Indoor thermal environment of wooden-plank wall dwellings in summer in Chongqing

Journal of Chongqing University English Edition [ISSN 1671-8224] Vol. 15 No. 3 September 2016 doi:10.11835/j.issn.1671-8224.2016.03.05 To cite this article: XU Ya-nan, YANG Zhen-jing, PENG Ming-xi. Indoor thermal environment of wooden-plank wall dwellings in summer in Chongqing [J]. J Chongqing Univ Eng Ed [ISSN 1671-8224], 2016, 15(3): 119-126. Indoor thermal environment of wooden-plank wall dwellings in summer in Chongqing XU Ya-nan, YANG Zhen-jing, PENG Ming-xi Faculty of Architecture and Urban Planning, Chongqing University, Chongqing 400030, P. R. China Received 23 March 2016; received in revised form 13 May 2016 Abstract: There are a large number of wooden-plank wall dwellings, a kind of traditional house with regional characteristics, existing in Chongqing area. We chose a typical house in Chongqing as the subject and measured it during summer to research the situation of the indoor thermal comfort of wooden-plank wall dwellings. Based on the particularity of local residents living habit and the characteristics of the local buildings, we analyzed the data of the field measurement and evaluated the thermal environment with APMV. The results show that the indoor thermal comfort of wooden-plank wall dwellings in summer is improved mainly by natural ventilation. Keywords: indoor thermal environment; field measurement; temperature and relative humidity; wind speed; thermal comfort CLC number: TU-87; TU241.5 Document code: A 1 Introduction a As a result of previous long-term practice, traditional dwellings has a good environmental adaptability which is attracting more people s attention. In China the research on the traditional houses began around 1930s [1]. From the 1940s, Liu investigated ancient XU Ya-nan ( 徐亚男 ): 1440829179@qq.com. Corresponding author, YANG Zhen-jing ( 杨真静 ): young30331@163.com. Funded by National Key Technology Research and Development Program of the Ministry of Science and Technology of China During the 12th Five Year Plan (2013BAJ11B04) and Funding Project for fundamental and Frontier Science of the Chongqing Science & Technology Commission (cstc2014jcyja90024) dwellings in Yunnan and Sichuan and published two papers Yunnan traditional dwellings and Sichuan residential constructions, which were the earliest writings about traditional dwellings and were collected in Ref. [2]. But there was no research on the traditional dwellings ecological until the early 1990s. Lu et al. [3-4] began the study about Chinese traditional dwellings climate adaptation and presented coping strategies such as ventilation, moisture, shade, insulation, and cooling to the hot and humid environment. From 1990s, a research team analyzed the ecological experiences of traditional cave dwellings on the Loess Plateau in Northwest, measured and simulated Shaanxi cave from the perspective of building technology, analyzed the cave interior and courtyard thermal physical environment, and then provided some advices and improvements [5]. Currently, wood, bamboo, earth, 119

Y. N. Xu, et al. stone and brick are the most common materials of traditional houses in Sichuan and Chongqing [6]. Wooden-plank dwellings, of which materials are wood, rain and fog, and less wind [7]. Therefore, the most intractable problem for the daily life of local residents is ventilation, cooling and dehumidification. [2] are widespread in Sichuan and Chongqing. Therefore, studying the thermal environment of wooden-plank dwellings and improving the indoor environmental quality are significant. We measured and evaluated the summer indoor thermal environment on a typical wooden-plank dwelling in Chongqing. 2 Materials and methods 2.1 Regional overview The subject is located in Baisha town, Jiangjin district, Chongqing (Fig. 1). The town are built along the Yangtze River, and backed by Daqi Mountain.. The town has a compact layout due to the shortage of land, and most buildings planes have a small width and a deep depth. Streets are narrow and both sides of the building have a large eave obscuring both sun and rain (Fig. 2). Fig. 2 Narrow street The Baisha town is teeming with wood, which supplies materials for local buildings. Almost walls are made by wooden planks. Specific approach to woodenplank wall is to mount planks sideways or vertically on the frame (Fangkuang in China). (Fig. 3) The thickness of a plank is about 2.5 cm and the width is 25 cm. In the middle and upper half of the wooden-plank wall, there are windows often. For the rich, wooden planks are coated with tung oil to prevent the wall from being exposed to moisture or damaged by worms [2]. In modern times, parts of the construction will be applied lime on the wall surface for beauty. 2.2 Research subject Fig. 1 Position of Baisha town A typical wooden-plank dwelling in Baisha town The annual average temperature of Baisha town is 17.9 C, the average annual rainfall is 1 030 mm and was chosen as a research object. The subject is an the average annual sunshine is 1 273 h, mainly adjacent to houses of wooden-plank wall. Its envelope performed as high-temperature, high humidity, much structure is preserved relatively complete, and always 120 intermediate households, with both east and west sides

