Adaptive thermal comfort in Australian school classrooms

This survey of thermal comfort in classrooms aimed to define empirically the preferred temperatures, neutral temperatures and acceptable temperature ranges for Australian school children, and to compare them with findings from adult populations. The survey was conducted in a mixture of air-conditioned, evaporative-cooled and naturally ventilated classrooms in nine schools located in three distinct subtropical climate zones during the summer of 2013. A total of 2850 questionnaires were collected from both primary (grade) and secondary (high) schools. An indoor operative temperature of about 22.5°C was found to be the students’ neutral and preferred temperature, which is generally cooler than expected for adults under the same thermal environmental conditions. Despite the lower-than-expected neutrality, the school children demonstrated considerable adaptability to indoor temperature variations, with one thermal sensation unit equating to approximately 4°C operative temperature. Working on the industry-accepted assumption that an acceptable range of indoor operative temperatures corresponds to group mean thermal sensations of ?0.85 through to +0.85, the present analysis indicates an acceptable summertime range for Australian students from 19.5 to 26.6°C. The analyses also revealed between-school differences in thermal sensitivity, with students in locations exposed to wider weather variations showing greater thermal adaptability than those in more equable weather districts.     

Application of adaptive thermal comfort methods for Iranian schoolchildren

ABSTRACT

Recent studies in primary schools highlight a need to develop the adaptive comfort model for schoolchildren in classrooms. This study investigates the application of the principal methods underlying the adaptive comfort theory for children relating thermal comfort indoors to the prevailing mean outdoor temperature. Children’s sensitivity to indoor temperature change are examined using data from a field study conducted in Iranian schools. This sensitivity is used to estimate the comfort temperatures in classroom situations with a minimum level of adaptation. Different metrics for the outdoor climate are employed to understand an expression of the climate which best predicts children’s comfort temperature. A sensitivity analysis is performed to derive the relation between indoor comfort and the climate that gives rise to the strongest correlation coefficient. Although the basic adaptive comfort relationships are applicable for children, the exponential method to calculate the prevailing mean with lower decay values leads to higher correlation with children’s comfort temperature. The slope of children’s comfort equation in relation to outdoor temperature is shown to be shallower than those of adults. Results indicate that children are more sensitive to temperature change within a single school day than across the overall survey period of several days.     

Field study on occupants’ thermal comfort and residential thermal environment in a hot-humid climate of China

This paper discusses thermal comfort inside residences of three cities in the hot-humid climate of central southern China. Only a few thermal comfort studies have been performed in hot-humid climates and none in Central Southern China. Field sampling took place in the summers of 2003 and 2004 by obtaining 110 responses to a survey questionnaire and measuring environmental comfort variables in three rooms in each of 26 residences. The objectives are to measure and characterize occupant thermal perceptions in residences, compare observed and predicted percent of dissatisfied and discern differences between this study and similar studies performed in different climate zones. Average clothing insulation for seated subjects was 0.54 clo with 0.15 clo of chairs. Only 48.2% of the measured variables are within the ASHRAE Standard 55-1992 summer comfort zone, but approximately 87.3% of the occupants perceived their thermal conditions acceptable, for subjects adapt to prevailing conditions. The operative temperature denoting the thermal environment accepted by 90% of occupants is 22.0–25.9°. In the ASHRAE seven-point sensation scale, thermal neutral temperature occurs at 28.6°. Preferred temperature, mean temperature requested by respondents, is 22.8°. Results of this study can be used to design low energy consumption systems for occupant thermal comfort in central southern China.     

Investigating the principal adaptive comfort relationships for young children

Thermal comfort surveys in school classrooms suggest that children have different thermal preferences to adults. This implies a need to revisit the current adult-based thermal comfort models. This paper investigates the principal adaptive comfort relationships that form the basis of adaptive comfort theory, using 2693 pupil thermal sensation responses and measured classroom temperatures from surveys in two naturally ventilated school buildings. The data were examined in two steps. Firstly, each survey set, obtained over one-day visits to the schools, was examined in order to derive the relationship between indoor temperature change and comfort vote with minimum impact of adaptation. Secondly, the data set was investigated over the entire survey period in relation to the weather experienced by the pupils in order to estimate their time for adaptation to outdoor temperature changes. The analysis shows that the basic adaptive comfort relationships are valid for children. However, a difference was found for the correlation coefficients of the comfort temperature to the outdoor running mean temperature between the schools, and a mismatch between their adaptive comfort equations. It is proposed that the difference in the consistency of the weather during the tests is the main reason for this discrepancy.     

