Abstract
Rammed earth (RE) is a low-tech recyclable building material with good heat storage and moisture absorption performance that can better maintain the stability of the indoor thermal environment and improve indoor comfort. With innovations in and the development of new technology, the field of rammed earth construction technology is gradually expanding. However, deficiencies in the thermal insulation of traditional rammed earth structures make it impossible for them to meet China’s building energy codes in cold regions. This study constructs a comprehensive evaluation index of the thermal performance of rammed earth walls that is based on the heat transfer mechanism, optimizing the thickness of the boundary conditions of the building interior’s design temperature, as well as the energy demand and economic efficiency. This research also offers a new design for the thermal insulation of rammed earth construction by combining the building energy savings design code with WUFI Pro software. This study demonstrates that the optimum thickness of rammed earth construction in Beijing is about 360 mm, the thickness of extruded polystyrene board (XPS) is 50 mm (for public buildings) and 70 mm (for residential buildings), and the structural form of external insulation offers the highest performance benefit. In addition, this work also evaluates the risk of condensation inside composite rammed earth construction, finding that there is a risk of condensation on the exterior side of the wall and at the interface between the insulation panels and rammed earth wall, thus requiring an additional moisture-proof layer. In this study, thermal mass and insulation are fully considered and a design strategy for rammed earth construction given quantitatively, providing a theoretical basis for the application of rammed earth materials in cold regions.
Highlights
With the development of modern rammed earth (RE) technology, earthen buildings have returned to being a topic of active interest
This study constructs a comprehensive evaluation index of the thermal performance of rammed earth walls that is based on the heat transfer mechanism, optimizing the thickness of the boundary conditions of the building interior’s design temperature, as well as the energy demand and economic efficiency
This research offers a new design for the thermal insulation of rammed earth construction by combining the building energy savings design code with WUFI Pro software
Summary
With the development of modern rammed earth (RE) technology, earthen buildings have returned to being a topic of active interest. RE buildings are warm in winter and cool in summer, maintaining the thermal stability of the building’s internal environment and reducing energy consumption for cooling and heating [4] This is because RE constructions are typically 300 mm to 600 mm thick [5] and can provide a large thermal mass compared to ordinary concrete blocks [4], leading to a time lag between the indoor temperature wave peak on hot summer days and reducing the impact of periodic outdoor temperature waves on the indoor environment [6,7]. Though some other scholars have improved the thermal performance of RE buildings by combining them with passive designs such as glazing, shading, and ventilation, yielding positive effects on building energy consumption [24,25], the poor thermal insulation of RE materials is a problem yet to be solved. The authors hope that the research findings will provide a basis and reference for the future design application of RE construction in cold climate zones
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