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In this paper, the authors first clarify the definition of building microclimate in free-running buildings and the relationship with summer thermal comfort. Next, field measurements were conducted to investigate the microclimate in a Chinese traditional vernacular house. Subsequently, the results of measurements were compared with a dynamic thermal and a CFD simulation in order to determine the building microclimate and thermal comfort of the present vernacular house over the period of an entire summer. The field measurements show the present Chinese vernacular house has its own independent building microclimate in summer, which is in accordance with the main character of microclimate in terms of different distributions of solar gain, air temperature and wind velocity in different spaces. The simulation results of the vernacular house could be matched well with the field measurements. According to the simulations, at night, a comfortable temperature could be obtained throughout most of the summer period whereas in the daytime the operative temperature was higher than the comfortable temperature for one-third of the summer period. Wind velocity in the semi-outdoor and outdoor spaces however, improves the thermal comfort significantly. The thermal comfort environment can thus not only change in time but also in space. This example of the vernacular building shows that it is possible to create comfortable conditions for the inhabitants when not only the indoor climate is taken into account but the whole building microclimate as defined in this paper. This paper also shows that the simulations can predict the building microclimate. [ABSTRACT FROM AUTHOR]

Abstract: The present paper presents a full procedure to develop an adaptive comfort model for South-East Asia. Meta-analysis on large number of observations from field surveys which were conducted in this region was employed. Standardization and bias control of the database were fully reported. Statistical tests of significance and weighted regression method applied in the analyses strengthened the reliability of the findings. This paper found a great influence of ‘Griffiths constant’ on the establishment of adaptive comfort equation and proposed an appropriate value. The adaptive comfort model generated is applicable to naturally ventilated building under hot and humid conditions of South-East Asia. The mean neutral comfort temperature (operative temperature, effective temperature, standard effective temperature) in naturally ventilated and air-conditioned building was compared and the differences have been discussed. The similar neutral standard effective temperature in both naturally ventilated and air-conditioned building proposes a new idea to implement SET* into building simulation tools to assess thermal comfort without the attention of building classification. Through the analysis, the effectiveness of behavioral adaptive actions on occupant''s thermal perception has been argued. The extended PMV-PPD model for hot humid conditions was examined and its applicability was recommended. Other comfort-related issues, the differences and similarities between various adaptive comfort models were also addressed. [Copyright &y& Elsevier]

Abstract Most thermal comfort standards and guidelines currently in use do not consider occupants' adaptive capabilities associated with real-world situations when predicting occupant thermal comfort in mechanically conditioned buildings, although the adaptive approach is commonly applied to naturally ventilated buildings. These standards are generally based on results derived from experiments conducted in climate-controlled chambers. In some cases, this can lead to overcooling of buildings while still not satisfying most of occupants. One common method to reduce peak electricity demand is via temporarily increasing cooling temperature setpoint during peak hours. However, the potential negative impacts on occupant thermal comfort and wellbeing calls for further study on this. This paper describes a study conducted on a university campus in the United States that investigated occupants' thermal sensation, acceptability, and preferences corresponding to increased cooling temperature setpoint in parts of the building that are temporarily occupied. The results revealed a potential for at least temporarily increasing cooling temperature setpoint (at least 2 °C) across this campus without impairing occupant thermal comfort. For operative temperatures between 22 and 24.5 °C, the average Actual Mean Vote (AMV) for the class sections remained in the ASHRAE comfort range and the self-reported thermal acceptability was above 80%. Occupants' thermal acceptability dropped to less than 80% when the temperature was increased to more than 24.5 °C, and the AMV values increased to more than 0.5 (on ASHRAE 7-point scale). The percentage of occupants who were involved in some sort of adaptive behavior did not considerably change with room temperature. Highlights • By temporarily increasing indoor operative temperature in campus classrooms from 21 to 25 °C, thermal acceptability remains above 80%. • At 23.5 °C, occupants' mean thermal preference and their actual mean votes equals zero, while thermal acceptability is above 90%. • Occupants' adaptive behavior in this study, with limited adaptive options, is not a function of the operative temperature. • Heat balance model under-predicts the percentage of dissatisfied occupants at environmental conditions warmer than neutral. [ABSTRACT FROM AUTHOR]

