Thermal perception,adaptation and attendance in a public square in hot and humid regions

Highly relevant to an individual's thermal perception, the thermal environment in outdoor public spaces impacts the use of such spaces. Thermal adaptation, which involves physiological, psychological and behavioral factors, also plays an important role in assessment of thermal environments by users. Given that these issues have rarely been addressed for outdoor environments in hot and humid regions, this study examines user thermal comfort in a public square in Taiwan. Physical measurements were taken and a questionnaire survey was used to assess the thermal comfort of subjects. The number of people visiting the square was also counted. Analytical results indicate that the thermal comfort range and neutral temperature of subjects was higher than those of people in a temperate region. Additionally, local subjects preferred a cool temperature and weak sunlight, and adapted to thermal environments by seeking shelter outdoors. Analytical results confirm the existence of thermal adaptation and illustrate the characteristics of, and variances in, thermal adaptation. During the cool season, the number of people visiting the square increased as the thermal index value increased. However, the number of people frequenting the square decreased as the thermal index increased during the hot season. These experimental results were compared with those for temperate regions, indicating that the human energy balance model cannot fully explain the influence of climate on use of public spaces; that is, psychological and behavioral factors also play important roles in outdoor thermal comfort. Study findings also elucidate design of outdoor public spaces in hot and humid regions.     

Air movement acceptability limits and thermal comfort in Brazil's hot humid climate zone

In hot humid climates, natural ventilation is an essential passive strategy in order to maintain thermal comfort inside buildings and it can be also used as an energy-conserving design strategy to reduce building cooling loads by removing heat stored in the buildings thermal mass. In this context, many previous studies have focused on thermal comfort and air velocity ranges. However, whether this air movement is desirable or not remains an open area. This paper aims to identify air movement acceptability levels inside naturally ventilated buildings in Brazil. Minimal air velocity values corresponding to 80% and 90% (V80 and V90) air movement acceptability inside these buildings. Field experiments were performed during hot and cool seasons when 2075 questionnaires were filled for the subjects while simultaneous microclimatic observations were made with laboratory precision. Main results indicated that the minimal air velocity required were at least 0.4 m/s for 26 °C reaching 0.9 m/s for operative temperatures up to 30 °C. Subjects are not only preferring more air speed but also demanding air velocities closer or higher than 0.8 m/s ASHRAE limit. This dispels the notion of draft in hot humid climates and reinforce the broader theory of alliesthesia and the physiological role of pleasure due to air movement increment.     

Effect of building interface form on thermal comfort in gymnasiums in hot and humid climates

The thermal environment and thermal comfort of a building are greatly affected by the design of the building interface form. Most contemporary architectural designs consider only the relations between architectural form and architectural beauty. Few studies on the correlation of architectural form and thermal comfort address the influence of architectural form on thermal comfort and thermal environment. These studies are particularly important for gymnasium architectures located in hot and humid areas, which have high requirements for thermal comfort. This paper presents an experimental investigation and an analysis of the effect of the building interface form of gymnasiums on thermal comfort in hot and humid subtropical regions durings ummer. Results showed that the influence of the top interface forms on thermal comfort is mainly dominated by the mean radiant temperature, which could be controlled to improve thermal comfort. The influence of side interface forms on thermal comfort is mainly dominated by air velocity, and thermal comfort could be improved by promoting natural ventilation on the side interface form design to reduce indoor heat. This research enhanced our understanding of the relation between the interface form and the thermal comfort of gymnasiums. In addition, this paper provides a theoretical reference for the sustainable design of gymnasiums in hot and humid climates.     

Thermal comfort and IAQ characteristics of naturally/mechanically ventilated and air-conditioned bedrooms in a hot and humid climate

