The basics of whole life carbon in construction

Carbon in construction

Do you know your GHG from your ESG? Or your SECR from your CRC?  Understanding whole life carbon in the built environment doesn’t need to be as baffling as some of the acronyms that accompany it. From de-mystifying terminology to exploring current methodologies for measuring carbon, here are the key basics of carbon in construction.

Carbon glossary

BECD – Built Environment Carbon Database – Developed by, and for, the construction industry, the BECD is a data repository that contains both a project and asset database. Free to access, it allows industry professionals to share and retrieve data on carbon emissions.

CO2e – carbon dioxide equivalent – a measure we use to report whole life carbon in the built environment. CO2e values are derived by converting different GHG’s to a single number using their global warming potential.

CRC – The CRC Energy Efficiency Scheme (CRC) started in April 2010 and closed with the final report in March 2019. It was designed to encourage large public and private sector organisations to reduce their carbon dioxide (CO2) emissions through energy efficiency.

Embodied carbon – This is all the energy used to create a product during the construction process, i.e. the sourcing and manufacturing of raw materials. This is also often referred to as ‘cradle to gate’ or ‘cradle to site’. In the modular system of a whole life carbon assessment its known as A1-A3 – the product stage. It also covers A4-A5, the construction stage.

Embodied carbon also includes the carbon emitted throughout its ‘use stage’ (B1-B7) – the maintenance, repair or refurbishment required to keep it functioning. In addition to this, includes the energy released during a building’s ‘end of life’ stage (C1-C4). In whole life carbon assessments, it’s often referred to as cradle to grave. However, it can also include one final stage – the potential reuse, recovery, and recycling potential of the assets (D).

Under the GHG Protocol, it falls under Scope 3 emissions.

EN15978 – this European Standard sets out the principles and calculation method for the environmental impacts from built projects, based on life-cycle assessment.

EPD – Environmental Product Declaration – a standardised way of reporting data about the environmental impacts of a product through its life cycle.

ESG – Environmental, social and governance – a framework that construction companies use to assess the impact their projects will have in these three key areas.

GHG – Greenhouse gases that are generally human-generated and released into the atmosphere that absorb and emit radiant energy (causing global warming).

Life Cycle Assessment – a complete study of the environmental impacts of a manufactured product over its lifetime. LCAs form the basis for EPDs (Environmental Product Declarations), which are reports linked to data results from the LCA.

Operational carbon – This includes all the emissions associated with the heating and lighting of the building, including water use. Under GHG Protocol, it falls under Scope 1 and 2 emissions.

Part Z – In addition to the changes set out under Building Regulation Approved Documents F, L, O and S (due to come into force by June 2025), the industry has proposed a new amendment, Part Z. This would ensure mandatory assessments and reporting of whole life carbon, with the aim of reducing the amount of embodied carbon across the construction industry. Although it’s unlikely to be legislated over the next few years, more local authorities across the country are asking for whole life carbon reporting in their planning requirements.

RSP – Reference Study Period – the number of years assumed for the analysis for the purposes of calculating whole life carbon assessments.

SECR – Streamlined Energy and Carbon Reporting – a reporting framework introduced by the government in 2019 that requires some businesses to report their emissions.

UoM – Units of Measure – When carrying out a WLCA it’s essential that units of measure are always specified and reported consistently for differing component and asset types. The RICS Standard provides guidance on this.

WLCA – Whole Life Carbon Assessment – the purpose of a WLCA is to measure the complete carbon footprint of a built asset or component throughout its life cycle. If conducted correctly, the WLCA will follow a structured method with a clearly defined scope that evaluates all the various stages from cradle to grave – i.e. the extraction and manufacturing of the asset or component to its operation, maintenance, and end-of-life. The RICS Professional Standard Whole life carbon assessment for the built environment (2nd edition) and International Cost Management Standard (ICMS 3) provide essential guidance for ensuring that reporting and benchmarking in WLCAs is standardised and consistent.