Y. N. Xu, et al. is inhabited compared with others. The building s orientation is south by east 19. In the south, there is a 31 to 12:00 on August 14, 2015, which is a typical 3.5 m wide street, and in the north, there is a riverside temperature, humidity, and wind speed (windows are sinking courtyard. The building plane is line-styled, always open and doors are always open except in the with 4.5 m wide and 14.4 m deep and its layout is night, so the wind speed is relatively large). Table 1 simple. On the south side, there is a living room facing shows measurement contents and instrument parameters, the street, there are two bedrooms (referred to as the and Fig. 4 show the specific point of measurement. summer time in Chongqing. Data recorded includes air mid-room and the north-room) in the centre and north that built on stilts. Under two bedrooms, there is a storage room. This kind of stilted building is one of the common practices of hillside building (Fig. 4). The building s roof is slopy with small grey tiles, and walls are wooden-planks. In the living room, the floor is concrete, roof is tall with no ceiling, and windows are wooden lattice without glass. In the midroom and north-room, the ordinary plastic sheeting is used as a simple ceiling, and the floor is built on stilts. The wall of the storage room is brick. 2.2 Testing program The effective measurement time is from 15:00 on July Fig. 3 Inside of a wooden-plank wall dwelling Table 1 Measurement contents and instrument parameters Measurement content Instrument parameter Ground temperature and air temperature of each room HOBO thermometer, UX100-014M Range: 20 C to 70 C Accuracy: 0.7 C Relative humidity of indoor and outdoor HOBO hygrometer, UX100-003 From 15:00 pm on July 31 to 12:00 am Range: 20 C to 70 C, 15 to 95% RH on August 14, 2015. Automatically recorded every 10 min. Accuracy: 0.7 C, 7.5 Wind speed in north-room DELTA anemometer, AP471S1 (1.1 m Range: 0.1 m/s to 40.0 m/s floor) [8] away from Data collection period and time interval the Accuracy: 0.2 m/s 121

Y. N. Xu, et al. a b c Fig. 4 Plane of objects and distribution of instruments: a) 1st floor plan, b) 1 floor plan, and c) sectional drawing 3 Results 3.1 Outdoor meteorological parameters Outdoor weather conditions during the measurements are as follows (Fig. 5): it is sunny from August 1th to 4th, and on the night of 4th, it began cooling. It is rainy on 8th, and turned sunny on 12th. Then the temperature gradually rises. The outdoor temperature ranges from 34 C to 23 C, the maximum temperature amplitude is 9 C a day, and the average temperature is 27 C. In addition, the outdoor air relative humidity during the test is 84.9. 88 of the time the relative humidity is greater than 60. On sunny days, the solar radiation reaches 700 W/m 2, and on cloudy days, it is less than 200 W/m 2. August 1th to 3th are averaged as a typical day for analysis because the temperature stabilization is appropriate and we mainly studied indoor comfort under the condition of a hot humid summer day. 3.2 Indoor thermal environment Fig. 6 shows the indoor and outdoor temperature during the typical day. From Fig. 6, we can see that the basic trend of each room s temperature is the same as the outdoor temperature. The average outdoor temperature is 29.2 C, and the highest and lowest is 33.6 C and 122