The characteristics of thermal comfort and indoor air quality (IAQ) in bedrooms, occupants’ perceptions and their impact on sleep quality are not often studied. It becomes even more interesting if climatic conditions allow Naturally/Mechanically Ventilated (NMV) concepts as opposed to Air-conditioning (AC) and this becomes very significant from an energy perspective. This paper reports our findings from such a study conducted in a hot and humid climate. Objective measurements of thermal comfort and IAQ were carried out during sleeping period in 12 NMV and 12 AC bedrooms over a period of 2 months. Questionnaire responses were sought from each subject at the end of the objective measurements to assess their perceptions on thermal comfort and indoor air quality of the bedrooms during sleep and their sleeping conditions. Although the “Historical” and “Immediate” responses for the NMV and AC bedrooms indicate that there was a good level of acceptability for both Thermal Comfort and Perceived Air Quality (PAQ), it was found that NMV bedroom was a better sleeping environment. The subjects’ immediate perception of PAQ and thermal comfort were reasonably correlated with their historical perceptions. The subjects’ perception of PAQ was fairly closely correlated to their perception of Thermal Comfort. There was a considerable increase in the carbon dioxide level in an AC bedroom relative to a NMV bedroom. However, there was no clear evidence to substantiate that sleeping duration decreased with increasing level of carbon dioxide, but the findings do suggest that high level of carbon dioxide may hinder the duration of sleep.     

Combined thermal acceptability and air movement assessments in a hot humid climate

In the ASHRAE comfort database [1], underpinning the North American naturally ventilated adaptive comfort standard [2], the mean indoor air velocity associated with 90% thermal acceptability was relatively low, rarely exceeding 0.3 m/s. Post hoc studies of this database showed that the main complaint related to air movement was a preference for ‘more air movement’ 3 and 4. These observations suggest the potential to shift thermal acceptability to even higher operative temperature values, if higher air speeds are available. If that were the case, would it be reasonable to expect temperature and air movement acceptability levels at 90%? This paper focuses on this question and combines thermal and air movement acceptability percentages in order to assess occupants. Two field experiments took place in naturally ventilated buildings located on Brazil’s North-East. The fundamental feature of this research design is the proximity of the indoor climate observations with corresponding comfort questionnaire responses from the occupants. Almost 90% thermal acceptability was found within the predictions of the ASHRAE adaptive comfort standard and yet occupants required ‘more air velocity’. Minimum air velocity values were found in order to achieve 90% of thermal and air movement acceptability. From 24 to 27 °C the minimum air velocity for thermal and air movement acceptability is 0.4 m/s; from 27 to 29 °C is 0.41–0.8 m/s, and from 29 to 31 °C is >0.81 m/s. These results highlight the necessity of combining thermal and air movement acceptability in order to assess occupants’ perception of their indoor thermal environment in hot humid climates.     

Thermal comfort in naturally ventilated buildings in hot-humid area of China

Human responses to thermal environments in naturally ventilated (NV) buildings in hot-humid area of China were systematically investigated in the present study. Thirty local inhabitants long-time living in NV buildings participated in the study and reported their thermal sensations and perceptions and adaptive behaviors while all physical and personal variables were collected. Based on a year-long survey, a close match of indoor physical variables and occupants’ clothing insulation with outdoor climate was found as an important feature of NV buildings. Integrated indices can capture more thermal contexts in the NV buildings in hot-humid area of China than simple indices. Thermal sensation was found to be a good linear function of SET* with the thermal neutrality of 25.4 °C and the 90% (80%) acceptable range of 23.5–27.4 °C (22.1–28.7 °C) in SET*. The adaptive evidences were obtained for clothing adjustment, window opening and using fan respectively and the modified PMV model was validated to be applicable in NV buildings in hot-humid area of China with an expectancy factor of 0.822. Comparisons with other field studies indicate that people can develop various human-environment relationships through thermal adaptation to local climate, resulting in different thermal neutral temperatures in various climates. The subjects in hot-humid area of China are more acclimated and tolerable with hot and humid environments and more uncomfortable and intolerable with cold environments while compared with those in temperate climates.     