Predicted percentage dissatisfied with ankle draft

Draft is unwanted local convective cooling. The draft risk model of Fanger et al. (Energy and Buildings 12 , 21‐39, 1988) estimates the percentage of people dissatisfied with air movement due to overcooling at the neck. There is no model for predicting draft at ankles, which is more relevant to stratified air distribution systems such as underfloor air distribution (UFAD) and displacement ventilation (DV). We developed a model for predicted percentage dissatisfied with ankle draft (PPD_AD) based on laboratory experiments with 110 college students. We assessed the effect on ankle draft of various combinations of air speed (nominal range: 0.1‐0.6 m/s), temperature (nominal range: 16.5‐22.5°C), turbulence intensity (at ankles), sex, and clothing insulation (<0.7 clo; lower legs uncovered and covered). The results show that whole‐body thermal sensation and air speed at ankles are the dominant parameters affecting draft. The seated subjects accepted a vertical temperature difference of up to 8°C between ankles (0.1 m) and head (1.1 m) at neutral whole‐body thermal sensation, 5°C more than the maximum difference recommended in existing standards. The developed ankle draft model can be implemented in thermal comfort and air diffuser testing standards.     

Thermal comfort in environments with different vertical air temperature gradients

The use of displacement ventilation for cooling environments is limited by the vertical temperature gradient. Current standards recommend a temperature difference of up to 3 K/m between the head and the feet. This paper reviews the scientific literature on the effect of vertical temperature gradients on thermal comfort and compares this to the results of our own experiments. Early experiments have demonstrated a high sensitivity of dissatisfied test subjects to changes in the temperature gradient between head and foot level. Recent studies have indicated that temperature gradients of 4‐5 K/m are likely to be acceptable, and the mean room temperature may have a greater sensitivity on the percentage of dissatisfied (PD). In new experiments, test subjects have evaluated the thermal comfort of different vertical air temperature gradients in a modular test chamber, the Aachen comfort cube (ACCu), where they have assessed vertical temperature gradients of ΔT/Δy = 1, 4.5, 6, 8, and 12 K/m at a constant mean room temperature of 23°C. The results of the different temperature gradients are in contrast to ANSI/ASHRAE Standard 55 (Thermal Environmental Conditions for Human Occupancy, Atlanta GA, American Society of Heating, Refrigerating and Air Conditioning Engineers, 2013) as the PD increases almost constantly with higher vertical air temperature gradients. The PD for the overall sensation increases by approximately 7% between gradients of 1 and 8 K/m. The evaluation of our own tests has revealed that vertical temperature gradients of up to 8 K/m or higher are likely to be acceptable for test subjects.     

Adaptive thermal comfort in primary school classrooms: Creating and validating PMV-based comfort charts

In this research the thermal comfort and thermal comfort parameters for children in primary school classrooms has been investigated. Actual thermal sensation and clothing insulation of children (age 9–11) in non-air-conditioned classrooms in three different schools in the Netherlands have been obtained. Results are available for a total of 24 days, covering winter, spring and summer conditions (year 2010). Questionnaires have been applied to obtain the actual thermal sensation and clothing insulation in the morning and afternoon of regular school days. In this period physical parameters (temperature, relative humidity, etc.) were recorded as well in order to derive the PMV.     

Thermal comfort in residential buildings – Failure to predict by Standard model

A field study, conducted in 189 dwellings in winter and 205 dwellings in summer, included measurement of hygro-thermal conditions and documentation of occupant responses and behavior patterns. Both samples included both passive and actively space-conditioned dwellings. Predicted mean votes (PMV) computed using Fanger's model yielded significantly lower-than-reported thermal sensation (TS) values, especially for the winter heated and summer air-conditioned groups. The basic model assumption of a proportional relationship between thermal response and thermal load proved to be inadequate, with actual thermal comfort achieved at substantially lower loads than predicted. Survey results also refuted the model's second assumption that symmetrical responses in the negative and positive directions of the scale represent similar comfort levels. Results showed that the model's curve of predicted percentage of dissatisfied (PPD) substantially overestimated the actual percentage of dissatisfied within the partial group of respondents who voted TS > 0 in winter as well as within the partial group of respondents who voted TS < 0 in summer. Analyses of sensitivity to possible survey-related inaccuracy factors (metabolic rate, clothing thermal resistance) did not explain the systematic discrepancies. These discrepancies highlight the role of contextual variables (local climate, expectations, available control) in thermal adaptation in actual settings. Collected data was analyzed statistically to establish baseline data for local standardized thermal and energy calculations. A 90% satisfaction criterion yielded 19.5 °C and 26 °C as limit values for passive winter and summer design conditions, respectively, while during active conditioning periods, set-point temperatures of 21.5 °C and 23 °C should be assumed for winter and summer, respectively.     

