Thermal Votes Research Articles

Experimental Study of the Effects of Siestas on the Nocturnal Sleep Quality and Thermal Comfort Levels under Thermoneutral Environment in Summer

It has been determined that siestas could potentially have both mental and physical influences on the human body. However, the effects of siestas on the nocturnal sleep quality and thermal comfort levels under thermoneutral environment had not yet been examined in detail. In order to explore the potential influences of siestas on nocturnal sleep, twenty subjects were recruited and divided into two groups based on whether they took siestas or not. During this study's experiment, the temperature was maintained at 25°C, and sleep duration was recorded throughout the night. In addition, thermal comfort votes (TCV) and thermal satisfaction votes (TSV) were obtained both before and after the nocturnal sleep. Furthermore, dopamine (DA) levels, which played important roles in emotional regulation, were measured after the nocturnal sleep. Results showed that the siesta group had a significant increase in self-reported nocturnal sleep quality (p < 0.05), although slight decreases in slow-wave sleep (SWS) duration and rapid eye movement (REM) duration were observed. Additionally, higher TCV and TSV values were reported in the siesta group (p < 0.05). Higher DA concentration was also detected in the siesta group after the nocturnal sleep. Furthermore, some correlations were illustrated between the thermal voting values and the sleep duration, as well as the DA concentration levels. Results implied that siestas could have an influence on the nocturnal sleep quality and thermal comfort levels under thermoneutral environment. Besides, DA concentration levels played an important role in the thermal comfort evaluations when exploring the influences of siestas on nocturnal sleep.

Equivalent contact temperature (ECT) for personal comfort assessment – analytical description and definition of comfort limits

This paper introduces the equivalent contact temperature (ECT) model for local thermal comfort assessment in contact areas for non-uniform environmental conditions. It aims to complete the comfort evaluation scheme of the equivalent temperature approach included in ISO 14505-2 by the contact areas back and buttocks that are currently neglected in the standard. For the assessment of local and overall thermal comfort of seated persons, these contact areas are of great importance, especially if exposed to personal comfort systems. Person-oriented climatization systems, such as seat heating and ventilation, are much more energy efficient than conventional HVAC systems and allow to incorporate the human individual into the system’s control loop. The ECT-approach is formally defined, analytically as well as mathematically derived and validated by a subject study. The results of the subject study (air temperature of 26 °C and 29 °C) confirm the cooling effect due to the seat ventilation and show fundamental correlations between ECTs and body part specific mean thermal votes for buttocks and back. Practitioner summary:The equivalent contact temperature model for local thermal comfort assessment in contact areas for non-uniform environmental conditions is formally defined, analytically as well as mathematically derived and validated by a subject study. It completes the existing equivalent temperature comfort scheme by both contact areas back a nd buttocks to improve thermal comfort assessment.

Meta-learning of personalized thermal comfort model and fast identification of the best personalized thermal environmental conditions

The model of personalized thermal comfort can be learned via various machine learning algorithms and used to improve the individuals’ thermal comfort levels with potentially less energy consumption of HVAC systems. However, the learning of such a model typically requires a substantial number of thermal votes from the considered occupant, and the environmental conditions needed for collecting some votes may be undesired by the occupant in order to obtain a model with good generalization ability. In this paper, we propose to use a meta-learning algorithm to reduce the required number of personalized thermal votes so that a personalized thermal comfort model can be obtained with only a small number of feedback. With the learned meta-model, we derive a method based on the backpropagation of neural networks to quickly identify the best environmental and personal conditions for a specific occupant. The proposed identification algorithm has an additional advantage that the thermal comfort, indicated by the mean thermal sensation value, improves incrementally during the data collection process. We use the ASHRAE global thermal comfort database II to verify that the meta-learning algorithm can achieve an improved prediction accuracy after using 5 thermal sensation votes from an occupant to make adaptations. In addition, we show the effectiveness of the fast identification algorithm for the best personalized thermal environmental conditions with a thermal sensation generation model built from the PMV model.