Advances in heating, ventilation and air conditioning (HVAC) technologies have dramatically improved the indoor thermal environment, but attention should be paid on how this would affect building occupants' thermal comfort perception. In this paper, we studied the mutually dependent relationship between indoor climate experience and occupants' comfort expectation. An intriguing experiment was conducted in China where wintertime indoor thermal environments in northern cities (with district heating) are much warmer than in southern region (without district heating). By analyzing the 4411 responses from four college-aged subject groups with different indoor thermal history, two interesting findings emerged. Firstly, people's understandings of thermal comfort change with their indoor thermal experiences. Those permanently live in lower-grade non-neutral thermal environment can achieve similar thermal comfort perception as those who live in long-term comfortable thermal conditions. Secondly, the dynamics of building occupants' thermal comfort adaptation project asymmetric trajectories. It is much quicker for occupants to accept neutral indoor climate than to lower their expectation and adapt to under-conditioned environments. These two phenomena can be well described by the index “demand factor”, which can serve as a reference for future thermal comfort study. [ABSTRACT FROM AUTHOR]

Buildings generate nearly 30% of global carbon emissions, primarily due to the need to heat or cool them to meet acceptable indoor temperatures. In the last 20 years, the empirically derived adaptive model of thermal comfort has emerged as a powerful alternative to fixed set-point driven design. However, current adaptive standards offer a simple linear relationship between the outdoor temperature and the indoor comfort temperature, assumed to sufficiently explain the effect of all other variables, e.g. relative humidity (RH) and air velocity. The lack of a signal for RH is particularly surprising given its well-known impact on comfort. Attempts in the literature to either explain the lack of such a signal or demonstrate its existence, remain scattered, unsubstantiated and localised. In this paper we demonstrate, for the first time, that a humidity signal exists in adaptive thermal comfort using global data to form two separate lines of evidence: a meta-analysis of summary data from 63 field studies and detailed field data from 39 naturally ventilated buildings over 8 climate types. We implicate method selection in previous work as the likely cause of failure to detect this signal, by demonstrating that our chosen method has a 56% lower error rate. We derive a new designer-friendly RH-inclusive adaptive model that significantly extends the range of acceptable indoor conditions for designing low-energy naturally-conditioned buildings all over the world. This is demonstrated through parametric simulations in 13 global locations, which reveal that the current model overestimates overheating by 30% compared to the new one. [ABSTRACT FROM AUTHOR]

The purpose of this study is to explore how a short-term thermal experience influences thermal comfort evaluation. Thermal experience, which refers to the previous thermal environment, may result in the formation of some “memory” on humans. When people enter another environment where the temperature is different from the previous one, the previous experience may result in some different feelings and changes on the evaluations of thermal comfort, comparing with staying in a steady state condition. In this paper, we mainly focus on short-term thermal experience within the time scale of minutes to hours. Climate chamber experiments were conducted for analysis and discussion. The experiment we designed had three sets of conditions: 1) started and ended at an air temperature of 20 °C, and experienced higher temperatures in between; 2) started and ended at an air temperature of 25 °C, and experienced higher or lower temperatures in between, and 3) started and ended at an air temperature of 30 °C, and experienced lower temperatures in between. The evaluations of thermal comfort of the subjects at different temperature conditions were recorded by questionnaires. We found that both comfort and discomfort resulted from the contrast between the current and previous conditions. Even though the initially poor thermal environment was improved a little bit, the evaluation of the thermal comfort would be improved a lot. Additionally, the decrease of thermal sensation caused by cold stimulation was more obvious than the increase due to hot stimulation. People's evaluations could be considered as a combination of both the past and the present feelings. [ABSTRACT FROM AUTHOR]

