Earth materials are commonly utilized due to their excellent wet properties and environmental friendliness. However, previous research has primarily focused on the impact of additives on the water vapor permeability of earth materials, neglecting the influence of particle size distribution. This has also hindered the quantitative assessment of the water vapor permeability of earth materials. To advance the use of earth materials in building energy conservation, this study develops a mathematical model for the water vapor permeability coefficient of earth materials. This model is derived from experiments that measure the water vapor permeability coefficient of earth materials with varying densities and earth-to-sand ratios, employing both experimental measurements and theoretical analyses. After being adjusted by a quadratic function of error rate and density, the average error rate of the mathematical model decreased from 5.73% to 1.3%, indicating its accuracy. Furthermore, by utilizing this model, the impacts of density, clay, sand, and gravel on the water vapor permeability coefficient of earth materials were quantitatively examined. The results indicate a negative correlation between the water vapor permeability coefficient of earth materials and density. When the clay–sand–gravel ratio was 3.8:5.0:1.2, the vapor permeability of the earth materials was the worst, whereas when the gradation ratio was 4.6:3.4:2.0, the vapor permeability was relatively optimal. The findings of this research can provide a reference for the scientific quantification of the thermo-physical property indices of earth materials in green building design systems.

In this study, to explore the applicability of passive house technology under PHPP assessment standards in Chinese areas hot in summer and cold in winter, Nanjing area was taken as an example, real cases were examines under PHPP assessment standards for passive houses in line with regional climatic differences. The present study focused on four aspects, namely the thermal insulation & heat preservation properties of the external enclosure structure, the mildew-growing temperature of the interior wall, the air-tightness property of the external enclosure structure, as well as the damp-proof performance of buildings. A numeric analysis was conducted using Dest software, and the German PHPP assessment standards for passive houses were eventually found not entirely applicable to Chinese areas hot in summer and hot in winter. Thermal insulation, damp-proof, and vapor-proof properties should be considered when designing passive house projects for such areas. Based on influential factors, this study proposed the climatically-reconstructed design for the external enclosure structure of passive houses and employed Energyplus for demonstration and analysis. Analytical findings suggested that the reconstruction plan is feasible.

Earth materials in construction demonstrate significant potential attributed to their accessibility, recyclability, and low energy demands for processing. Modern techniques have enhanced their mechanical strength and durability, enabling their application in load-bearing and infill walls while preserving ecological benefits. However, existing studies on indoor heat–humidity regulation primarily emphasize material parameters and macro-level performance. Moreover, the dynamic interactions between the unique thermal storage–release mechanisms and indoor environments have not been systematically analyzed. With the Kelvin equation, capillary mechanics, adsorption theories, and microstructural analysis were integrated in this study to quantify cyclic capillary condensation and evaporation in microvoids. The results reveal that earth materials contain abundant medium-sized pores (19.85–53.83 nm) sustaining vapor exchange with their surroundings. Capillary condensation occurs 0.86–0.96 times the planar surface vapor pressure, influenced by pore size (negatively correlated) and temperature (negatively correlated). During the daytime, capillary evaporation occurs in the nanopores of the raw earth wall under the influence of the outdoor environment’s cyclical temperature and humidity. This process absorbs heat from the indoor environment and raises the ambient humidity. During the nighttime, capillary condensation occurs in the pores, releasing heat to the indoor area and absorbing moisture from the environment, contributing to the balance of the indoor thermal environment of the earth buildings. The findings lay a scientific foundation for quantitatively evaluating earth buildings’ indoor climate control performance, supporting their integration into green building systems. This research bridges knowledge gaps in micro-to-macro thermal dynamics while advancing the ecological optimization of materials for sustainable architecture.