哈尔滨市住宅环境热舒适测试结果分析

对哈尔滨市冬季居民热舒适现场研究结果做了进一步分析和总结，重点讨论了不同性别的人体热感觉和热中性温度及预测不满意百分数PPD的最小值问题，并与寒冷地区及其他热舒适现场研究结果进行了对比分析。     

Behavioural responses to cold thermal discomfort

Heating energy demand in buildings depends in part on occupants' behavioural responses to thermal discomfort during the heating season. The understanding of this has become one of the priorities in the quest to reduce energy demand. Thermal comfort models have long been associated with occupants' behaviour by predicting their state of thermal comfort or rather discomfort. These assumed that occupants would act upon their level of discomfort through three types of response: mechanisms of thermoregulation, psychological adaptation and behavioural responses. Little research has focused on the behavioural aspect. One of the key challenges is to gather accurate measurements while using discreet, sensor-based, observation methods in order to have minimum impact on occupants' behaviour. To address these issues, a mixed-methods approach is introduced that enables the establishment of a three-part framework for mapping behaviour responses to cold sensations: (1) increasing clothing insulation level; (2) increasing operative temperature by turning the heating system on/up; and (3) increasing the frequency, duration and/or amplitude of localized behaviour responses such as warm drink intake or changing rooms. Drawing on this framework, an extended model of thermal discomfort response is introduced that incorporates a wider range of observed behaviours.     

青海乡域中小学教室内学生冬季的热舒适性

对青海乡域4所典型中小学校10间教室冬季室内温湿度、风速、黑球温度等热环境参数进行现场测试,同时对420余名青少年学生的衣着情况、热感觉评价等进行了主观问卷调查。对测试和调查结果进行统计分析,得到实测和预测热中性温度分别为13.8和14.5℃,热期望温度为16.2℃,90%的学生感到满意的舒适温度范围为15.8~18.7℃。在当地寒冷的气候条件、学生衣着习惯、心理期望及生理特性等因素影响下,中小学生形成了对偏冷环境的适应性,提出可利用适应性PMV模型(aPMV)对中小学生平均热感觉进行准确预测。可为乡域中小学教室冬季热环境设计提供依据。     

焦作夏季居住建筑人体热舒适现场研究

采用环境参数测量与问卷调查同步进行的方式,研究了混合供冷模式下人们的热舒适性。结果显示,该地区夏季实测热中性温度为27.7℃,预测热中性温度为25.4℃,由热感觉法和直接询问法得到的80%可接受温度范围的上限分别为28.8℃和29.2℃,由这两种方法得到的期望温度分别为27.4℃和24.0℃;在混合供冷模式下,由于存在由空调环境进入非空调环境的情况,所以对热环境的不满意率要高于自然通风状态,可接受温度上限比自然通风状态低。     

热湿工况下工位辐射空调的热舒适实验研究

为研究热湿工况下使用工位辐射空调的人体热舒适情况,在人工环境实验室内,通过改变环境背景温度来影响人体的热感觉,并采用热感觉投票(TSV)作为评价标准,重点研究了人体头部、躯干、上肢、下肢以及整体热感觉情况。实验结果表明,尽管背景环境参数超出舒适范围,但使用工位辐射空调能维持受试者的舒适状态,即背景温度稳定在28℃时,平均整体热感觉投票值低于+0.2;背景温度为30℃时,受试者热感觉仍能满足ASHRAE规范中规定的80%可接受范围要求。     

湖南某大学校园建筑环境热舒适调查研究

对湖南某大学校园内建筑的环境热舒适度进行了现场调查和分析,采取现场测试与问卷调查相结合的方法。共测试了20间教室和5间学生宿舍,收集问卷调查表1273份。发现温度、风速、着衣热阻等参数对热舒适有明显的影响,但相对湿度对热舒适的影响不大。学生可接受的作用温度范围比ASHRAE标准规定的舒适区温度范围要宽得多,PMV指标与实际情况存在较大差别。讨论了适应性问题,推导出了室内舒适温度与室外平均温度之间的关系式,并将所得结果与其他研究成果进行了比较。     

我国湿热地区人群基础热舒适反应研究(3):冬夏对比分析

沿用经典热舒适研究方法,对我国湿热地区自然通风环境受试者分别进行夏季和冬季气候室实验,并对其心理反应与生理反应作冬夏季对比,得到其热反应的季节性变化特征为:与夏季相比,冬季的热感觉保持不变,但热舒适度与可接受度在低温环境显著降低,而在高温环境显著升高;心率显著增加,皮肤温度有所升高,在高温环境下的皮肤湿润度有所降低.季节性变化特征为湿热地区人群心理适应与生理习服提供了重要证据.     

