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Coupled heat and moisture transfer has a severe influence on building envelop durability. This phenomenon has more concerns as the rapid development of new moisture buffering materials. In this paper, a detailed description of hollow concrete block filled with compressed straw bricks is presented. In order to reveal heat and moisture coupling mechanism of the multilayer energy-saving wall, a series of tests were developed based on our designed controllable coupled heat and moisture test. The experiments were divided into 3 groups according to directions of heat and moisture transfer and the variations of boundary conditions. The temperature and humidity profiles within the wall thickness through two different directions are monitored during the test. The experimental results highlight the important influence of temperature and relative humidity gradient on the hygrothermal properties of the multilayer wall. It also illustrates that filling compressed straw bricks into hollow concrete block can hinder heat transfer and improve moisture buffering performance of multilayer wall. Based on our developed model, a piece of software (HMCT 1.0) to simulate the hygrothermal performance in multilayer wall was proposed for deep understanding of the experimental results. A good agreement was found between simulation results and tested values. [ABSTRACT FROM AUTHOR]

In recent years, the ground source heat pump (GSHP) system has been widely used due to its high unit efficiency, considerable energy conservation and low operating cost. However, the heat transfer efficiency of ground heat exchangers (GHE) in some projects decreases year by year. This results in the decrease of performance of the GHSP system. This is mainly because of lacking of the deep research about the heat and moisture transfer influence on the GHE in unsaturated soil. In this paper, a new model for predicting the soil thermal conductivity under different temperatures was developed. By comparing with the Campbell and de V-1 models, the new model showed better performance on predicting the soil thermal conductivity. Thereafter, a coupled heat and moisture transfer model in unsaturated soil was established for the GHE. In addition, the mode1 was verified by comparing its results against those established by other researchers. By the results, it was found that the model calculation results agreed well with the experimental data in the literature. Finally, the effects of different factors, including the soil types, soil porosity on the characteristics of the GHE were studied. [ABSTRACT FROM AUTHOR]

The buildings are exposed to the hot-humid climate with high temperature and humidity in hot summer and cold winter zone of China. Moisture transfer and accumulation within exterior walls have notable effect on the cooling and heating transmission load. Finally, it will influence the thickness of insulation. In this paper, a coupled heat and moisture transfer model which considers the effect of the moisture transfer on heat transfer is presented to calculate the cooling and heating transmission load. Then, the optimum insulation thickness of exterior walls is determined by using the P 1 – P 2 economic model. Three representative cities, Changsha, Chengdu and Shaoguan, are chosen as the sample cites. The results show that the optimum thickness of extruded polystyrene (XPS) is between 0.053 and 0.069 m and the optimum thickness of expanded polystyrene (EPS) is between 0.081 and 0.105 m. The maximum lifecycle saving varies from 16.60 to 28.50 $/m 2 and the payback period varies from 1.89 to 2.56 years. EPS is more economical than XPS as insulation because of its lower lifecycle total cost. The comparisons are made between the results based on the coupled heat and moisture transfer model and the transient heat transfer model without considering the influence of moisture transfer. [ABSTRACT FROM AUTHOR]

The building envelopes are exposed to the hot-humid climate with high humidity in hot summer and cold winter zone (HSCW) of China. The moisture transfer may severely influence the conduction loads through exterior walls. In this paper, a coupled heat and moisture transfer model is developed and validated to investigate the thermal performance of exterior walls. The conduction loads through a typical exterior wall are used to evaluate the effect of moisture transfer on the thermal performance of exterior walls in HSCW zone of China. The results show that the peak cooling and heating loads are overestimated by 2.1–3.9% and 4.2–10.1%, respectively, when ignoring moisture transfer. In cooling season, the sum of the latent load accounts for 14.3–52.2% of the sum of the total load and the yearly latent load accounts for 4.9–6.1% of the yearly total load when considering moisture transfer. The total cooling, heating and the yearly load are underestimated by 9.9–34.4%, 1.7–4.0%, and 5.2–6.8%, respectively, when ignoring moisture transfer. The results indicate that ignoring moisture transfer causes significant discrepancy in predicting the conduction loads. A detailed model considering moisture transfer in building envelope is essential to accurately evaluate the building energy performance in HSCW zone of China. [ABSTRACT FROM AUTHOR]