Indoor thermal environment and energy saving for urban residential buildings in China

The purpose of this survey is to investigate the actual conditions of the residential indoor thermal environment in urban areas in China for evaluating thermal comfort and predicting the energy conservation feasibility for space heating and cooling.The apartment homes under investigation were located in the urban areas of nine major cities. The questionnaire survey revealed building characteristics, the types of space heating and cooling system in use, aspects of life style, during winter and summer seasons, and so on. The measurement showed that winter indoor temperatures in Harbin, Urumqi, Beijing and Xi’an remain at a relatively stable level near 20 °C due to the central heating system installed. However in the other cities lacking central heating systems, indoor temperatures fluctuated as a function of the change of outdoor temperature. On the other hand, summer indoor evening temperatures in Shanghai, Changsha, Chongqing and Hong Kong were higher than the comfort zone of ASHRAE. Therefore it is expected that energy use for space heating and cooling in the southern China will increase in the near future because of occupants’ requirement for comfortable indoor environment. Based on the results yielded by this study, in Beijing the calculation of space heating and cooling loads indicated that the energy used to heat indoor spaces can be halved by installing thermal insulation and properly sealing the building.     

Research on seasonal indoor thermal environment and residents' control behavior of cooling and heating systems in Korea

Indoor thermal environments and residents' control behavior of cooling and heating systems were investigated in Seoul, Korea and compared with the results of previous studies. Twenty-four houses in summer, six houses in autumn and 36 houses in winter were used in this study. The measurement of temperature, humidity and air conditioner usage behavior was carried out. The clo-value, thermal comfort, sensation and basic data of the houses were also investigated. The indoor thermal environment in the summer had a high temperature and a high humidity ratio compare to standard comfort zone. Most of the indoor thermal environments at the time of starting the air conditioner in the summer were out of the comfort zone. Some of the data recorded while the air conditioner was stopped were in the comfort zone, but in many cases the temperature was relatively higher than comfort zone. Most indoor climate distributions in the winter were in the comfort zone and the indoor climate in autumn coincided well with the criteria of the comfort zone. Compared with results of previous studies in these 25 years, indoor ambient average temperature in winter has increased and the comfort temperature has increased in the heating period and decreased in the cooling period. This result indicates that the development of an HVAC system has created an expectation of comfort for residents and has shifted their thermal comfort zone warmer in winter and cooler in summer.     

A field study of the thermal comfort in residential buildings in Harbin

This field study was performed during the winter of 2000–2001 in order to investigate the thermal environment and thermal comfort in residential buildings in Harbin, northeast of China. A total of 120 participants provided 120 sets of physical data and subjective questionnaires. An indoor climate analyzer and a thermal comfort meter made in Denmark were used to collect the measured parameters of the indoor environment, the predicted mean vote (PMV), and predicted percentage of dissatisfied (PPD). The conclusions are as follows: males are less sensitive to temperature variations than females; the neutral operative temperature of males is 1 °C lower than that of females; Harbin subjects are as sensitive to temperature variations as the Beijing and Tianjin subjects; the minimum value of PPD (7.5%) is similar to the Tianjin occupants; both the sensitivity and the minimum value of PPD are lower than those of the foreign field studies.     

Future trends of building heating and cooling loads and energy consumption in different climates

Principal component analysis of dry-bulb temperature, wet-bulb temperature and global solar radiation was considered, and a new climatic index (principal component Z) determined for two emissions scenarios – low and medium forcing. Multi-year building energy simulations were conducted for generic air-conditioned office buildings in Harbin, Beijing, Shanghai, Kunming and Hong Kong, representing the five major architectural climates in China. Regression models were developed to correlate the simulated monthly heating and cooling loads and building energy use with the corresponding Z. The coefficient of determination (R²) was largely within 0.78–0.99, indicating strong correlation. A decreasing trend of heating load and an increasing trend of cooling load due to climate change in future years were observed. For low forcing, the overall impact on the total building energy use would vary from 4.2% reduction in severe cold Harbin (heating-dominated) in the north to 4.3% increase in subtropical Hong Kong (cooling-dominated) in the south. In Beijing and Shanghai where heating and cooling are both important, the average annual building energy use in 2001–2100 would only be about 0.8% and 0.7% higher than that in 1971–2000, respectively.     