Measurement of thermal stratification in large single-cell buildings

This paper describes measured temperature profiles and thermal stratification in eight aircraft hangar buildings during the heating season. Presented also is the predicted impact of thermal stratification on heating energy requirements. The hangar buildings included two main ceiling heights (9.35 and 17.1 m (31 and 56 ft)), two ceiling types (flat and Quonset), two types of heating systems (vertical discharge forced warm air and downdraft convective unit heaters), and various types of large external doors. Measured stratification, expressed by floor-to-ceiling temperature differential, is in the range 4–11 °C (7.2–20 °F). Two air layers existed in the hangar bay area, a warm upper air layer and a cooler lower air layer. The lower air layer (up to 2 m (7 ft) high from the floor) is characterised by a steep vertical temperature gradient in the range 0.8–2.6 °C/m (0.4–1.4 °F/ft). In the upper air layer, above 2 m, the vertical temperature gradient shallows considerably to 0.5 °C/m (0.3 °F/ft). Results indicate that thermal stratification can have a significant impact on the building's heating energy requirements. In the hangar buildings studied, predicted excess heating energy requirements due to 8 °C floor-to-ceiling temperature differential can be as much as 38% as compared to the case with no stratification.     

哈尔滨高校教室热舒适现场研究

为了研究高校教室在学生上课期间的热环境和人体热舒适,在哈尔滨高校教室进行了现场研究。在测量室内热舒适参数的同时,学生填写对室内环境的热感觉和热舒适主观调查表,共调查了1285人次,得到了1285份人体热反应的样本。现场测试结果表明,哈尔滨高校自然通风教室全年人体热中性温度为23.4℃(t0)。     

Thermal perceptions,general adaptation methods and occupant's idea about the trade-off between thermal comfort and energy saving in hot–humid regions

A field study conducted in workplaces and residences in Taiwan is carried out to clarify two questions in detail: (1) do people in the tropical climate regions demonstrate a correlation between thermal sensation and thermal dissatisfaction the same as the PMV–PPD formula in the ISO 7730; and (2) does the difference in opportunities to choose from a variety of methods to achieve thermal comfort affects thermal perceptions of occupants? A new predicted formula of percentage of dissatisfied (PD) relating to mean thermal sensation votes (TSVs) is proposed for hot and humid regions. Besides an increase in minimum rate of dissatisfied from 5% to 9%, a shift of the TSV with minimum PD to the cool side of sensation scale is suggested by the new proposed formula. It also reveals that the limits of TSV corresponding to 80% acceptability for hot and humid regions are −1.45 and +0.65 rather than −0.85 and +0.85 suggested by ISO 7730. It is revealed in the findings that the effectiveness, availability and cost of a thermal adaptation method can affect the interviewees' thermal adaptation behaviour. According to the discussion of interviewees' idea about the trade-off between thermal comfort and energy saving, it is found that an energy-saving approach at the cost of sacrificing occupant's thermal comfort is difficult to set into action, but those ensure the occupant's comfort are more acceptable and can be easily popularized.     

The Effects Of Air Temperature And Relative Humidity On Thermal Comfort In The Office Environment

The objective of this study was to assess the effect of air humidification and temperature on thermal comfort in sedentary office work. A blinded twelve-period cross-over trial was carried out in two similar wings of an office building, contrasting 28–39% steam humidification with no humidification, corresponding to 12–28% relative humidity. The length of each period was one working week. The study population was 169 workers who judged their thermal sensations in a weekly questionnaire. The percentage of dissatisfied was lowest when the air temperature was 22 °C. At 22 °C an increase in relative humidity raised the mean thermal sensation only slightly. At 20 °C when the air was humidified there were fewer workers who judged their air temperature as being too low. On the other hand, at 24 °C humidification increased the percentage of workers who judged their air temperature to be too high. The percentage of dissatisfied increased rapidly when the air temperature was outside of its optimum value, 22 °C. The percentage of workers complaining about draft increased when the air temperature was lower than 22 °C. Thus we consider that the temperature range from 20 to 24 °C during wintertime may be too wide without individual temperature control from the point vzew of thermal comfort. We recommend that the air temperature should be kept between 21 and 23 °C if no individual control is available. The best solution would be individual temperature control permitting adjustment of the temperature at 22 ± 2 °C.     

不同城市自然通风建筑热舒适状况研究

通过上海、长沙自然通风建筑内进行的人体热舒适调查研究，并结合有关文献中北京和天津热舒适研究的成果，对我国目前不同城市自然通风建筑内热舒适状况进行探讨。结果认为，我国自然通风建筑内热中性温度均略高于ASHRAE推荐范围，采用实测的舒适温度作为空调温度可节约大量的能量。