Physiological and perceptual responses of exposure to different thermal environments at low pressure (61.6 kPa)

In aerospace and military activities, people tend to encounter hypobaric and hypoxic extreme environments caused by the high-altitude, which can lead to physiological and perceptual changes of the human body, thus affecting work efficiency and health. In this study, ambient temperature is set at 21 °C, 26 °C, 30 °C, and altitude is set at 4000 m, with humidity of 40% and air velocity of less than 0.3 m/s. Besides, 13 healthy subjects were recruited to continuously measure their physiological parameters, including axillary temperature, local skin temperature, blood oxygen saturation, heart rate, and blood pressure, and the subjective parameters of overall and local thermal sensation. The main results are as follows: At 21 °C, the axillary temperature declined slightly over time. Also, there was a linear correlation between local skin temperature and thermal sensation. The heart rate and sweating rate under 30 °C were higher than under other conditions(P < 0.05). However, there was no significant difference in sweating rate between 21 °C and 26 °C(P = 0.99). Meanwhile, the sweat volume increased linearly with time under the three conditions(P < 0.001). The blood oxygen saturation was 82.2–83.6% at low pressure(61.6 kPa). Regarding thermal sensations, more than 84% of people felt neutral at 26 °C. This study found that the feet and calves were most sensitive to environmental temperature at 61.6 kPa. The human body's mean sensation thermal vote(MSTV) was kept in the range of −0.5∼+0.5, and the mean skin temperature in the thermal comfort zone was about 32.3–33.9 °C. Also, the recommended environmental temperature should be in the range of 23.3–28.6 °C.

The impact of street geometry on outdoor thermal comfort within three different urban forms in severe cold region of China

This paper focuses on the influence of urban morphology on pedestrian outdoor thermal comfort in Harbin, located in the severe cold region of northeast China. Three typical districts with different urban densities and street layouts were investigated. Field measurement and thermal comfort questionnaire survey were carried out from July 2020 to January 2021. Regression analysis was performed and the neutral physiological equivalent temperature (PET) range was 14.5–22.8 °C. In addition, the PET range was 7.9–27.3 °C when 80% of thermal votes were “acceptable”. ENVI-met was verified and utilized to assess the mesoscale and street-scale impact of urban morphology on thermal comfort in hot and cold seasons. Measurement results shows that the PET variation caused by urban morphology was more significant in the transition season, with the maximum PET difference of 7.6 °C observed at the mid-rise district and the minimum value of 4.4 °C in the low-rise area. Simulation results indicate that the average building height significantly affects the background Ta and PET distribution within the block. Mean radiant temperature (MRT) and PET are highly correlated to sky view factor (SVF) in summer, while in winter, PET is related to SVF only in the low-rise district. Based on the thermal comfort calendar in both hot and cold seasons, shallow and medium canyons (0.5 < H/W < 1.5) are more favorable in severe cold climate, and the optimum streets are near the N–S orientation, followed by intermediate orientations, while deeper canyons (H/W > 1.5) are not recommended due to the lack of solar absorption.

Application of an occupant voting system for continuous occupant feedback on thermal and indoor air quality – Case studies in office spaces

Smartphone applications or electronic devices in the form of occupant voting systems (OVS) have demonstrated to be feasible for acquiring feedback from occupants to support the building operation manager to identify indoor environmental quality (IEQ) problems and inappropriate control settings of heating, ventilation and air-conditioning (HVAC). The present paper aims to contribute to the growing research on OVS as a tool to support building operation management. The paper presents a study about a tangible OVS, denoted TiAQ, that occupants could use to vote on their here-and-now experiences regarding the thermal environment and indoor air quality. The main objectives were to identify whether there was an alignment between the votes collected with TiAQ and the monitored IEQ variables as well as to demonstrate the use of occupant votes to identify problematic IEQ conditions and appropriate strategies for HVAC control. The study demonstrated that thermal votes collected with TiAQ could be related to the variations in the indoor temperature and ventilation airflow. Additionally, collected votes could identify i.a. poorly set indoor temperature setpoint and appropriate control strategies that could reduce energy use by 46% and increase thermal comfort and cold complaints by 6% if current airflow and indoor temperature setpoint were lowered.

