Thermal environment in rammed earth structures: a systematic review on thermal comfort, thermal performance, and climate strategies

Abstract

The global movement towards sustainable building practices has shifted the focus towards energy-efficient alternatives like rammed earth structures to reduce environmental impact without disturbing human comfort and well-being. Especially in light of climate change, rammed earth presents promising solutions because of its notable thermal mass and capability to regulate indoor temperatures. Despite numerous studies and reviews, the collective understanding and complex interplay between thermal comfort, performance, architectural factors, and climatic conditions in rammed-earth structures remains insufficiently explored. This paper systematically investigates the advancements in the thermal performance of rammed earth and its effectiveness in providing thermal comfort, focusing on the role of material composition, construction methods, and climate-responsive strategies. The scientometric analysis showed that hygrothermal studies and the inclusion of phase-changing material(PCM) are the current key focus areas. A standardized climate zone-specific adaptable model is needed to optimize thermal comfort across climatic and seasonal variations, with more studies in colder alpine climates. Although studies focus on typical stabilized rammed earth (53%), composite materials and composite structures are thermally better under seasonal variations. By modifying material, geometry, and the use of external devices, thermal simulation is a more suitable option for understanding the indoor thermal environment, which is effective and cost-saving compared to full-scale experiments. Moreover, material modification has been used the most as a climate-responsive strategy for passive heating of rammed earth structures. Developing climate-specific strategies along with climate-specific adaptive comfort models should be included in the thermal comfort standardization of rammed earth.