When we talk about reducing carbon emissions in construction, the focus is often on operational emissions from heating and powering a building. As our built environment becomes more energy efficient, however, we need to think more closely about so called “embodied carbon” – this is the carbon emissions produced from products during their manufacture, installation, maintenance and at the end of life of the building.
What is the purpose of a Life Cycle Assessment?
Life cycle assessments (LCAs) provide a powerful tool which not only offer an insight into embodied carbon, but a whole range of other environmental impacts across the lifespan of a product.
Content Guidelines: LCAs and reducing embodied carbon
There are a number of different LCA standards and approaches available. These can vary from cradle-to-gate which looks solely at environmental impacts from sourcing and manufacture, through to cradle-to-cradle which considers impacts all the way through to re-use. Here in the UK, LCAs are carried out as part of an Environmental Product Declaration (EPD) using either BS EN 15804: 2012 + A1: 2013 or BS EN 15804: 2012 + A2: 2019. These standards provide clear rules for the LCA, ensuring the results are comparable and transparent.
Learn more about EPDs and EN 15804
Accurate LCAs are set to become an increasingly important part of reducing greenhouse gas emissions going forward. As we reduce the operational energy of our buildings, and decarbonise supply, it should be possible for many buildings to reach net-zero operational carbon emissions. This will mean that tackling embodied carbon from products will be the only effective route to further carbon reductions.
EPDs based on LCAs help to inform specifiers, allowing them to gain a clearer idea of what the long-term embodied carbon emissions from different specifications are likely to be. They also allow manufacturers to identify specific areas for improvement with a product. For example, in the 2019 version of BS EN 15804, Global Warming Potential (GWP) is broken down into four indicators:
- GWP total;
- GWP fossil fuel derived;
- GWP biogenic – carbon cycle within natural systems (i.e. CO2e from forestry industry taking into account carbon removed by people when the tree is cut down); and
- GWP land use change – i.e. grassland used to produce silage into housing estate.
As part of the EPD certificate, the total emissions from each indicator is further separated into the different stages (modules) in a product’s lifespan, allowing targeted improvements.
Content Guidelines: How LCAs can address other environmental impacts
Of course, GWP is just one of a number of indicators which are considered as part of an EPD. Other core indicators in BS EN 15804: 2012 + A2: 2019 include:
- Ozone Depletion Potential (ODP);
- Acidification Potential (AP)– contribution soil acidification and to acid rain; and
- photochemical oxidation potential – covering key sources of air pollution such as NOx and volatile organic compounds (VOCs).
Together, these indicators help to provide a more complete picture of how different specifications of products will impact the environment and the health of those around them throughout the lifespan of the building (and beyond). For this reason, data derived from product LCAs is essential to meet leading sustainability and health and wellbeing standards such as BREEAM, WELL and LEED.
This approach also helps to avoid unintended consequences as manufacturers take steps to address embodied carbon. For example, back in 2001 a vehicle tax was introduced making it cheaper to run less CO2 intensive cars. As a result, many drivers switched to diesel cars. Unfortunately, whilst these produce less CO2 per mile compared with petrol cars, they also emit far more particulates and NO2. This contributed to worsening air quality levels, particularly within urban locations, and was linked with increased hospitalisations.
The benefits of adopting a more balanced, holistic approach to assessing the embodied environmental impact of construction products, we can:
- avoid these issues;
- ensure our buildings support healthier environments throughout their lifespan; and
- provide improved circularity at end of life.