Published: 10/05/2023
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
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.
GHG – Greenhouse gases that are generally human-generated and released into the atmosphere that absorb and emit radiant energy (causing global warming).
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.
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.
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.
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.
Source: BCIS
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.
It’s not as easy as 123
Currently, there’s no consistent application of the methodology on how to measure carbon, and a lack of available, consistent data. If the goal is to lower our emissions in the built environment, we need to compare our performance against other projects, and garner insights from them in the evaluation process.
However, we do already have guidance on how to assess the impacts of design choices that include recommended default assumptions, in the absence of anything more specific for construction projects.
What is the current guidance for methodology for measuring carbon?
The RICS (Royal Institution of Chartered Surveyors) Professional Statement, which is free to members and non-members, used the foundation of EN15978 for its guidance on how to measure and what to include. It’s currently in the process of being updated and is now available for consultation.
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.
Source: BCIS
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 key, but we don’t yet have enough of it to help us.
However, BCIS is part of a pan-industry initiative called the Built Environment Carbon Database (BECD) which is looking to address this.
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