Multi-criteria decision making of integrating thermal comfort with energy utilization coefficient under different air supply conditions based on human factors and 13-value thermal comfort scale

This study investigates the influence of the supply vane angles and supply air temperature on the ventilation performance which is described by thermal comfort and EUC (energy utilization coefficient). And the performance optimization is investigated based on human factors (gender and metabolic rate) with a 13-value thermal comfort scale. Firstly, this study conducts the experiments on the supply vane angles and supply air temperature to research ventilation performance with both consideration of human factors and the application of a 13-value thermal comfort scale to vote. Secondly, Nishi's 8-point method is used to calculate thermal comforts which are applied to validate the reliability of thermal vote results. Then, the SPA-TOPSIS (technique of order preference by similarity to an ideal solution based on the set pair analysis) method is used to optimize the performance and get objective weights of thermal comfort and EUC. Finally, there is a discussion on the effect of gender and metabolic rate on ventilation performance based on the calculated objective weights. The results of the experiments show that the thermal comfort votes have a significant relationship with the supply vane angle, supply air temperature, gender and metabolic rate, and for human factors, the metabolic rates have a greater effect on the ventilation performance than gender.

Comparative assessment of HVAC control strategies using personal thermal comfort and sensitivity models

Research efforts have demonstrated the potentials of improving the performance of Heating, Ventilation, and Air-Conditioning (HVAC) systems by leveraging personalized thermal comfort preferences and profiles. However, there are remaining challenges for effective control in collective conditioning in multi-occupancy scenarios. In this study, we have investigated the impact of personal thermal comfort sensitivities – distinct individual reactions to temperature variations– on collective conditioning. To this end, we have explored whether taking the thermal comfort sensitivity into account influences the selection of temperature setpoints and the overall probability of achieving comfort. We have also examined the impact of different thermostat temperature resolutions (0.1, 0.5, and 1.0 °C) on these factors with a hypothesis that finer resolutions could aid in achieving improved overall thermal comfort. In doing so, we have proposed an agent-based control mechanism to simulate the multi-occupancy space, controlled by an HVAC agent to provide air conditioning for multiple human agents using three operational strategies to compare conventional strategies with our proposed approach. The first strategy relies on majority thermal votes, the second one relies on the gap between thermal preferences (i.e., preferred temperature) and ambient temperature, and the third strategy uses thermal comfort sensitivity in addition to preferences. The investigations were conducted by using stochastically modeled comfort profiles (six actual comfort profiles and 15 mathematically synthesized profiles from actual data). These profiles were used to model the behavior of human agents in diverse multi-occupancy scenarios, modeling two to ten occupants in a space for different thermostat temperature resolutions. Our investigations demonstrated that thermal comfort sensitivity plays a statistically significant role in collective conditioning as it resulted in changes of temperature setpoint in 86% of cases and a higher probability of achieving collective comfort.

Interferences of urban form on human thermal perception

Thermal perception entails to a certain extent visual aspects, which are taken into account when subjects are requested to express their thermal votes to a given indoor or outdoor space. This study concentrates on human cognition and preconceptions of thermal behavior from projected 360° imagery. Urban scenes have been shown with the concurrent administration of thermal perception questionnaires to two distinct sample groups: 1) volunteer participants (n = 86) who filled out online responses to questions regarding thermal perception in undisclosed locations; 2) undergraduate students (n = 85) under temperature-controlled conditions in a computer lab. Both groups have evaluated three different 360° urban scenes with varying morphology attributes using the provided web link to the 360° VR platform Roundme. Method of analysis included means, medians, statistical significance (p-value) and percentage graphs of perceived thermal sensation. Despite the absence of any information regarding location, season and time of day of the scenes, both groups expressed different perceptions with respect to the estimated thermal conditions and thermal comfort levels for the observed urban scenes, consistently attributing windier and warmer thermal conditions to an urban square location and less so to a street canyon.

