Abstract
The climate crisis is one of the most important problems today. In the process of human building, the use of cement, steel, and other industrial materials in the process of building construction and recycling has brought a huge burden to the natural environment. Earth is one of the oldest building materials, its availability and insulation make it an excellent constructive solution in human history. Among several existing earth construction techniques, rammed earth is one of the most relevant. In this paper, a numerical model of the rammed earth folk house in Mianyang was established, and an experimental device was built to verify it. With the typical meteorological year data of Mianyang in northwest Sichuan, the heat and moisture transfer in rammed earth wall, as well as the indoor thermal and moisture environment were numerically simulated. The results show that the rammed earth wall weakens the temperature fluctuation of the inner surface of the wall and makes the peak temperature of the inner surface of the wall lag the outer surface. The relative humidity in the center of the rammed earth wall can be maintained at about 60%, both in winter and summer. The moisture absorption and desorption capacity of rammed earth walls without inner decorative materials is about three times that of gypsum board, and the use of a waterproof coating will render the rammed earth wall almost unable to adjust the indoor relative humidity. Additionally, the use of decorative materials will increase the fluctuation range of indoor relative humidity and the risk of mold breeding.
Highlights
The 75th UN General Assembly held in September 2020 proposed that the climate crisis is one of the most important problems today
In the process of human building, cement, steel and other industrial materials used in the process of construction and recycling are responsible for 33% of the emissions, 40% of the material consumption and 40% of all waste [1], which has brought a huge burden to the natural environment
The water vapor permeability of the rammed earth was set to 1.20 × 10−11, the thermal conductivity was set to 0.657 W/mK, the rammed earth wall density was set to 2160 kg/m3 [34]
Summary
The 75th UN General Assembly held in September 2020 proposed that the climate crisis is one of the most important problems today. Rammed earth has a good capacity to reduce the thermal amplitude inside the building [13], as well as the characteristics of moisture absorption and release. UMIDUS considers vapor diffusion and capillary flow of liquid water, which can be used to calculate the coupled heat and moisture transfer in porous media. MOIST, HygIRC, UMIDUS, and WUFI have the same governing equations for calculating the heat and moisture transfer inside the building envelope. Their differences lie in the setting of surface boundary conditions, material properties, and numerical calculation methods. The. Energies 2022, 15, 1936 convective heat transfer coefficient on the internal and external surfaces of the rammed earth wall was set as 8.72 W/m2K and 23.26 W/m2K [36], respectively. The water vapor permeability of the rammed earth was set to 1.20 × 10−11, the thermal conductivity was set to 0.657 W/mK, the rammed earth wall density was set to 2160 kg/m3 [34]
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