覆土建筑冬季室内热舒适性研究

通过对西安地区某覆土建筑冬季室内热环境的测试,分析了测试房与对比房的温度测试数据。结果表明测试房内各测点逐时温度均高于对比房,室内温度变化幅度也明显小于对比房,且覆土建筑的室内温度略高于当地室内设计采暖温度。在测试的基础上采用主观温度法对室内热舒适性进行参考性评价,结果显示测试房室内热环境较好地满足了使用者对热舒适的需求。因此,覆土建筑在冬季能够有效维持室内温度,提高热舒适性,同时能够降低建筑采暖能耗。     

CFD study on effect of the air supply location on the performance of the displacement ventilation system

The purpose of this paper is to investigate using a numerical simulation (computational fluid dynamics or CFD) the effect of the air supply location on the design and performance of the displacement ventilation (DV) system. The results are reported in terms of thermal comfort and indoor air quality. The study focuses on the typical Hong Kong office under local thermal and boundary conditions. This includes the high cooling load used in Hong Kong. Several pollutants typically found in the office such as carbon dioxide and volatile organic compounds (VOCs) were investigated. The results indicate that the supply should be located near the center of the room rather than to one side of the room. This will provide a more uniform thermal condition in the office. The DV system was found to be effective in dispersing VOCs within an office environment for all cases studied. The exhaust was found to have minimal effect on the thermal comfort. For a DV system in Hong Kong, it is possible to use 100% fresh air without extra energy consumption.     

Parametric study on the performance of green residential buildings in China

The parametric study of the indoor environment of green buildings focuses on the quantitative and qualitative improvement of residential building construction in China and the achievement of indoor thermal comfort at a low level of energy use. This study examines the effect of the adaptive thermal comfort of indoor environment control in hot summer and cold winter (HSCW) zones. This work is based on a field study of the regional thermal assessment of two typical cases, the results of which are compared with simulated results of various scenarios of “energy efficiency” strategy and “healthy housing” environmental control. First, the simulated results show that the adaptive thermal comfort of indoor environment control is actually balanced in terms of occupancy, comfort, and energy efficiency. Second, adaptive thermal comfort control can save more energy for heating or cooling than other current healthy housing environmental controls in China's HSCW zone. Moreover, a large proportion of energy use is based on the subjective thermal comfort demand of occupants in any building type. Third, the building shape coefficient cannot dominate energy savings. The ratio of the superficial area of a building to the actual indoor floor area has a significant positive correlation with and affects the efficiency of building thermal performance.     

People who live in a cold climate: thermal adaptation differences based on availability of heating

Are there differences in thermal adaptation to cold indoor environments between people who are used to living in heating and non‐heating regions in China? To answer this question, we measured thermal perceptions and physiological responses of young men from Beijing (where there are indoor space heating facilities in winter) and Shanghai (where there are not indoor space heating facilities in winter) during exposures to cold. Subjects were exposed to 12°C, 14°C, 16°C, 18°C, 20°C for 1 h. Subjects from Beijing complained of greater cold discomfort and demonstrated poorer physiological acclimatization to cold indoor environments than those from Shanghai. These findings indicate that people's chronic indoor thermal experience might be an important determinant of thermal adaptation.     

寒冷地区被动式太阳能系统集热部件玻璃热性能研究——以陕西西安农村为例

目前节能玻璃种类繁多,不同气候区建筑外围护结构透光部分选用的玻璃也有所不同.对于采用被动式太阳能系统的建筑,不可盲目使用节能玻璃作为集热部件.被动式太阳能系统集热部件的关键部件(玻璃及框材)应根据气候条件因地制宜的选用.分析了西安农村地区常用的各种节能玻璃的传热系数、太阳能得热系数等性能指标,得出适宜应用在寒冷地区被动式太阳能建筑集热部件的节能玻璃类型.此种材料可有效地提高太阳能得热和室内热环境的舒适度,减少采暖能耗.     

Thermal sensation of Hong Kong people with increased air speed,temperature and humidity in air-conditioned environment

In the warm and humid climate zone, air-conditioning (AC) is usually provided at working places to enhance human thermal comfort and work productivity. From the building sustainability point of view, to achieve acceptable thermal sensation with the minimum use of energy can be desirable. A new AC design tactic is then to increase the air movement so that the summer temperature setting can be raised. A laboratory-based thermal comfort survey was conducted in Hong Kong with around 300 educated Chinese subjects. Their thermal sensation votes were gathered for a range of controlled thermal environment. The result analysis shows that, like in many other Asian cities, the thermal sensation of the Hong Kong people is sensitive to air temperature and speed, but not much to humidity. With bodily air speed at 0.1–0.2 m/s, clothing level 0.55 clo and metabolic rate 1 met, the neutral temperature was found around 25.4 °C for sedentary working environment. Then recommendations are given to the appropriate controlled AC environment in Hong Kong with higher airflow speeds.     