Productivity model in hot and humid environment based on heat tolerance time analysis

Thermal environment is one of the most important factors that have impact on workers' productivity. There are many hot and humid workshops in China, whose thermal environment characteristics are the high temperature, high humidity and little radiation intensity. Working in hot and humid environment for a long time not only can extremely do harm to human body health, but also probably induce accidents due to the fall of productivity. In this paper, human body experiment and statistics analysis with the software of EXCEL were applied to establish a heat tolerance time model and a productivity model in hot and humid environment. Firstly, a chamber stimulating hot and humid environment was built and the experiment on heat tolerance and productivity in this chamber was completed. Heat tolerance time and productivity in different environments were tested with the change of air temperature and humidity in the environment chamber. According to the experiment results, regressive formulas for heat tolerance time changing with thermal environment parameter (WBGT) in three conditions of physical labour intensity were provided by statistics methods respectively. On this basis, the function of productivity changing with heat tolerance time and thermal environment parameter (WBGT) in three conditions of physical labour intensity using multiple linear regression analysis tool of EXCEL were obtained finally. F-test was also applied to verify the significance of all the established regression equations. The result shows that the effect of curve regression is significant and the regression function gives important statistic meaning and practical value to work time determination and productivity prediction in hot and humid environment.     

Thermal acceptability assessment in buildings located in hot and humid regions in Brazil

The objective of this paper was to perform an analysis on thermal acceptability in naturally ventilated (NVB) and air-conditioned buildings (ACB) located in hot and humid climates in Brazil. Experiments were carried out in April and November 2005 with 1.301 questionnaires based on ISO 10551:1995(E). Indoor and outdoor climatic variables were monitored simultaneously. The results revealed that 53% of the occupants of NVB and 78% of ACB were thermally satisfied. However, some restrictions were observed with the applications of the following methodologies: ISO/FDIS 7730:2005(E); ANSI/ASHRAE Standard 55:2004; Adaptive Temperature Limits (ATG) and prEN15251: 2005(E). Differences were observed between thermal sensation (TSV) and predicted mean vote (PMV) and between the subject's percentages expressing thermal unacceptability of the environment and the PPD calculated according to ISO/FDIS 7730:2005(E).     

Outdoor thermal comfort: Analyzing the impact of urban configurations on the thermal performance of street canyons in the humid subtropical climate of Sydney

The quality of outdoor space is becoming increasingly important with the growing rate of urbanization. Visual, acoustic, and thermal balance degradation are all negative impacts associated with outdoor comfort in dense urban fabrics. Urban morphology thus needs assessment and optimization to ensure favorable outdoor thermal comfort (OTC). This study aims to evaluate the thermal performance of streets in residential zones of Liverpool, NSW, Australia, and tries to improve their comfort index (Physiological Equivalent Temperature) to reveal optimum urban configurations. This evaluation is done by investigating the following urban design factors affecting OTC using computational simulation techniques: street orientation, aspect ratio, building typology, and surface coverage. Our findings reveal that street canyon orientation is the most influential factor (46.42%), followed by aspect ratio (30.59%). Among the influential meteorological parameters (air temperature, wind speed, humidity and solar radiation), wind velocity had the most significant impact on the thermal comfort of the outdoor spaces in this coastal region, which typically experiences intense airflow. The results of our analysis can be utilized by multiple stakeholders, allowing them to understand and extract the most vital design factors which contextually influence the thermal comfort of outdoor spaces. Outdoor thermal comfort has a direct effect on the health and wellbeing of occupants of outdoor spaces.     

Thermal comfort and IAQ assessment of under-floor air distribution system integrated with personalized ventilation in hot and humid climate

The potential for improving occupants’ thermal comfort with personalized ventilation (PV) system combined with under-floor air distribution (UFAD) system was explored through human response study. The hypothesis was that cold draught at feet can be reduced when relatively warm air is supplied by UFAD system and uncomfortable sensation as “warm head” can be reduced by the PV system providing cool and fresh outdoor air at the facial level. A study with 30 human subjects was conducted in a Field Environmental Chamber. The chamber was served by two dedicated systems – a primary air handling unit (AHU) for 100% outdoor air that is supplied through the PV air terminal devices and a secondary AHU for 100% recirculated air that is supplied through UFAD outlets. Responses of the subjects to the PV-UFAD system were collected at various room air and PV air temperature combinations. The analyses of the results obtained reveal improved acceptability of perceived air quality and improved thermal sensation with PV-UFAD in comparison with the reference case of UFAD alone or mixing ventilation with ceiling supply diffuser. The local thermal sensation at the feet was also improved when warmer UFAD supply air temperature was adopted in the PV-UFAD system.     