Y. N. Xu, et al. 25.2 C. Indoor temperature is always higher than the outdoor except in the living room during 9:00 to 17:00. Meanwhile, the maximum temperature of living room, mid-room, north-room increased in turn, which are 33.4 C, 34.4 C and 35.2 C, and it is the highest in the north-room. The minimum are, respectively, 27.1 C, 26.9 C, and 26.6 C, and the lowest temperature is in the north-room too. It is mainly because that the building is headed to the south by east 19, so the north-room is influenced by western exposure slightly in the afternoon. Furthermore, north-room is built on stilts, and air temperature under the floor is higher than the ground temperature in the afternoon and lower than the ground temperature in the morning. In the morning, the living room is radiated by ground whose temperature is higher while the north-room is affected by a lower temperature of the air underfloor. So the temperature in the northroom is lower than the living room. In the evening, the living room is affected by ground whose temperature is lower and there is a narrow street with large eaves shade in the south, while the north-room is affected by warmer air under the floor. So the living room s temperature is lower than the north-room s. Because the mid-room is located between the living room and north-room, the air temperature inside the mid-room is the same. It should be mentioned that the simple plastic sheeting ceiling in mid-room and north-room does not play any role. In addition, the heat lag of the house is about 1.0 h to 1.5 h and the maximum is in the living room with only about 1.5 h. It is mainly because the wood is light and its heat storage ability is bad. But the heat storage ability of living room s ground is better. It also explains why the temperature in the living room varied slower than that in the mid-room and north-room. Fig. 7 shows indoor and outdoor humidity results in typical days. As we can see from Fig. 7, both the indoor and outdoor relative humidity are high and go up to the maximum during 4:00 am to 8:00 am. Around 9:00 am, as solar radiation and temperature go up, the relative humidity begins to decline. At around 17:00, both indoor and outdoor relative humidity are the lowest and closest to each other, and then begin to rise. Doors are closed at night, so the indoor humidity is lower than the outdoor humidity. The temperature between indoor and outdoor was very small in summer and the wood blank can keep moisture, therefore there was no condensation found in the house. According to experience of health workers, normal indoor humidity should range from 30 to 60 approximately [9]. But in three-quarters a day, the indoor relative humidity was higher than 60. Therefore, the indoor humidity environment is not ideal. 3.3 Indoor wind speed Fig. 8 shows the result of indoor wind speed during the measurement period. According to statistics, there are 60 of the time when wind speed is greater than 0.30 m/s, and the average wind speed is 0.37 m/s during the measurement period. From August 9th to 13th, the indoor wind speed is very regular, and wind speed at night is about 0.25 m/s. During the day the wind speed reaches 0.30 m/s or more, even up to 0.50 m/s or more sometimes. During the period of 1th to 8th, although the wind speed curve was not as regular as the latter, it still can be seen that the indoor wind speed decreased at night and increased in the daytime. In many naturally ventilated buildings, the wind speed greater than 0.20 m/s and less than 0.8 m/s is advantageous [10]. The indoor wind speed of the subject reached to 0.30 m/s almost all the time, which is fairly pleasant. The reason of high indoor wind speed is that windows and doors are always open except at night. Meanwhile, there is a river in the north, which forms a land-river breeze environment. 3.4 Evaluation on thermal environment Since the subject belongs to thermal environment in 123

Y. N. Xu, et al. free-running building and conforms to the requirements of Evaluation standard for environment in civil buildings indoor thermal [11], the thermal environment of the subject can be evaluated by method of calculation, APMV or adaptive predicted mean vote, mentioned in the standard. APMV calculated by APMV=PMV/(1+ PMV), where is the adaptive coefficient and its value is based on the different building types and PMV. of residential buildings in summer is 0.21. PMV is the predicted mean vote. Table 2 shows the value of variable required for PMV. Fig. 5 Outdoor meteorological parameters (from August 1th to 14th, 2015) Fig. 6 Indoor and outdoor temperature in the typical day Fig. 7 Indoor and outdoor humidity in the typical day 124 (1)

Y. N. Xu, et al. Fig. 8 Indoor wind speed during the measurement period (from August 1th to 14th, 2015) Fig. 9 shows the results of AMPV obtained by calculation. It can be seen from Fig. 9 that most of the time, APMV in the living room varies between 1. According to statistics, on the typical day, 21% of the time the value of APMV exceeds 1, which is in the thermal environment category Ⅲ. Obviously, most of the time, the living room reaches thermal environment category Ⅱ. Clothing insulation Table 2 Value of variable required for PMV Metabolic rate 0.8 Air temperature Mean radiant temperature Wind speed relative humidity Take 0.1 clo during 11:00 to 23:00 Take 0.3 clo during 23:00 to 11:00 Value of actual measurement Replaced by air temperature because the temperature of wall surface s radiation is tiny Value of actual measurement Value of actual measurement natural ventilation. In terms of architectural form, built on stilts makes the floor half on ground and half superterranean, which makes the living room take full advantage of the earth energy in the day and the northroom make the best of cooling capacity of air especially under the floor at night. On the other hand, the house located in south of Yangtze River, so cool breeze coming from the river improves the indoor thermal comfort. a b 4 Discussion From the above analysis, wooden-plank dwellings indoor temperature is slightly higher than the outdoor. The indoor relative humidity is high, but thermal comfort calculated by APMV is ideal and similar to the occupant s actual feelings. The results lie in two respects: features in architectural form and good Fig. 9 a) Value of APMV, and b) percentage of APMV in the typical day 125