Semi-Transparent Photovoltaic (STPV) windows have the potential of active energy-saving and have attracted more attention in recent years. Due to the selective absorption effect of solar cells on solar radiation, the indoor thermal environment and human thermal comfort of buildings integrated with STPV windows are considerably different from that with clear glass windows, and there are few studies on this. In this paper, the indoor human thermal comfort of buildings integrated with STPV window was investigated. Firstly, experiments and subjective questionnaires for the indoor environment were conducted in STPV and clear glass window buildings respectively. Secondly, the influence of illuminance on thermal sensation was statistically analyzed, with the consideration of visual effect, non-visual effect, as well as visual and non-visual coupling effect respectively. On this basis, an innovative thermal comfort evaluation method was provided. The thermo-physiological effect, light-physiological effect and light-psychological effect were comprehensively considered in this method. Finally, the reliability was verified by comparing with TSV. According to tests and questionnaires, it was found that the indoor thermal environment of the STPV window was an uneven thermal environment, and the subjective thermal sensation was more inclined to be slightly warm. When investigating the effect of illuminance on thermal sensation considering visual and non-visual coupling effect, it was found that illuminance had a significant influence on thermal sensation in different illuminance ranges. Meanwhile, it indicated the coupled effect of thermal environment and daylight environment on the thermal comfort of human. • The thermal environment and human thermal sensation for buildings integrated with STPV window are studied. • The influence of illuminance on human thermal comfort through visual effect and non-visual effect is investigated. • An adaptive thermal comfort evaluation method for buildings integrated with STPV window is proposed. [ABSTRACT FROM AUTHOR]

Previous adaptive thermal comfort research mainly emphasized the correlations between outdoor climate and thermal adaptation. In this paper, we explore the influence of indoor thermal experience on occupants' thermal adaptation, especially with regard to physiological adaptation. We also investigate whether people with distinct cold indoor exposures have different levels of physiological adaptation to cold environment. A comparative experiment, including both physiological measurements and subjective questionnaires, was conducted in China where winter indoor climates in the northern region (with pervasive district heating) are much warmer than the southern region (without district heating). Two subject groups were recruited, namely: (a) N–N group - subjects who had lived in the northern China with district heating all their life, and (b) S–N group - subjects who grew up in the southern region without district heating but recently moved to the north. The results indicate that S–N subjects who had lived their entire lives in cold wintertime indoor climates had slither physiological response and felt less uncomfortable in mild cold exposures than N–N subjects who lived in neutral-to-warm wintertime indoor climates. The findings suggest that indoor thermal exposures can also influence occupants' thermal adaptation, which can reserve as a reference to the future adaptive thermal comfort model. [ABSTRACT FROM AUTHOR]

India is witnessing unprecedented growth trends in building construction, particularly office spaces. Indian offices are designed to operate at 22.5 ± 1 °C all year round to meet the stringent “Class A” specifications outlined by international standards in the absence of an India-specific comfort standard. This paper proposes an India Model for Adaptive Comfort – IMAC – based on the field surveys administered in 16 buildings in three seasons and five cities, representative of five Indian climate zones. A total of 6330 responses were gathered from naturally ventilated, mixed mode and air-conditioned office buildings using instantaneous thermal comfort surveys. Occupants in naturally ventilated Indian offices were found to be more adaptive than the prevailing ASHRAE and EN models would suggest. According to the IMAC model, neutral temperature in naturally ventilated buildings varies from 19.6 to 28.5 °C for 30-day outdoor running mean air temperatures ranging from 12.5 to 31 °C. This is the first instance where a study proposes a single adaptive model for mixed mode buildings asserting its validity for both naturally ventilated and air-conditioned modes of operation in the building, with neutral temperature varying from 21.5 to 28.7 °C for 13–38.5 °C range of outdoor temperatures. For air-conditioned buildings, Fanger's static PMV model was found to consistently over-predict the sensation on the warmer side of the 7-point sensation scale. [ABSTRACT FROM AUTHOR]

