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Whole Life Carbon Assessments: The system for assessing the environmental cost of buildings

Whole Life Carbon Assessments: The embodied carbon: this is the total amount of carbon used to extract, process and manufacture the materials that are used to construct the building.

"The built environment and construction sector accounts for 38% of global carbon emissions and it has been estimated that globally we build the equivalent of a city the size of Paris every week."

How do we measure the environmental impact of buildings? This article explores an approach that is industry standard in the UK: Whole Life Carbon Assessments.

Embodied & Operational Carbon

The environmental footprint of a building breaks down into two categories:

  • The embodied carbon: this is the total amount of carbon used to extract, process and manufacture the materials that are used to construct the building. This also includes:

    • The carbon cost of transporting those materials to every point in the supply chain to the factory gate ('Cradle to Gate')

    • Transport to site and construction (including, for example, fuel to run construction machinery on site)

    • Maintenance and replacement of components (such a lightbulbs, carpets, windows and internal linings)

    • Finally, the environmental cost of demolishing, recycling and disposing of the building

  • The operational energy use: the total amount of carbon used to run the building. This is commonly electricity and gas.

Together, the embodied carbon and operational energy use form the 'whole life' carbon footprint of the building. This is assessed using a Whole Life Carbon Assessment (WLCA). There is a European Standard for conducting WLCAs (EN 15978) that breaks down the life cycle of a building into four alphabetical stages:

  • A1-A3: Product - 'Cradle to Gate' activities

  • A4-A5: Construction process - Transport of products to site and construction

  • B1-B5: Use - Maintenance, repair, replacement, refurbishment, operational energy use and operational water use of the building

  • C1-C4: End of Life - Deconstruction, demolition, transport of products to a disposal facility

  • D: Benefits beyond the system - Reuse, recovery and recycling potential

As you can imagine, conducting a whole life carbon assessment is a complex exercise that requires a large amount of data.

For A1-A3 carbon emissions, manufacturers publish Environmental Product Declarations (EPD's) that state the overall environmental footprint of their product.

The Royal Institute of Chartered Surveyors publishes guidance on reasonable assumptions for calculating elements such as fuel consumption (transport) or sequestration (the capturing of carbon within materials like timber). These methodologies are being incorporated into software packages such as OneClickLCA to streamline the workflow for consultants.

Whilst an effective standard and methodology for calculating carbon emissions is in place, below are some of the key barriers to successful and accurate calculations. This was summarised in a report by the WBCSD | Net Zero Buildings: Where do we stand?:

  • A lack of open-source, reliable and accessible product data

  • A lack of skilled consultants

  • A lack of collaboration within the construction industry

  • Not enough manufacturer's publishing quality EPD's

This report is reflective of my experience. However, clients, underpinned by their own sustainability goals, are demanding more environmental accountability from consultant teams and manufacturers. I consider this to be a very positive step, as it is leading to the rapid change that is needed within the industry to respond to the climate emergency.


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