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Life Cycle Assessment (LCA)
LCA is a modelling methodology used to quantify carbon emissions (Embodied & Operational) and other environmental impacts of a product or process through specific life cycle stages using biophysical indicators such as Global Warming Potential, Eutrophication Potential, Ozone Depletion Potential, Smog Formation Potential, Acidification Potential, etc.
Assessment Scope
The assessment scope should describe which building elements and life cycle stages are included in the study.
//Diagram Whole Life Carbon BS EN 15978 Modular Reporting Structure
Environmental Product Declaration (EPD)
An EPD is a third-party verified document typically prepared by a manufacturer which contains data about the impact of a product or process. Most EPDs only cover the cradle-to-gate stages material extraction [A1], transportation to plant [A2], and manufacturing [A3] because these are the stages within the manufacturer's purview. There is a lack of data on embodied carbon impacts for the maintenance [B2], repair [B3], refurbishment [B4-B5] and end-of-life [C1-C4] stages, and usually these impacts are estimated by using datasets beyond EPDs.
FAQ
What units are used for embodied carbon?
Embodied carbon is used as shorthand for Global Warming Potential (GWP). GWP is measured in carbon dioxide equivalents (kgCO2e). This unit converts all emissions that contribute to global warming, such as CH4, into CO2e by multiplying by their relative strength in producing warming.
What is this LCA good for?
LCA is valuable to inform early design decisions which aim to minimise the building’s whole life carbon impacts. A further assessment should be undertaken at practical completion, which should measure the as-built outcome, in place of modelled assumptions. LCA is most useful for relative, rather than absolute, comparisons. Ideally the analysis can be used for comparing design options, making material selections, and setting design priorities.
What is biogenic carbon?
Biogenic carbon is the process of carbon sequestration that takes place during the growth phase of bio-based materials, and is usually assigned during the cradle-to-gate impacts. Some LCAs account for these processes, others do not. If carbon sequestration is accounted for, it is best practice to account for the amount of this carbon that is released at end-of-life.