In this paper we explore the notion of comfort expectations and ask the question whether they change as a result of long-term exposure to mild indoor climates. A comparative questionnaire survey was conducted in China where indoor thermal environments during winter in the northern region (with pervasive district heating) are much warmer than in the southern region (without district heating). Four subject groups were surveyed 1) subjects who had lived in the northern region of china with district heating all their life, 2) subjects who grew up in the southern region without district heating but as adults had moved to the north where district heating was pervasive, 3) subjects who had lived in the southern region of china without district heating all their life, and 4) subjects who grew up in the northern region with district heating but as adults had moved to the north where district heating was non-existent. Subjects who had lived their entire lives in the northern region with neutral-to-warm indoor climates had quite similar comfort perceptions and expressed the same levels of thermal acceptability as did those subjects whose life had been spent in the southern region, devoid of any district heating. Statistical analysis of the two sub-groups who migrated, north or south, indicated that it building occupants get accustomed to the thermally neutral lifestyle more easily and faster than do their counterparts who went from thermally neutral indoor climates of the north to the cold and uncomfortable indoor climates of the southern regions of China. [ABSTRACT FROM AUTHOR]

Thermal comfort is fundamental to indoor environmental design and operation as well as indoor thermal environment evaluation. This paper has reviewed the historic evolution of thermal comfort research during the last century using a systematic approach and a particular focus on adaptive thermal comfort studies. A large number of published articles as well as standards and guides were collected and screened based on a rigorous search method to ensure the literature database was both focused and complete. A further evaluation of representative prediction models has been conducted by applying the models to a large database and comparing the differences in their performance. Based on the review analysis, three representative thermal environment assessment approaches were classified as the heat balance approach, the adaptive regression-based approach and the adaptive heat balance approach. The strengths and constraints of each approach were analyzed. Comparisons of different models in the adaptive heat balance approach were conducted using the ASHRAE databases I&II. Thermal comfort theory and approaches have been developed which underpin standards and guidelines in building and engineering system design, operation and evaluation though there are pros and cons of different methods. The heat balance approach features the detailed parameters of design criteria of indoor thermal environments. The adaptive regression-based approach played an important role in raising awareness of adaptive capacities and paved the way towards first implementations into standardization. The adaptive heat balance approach combines the heat balance and the adaptive regression approaches and leads towards future improvements in adaptive comfort modelling. It demonstrates very good performance and its inclusive approach offers potential for further breakthroughs in reducing the limitations of the existing methods. • Comprehensive literature review of the development progress of thermal comfort research. • Three representative thermal environment assessment approaches were classified. • They are the heat balance, the adaptive regression-based, and the adaptive heat balance approaches. • The adaptive heat balance approach bridges the gap of the heat balance and the adaptive regression approaches. [ABSTRACT FROM AUTHOR]

Abstract: The building sector has a significant share in a county's total greenhouse gas emissions, and as a reaction to the Kyoto commitment most countries are constantly adjusting building energy requirements in order to reduce greenhouse gas emissions and mitigate the climate change. While it is easier to set standards for the building fabric and for technical systems, the impact of occupants on comfort and energy performance in buildings has proven to be important, but is a lot harder to account for. This paper therefore aims to investigate the magnitude of influence of occupants in relation to climate and architectural design on thermal comfort and CO2 emissions in offices in different climate zones of the world. The aim is to identify typical patterns and key parameters for optimisation. For this purpose, a parametric study for a typical cellular office room has been conducted using the simulation software EnergyPlus. Two different occupant scenarios are each compared with three different architectural design variations and modelled in the context of three different locations for the IPCC climate change scenario A2 for 2030. The evaluation of the results is focused on two different modes of operation. For natural ventilation adaptive thermal comfort according to ASHRAE Standard 55 has been evaluated, and for mixed mode operation final energy consumption and resulting CO2 emissions. The results indicate a first approach to estimate comfort levels based on climatic data, architectural design priorities and occupancy. Additionally, warmer climates seem to have larger optimisation potential for comfort and energy performance in offices compared to colder climates. [Copyright &y& Elsevier]