Pemilihan dan Implementasi Strategi Peningkatan Kenyamanan Termal Ruang Kuliah

Optimum conditions help us think and work better. Thermal comfort in lecture buildings is important to maintain students’s comfort and help them concentrate on study. The fastest way to achieve expected thermal comfort inside the lecture room is using air conditioner, however, compensation on high electricity bills and degradation of the environmental quality has to be made. Therefore, the aim of this paper is to find and promote several environmental friendly strategies which can provide comfort to users in one hand, but also can reduce energy consumption in another hand. There have been several strategies in records to increase thermal comfort in buildings. To select the best and the most appropriate alternative, Analytical Hierarchy Process method was used by setting the criteria, sub-criteria, and alternatives to increase thermal comfort in lecture buildings of Andalas University. To test the selected alternative, thermal comfort inside two lecture rooms were evaluated experimentally. The comfort level was evaluated using PMV (Predicted Mean Vote) and PPD (Predicted Percentage Dissatisfied) model. For all experimental conditions, PMV and PPD results and individual thermal vote results showed a good match statistically meaning that the PMV and PPD models could predict thermal condition inside the lecture rooms. Results also showed that the presence of natural vegetation infront of glass windows of the lecture rooms statistically improved thermal comfort sensations of students under natural ventilation mode and reduced thermostat setting under air conditioning mode.

Comprehensive Evaluation of Energy and Environmental Performances of an Extensive Green Roof of a Building in Subtropical Climate

Green roof has been investigated to be one of the effective means for improving the building energy performance and relieving the urban heat island (UHI) effect. This study presents a case study in South China with a subtropical climate to evaluate the benefits of extensive green roof to the building energy, indoor and outdoor thermal environment through field tests and simulations. During the field tests in summer, a room on the top floor of a residential building was covered with green roof as the studied room, and another similar room with conventional roof was regarded as the reference room. The field tests showed that the green roof has better thermal behaviors in terms of heat insulation and thermal resistance capacities. The field measurements and thermal voting tests revealed that better comfort indoor thermal comfort and lower outdoor air temperature above the roof (reduction by 0.9-3°C) can be achieved using the green roof. Based on the results of field measurements and simulation study, 32.7% of the mean daily energy was saved by using the green roof for the room studied, and 0.75% of the total electricity consumption of the city was estimated to be saved if 15% of the buildings in the city are covered with green roofs.

Implementation of the equivalent temperature measurement system as a part of the vehicle Heating, ventilation and Air-conditioning unit

Thermal comfort evaluation based on the Comfort zone diagram is relatively new and promising method [1] developed by Hakan O. Nilsson [2]. The method was developed mainly for non uniform indoor environments [3] such as vehicle cabins [4]. Mean thermal vote (MTV) is correlated with equivalent temperature, which is typically measured by a thermal manikin with clothing or by a sensor with heated surface. This fact is the advantage of this method because prediction of thermal comfort is based on a measurable physical phenomenon which is called dry heat loss. The essence of this method inspired us to develop a measurement system that will be based on miniaturised and cost effective equivalent temperature sensors. Such sensors could be easily integrated into the surroundings of seated human and could provide data about local thermal comfort as feedback information for HVAC control unit. Our project, which started last year, is called Innovative control for Heating, Ventilation and Air Conditioning systems, iHVAC.

Implications of air-conditioning use on thermal perception in open spaces: A field study in downtown Rio de Janeiro

The interference of thermal history in a person's thermal perception has been explored by several authors and this has been one of the pillars of the concept of adaptive comfort. Given that a general trend towards a more frequent usage and ownership of air-conditioning (AC) units or central systems is taking place worldwide, and considering the fact that AC-users show a diminished tolerance to heat stress when compared to more acclimatized persons, this paper discusses the consequences of AC-usage in climate-responsive urban design. Rio de Janeiro (22° 54′ 10″S, 43° 12′ 27″W) has a tropical climate with summer rains (Aw) and is characterized by frequent heat stress conditions. In such context, air conditioning is a common strategy to reduce indoor heat in buildings. The purpose of this study was to analyze the influence of AC-usage in the thermal perception of a large group of urbanites as regards to Rio's outdoor thermal conditions. Thermal votes were assessed by means of standard questionnaires in several field monitoring campaigns. Meteorological variables, measured on site with a portable weather station were post-processed to UTCI values (Universal Thermal Climate Index). Field data showed significant differences among groups of respondents who reported having access to AC-units (or central systems) at home and/or at work in terms of thermal sensation votes. By applying the derived set point UTCI values for two subgroups (AC-users against non users) to Rio de Janeiro's TMY2 (typical meteorological year) data, a significant rise in the annual percentage of heat stress hours was found for AC-users, in magnitude even higher than expected changes in annual heat stress percentages due to climate-responsive urban planning and thus increasing the demands on heat stress mitigation strategies.

