to 1.5°C.

2018 - Intergovernmental Panel on Climate Change (IPCC) Special Report

With the adoption of the Paris Agreement, the UNFCCC invited the IPCC to provide a Special Report in 2018 on ‘the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emissions pathways’.

The IPCC stated that to avoid climate catastrophe, global emissions must be halved by 2030 and at net zero by 2050. Action needs to be “rapid, fair-reaching and unprecedented” to make an impact.

2019 - UK declares Net Zero by 2050

As a result, 2019 was the year of climate emergency declarations, with hundreds of governments around the world declaring a climate emergency, including the UK.

In June 2019, the UK Government was the first major economy in the world to pass laws to bring all greenhouse gas emissions to net zero by 2050. This is the Climate Change Act 2008 (2050 Target Amendment) Order 2019, passed to increase the UK's commitment to a 100% reduction in emissions by 2050.

2021 -  UK fast tracks climate change target

On 20 April 2021, the Government announced that it “will set the world’s most ambitious climate change target” to reduce emissions by 78% by 2035 compared to 1990 levels as part of its sixth carbon budget.

2021 - Future Buildings Standard Consultation

As part of the process of developing the Future Buildings Standard, the Ministry of Housing, Communities and Local Government (MHCLG) launched a consultation on changes to the Building Regulations, specifically affecting Part F (ventilation) and Part L (conservation of fuel and power). The aim of the Future Buildings Standard is to improve the energy efficiency and sustainability of new and renovated buildings.

How is the construction industry contributing to climate change?

According to the World Green Building Council (WGBC), buildings and construction currently account for around 40% of global energy-related CO2 emissions. To have any hope of providing a sustainable environment for the world’s 9.7bn people by 2050, there needs to be drastic change across the design, construction, use and reuse of buildings and infrastructure.

Yet, the WGBC 2019 Global Status Report for Buildings and Construction tells us that the sector is not on track with the level of climate action necessary. On the contrary, final energy demand in buildings in 2018 rose 1% from 2017, and 7% from 2010.

With the world’s building stock set to double by 2050, the WGBC has set out eight priority areas: urban planning; new buildings; retrofits for existing buildings; building operations; appliances, lighting, cooking and systems; materials; resilience of buildings; and clean energy. These roadmaps and actions are being adapted nationally.

As operational energy efficiency increases, the impact of embodied carbon emissions in buildings offers further potential.

Embodied carbon and its future role in construction

In terms of construction, the Government’s Ten Point Plan presents a clear push, focusing on areas such as greener buildings and infrastructure. It is designed to mobilise £12 billion of government investment and potentially three times as much from the private sector, to create and support up to 250,000 green jobs.

The Construction Playbook also outlines green initiatives for the construction industry, promoting the use of carbon assessments to understand and minimise greenhouse gas emissions of projects. In 2021, the Government also announced a £338 million package for a greener travel infrastructure.

Currently though, incentives or requirements for net-zero embodied carbon are lacking. The government has set out its plans and timeframe for its new Future Homes Standard, which aims to 'radically improve' the energy performance of new homes, making them 'zero carbon ready' by 2025. Yet, it fails to mention embodied carbon.

Thankfully, construction leaders are not waiting for legislation to enforce embodied carbon reduction and there is a shift in behaviour. Of course, schemes like the Building Research Establishment Environmental Assessment Method (BREEAM) and Leadership in Energy and Environmental Design (LEED) have been around since the 1990s but it was more common for a “cost first” mindset to be applied on projects. Now, more clients are genuinely, wanting to build greener.

As reported by RIBA, increasingly, clients in all sectors are commissioning Whole Life Carbon (WLC) assessments as part of the project requirements. This is primarily driven by environmental considerations but also makes economic sense. Important benefits of WLC assessments include: a better understanding of the sourcing and processing of materials and products; an understanding of long-term post completion considerations such as maintenance, durability and lifespan; and making plain the carbon value of retaining existing built fabric.

Contractors are instigating positive change as well, with many of the UK's largest construction companies pledging targets around carbon emissions. Examples include Willmott Dixon committing to net-zero in its operations by 2030 and its supply chain by 2040 and Kier, net-zero across its own operations and supply chain by 2045. Others include Mace, Skanska and Balfour Beatty.

Engineering leaders too are pushing the view that engineers have a “responsibility” to help industry forward. This year, net-zero carbon is a primary focus for the Institution of Civil Engineers (ICE), as promoted by ICE President Rachel Skinner as part of her inaugural address in an inspirational film - Shaping Zero.

Shaping Zero: Towards net zero carbon for infrastructure from ICE Group on Vimeo.

Likewise, in 2019, UK structural engineering consultancies declared a Climate and Biodiversity Emergency, recognising the need to show leadership and drive real improvements. A Climate Emergency Group was formed, where they launched research into how they can improve design, the areas in which they are overusing materials and to help mitigate its effects by changing the way buildings and infrastructure are designed, commissioned and constructed.

Engineers have a key and central role in changing the way that future structures and infrastructure are designed and built.

More manufacturers are also looking at how to improve the sustainability of their products with a product’s sustainability now a selling point. For example, steel manufactured from electric arc furnaces has much lower embodied carbon than that made from a basic oxygen furnace. Other innovative technologies include low carbon concrete or cross-laminated timber (CLT).

Sustainable construction is happening. Architects are taking a leaner, low-tech approach in the sense of fewer components, natural, low-embodied carbon materials and reduced dependence on technology and mechanical servicing.

However, to create leaner buildings, there is a greater reliance on new digital modelling technology to quantify outcomes. The advancements in digital design tools and embodied carbon calculators like Tekla’s Embodied Carbon Calculator, available within Tekla Structural Designer, now vital to the design process.

Embodied carbon totals for all members in Tekla Structural Designer

Embodied carbon is just one part of the sustainability picture and whilst embodied carbon calculations are not mandated or a legislative requirement at the moment, they may become so in the future, playing a key role in designing and building better, smarter and greener.

Find out more

To learn more about reducing embodied carbon with Tekla software, please visit our resources page. If you have any questions or would like to book a demo, get in touch.

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