Abstract: This paper presents an exhaustive overview of the field studies carried out in the past few decades on human thermal comfort. To get a better grasp of patterns in observed data and to facilitate comparison across investigations, the thermal comfort field studies are grouped using the Köppen–Geiger climatic classification of their locations. Effects of relevant environmental, physiological, and other aspects that can have an effect on thermal comfort are reviewed and discussed. Field studies across the board show that people have considerable capacity to adapt to their surroundings provided they have sufficient adaptive opportunities. This observation holds good for both air-conditioned as well as free running buildings. However, studies show that conditioned spaces have narrower comfort zones compared to free running buildings. Across climatic zones, most popular means of adaptation are related to the modification of air movement and clothing. The ease, economy, and effectiveness (the 3 ‘E’s) of adaptive opportunities play a major role in occupants' adaptation to the surroundings. Studies show that individuals are likely to perceive the same thermal environment differently and environments lacking adaptive avenues normally receive poor comfort ratings. Studies also indicate that for adaptive comfort equations, the running mean temperature may be a better outdoor index compared to the monthly mean temperature. [Copyright &y& Elsevier]

Abstract: This paper investigates the impact of a climate change scenario on comfort and energy performance in offices, in relation to the influence of building design and occupants. It focuses on a typical cellular office room in the context of Athens, Greece, as input for a parametric study using the building simulation software EnergyPlus. Three different building design variations are combined with two different occupant scenarios and a standard weather data set as well as the IPCC climate change scenario A2 for 2020, 2050 and 2080. Results are investigated from two different perspectives: For naturally ventilated buildings the evaluation is related to adaptive thermal comfort according to ASHRAE Standard 55 and EN 15251. And for mixed mode context the evaluation is focused on the resulting impact on final energy consumption, greenhouse gas emissions, peak heating and cooling loads and the percentage of working time when the building is free-running. The results indicate a significant impact of the climate change scenarios on adaptive thermal comfort, and they indicate differences in evaluation between ASHRAE Standard 55 and EN 15251. The comparison of climate change, building design and occupant scenarios indicates that building design is the key to thermal comfort optimisation, whereas the major mitigation potential regarding energy consumption and greenhouse gas emissions is related to occupant behaviour. [Copyright &y& Elsevier]

Temperatures in Mediterranean cities are rising due to the effects of climate change, with a consequent increase in the heat waves frequency. Recent research has shown the tempering potential of semi-outdoor spaces such as courtyards, which are semi-enclosed spaces that are widely used by the users of buildings in Mediterranean cities. International standards addressing thermal comfort parameters provide technical guidelines for indoor spaces only. Expanding this concept, this paper focuses on the potential to extend and interpret the existing calculation models for indoor thermal comfort, EN 16798 and ASHRAE 55, to determine thermal comfort, monitoring two different courtyards in Cordoba, Spain, during both typical summer and heat wave periods. The results show that during the typical summer, the monitored courtyards can reach temperatures up to 8.4 °C cooler than outside. Subsequently can be considered to be in thermal comfort on average for 88% of the time according to EN 16798, and 75% according to ASHRAE 55, which drop to 71% and 52% respectively during heat wave (HW) periods, in spite of increasing thermal gap (TG) up to 13.9 °C. The results are also compared with the PET indicator used for evaluation of outdoor thermal comfort, which provides comparable figures: 81% summer and 73% HW. Implications of implementing passive shading strategies to increase comfort in these transition spaces are also evaluated. The research highlights the thermal potential and usefulness of courtyards in warm climates, so they can ultimately be included in the building analysis as a potentially comfortable and habitable space. • Courtyard was included in the building analysis as a comfortable and habitable space. • Comfort adaptive assessment according to EN 16798, ASHRAE 55 and PET were confronted. • Courtyard tempering achieves a TG up to 8.4 °C in summer and 13.9 °C in a heatwave. • In warm locations, courtyards can be under comfort more than 75% of the day. • Shadow quantification proves to be a major strategy regarding extreme temperatures. [ABSTRACT FROM AUTHOR]