Bayesian adaptive comfort temperature (BACT) of air-conditioning system in subtropical climate

Indoor thermal climate is an important issue affecting the health and productivity of building occupants. In the designing of commercial air-conditioning systems, it is believed that the conventional fixed temperature set point concept is limited because indoor comfort temperature depends on the business culture, such as the nature of activities and dress code of occupants, etc. Researchers have been interested in investigating adaptive temperature control for a realistic in-situ control of comfort. Unfortunately, those studies put great emphasis on energy saving opportunities and sometimes might result in thermal discomfort to individuals. This study argues that complaints of thermal discomfort from individuals, despite representing only a small portion of the population, should not be ignored and can be used to determine the temperature setting for a population in air-conditioned environment. In particular, findings of a new notion of Bayesian adaptive comfort temperature (BACT) in air-conditioned buildings in a humid and subtropical climate like Hong Kong are reported, and the adaptive interface relationship between occupants’ complaints of thermal discomfort and indoor air temperature is determined. This BACT algorithm is intended to optimise the acceptance of thermal comfort, as determined by physical measurements and subjective surveys.     

上海高层住宅室内热舒适研究

在近两年的冬夏季节,现场测试了上海高层住宅室内温度和相对湿度、风速等参数,并通过问卷方式调查了住户的热环境状况。调查结果表明,在自然通风条件下,冬夏两季上海高层住宅的热环境皆处于ASHRAE给定的舒适区之外,实测计算结果与问卷统计结果存在的差异,显示了上海居民对冬季热环境有一定的适应性。     

重庆中海拔村镇住宅毛细管供暖性能实测分析

夏热冬冷地区冬季室内阴冷潮湿、热舒适性差,属于非传统供暖区。通过对重庆村镇住宅供暖现状的调研,了解了该地区冬季室内热舒适状况和供暖需求。选取重庆村镇地区某住户,对实际供暖系统运行状况进行了测试,针对不同供水温度进行了供暖效果和运行能耗对比分析。结果表明,空气源热泵结合毛细管地板辐射供暖系统供水温度为35、40、45、50℃时均能满足冬季供暖需求,35℃工况下的耗电量仅占40、45、50℃工况下的83.0%、66.8%和57.7%。     

兼顾节能效益的建筑室内热舒适温度调整研究

各气候区居民对室内热舒适的要求随其穿着习惯、对热环境的适应能力等而异,采暖或制冷温度应有所差别,然而现有建筑节能设计标准按统一标准提供室温控制建议。采用ISO7730的PMV热舒适模型分析各气候区的合理参数,计算得到室内热舒适温度,并通过与实测值比较验证理论计算的合理性;在此基础上,分别计算按既有统一室温建议与热舒适温度控温的热舒适性和能耗,提出冬季适当提高采暖温度以提升热舒适度、夏季适当提高制冷温度以实现热舒适度和节能双赢的调整建议。     

Field study of human thermal comfort and thermal adaptability during the summer and winter in Beijing

This study was conducted during the summer and winter in Beijing. Classrooms and offices in a university were used to conduct the survey. The respondents’ thermal sensation and thermal adaptability in both seasons were analyzed. During the study, indoor environmental parameters including air temperature, mean radiant temperature, relative humidity, and air velocity were measured. The respondents’ thermal sensation was determined by questionnaire.A relationship between indoor temperature and thermal sensation was found. In the summer study, the “scissors difference” between TSV and PMV was observed in the air-conditioned environments if the temperature was out of the neutral zone. People had higher tolerance in the hot environment than PMV predicted. During winter, the outdoor temperature had a prominent influence on thermal adaptability. The low outdoor temperature made people adapt to the cold environment. When the indoor temperature was heated to a high temperature by space heating facilities, respondents felt uncomfortable since their adaptability to the cold environment was nullified.Furthermore, the differences in thermal responses between respondents from North and South China showed that the different climates of people's native regions also affected their thermal comfort and adaptability.     

Statistical analyses on winter energy consumption characteristics of residential buildings in some cities of China

The purposes of this paper are to analyze winter energy use of residential buildings in different cities of China, and to figure out the influence factors of winter residential energy use. The investigated residences were located in seven typical cities of five architectural thermotechnical design zones. Questionnaire surveys revealed building characteristics, household characteristics, the utilization of domestic appliances, and thermal environment in winter. Winter energy consumption in different cities bears obvious regional characteristics. In south China, Hong Kong has the largest mean household energy use amount, and Changsha and Chongqing follow Hong Kong; Kunming in the warm zone has the small energy use. In north cities, if district space heating is excluded from total energy use, Urumqi and Xi’an have the energy use at the smallest level, but space heating use is very huge. The energy use amounts of space heating of Tangshan, Urumqi and Xi’an are several times as large as the amounts of all the end uses in the southern cities. The analysis on influence factors of winter energy use are made for Chongqing and Hong Kong, respectively, by Quantification Theory I, and the results show there exist obvious differences in influence factors between the two cities.     