Y. N. Xu, et al. 5 Conclusions For wooden-plank dwellings, the temperature difference between indoor and outdoor was small as well as the relative humidity. Thermal inertia and heat lag were little, but good natural ventilation increased the indoor comfort level. Therefore, it is crucial for wooden-plank dwellings to have a good natural ventilation in hot and humid sunny summer. And it is better to make the floor half on ground and half superterranean to keep the temperature of living room not too high in the day and bed room comfortable at night. References [1] LU Y D. 50 years research on Chinese folk house [J]. Architectural Journal, 2007(11): 66-69. (In Chinese). 陆元鼎. 中国民居研究五十年 [J]. 建筑学报,2007(11): 66-69. [2] LIU Z P. A brief history of Chinese residential buildings: city, residential, garden [M]. China Building Industry Press, 2000. (In Chinese). 刘致平. 中国居住建筑简史 : 城市住宅园林 [M]. 北京 : 中国建筑工业出版社,2000. [3] LU Y D MA X Z, DENG Q S. Local dwellings in Guangdong [J]. Architectural Journal, 1981(9): 29-36. (In Chinese). 陆元鼎, 马秀之, 邓其生. 广东民居 [J]. 建筑学报, 1981(9):29-36. [4] LU Y D, WEI Y J. Guangdong Residence[M]. Architectural Journal, 2007(11): 66-69. (In Chinese). 陆元鼎, 魏彦钧. 广东民居 [J]. 中国建筑工业出版社,1990. [5] YI Y. Liu Jiaping and ecological dwellings [J]. China Construction, 2006(2): 28-29. (In Chinese). 亦意. 刘加平与生态民居 [J]. 中华建设,2006(2):28-29. [6] WU Y. Research on regional characteristics of bashu traditional building [D]. Chongqing: Chongqing University, 2007. (In Chinese). 吴樱. 巴蜀传统建筑地域特色研究 [D]. 重庆 : 重庆大学, 2007. [7] Meteorological Information Center of China. Special meteorological data set about China building thermal environment analysis [M]. Beijing: China Building Industry Press, 2005. (In Chinese). 中国气象局气象信息中心气象资料室. 中国建筑热环境分析专用气象数据集 [M]. 北京 : 中国建筑工业出版社,2005. [8] Ministry of Housing and Urban-Rural Development of the P. R. China. Standard of text methods for thermal environment of building: JGJ/T 347-2014 [S]. Beijing: China Architecture & Building Press, 2015. (In Chinese). 中华人民共和国住房和城乡建设部. 建筑热环境测试方法标准 :JGJ/T 347-2014[S]. 北京 : 中国建筑工业出版社,2015. [9] LIU J P. Architectural physics [M]. Beijing: China Building Industry Press, 2012. (In Chinese). 刘加平. 建筑物理 [M]. 北京 : 中国建筑工业出版社, 2012. [10] GUO C M, ZHANG Y F, LI S Y. Thermal comfort evaluation and analysis of natural ventilation environment [J]. Heating, Ventilation and Air Conditioning, 2010, 40(10): 76-80. (In Chinese). 郭春梅, 张于峰, 李胜英. 自然通风环境热舒适性评价与分析 [J]. 暖通空调,2010,40(10):76-80. [11] Ministry of Housing and Urban-Rural Development of the P. R. China, General Administration of Quality Supervision, Inspection and Quarantine of the P. R. China. Evaluation standard for indoor thermal environment in civil buildings: GB/T 50785-2012 [S]. Beijing: China Architecture & Building Press, 2012. (In Chinese). 中华人民共和国住房和城乡建设部, 中华人民共和国国家质量监督检验检疫总局. 民用建筑室内热湿环境评价标准 :GB/T50785-2012 [S]. 北京 : 中国建筑工业出版社,2012. 126