title: Building with earth: implementation strategies, evaluation model, and mitigation of climate change
Creators: name: Estève-Bourrel, Pierre
Publisher: name: The University of Edinburgh
Year: 2025
Subjects: subject: Earth construction
subject: Interviews
subject: Parametric Design
subject: Structural analysis
subject: Life Cycle Assessment
subject: Energy assessment
subject: Climate mitigation
subject: Sensitivity analysis

description: Architecture in its vernacular form arose first from the need for security and then for climate control, playing with spatial design and materials. Spatial design and materials have been relegated to a purely aesthetic movement since the arrival of fossil-fuel based air conditioning machines marked the advent of modern architecture. Awareness of the finiteness of resources and the climate crisis has led designers and builders to work towards a paradigm shift in construction, reintegrating vernacular architecture into a more virtuous way of building. In this context, earth building is of interest, with a heritage rooted in all continents and a polymorphism of techniques that can be adapted to many contexts. This research work therefore presents a proposed answer to the question `How can the environmental relevance of the use of earthen materials be assessed using a contemporary approach in a European context?' A dual approach to the question is adopted: firstly, from the perspective of earth building professionals - architects, engineers, builders, researchers or clients; and secondly, through the engineering of a structural, energy and environmental assessment model based on the tools of designers. Earth building professionals have highlighted the importance of knowing the local regulatory framework to set appropriate performance targets and develop a project strategy involving all stakeholders, including designers, builders and certifiers. Coordination between these actors is a prerequisite for the integration of earthen materials in a construction project. Secondly, they emphasised the importance of design adapted to the specific characteristics of the material to ensure the durability of the earth components during the construction and operation of the building. In the case of a load-bearing earth structure, a number of precautionary principles must be observed, such as working in compression and load distribution. Small-scale load-bearing projects are carried out without engineers, respecting the rules of minimum slenderness, while large-scale projects are carried out with advanced modelling and strict quality control. Once regulatory and good practice conditions are met, earthen materials are used in bioclimatic or passive design strategies, or as replacements for environmentally intensive components. However, the thermal regulation, the complexity of the thermal dynamic assessment and the complexity of the environmental data make it difficult to demonstrate the environmental performance of earth construction. The parametric assessment model was developed in response to the need identified in the interviews to assess the environmental performance of earth construction. This model, adapted to load-bearing earth construction, first assesses a sound earth structure that complies with current building codes. Once the structure has been defined, an energy assessment, calibrated on a monitored earth building, is carried out and finally integrated into a whole life cycle environmental assessment. A sensitivity analysis of the model, consisting of architectural, mechanical, structural or contextual input parameters, highlights the influencing parameters. Aspects to be considered in structural design include design strength or shear loads; in energy use, thermal mass and insulation coupling with natural ventilation; in environmental assessment, the choice of heating/cooling system or the transport of earthen materials. The relevance of using straw-insulated earth construction in future climates was then assessed against conventional construction systems: a heavy concrete/mineral insulation system and a light wood frame filled with cellulose. While the wood/cellulose and earth/straw systems meet the short-term (2030) environmental targets, the concrete/mineral system does not. However, it is necessary to consider the carbon sequestration of bio-based materials in the wood and earth systems to achieve the 2050 net zero carbon target. Finally, by considering thermal comfort, it was possible to assess the superior performance of the earth system in mitigating thermal stress in future climates compared to the lightweight wood frame system.