Statistical analyses on summer energy consumption characteristics of residential buildings in some cities of China

The purposes of this paper are to analyse energy consumption characteristics and to find out influence factors of residential energy consumption in summer in typical cities of China. The investigated residences were located in seven cities of five architecture thermotechnical design zones. Questionnaire surveys revealed housing unit characteristics, household characteristics, the possession and utilization of domestic energy consuming appliances and indoor thermal environment in summer. Energy consumption analyses show that summer energy consumption amounts in different cities bear distinct regional characteristics: the household amounts of electricity use are largest in Hongkong, and the values are smaller but still at a high level in Beijing, Shanghai and Changsha, and at the smallest level in Kunming, Harbin and Urumqi, while the difference in gas use is small among these cities. Influence factor analyses show that city locations, housing unit characteristics, the utilization of space coolers and water heaters, household characteristics, and subjective evaluation of indoor thermal environment all contribute to the residential energy consumption in summer when taking all the families in the seven cities as the sample collectivity, while detail analyses for separate cities shows each city has its own characteristics. In Shanghai, the satisfaction rate of thermal environment, the possession and operation of air conditioners and housing unit characteristics greatly affect the summer energy consumption, but the electrical fan is judged as the non-influence factor, while in Urumqi, the possession and operation of electrical fans and the categories of water heaters have remarkable effect, and the influence of housing unit characteristics is also distinct, but the number of air conditioners and their usage contribute little to energy use due to the cool climate.     

香港地区应用干式风机盘管系统节能和室内空气品质分析

冷板辐射加置换通风空词系统在保证室内环境的前提下比常规全空气空调系统节能,但在天气湿热的香港地区应用会出现冷板凝露现象,且采用置换通风方式,风量有限从而影响热舒适性.本文将干式风机盘管系统与独立除湿通风系统组合应用于香港地区办公楼,干式风机盘管系统处理室内显热负荷,独立除湿通风系统承担室内湿负荷和室外全热负荷.采用EnergyPlus软件模拟分析了该空调系统在香港地区某办公楼中的使用性能,结果表明该系统能很好地控制室内温、湿度,特别是湿度,与常规全空气空调系统相比,全年节能达10.3%.     

哈尔滨地区既有住宅冬季室内热环境研究及其优化设计

2013年对哈尔滨地区部分既有住宅室内温度测试发现:典型起居室室内平均温度16.2℃,点测90%室内不足18℃;遂采用正交实验法和全因素实验法对哈尔滨地区既有住宅就围护结构及采暖方式进行优化。对比Fluent模拟结果发现,当使用壁挂式采暖器时,采暖温度起主要影响作用,以EPS保温板为例:370 mm外墙选用90 mm厚保温层、PVC三玻窗、采暖器表面温度65℃。当采用表面温度23℃低温辐射供暖时,保温层对其影响较大,370 mm外墙选用100 mm厚保温层、20 mm双玻塑钢窗,当墙体厚度为490 mm时将保温层减少5 mm。     

New concepts and approach for developing energy efficient buildings: Ideal specific heat for building internal thermal mass

The shortcomings or limitations of the traditional approach to developing energy efficient buildings are that they can not determine: (1) the ideal thermophysical properties of building envelope material, where “ideal” means that such material can use ambient air temperature variation and/or solar radiation efficiently to keep the indoor air temperature in the thermal comfort range with no additional space heating or cooling; (2) the best natural ventilation strategy; (3) the minimal additional energy consumption for space heating in winter or air-conditioning in summer. To overcome these problems, some new concepts for developing energy efficient buildings are put forward in this paper. They are the ideal thermophysical properties of the building envelope material, the ideal natural ventilation rate, and a minimal additional space heating or cooling energy consumption. A new approach for determining these properties is also developed. In contrast to the traditional approach (the thermophysical properties of building envelope material are known and constant so that the relating equations describing the indoor air temperature tend to be linear differential equations), the new approach solves the inverse problem (thermophysical properties, etc. of a buildings are unknown), whose solution can be a function instead of a value. As a first step, the ideal specific heat of the building envelope material for internal thermal mass is analyzed for buildings located in various cities in different climatic regions of China, such as Beijing, Shanghai, Harbin, Urumchi, Lhasa, Kunming and Guangzhou. We found that the ideal specific heat is composed of a basic value and an excessive one which is of δ function for the cases studied. Some limitations that would need further study are introduced in the end of the paper.