Numerical analysis of a ground-source heat-pump system in traditional Japanese “Kyo-machiya” dwellings

Kyo-machiya, which is a traditional wooden dwelling in Kyoto, is generally equipped with a shallow well. The well water can be potentially utilized as a heat source with a geothermal heatpump system without incurring a high drilling cost. Hereby, more energy saving in the traditional dwelling can be realized with the heat-pump system. However, an appropriate technique to utilize geothermal heat from a shallow well has not been established yet in Japan. To promote the geothermal use, we have continued an experiment to evaluate the practicability of a simple geothermal heat-pump system installed in a shallow well since the winter of 2013. In this study, the condition of the water flow in the well was examined using the computational fluid dynamics (CFD) technique, and the velocity of flow of the groundwater into the well was also estimated. We show that constant buoyancy was generated because of the temperature difference due to the heat-pump operation. Based on the results, a three-dimensional heattransfer numerical analysis model, proposed in the previous study, was developed so that moisture transfer in the ground could be considered. Using the estimated buoyancy of the well water and the groundwater velocity, the calculated results seemed to reproduce the characteristic of the measured value. Furthermore, we show that the groundwater velocity has a large influence on the well water temperature

Effect of Air Pressure on Moisture Transfer inside Porous Building Materials Three-dimensional Behavior of Moisture and Air

The effect of air pressure on moisture transfer inside porous building materials cannot be ignored in cases in which air cannot escape through the surfaces of the materials; in such cases, the air is compressed by the movement of the moisture. Therefore, in a situation in which most surfaces of a specimen are sealed or treated with surface-protecting materials (a situation that is often encountered in typical water-absorption tests), the experimental results may differ from those without sealed or treated surfaces. In the present study, the influence of air pressure on moisture transfer was investigated quantitatively. First, the following water-absorption test was conducted. Water infiltrated into a brick through its top surface, whereas the side surfaces were sealed to prevent the transfer of moisture and air. The bottom surface was exposed to the ambient air. The water content was measured twodimensionally during the experiment using gamma-ray attenuation. Next, to investigate how air pressure affects water infiltration, another experiment was conducted after sealing the bottom surface. The air inside the brick was expected to be compressed by the infiltrating water when the bottom surface was sealed. A water-absorption test was then performed after a small hole was made in a side surface of the bottom-sealed brick to reduce the interior air pressure. Finally, we analyzed the experiments numerically using a three-dimensional calculation model for simultaneous air and moisture transfer, assessing the validity of the model by comparing the calculated and measured water contents. The experimental and numerical results show that water infiltration is slowed by higher air pressure inside the specimen when it is difficult for air to escape. It is also shown that the hole in the side surface helped limit the rise in air pressure to some extent

Evaluating the Energy Consumption and Heat Loss in the Hot Water Supply and Heating Systems of a Nursing Home

The demand for nursing homes has increased recently due to an increase in the aging population in Japan. Nursing homes are generally equipped with hot water supply and heating systems for bathing, preparing meals, and heating rooms. This equipment utilizes a considerable amount of energy. Few studies have measured heat loss from the hot water supply and heating systems in such facilities. This study evaluated the hot water supply and heating systems of a nursing home located in a cold climate area in Japan. The temperature and flow rate of the hot water were continuously measured, and the energy consumption and heat loss for each subsystem were calculated. These results clarified that the energy consumption in the hot water supply subsystem was slightly larger than that in heating subsystem. Inefficiencies of the system were also continuously evaluated throughout the study. Heat losses in piping attributed to 38% of the total energy consumed by the hot water supply subsystem. Subsequently, a thermal analysis of the hot water subsystem was performed. The calculated return temperature agreed with the measured return temperatures when the resistance of thermal insulation was decreased by an average of 45%; this result was possibly due to the deterioration of thermal insulation materials or the presence of thermal bridges

Relationship between Environmental Conditions and Algal Growth on the Exterior Walls of the Ninna-ji Temple, Kyoto

