論文の公開元へインドネシア都市部のカンプンにおける低コスト住宅において実現可能な室内熱環境改善方策の究明に関する研究
概要
Despite managing the factors dedicated to household energy consumption and its indoor thermal comfort conditions, 41% of low-cost dwellings in Indonesia having more constraints in providing adequate housing conditions due to insufficient financing and lack of infrastructure quality. Therefore, providing affordable strategies improving indoor thermal comfort and heat risk mitigation of such dwellings become essential. Given this background, this study generally emphasizes the series of observation, site-measurement and evaluations, and numerical building simulation to seek the best strategy in term of improving indoor environment quality and heat risk mitigation of low-cost dwellings located in Surakarta City, Central Java Province, Indonesia.
Chapter 1 contains the background and potential common issues to addressed through this study. A framework for indoor environmental quality improvement and heat risk mitigation and several previous study to emphasize strategies to improve indoor environmental quality are briefly described in literature are briefly described in literature review sub-chapter. At the end part of the chapter, significance and objectives of present study are included.
Chapter 2 presents the characteristics and the diversity of indoor thermal environment among low-cost dwellings. Activity snapshots such as field measurement and survey on occupant’s thermal comfort and preferences showed a diverse indoor thermal environment of 17 observed dwellings. It exhibited approximately 38% to 80% of the total measurement period with the indoor air temperature above 29 oC. Based on ASHRAE 55 2010 and IS 7730 2005, it is out of range 90% thermal neutrality. The characteristics of dwelling with low thermal insulation performance are not necessarily equal with respect to the houses that have longer time durations of hot indoor conditions. Conversely, houses with a small decrement factor, i.e. relatively high shelter function of building envelopes, exhibit much higher indoor temperature compared to outdoor temperature during night-time owing to the reduced nocturnal radiation cooling and heat storage in the building envelope.
Chapter 3 reports the occupant’s perception, preference, and acceptability to current indoor thermal conditions of low-cost dwellings. According to thermal sensation votes (TSVs) and thermal preference votes (TPVs) obtained from the questionnaire survey applied to 102 occupants under different conditions of indoor thermal environment, all of the occupants exposed to the room air temperature between 24.5 oC to 27 oC recognized as thermal condition as neutral and no need to change. The comfort temperature derived from the Griffith method showed the highest proportion of subjective comfortable temperatures from all respondents ranged between 28 oC and 30 oC, whereas the mean and median comfortable temperatures were 28.3 oC and 28.6 oC, respectively. In the context of physical factors of dwellings, the significant factors affecting indoor thermal conditions based on Spearman’s rank correlation with a confidence interval (CI) of 95% revealed the heat capacity of a building envelope per unit interior volume showed a strong linear correlation with the parameter of decrement factor f regardless of the occupant’s behavioural conditions. Additionally, the ratio of the floor area per house volume, i.e. the inverse of the ceiling height, shows relatively high correlation coefficients for indoor air temperature at 75th percentile (Tp75).
Chapter 4 reveals association between the prevalence of occupants’ health problems to their
demographic and subjective indoor environment quality of investigation through cross-sectional design study with a questionnaire survey. Among the observed demographic factors, economic conditions were identified as the most significant factor associated with health problems. When compared to the high-income group, we found that the low-income group was more vulnerable to several health problems related to mental health, bodily pains, the digestive tract, and respiratory functions. In addition, according to SEM analysis, thermal discomfort experiences of the respondents had significant direct effects on their health problems.
Chapter 5 examines three affordable cooling strategies to improve indoor thermal environment by employing a numerical simulation model using TRNSYS program. The cooling strategies owing to air infiltration rate (strategy 1), roof shading for solar blockage (strategy 2), and heightened the wall construction (strategy 3) were generally assessed to obtain its effectiveness by quantifying indoor air temperature differences between initial conditions and cooling strategy cases among the dwellings classified as three types based on its wall construction materials i.e. plywood wall, brick wall , and plaster-brick wall. The strategy attributed to increasing air infiltration showed maximum 0.9 oC decrease in indoor air temperature of low-cost dwelling with plaster-brick wall construction. On the other hand, the strategy adopted roof shading for solar blockage exhibited 2 oC maximum reduction in indoor air temperature for dwelling with plywood wall construction, while only 1oC and 0.7 oC reductions were found respective to dwellings with brick and plaster-brick wall constructions. Meanwhile, 1.2 oC and 0.6 oC of maximum reductions of indoor air temperature of dwellings with plaster-brick and brick walls respectively were observed by adopting third strategy attributed to heightening wall construction. For all strategies simultaneously applied to the dwelling models, maximum simulated indoor air temperature reductions of House 1,2, and 3 are 1.7 oC, 1.6 oC, and 1.6 oC respectively. This attempt seemed the best method to achieve maximum cooling effects for house with brick wall and plaster-brick wall constructions. Nevertheless, strategy adopting roof shading for solar blockage is the most beneficial for house with plywood wall construction to obtain maximum cooling effects.
Finally, Chapter 6 provides conclusion and recommendation for the future research based on the results of the work within this study.
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