Sensitivity analysis of the impact of environmental product declaration values on whole life carbon assessment: A case study using expanded polystyrene insulation for the retrofit of a building in Turkiye

Until recently, reducing the energy required to service a building (the operational energy) was the main aim of controlling carbon emissions from the built environment. It is now recognised that the energy required to make a building (the embodied energy) also has a crucial role in creating a net zero carbon future. The methodologies for quantifying embodied carbon are less developed than those for operational carbon, and more research is required to refine the embodied carbon metrics used when a building’s whole-life carbon emissions are calculated in a Life Cycle Assessment (LCA). One such metric is the Environmental Product Declaration (EPD), a document which can be used in different countries to quantify a product's environmental performance. EPDs are crucial data for conducting an LCA study of a building. However, despite recent efforts to standardise them, there are still inconsistencies between EPDs produced by different countries or manufacturers, even for materials with similar thermal and physical properties. This study considered some of the reasons for variations in EPDs for one product type, expanded polystyrene insulation (EPS). Factors such as (i) the LCA databases and software generators used for the EPDs, (ii) material mixes and manufacturing methods, (iii) country energy production mixes, and (iv) transportation distance from material source to the factory were considered in the analysis. As a case study, this paper examined the effects of selecting different EPDs for expanded polystyrene insulation on the final LCA results from the retrofit of a mid-rise residential building in Turkiye. Differences in EPDs demonstrated a fourfold difference between the highest and lowest upfront carbon impact results of building retrofit. This size of discrepancy indicates the need to choose the most appropriate EPD for a building/location when performing an LCA. Selecting an EPD when conducting an LCA for a new building or retrofit is generally left to the assessor’s judgment and knowledge, which varies greatly depending on the assessor’s background, especially in the construction sector. This study suggests an informed decision-making method over an example of EPS insulation material when the EPD options were none or limited to building locations like Turkiye.