Compared with the static thermal comfort models like predicted mean vote (PMV) model, adaptive thermal models have a wider range of adaptability. The traditional concept of adaptive thermal comfort is that residents actively adapt to environmental changes. In this paper, a K-nearest neighbors (KNN)-based thermal comfort model is developed to establish a personalized adaptive thermal comfort environment to adapt to the preferences of the occupants. The KNN-based thermal comfort model can adjust the thermal comfort boundary for one specific individual person according to the changing environmental conditions. An artificial intelligent (AI) environmental controller has been built for studying the KNN-based thermal comfort model. 34 volunteers have been invited for testing the effectiveness of the KNN-based thermal comfort model. The test results manifested that the percent accuracy of the KNN model with 1000 sets of training data could reach up to 88.31% and can meet practical demand. The proposed thermal comfort model can help different people establish their personal indoor thermal comfort environment and promote the development of the intelligent and personalized air-conditioning systems. • A K-nearest neighbors (KNN)-based thermal comfort model is developed. • It establishes personalized adaptive thermal comfort environment. • An artificial intelligent (AI) environmental controller has been built. • It helps different people establish their personal thermal comfort environment. • It promotes the development of personalized air-conditioning systems. [ABSTRACT FROM AUTHOR]

Abstract: Standards governing thermal comfort evaluation are on a constant cycle of revision and public review. One of the main topics being discussed in the latest round was the introduction of an adaptive thermal comfort model, which now forms an optional part of ASHRAE Standard 55. Also on a national level, adaptive thermal comfort guidelines come into being, such as in the Netherlands. This paper discusses two implementations of the adaptive comfort model in terms of usability and energy use for moderate maritime climate zones by means of literature study, a case study comprising temperature measurements, and building performance simulation. It is concluded that for moderate climate zones the adaptive model is only applicable during summer months, and can reduce energy for naturally conditioned buildings. However, the adaptive thermal comfort model has very limited application potential for such climates. Additionally we suggest a temperature parameter with a gradual course to replace the mean monthly outdoor air temperature to avoid step changes in optimum comfort temperatures. [Copyright &y& Elsevier]

Human thermal adaptation is widely recognized to achieve building energy saving. However, the energy-saving potential of traditional dwellings based on adaptive thermal comfort of residents in cooling and heating periods has not been fully explored. This paper takes the traditional dwellings in the Small West Lake area in Nanjing, China as an example, and explores the thermal comfort of local residents. Then, based on the annual thermal neutral temperature of local residents, a dynamic control strategy of temperature setting points throughout the cooling and heating periods was proposed, and compared with the traditional constant indoor condition from the perspective of heat transfer. The results show that the proposed dynamic controlling method can reduce the energy consumption for maintaining heating or cooling by 26.87%–36.51% in the whole year under the climatic environment of Nanjing, China. The average thermal neutral temperatures are 27.63 °C in summer and 14.44 °C in winter. The thermal sensitivity of residents in traditional Chinese dwellings in winter is lower than that in summer. This study shows the applicability of the adaptive thermal comfort model to traditional Chinese dwellings and a relaxation in the presence of strict set-point temperatures. It is recommended to consider the adaptive thermal comfort of residents into the design of air conditioning or heating systems, which can achieve great energy-saving effect. • The field study of thermal comfort of residents in traditional Chinese dwelling was carried out. • The neutral temperature of residents in traditional Chinese dwellings is 27.63 °C in summer and 14.44 °C in winter. • A dynamic control strategy of indoor setting temperature was proposed. • The proposed control strategy was proved to have energy saving potential. [ABSTRACT FROM AUTHOR]