我国湿热地区人群基础热舒适反应研究(2):研究结果的对比分析

基于我国湿热地区人群的气候室实验结果,从心理热反应、生理热反应和生理-心理关系等多方面对国内外研究结果进行了系统对比与分析,发现现行国际标准不适用于我国湿热地区,生理热习服和心理热适应是其重要原因。考虑热习服和热适应的影响作用,建立我国湿热地区人群的生理热调节模型与心理-生理模型,是掌握其基础热舒适反应规律、合理制定热环境标准的重要途径。     

Evaluating thermal comfort conditions and health responses during an extremely hot summer in Athens

In summer 2007, in the city of Athens, Greece, extremely high air temperatures were recorded, inducing heat discomfort conditions in the urban environment. Four biometeorological indices were calculated in order to evaluate human thermal sensation and thermal comfort: Actual Sensation Vote (ASV), Thermal Sensation-Ginovi method (TS), Discomfort Index (DI) and Heat Load Index (HL). Data included measurements of ambient temperature, temperature of the surrounding ground surface, relative humidity, air pressure, wind velocity and solar radiation obtained from National Observatory of Athens (NOA) station. During this period the daily number of patients probably affected by heat in emergency department units of cardiac clinics of four public general hospitals in Athens was recorded. The results revealed high values of DI and HL indices, demonstrating severe heat stress conditions during the last ten day period of June and July, while the ASV tends to classify too many cases into the comfort zone compared to TS, DI and HL. The statistical analysis revealed a negative relationship between the number of heat affected patients and the estimated indices values.     

Effect of age, gender, economic group and tenure on thermal comfort: A field study in residential buildings in hot and dry climate with seasonal variations

Energy consumption in Indian residential buildings is one of the highest and is increasing phenomenally. Indian standards specify comfort temperatures between 23 and 26 °C for all types of buildings across the nation. However, thermal comfort research in India is very limited. A field study in naturally ventilated apartments was done in 2008, during the summer and monsoon seasons in Hyderabad in composite climate. This survey involved over 100 subjects, giving 3962 datasets. They were analysed under different groups: age, gender, economic group and tenure. Age, gender and tenure correlated weakly with thermal comfort. However, thermal acceptance of women, older subjects and owner-subjects was higher. Economic level of the subjects showed significant effect on the thermal sensation, preference, acceptance and neutrality. The comfort band for lowest economic group was found to be 27.3-33.1 °C with the neutral temperature at 30.2 °C. This is way above the standard. This finding has far reaching energy implications on building and HVAC systems design and practice. Occupants’ responses for other environmental parameters often depended on their thermal sensation, often resulting in a near normal distribution. The subjects displayed acoustic and olfactory obliviousness due to habituation, resulting in higher satisfaction and acceptance.     

A new type of double-skin façade configuration for the hot and humid climate

The performance of the double-skin façade depends closely on the chosen ventilation means within its intermediate space. The modes of ventilation could be natural (buoyancy driven), forced (mechanically driven) or mixed (both natural and forced). Oesterle et al. has attempted to classify the double-skin constructions into four different types, namely box window façade, shaft-box façade, corridor façade and multi-story façade. A number of interesting investigations and findings are reported in the literature pertaining to passive ventilation in buildings and the thermal performance of double-skin facades. The researches have revealed close link between natural ventilation design and the function of double-skin façade. Most of them are using the idea of stack effect or the solar chimney concept and found that passive ventilation in summer is possible even for multi-storey buildings. It was found that significant energy saving is possible if natural ventilation could be exploited through the use of double-skin façade. In this research, CFD was used to analyse various thermal comfort parameters with different double façade configurations to determine a new type of double-skin façade configurations which will provide a better indoor thermal comfort in the hot and humid climate through natural ventilation strategies for the high-rise buildings.     