6th International Building Physics Conference, IBPC 2015We can find that many building facades are discoloured black and/or green. Some previous studies showed that the soiling of building facades is caused by the growth of airborne algae. The algal growth is strongly influenced by the water supply, including the rain, the condensation, and high humidity. However, the influence of the other environmental factors, such as the solar radiation, the temperature, and the wind on the algal growth, has not been investigated yet. The relationship between the algal growth and the environmental factors on the building facades which the algae grow for long term has not been investigated. Therefore, we quantified the relationship between the algal growth and the environmental factors based on the field survey on the algal growth in Kyoto City and the measurement on the building facades at Kusyo Myojin Shrine, Ninnna-ji Temple in Kyoto, Japan. Kusyo Myojin Shrine was constructed from 1641 to 1647. Some parts of the roof, walls and the painting were repaired from 2004 to 2006. However, the building facades have already been colored black by the algal growth. To investigate the cause of the soiling by the algal growth, the ambient conditions, and surface temperature and humidity of walls were has measured since 2011. The soiling state of the walls was investigated by the L* values and the photographs of the walls. As a result, the order of the L* values of the wall surfaces agreed well with the darkness of the photographs. We concluded that the algal growth and death on the wall surface were affected by the surface temperature of the wall

Traditional Town Houses in Kyoto, Japan: Present and Future

Climate change is an important issue that affects energy consumption, causes health problems, such as heat stroke, and requires urgent countermeasures. Serious health problems, including cardiac arrest, often occur in winter in traditional residences in Japan. Cooling-heating energy is required to maintain a healthy thermal environment. Although energy efficiency standards for buildings have been introduced worldwide to reduce energy consumption and various passive energy-saving methods are being investigated, traditional residences still face difficulties in conducting renovations because of various restrictions, such as the conservation of historical or aesthetic values. In this study, these issues and their appropriate countermeasures were investigated for a traditional townhouse in Kyoto, Japan, “Kyo-machiya” (including its new form “Heisei-no-Kyo-machiya”). The potential of reducing heating and cooling loads was examined by conducting numerical analysis considering residents’ lifestyles. Field surveys of the indoor environment were conducted in both summer and winter. It was revealed that by optimizing the times and positions of opening and closing the windows and indoor partitions, the indoor air flow could be adjusted from both thermal comfort (cooling in summer) and discomfort (cold drafts in winter) perspectives, leading to improving the indoor environment without using energy

Energy-saving Renovation of Kyo-machiya Considering the Moisture Buffering Effect of Soil Walls

Kyo-machiya, a type of traditional townhouse in Kyoto, is considered as cultural heritage that needs to be preserved. However, the high air leakage due to its unique structure and poor thermal insulation because of its traditional appearance may lead to high heating energy consumption. Therefore, an appropriate energy-saving renovation technique is proposed. However, the lack of quantitative analysis hinders the establishment of effective renovation guidelines focused on the energy-saving and healthy indoor environments of Kyo-machiya. Previously proposed retrofits were conducted using conventional methods with limited effectiveness. The soil wall in Kyo-machiya has an impact on indoor environments and is considered as a significant feature, and its appearance is crucial for the residents. Also, the soil wall has a moisture-buffering effect. Therefore, the adoption of interior insulation should be considered with caution. In addition, high air leakage is not fully resolved via the conventional methods. In this study, we used a numerical model of a typical traditional Kyo-machiya to evaluate different renovation designs, including interior and exterior insulation, vapour/moisture proof solutions, and effectiveness of enhancing air tightness. Finally, we proposed a renovation plan based on the conventional methods, considering the balance between energy-saving and hygrothermal risk

Traditional Town Houses in Kyoto, Japan: Present and Future

Climate change is an important issue that affects energy consumption, causes health problems, such as heat stroke, and requires urgent countermeasures. Serious health problems, including cardiac arrest, often occur in winter in traditional residences in Japan. Cooling-heating energy is required to maintain a healthy thermal environment. Although energy efficiency standards for buildings have been introduced worldwide to reduce energy consumption and various passive energy-saving methods are being investigated, traditional residences still face difficulties in conducting renovations because of various restrictions, such as the conservation of historical or aesthetic values. In this study, these issues and their appropriate countermeasures were investigated for a traditional townhouse in Kyoto, Japan, “Kyo-machiya” (including its new form “Heisei-no-Kyo-machiya”). The potential of reducing heating and cooling loads was examined by conducting numerical analysis considering residents’ lifestyles. Field surveys of the indoor environment were conducted in both summer and winter. It was revealed that by optimizing the times and positions of opening and closing the windows and indoor partitions, the indoor air flow could be adjusted from both thermal comfort (cooling in summer) and discomfort (cold drafts in winter) perspectives, leading to improving the indoor environment without using energy

Frost damage to roof tiles: Ice distribution in freeze-thaw experiment

In this paper, frost damage to roof tiles, which is among the most serious causes of deterioration, was discussed. Freeze-thaw experiments were conducted and frost damages similar to that observed in a field survey were reproduced. The experimental results were examined by numerical analysis focusing on ice content distribution and temperature