Air conditioning and the neutral temperature of the Indonesian university students

Recent thermal comfort studies conducted in two private universities, namely Universitas Tarumanagara (Untar) and Universitas Mercu Buana (UMB) in Jakarta, Indonesia, showed a result that is fairly different from the previous thermal comfort studies carried out in this country. This study involved 90 students and collected 900 thermal votes. Students' comfort temperature in both universities was significantly lower than the previous comfort study conducted in Jakarta (1993), and it was almost similar compared to the previous study in Bandung with a lower outdoor temperature. As the study also collected information about the students about the use of air conditioning (AC) in their accommodations, it has revealed that nearly 100% students of Untar lived in AC accommodations, while only 50% students of UMB used AC in their accommodations. This paper discusses the whole study and draws some conclusions from it.

A correlation linking the predicted mean vote and the mean thermal vote based on an investigation on the human thermal comfort in short-haul domestic flights

The results of an experimental investigation on the human thermal comfort inside the cabin of some Airbus A319 aircrafts during 14 short-haul domestic flights, linking various Italian cities, are presented and used to define a correlation among the predicted mean vote (PMV), a procedure which is commonly used to assess the thermal comfort in inhabited environments, and the equivalent temperature and mean thermal vote (MTV), which are the parameters suggested by the European Standard EN ISO 14505-2 for the evaluation of the thermal environment in vehicles.The measurements of the radiant temperature, air temperature and relative humidity during flights were performed. The air temperature varied between 22.2 °C and 26.0 °C; the relative humidity ranged from 8.7% to 59.2%. The calculated values of the PMV varied from −0.16 to 0.90 and were confirmed by the answers of the passengers. The equivalent temperature was evaluated using the equations of Fanger or on the basis of the values of the skin temperature measured on some volunteers.The correlation linking the thermal sensation scales and zones used by the PMV and the MTV resulted quite accurate because the minimum value of the absolute difference between such environmental indexes equalled 0.0073 and the maximum difference did not exceed the value of 0.0589. Even though the equivalent temperature and the MTV were specifically proposed to evaluate the thermal sensation in vehicles, their use may be effectively extended to the assessment of the thermal comfort in airplanes or other occupied places.

Case study of skin temperature and thermal perception in a hot outdoor environment

Focusing on the understanding and the estimation of the biometeorological conditions during summer in outdoor places, a field study was conducted in July 2010 in Athens, Greece over 6 days at three different sites: Syntagma Square, Ermou Street and Flisvos coast. Thermo-physiological measurements of five subjects were carried out from morning to evening for each site, simultaneously with meteorological measurements and subjective assessments of thermal sensation reported by questionnaires. The thermo-physiological variables measured were skin temperature, heat flux and metabolic heat production, while meteorological measurements included air temperature, relative humidity, wind speed, globe temperature, ground surface temperature and global radiation. The possible relation of skin temperature with the meteorological parameters was examined. Theoretical values of mean skin temperature and mean radiant temperature were estimated applying the MENEX model and were compared with the measured values. Two biometeorological indices, thermal sensation (TS) and heat load (HL)-were calculated in order to compare the predicted thermal sensation with the actual thermal vote. The theoretically estimated values of skin temperature were underestimated in relation to the measured values, while the theoretical model of mean radiant temperature was more sensitive to variations of solar radiation compared to the experimental values. TS index underestimated the thermal sensation of the five subjects when their thermal vote was 'hot' or 'very hot' and overestimated thermal sensation in the case of 'neutral'. The HL index predicted with greater accuracy thermal sensation tending to overestimate the thermal sensation of the subjects.