Why do we need to measure carbon emissions?

Approximately 40% of GHG emissions come from the built environment. The latest predictions indicate that, if left unchecked, these could double by 2050. This is likely to have severe adverse environmental, social and financial effects around the world.

How do we measure GHG emissions in the built environment?

The amount of carbon is measured and reported in kg or tonnes. We measure two types:

Embodied and operational

Embodied: all the energy used to create a product during the construction process – this includes extraction of raw materials, their transportation, installation and maintenance, and their end-of-life process.

Operational: this includes all the emissions associated with the heating and lighting of the building and is dependent on the number of people using it.

Whole Life Carbon Assessments (WLCAS)

Government regulation has tended to focus on the reduction of operational carbon – for example, Part L of 2022’s updated Building Regulations for England set standards for the energy performance of new and existing buildings.

However, there is a growing body of evidence regarding the substantial contribution that embodied (or Scope 3) carbon emissions make to total greenhouse gas emissions. In 2021, UKGBC reported that annual embodied carbon emissions in the UK originating from the construction, maintenance and demolition of buildings amounted to 40-50 million tonnes of CO2 – more than the combined emissions from aviation and shipping. A report in 2023 by Akerlof, Carbon Blond Spots, estimated that Scope 3 emissions account for 94-98% of Tier 1 contractors’ emissions.

While the reporting of embodied carbon is not yet mandated, the move towards whole life carbon assessments (WLCAs) does appear to be gaining traction across the industry. The results of a survey, released in April 2024 by the construction consultancy firm RLB, found that 33% of contractors are being asked by clients to provide WLCAs on schemes, a substantial increase from last year’s 14%. In addition to this, Westminster City Council is the latest local authority to ask for WLCAs for all major redevelopment schemes. These developments confirm the industry needs to get better at assessing, evaluating and comparing the carbon impact of both retrofit designs and materials in new builds.

What are the various stages of carbon measurement life cycle?

From appraisal to end of life, carbon can be measured through the various stages of the building or project’s life cycle.

What are the typical amounts of emissions throughout a building’s life?

Design – 0.5%

Manufacture – 35%

Distribution – 0.1%

Construction – 1%

Operation – this accounts for the most emissions at around 63%

Refurbishment – potential demolition – 0.4%

These amounts all vary quite dramatically depending on the size, specification and usage of the building. For example, a building that requires minimal heating during its operation will very likely have a much higher proportion of emissions in the manufacture and construction phases.

To put these numbers into context:

We emit 34 billion tonnes each year, across the globe.

In 1950 the world emitted 6 billion tonnes.

Get it right, from the start

Whatever we build today should last many years. The choices we make in the design phase of construction have a direct impact on the costs related to the building and the amount of maintenance it will need.

But, perhaps most importantly of all, these choices also influence the amount of environmental emissions throughout its life cycle. Our ability to reduce emissions diminishes as the project progresses. Therefore, it’s important to make the right decisions as early as possible.

A new industry standard

One of the toughest challenges for the industry to overcome was an inconsistent application of the methodology on how to measure carbon, as well as a lack of available, consistent data.  In order to lower emissions in the built environment, we needed to compare our performance against other projects, and garner insights from them in the evaluation process.

However, the industry has made substantial progress in this area. The BECD continues to collect, analyse and benchmark both project and asset data and we now have a far more comprehensive standard for WLCAS – in November 2023 RICS published the second edition of its Whole life carbon assessment for the built environment, effective from July 2024.

The guidance recommends that all WLCAs follow a modular structure for carbon reporting, which breaks down the built asset’s life cycle into stages and modules (see figure below). This has been adapted from the European Standard EN 15978 that assesses the sustainability of construction works at both product and building level. With the built environment responsible for around 40% of global carbon emissions it’s crucial for countries across the world to have a globally consistent method for carbon life cycle reporting across international infrastructure and construction projects. Therefore, the standard is also aligned with The International Cost Management Standard 3, which was updated in August 2022. In addition to this, the industry now has the UK Net Zero Carbon Building Standard (UKNZCBS). Launched in September 2024, the pilot version offers a clear and consistent methodology that defines the steps for achieving a net zero carbon building.

