How Multicriteria Environmental Assessment Alters Sustainability Rankings: Case Study of Hempcrete and Prefabricated Walls

The construction sector emphasises circular economy principles that prioritise eco-design strategies, particularly the usage of secondary raw materials. The growing interest in using industrial hemp as a sustainable building material in the construction sector is driven by its versatility. Industrial hemp has been preferential in comparison to other traditional building materials due to its lower global warming impact. Claims regarding the environmental benefits of hemp-containing construction materials based on the single impact category could be misleading; therefore, life cycle assessment (LCA) studies including multiple environmental indicators should be implemented. This study aims to compare two alternative wall designs regarding their environmental impacts. The comparative LCA study for hempcrete and prefabricated walls used in residential buildings was assessed using IPCC and ReCiPe life cycle impact assessment methods. The study highlighted a significant discrepancy depending on the number of environmental indicators considered, as well as between characterised and weighted LCA results. A hempcrete wall was recognised as a slightly (13.63%) better alternative when assessed by the single-issue IPCC method, while its total burden assessed by the ReCiPe method was recognised to be significantly (2.78 times) higher. Based on the results from this case study, regulators could re-evaluate the appropriateness of reporting LCA results solely on the midpoint level, particularly when limited to a single impact indicator, while producers in the construction sector should recognise the threat of greenwashing when reporting using a single impact indicator only.