Quantifying individual adaptive processes: first experiences with an experimental design dedicated to reveal further insights to thermal adaptation

Due to more frequent unusual weather phenomena being observed, there is an urgent need to identify and quantify the abilities of occupants to adapt to climate changes. The adaptive comfort model identifies behavioural, physiological and psychological adaptive processes. However, besides giving a statistical approximation of their general effect on the thermal perception vote, little is known about the individual contributions of the three types of adaptive processes to this effect. Knowing such portions would enable us to extend the existing comfort models in such a manner that they incorporate adaptive (re-)actions of the occupant. This could be used for the design of passively cooled buildings, particularly with regard to interaction between occupants and the building (envelope) for individual adjustment of the thermal indoor environment. This article describes first experiences with a new experimental design dedicated to reveal further insights to the adaptive processes along with the description of requirements for the inside–outside climate chamber currently under construction in Karlsruhe.

Assessment of daytime outdoor comfort levels in and outside the urban area of Glasgow, UK

To understand thermal preferences and to define a preliminary outdoor comfort range for the local population of Glasgow, UK, an extensive series of measurements and surveys was carried out during 19 monitoring campaigns from winter through summer 2011 at six different monitoring points in pedestrian areas of downtown Glasgow. For data collection, a Davis Vantage Pro2 weather station equipped with temperature and humidity sensors, cup anemometer with wind vane, silicon pyranometer and globe thermometer was employed. Predictions of the outdoor thermal index PET (physiologically equivalent temperature) correlated closely to the actual thermal votes of respondents. Using concurrent measurements from a second Davis Vantage Pro2 weather station placed in a rural setting approximately 15 km from the urban area, comparisons were drawn with regard to daytime thermal comfort levels and urban-rural temperature differences (∆T(u-r)) for the various sites. The urban sites exhibited a consistent lower level of thermal discomfort during daytime. No discernible effect of urban form attributes in terms of the sky-view factor were observed on ∆Tu-r or on the relative difference of the adjusted predicted percentage of dissatisfied (PPD*).

A New Approach to Evaluate Various Thermal Environments

Predicted mean vote (PMV) has been recognized as one internationally adopted measurement criterion of thermal comfort. It has been applied in an air-conditioned environment but may be less applicable to naturally ventilated (NV) buildings. In this study, a new approach was developed to evaluate the impact of thermal environment on human comfort. An effective algorithm has been devised to enable a selection of the steady physiological response most appropriate in a required situation. Three physiological parameters—mean skin temperature, skin wettedness, and skin evaporative heat loss—are computed for correlation with the actual thermal comfort vote based on published data. With previous research findings, the correlation is derived in an expert system. Human thermal adaptation, which is overlooked in PMV but actually affects thermal comfort in NV environments, has been incorporated. This approach may offer a more accurate estimation of values of thermal mean vote, especially when the evaporative heat loss is used in the evaluation. In the study, the estimation error in NV buildings was reduced by 61%, leading to a better prediction of thermal acceptability. As a conclusion, this approach may yield a better evaluation of the thermal environment than the conventional PMV in NV buildings.

A field study of occupant thermal comfort and thermal environments with radiant slab cooling

This paper presents the findings of a field study of occupant thermal comfort and thermal environments with a radiant slab cooling system. The study combined field measurements and questionnaires based on the ASHRAE RP-921 project protocol. A total of 116 sets of data from 82 participants were collected in summer and winter. The results reveal that occupant whole-body thermal sensations with radiant cooling were consistent with the PMV model. The main advantage of radiant cooling for thermal comfort was found to be reduced local thermal discomfort with reduced vertical air temperature difference as well as reduced draft rate. The survey results revealed that 14–22% of participants in the study reported local cold discomfort in the arm–hand and the leg–foot regions. The results indicated that there may be lower limits on air speeds acceptable to occupants. Statistical analysis indicated that occupant thermal votes were free of significant correlation with personal, contextual and psychological factors. Suggestions to improve the questionnaire and the field survey process are offered.