Project life cycle

The project life cycle (from A-D) shows the emissions associated with each stage of the project life cycle – from extracting materials to construction, operational and end of life.

^{Source: RICS}

The methodology aims to collate the various stages A B C D against each of the common elements used in the built environment.

The RICS recognises this could be extremely time-consuming so it highlights those that will make the most amount of impact in reducing emissions.

^{Source: RICS}

Reference Study Periods (RSPs)

These are RICS recommended defaults that cover the operational phase of the building. They vary from 60 to 120 years across domestic, non-domestic and infrastructure projects. RICS recommends these are factored into assessments as it will have an obvious bearing on the figures calculated. There is a current debate in the industry around whether the length of these periods is long enough.

^{Source: RICS}

What does the methodology calculate?

A1-3 The Product Stage

In order to calculate the embodied carbon of a construction solution you need to multiply the quantity by the emissions factor of each material used. You need to make sure that the units of measure are the same. The RICS mandates that the source of data is clearly stated.

The best source of emissions data comes from Environmental Product Declarations (EPDs) – these calculate the environmental footprint of a product throughout its lifecycle and are becoming more common in the construction industry.

In the absence of an EPD for the material you want to use, you can use other data, but it must be clearly stated in the assessment.

A4-5 The Construction Stage

It’s important to account for the impacts of transporting your materials to site. In the absence of real data, RICS recommends defaults distances and methods of transport.  These include distances for road and sea, and various transport scenarios.

It’s also important to account for the emissions generated when installing and constructing your project. This will include energy used on site such as a powering construction plant and site accommodation.

The RICS methodology also provides defaults for the construction stage to help calculate emissions for the installation process.

In order to calculate the whole life carbon emissions of your project, you can’t stop at the construction stage – you must also look at all of the ongoing emissions over the RSP covering maintenance, replacements, and operational energy usage, from heating and lighting.

This process is relatively simple but can be very time-consuming!

The RICS methodology provides defaults for the use stage including the lifespan of components, using data from the BCIS.

End of life calculation

This covers decommissioning, demolition or processing and disposal of waste, which must all be accounted for. RICS provides default values that include the reuse or recycling of metals and disposal.

Government regulation

Currently there is no government regulation to make measuring carbon on construction projects mandatory. However, many businesses are looking to report and reduce their emissions as part of their ESG strategies.

The SECR, introduced by government in 2019, requires some large companies to report their emissions – both direct and indirect but we are seeing smaller organisations starting to do this without a mandate.

Environmental reporting is only going to increase over the forthcoming years.

The significance of data

The current default assumptions in the RICS methodology have their value, but we need to move away from averages and generic numbers to make sure we are making the right decisions.

Data is the missing part of the puzzle and we need more of it to support the decarbonisation of the built environment. In October 2023, BCIS launched a pan-industry initiative called the Built Environment Carbon Database (BECD) – in partnership with organisations operating across every part of the construction sector – to find a way to share our knowledge, learning and data.

Designed to become the main source of carbon estimating and benchmarking for the UK construction sector, we continue to analyse the quality of the data we’re capturing, to ensure consistency in how each asset is reported.

We know that improving the process of balancing cost and carbon choices in construction is a key source of concern and confusion for our clients. This is why BCIS has developed the Cost and Carbon Database Materials Database to ensure it’s easier and simpler to make better-informed decisions regarding cost and carbon.

This service provides comparisons for cost and carbon data, using independent datasets that include past and future inflation data from our BCIS Indices. To find out more visit the BCIS Cost and Carbon Materials Database here.

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