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As a traditional building material, rammed earth has gained popularity for its environmental friendliness and reusability. In this study, the hygrothermal performance of the wall material of traditional rammed-earth dwellings was experimentally measured, and the indoor and outdoor temperature and humidity variations of rammed-earth dwellings were experimentally measured for five days. Considering temperature and relative humidity as the driving potential for heat and humidity transfer and air penetration, an unsteady model of heat and humidity transfer of the rammed-earth wall and indoor and outdoor air was established. The accuracy of the model was verified using the measured data. The model was used to determine the rationality of the wall thickness in local rammed-earth dwellings. Based on data from typical local meteorological years, the indoor temperature and humidity changes in rammed-earth dwellings were numerically predicted. The average indoor temperature and humidity in summer were 26.56°C and 69.74%, and the variances were 3.26 and 43.17, respectively. The average indoor temperature and humidity in winter were 7.25°C and 83.62%, and the variances were 1.14 and 14.83, respectively. The research results demonstrate that a rammed-earth wall significantly reduces the influence of outdoor temperature fluctuation on the indoor thermal environment, with good humidity regulating performance. [ABSTRACT FROM AUTHOR]

Building construction accounts for 40% of the global anthropogenic greenhouse gas emissions. The drastic increase in the energy costs of building materials has drawn attention to earth materials, such as rammed earth. In this study, the hygrothermal properties of rammed earth in the Tibetan Autonomous Prefecture, Sichuan Province, China were measured and compared with results from previous studies. To analyze the hygrothermal performance of a rammed earth wall, a numerical model was established and verified. The coupled heat and moisture transfer in the area of the common rammed earth wall and the moisture barrier wall was simulated with different indoor conditions, orientations, and thicknesses. The numerical results were observed to be consistent with the experimental data. In contrast to results from other studies, the earthen material analyzed in this study exhibits less vapor transfer, but better thermal stability and moisture buffering. The moisture barrier increases the average moisture content of the rammed earth wall, but reduces the maximum moisture content, thereby protecting the wall. The moisture barrier probably also reduces the moisture buffering capacity of the wall. The moisture barrier has no significant effect on heat transfer; even a west-facing wall reduces heat loss by only 3% in this area. • The studied earthen material has lower diffusivity and higher effusivity. • The moisture barrier results in a maximum reduction in moisture transfer of 35%. • The increase of moisture transfer reduces the heat loss of the wall for the whole year. • The moisture barrier will be more effective used on rammed earth wall facing west. [ABSTRACT FROM AUTHOR]

Most published works have considered the influence of a single factor on the thermal or hygroscopic properties of the modified soil materials, but few studies have focused on the influence of multi-factor. Therefore, an L 9 (34) orthogonal array test design was adopted in this study to investigate the effects of cement, lime, fly ash, and moisture on the hygroscopic properties of modified soil composites. They were chosen as chemical additives because they are the most common and widely used industrial building materials in the construction of modern buildings. Based on results from range analysis and mean square deviation analysis, the important order of the four factors on the hygroscopic properties was achieved, then the optimum proportion is found. The results show that cement has the most obvious effect on the equilibrium moisture content in 52.89% relative humidity (RH) among the four factors, and fly ash flow is second, moisture content has a minimal effect. By optimizing the parameters, when the cement content was 7%, lime content was 5%, fly ash content was 4% and the moisture content was 10%, the highest average equilibrium moisture content of 1.625% was obtained. The optimized modified soil composites have excellent hygroscopic properties and compressive strength meets the corresponding safety requirements, so it has potential for application and development in the field of soil architecture. • The isothermal absorption-desorption of modified soil composites is irreversible. • The optimum formula is 7% cement, 4% fly ash, 5% lime, and 10% moisture content. • Cement significantly impacts the hygroscopic property of modified soil composites. • Moisture content slightly impacts the hygroscopic property of studied materials. [ABSTRACT FROM AUTHOR]