Life cycle assessment (LCA) of natural vs conventional building assemblies

Natural earthen and bio-based building materials are critically needed to dramatically reduce energy-intensive and extractive construction practices that are the hallmark of the modern building industry. Building assemblies such as cob, light straw clay and rammed earth were shown to provide an optimal indoor environment for occupant comfort and health. Despite these advantages, natural materials are still not widespread in mainstream construction for two primary reasons: technical data is inadequate to quantify their energy performance in different climates, and environmental measures are missing to perform decision making throughout the design process. This paper presents an environmental life cycle assessment (LCA) of natural earthen and bio-based materials compared to conventional building materials in 6 climates: hot desert, desert, semi-arid, Mediterranean, temperate, and continental. Results show that, when coupling the embodied and operational environmental impacts, the natural assemblies reduce energy demand by 32-59% in the hot desert climates, 29-55% in semi-arid climates, 46-73% in Mediterranean climates, 34-57% in temperate climates and 27-50% in continental climates as compared to conventional assemblies. The operational impacts are shown to be highly dependent on the thermal properties and climate zone, but in all cases natural assemblies outperform conventional assemblies. In particular, light straw clay and insulated rammed earth are the top performers for all 6 climates. The work presented in this paper contributes critically needed environmental quantifications to catalyze the advancement of healthier and more environmentally sound commitments to ecological construction worldwide.