Life Cycle Assessment (LCA) is becoming a more important factor across the built environment as the focus remains on carbon emissions and their impact on the planet. LCA provides both the big picture and the fine details needed to understand a building’s lifetime impact on the environment and take the necessary steps to reduce it.

Before understanding Life Cycle Assessment and its importance, it’s vital to understand the stages of Greenhouse Gas (GHG) emissions examined. This includes Whole Life Carbon and the two subsets of Embodied Carbon and Occupational Carbon.

Greenhouse Gas emissions are made up primarily of Carbon Dioxide (CO2) as well as smaller amounts of Methane (CH4), Nitrous Oxide (N2O) and more.

What is Whole Life Carbon?

Whole Life Carbon is the sum of greenhouse gas emissions from the full life-cycle stages of a building and the relevant materials. This covers raw material extraction, transportation, manufacturing, construction, maintenance, renovation, and end-of-life/demolition.

A Whole Life Carbon assessment provides the broadest and most complete picture of a building’s total carbon emissions across its lifespan. Moreover, within this term, there are two further subsets. These are:

• Embodied Carbon: the amount of GHG emissions emitted during the production of materials and during construction, as well as during operation (such as refurbishments and retrofit work) and end of life (including deconstruction and waste processing).
• Operational Carbon: the amount of GHG emissions emitted once a building is in use (operational). This includes the energy needed to heat, cool and power the building.

Assessing the amount of carbon produced throughout a building’s lifetime not only identifies ways to reduce the embodied carbon in the building’s specification but also considers ways to reduce this once the building is occupied. There is also scope to identify the potential circular economy benefits, such as by keeping materials in circulation and avoiding waste through reuse.

What is Embodied Carbon?

Although all stages are vital to analyse, embodied carbon is a key metric to understanding a building’s environmental impact and to achieving Net Zero Carbon in our industry.

Due to increased awareness and innovation, our buildings’ operational costs and emissions have decreased over the last decade. The embodied emissions, however, have remained relatively constant since 2010. As a consequence, embodied carbon is becoming a greater proportion of a building’s Whole Life Carbon emissions – expected to be over half by 2035.

The measurement of embodied carbon is done by multiplying the estimated quantity of each material by a carbon factor (this is normally measured in kgCO2 e per kg of material). With this information, decisions can be made on which materials to use throughout a project to reduce its carbon emissions and environmental impact.

What is Life Cycle Assessment?

Life Cycle Assessment (LCA), or Life Cycle Analysis, assesses the potential environmental impacts of a building and its materials. The assessment covers all stages of a building’s lifespan, including the raw extraction of materials, manufacturing, and end-of-life/demolition.

An LCA is usually conducted in four stages:

• Stage 1 – Goal and scope definition.
• Stage 2 – Inventory analysis.
• Stage 3 – Impact assessment.
• Stage 4 – Interpretation.

The assessment considers all relevant environmental inputs and outputs, including oil, water and land use, as well as emissions into the air, water and soil. From this, factors such as the building’s Global Warming Potential (GWP), Acidification and Eutrophication (overfertilization) can be understood.

An LCA report allows for a greater understanding of a building’s impact on the environment and can lead to more informed decisions on the materials used. This includes which raw materials are involved, how they are produced, where they come from, and how they are transported to the site. The goal of an LCA is not only to collate the necessary data but to facilitate decisions and lead to more sustainable and carbon-neutral buildings.

Since 2018, a Life Cycle Assessment report has been mandatory for all projects requiring a BREEAM rating. As a recommendation, from December 2023, an LCA should be mandatory for all projects over 1,000 m2 or more than 10 dwellings. However, early adoption of the assessment is encouraged.