A comparison of the thermal adaptability of people accustomed to air-conditioned environments and naturally ventilated environments

It has been reported previously that people who are acclimated to naturally ventilated (NV) environments respond to hot and warm environments differently than people who are acclimated to air-conditioned (AC) environments. However, it is not clear whether physiological acclimatization contributes to this discrepancy. To study whether living and working in NV or AC environments for long periods of time can lead to different types of physiological acclimatization, and whether physiological acclimatization has an important influence on people's responses of thermal comfort, measurements of physiological reactions (including skin temperature, sweat rate, heart rate variability, and heat stress protein 70) and thermal comfort responses were conducted in a 'heat shock' environment (climate chamber) with 20 people (10 in the NV group and 10 in the AC group). The results showed that the NV group had a significantly stronger capacity for physiological regulation to the heat shock than the AC group. In other words, the NV group did not feel as hot and uncomfortable as the AC group did. These results strongly indicate that living and working in indoor thermal environments for long periods of time affects people's physiological acclimatization. Also, it appears that long-term exposure to stable AC environments may weaken people's thermal adaptability. PRACTICAL IMPLICATIONS: This study examined the psychological and physiological differences of thermal adaptability of people used to air-conditioned environments and naturally ventilated environments. The results suggested that long-term exposure to stable air-conditioned environments may weaken people's thermal adaptability. Therefore, it might be advantageous for people to spend less time in static air-conditioned environments; this is not only because of its possible deleterious impact on people's physiological adaptability, but also because the air-conditioners' high-energy consumption will contribute to the effects of global warming.     

Numerical study on the effects of aspect ratio and orientation of an urban street canyon on outdoor thermal comfort in hot and dry climate

This paper discusses the contribution of street design, i.e. aspect ratio (or height-to-width ratio, H/W) and solar orientation, towards the development of a comfortable microclimate at street level for pedestrians. The investigation is carried out by using the three-dimensional numerical model ENVI-met, which simulates the microclimatic changes within urban environments in a high spatial and temporal resolution. Model calculations are run for a typical summer day in Ghardaia, Algeria (32.40°N, 3.80°E, 469 m a.s.l.), a region characterized by a hot and dry climate. Symmetrical urban canyons, with various height-to-width ratios (i.e. H/W=0.5, 1, 2 and 4) and different solar orientations (i.e. E–W, N–S, NE–SW and NW–SE), have been studied. Special emphasis is placed on a human bio-meteorological assessment of these microclimates by using the physiologically equivalent temperature (PET).     

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.     

Thermal comfort and workplace occupant satisfaction—Results of field studies in German low energy office buildings

The issues of comfort and workspace quality in buildings have gained much importance with the European “Energy Performance of Buildings Directive” of 2001. New energy efficient building concepts and technologies require a revision of comfort standards, which were developed for air-conditioned buildings only. Particularly, the question of recommendable upper indoor temperature limits needs further investigation. In addition, a broader approach to occupant satisfaction in buildings is necessary with respect to overall building performance.     

Energy analysis of the personalized ventilation system in hot and humid climates

Personalized ventilation (PV) is an individually controlled air distribution system aimed at improving the quality of inhaled air and the thermal comfort of each occupant. Numerous studies have shown that PV in comparison with traditional mechanical ventilation systems may improve occupants’ health, inhaled air quality, thermal comfort, and self-estimated productivity. Little is known about its energy performance.In this study, the energy consumption of a personalized ventilation system introduced in an office building located in a hot and humid climate (Singapore) has been investigated by means of simulations with the empirically tested IDA-ICE software. The results reveal that the use of PV may reduce the energy consumption substantially (up to 51%) compared to mixing ventilation when the following control strategies are applied: (a) reducing the airflow rate due to the higher ventilation effectiveness of PV; (b) increasing the maximum allowed room air temperature due to PV capacity to control the microclimate; (c) supplying the outdoor air only when the occupant is at the desk. The strategy to control the supply air temperature does not affect the energy consumption in a hot and humid climate.     

我国湿热地区人群基础热舒适反应研究(1):实验方法与结果

采用经典热舒适研究方法,于2008年夏季对我国湿热地区典型人群受试者作了气候室实验,在凉-暖范围内6个不同温湿度组合的工况下进行了问卷投票和生理指标测试。结果显示,受试者的热中性温度为26.9℃(修正温度);受试者夏季偏爱稍凉的热感觉(-0.2);潮湿感中性对应的水蒸气分压力约为3500Pa;热中性对应的平均皮肤温度为33.2℃;平均皮肤温度与皮肤湿润度是预测热感觉与热舒适的重要参数;心率与热感觉存在线性关系,血压在偏凉环境下与热感觉呈线性关系,在偏暖环境下变化不大。