Standard Effective Temperature Research Articles

Overheating in the Tree Shade of Urban Parks: A Field Study of Thermal Adaption in China

With increased atmospheric temperature, temperatures in the shade of trees in parks also increase, and people are faced with high temperature challenges. In this study, thermal comfort in the shade of the trees of an urban park during summer in China was assessed. The subjective responses of the respondents were recorded via questionnaires, and environment parameters were measured. The results show that the air temperature in the shade was 31.1 ± 3.0 °C during the day, and that it peaked at 36.9 °C; the globe temperature was 31.3 ± 3.1 °C, and it peaked at 40.1 ℃. Respondents’ clothing insulation was 0.31 ± 0.08 clo, and the effect of clothing adjustment on thermal adaptation was limited. Thermal sensation is linearly related to standard effective temperature (SET), and the upper limit of 80% acceptable SET was 32.1 °C. At different temperature values, the proportion of expected airflow enhancement exceeded 50%. The respondents preferred a neutral-warm sensation. Moreover, there was an obvious thermal adaptation, with thermal history and psychological adaptation being the main factors affecting thermal comfort. This study confirmed the value of shade and provided us with guidance for park planning and design.

A Systematic Review on Human Thermal Comfort and Methodologies for Evaluating Urban Morphology in Outdoor Spaces

The exponential growth of urban populations and city infrastructure globally presents distinct patterns, impacting climate change forecasts and urban climates. This study conducts a systematic review of the literature focusing on human thermal comfort (HTC) in outdoor urban environments. The findings indicate a significant surge in studies exploring HTC in open urban spaces in recent decades. While historically centered on Northern Hemisphere cities, there is a recent shift, with discussions extending to various metropolitan contexts in the Southern Hemisphere. Commonly employed urban categorization systems include Sky View Factor (SVF), Height × Width (H/W) ratio, and the emerging Local Climate Zones (LCZs), facilitating the characterization of urban areas and their usage. Various thermal indices, like Physiological Equivalent Temperature (PET), Predicted Mean Vote (PMV), Universal Thermal Climate Index (UTCI), and Standard Effective Temperature (SET), are frequently utilized in evaluating external HTC in metropolitan areas. These indices have undergone validation in the literature, establishing their reliability and applicability.

Assessing and enhancing the applicability of standard effective temperature in outdoor thermal sensation prediction for continental climates

Accurate thermal sensation prediction is crucial for assessing outdoor thermal environments. This study aims to enhance the applicability of the standard effective temperature (SET*) in continental climates for a more comprehensive evaluation of outdoor thermal comfort. Taking Zhengzhou, China as an exemplar, a comprehensive 12-day survey involving questionnaire surveys and microclimatic measurements was conducted in residential communities during the summer, autumn, and winter seasons. Based on this, the relationship between the SET* and thermal sensation was explored. Furthermore, the SET*-original thermal sensation scale was modified using linear and probit regression, and the accuracy of modified scale was assessed using predicted accuracy percentage (PAP) and mean absolute error (MAE). The results indicated that the SET*-original scale performs poorly in predicting thermal sensation in continental climates (P = 27.3 %, MAE = 1.24). The modified scale using probit regression model was better suited for continental climates (P = 39.5 %, MAE = 0.87). It outperformed the modified scale obtained through a linear regression model, with PAP increasing by 5.9 % and MAE decreasing by 0.04. The SET*-modified scale extended thresholds at the colder end and significantly enhanced predictive accuracy for colder conditions, making it more suitable for predicting thermal perception in continental climates.

Development of the Universal Standard Effective Temperature for evaluating thermal comfort across different metabolic rates

The standard effective temperature (SET) is a widely recognised index in thermal comfort studies worldwide. The definition of the standard environment is crucial to the validity of SET. It allows SET to evaluate thermal comfort levels in various clothing insulations, air velocities, and metabolic rates. The thermal sensation votes (TSV) should be equivalent when the SET remains constant. Previous studies have focused on applying SET to analyse thermal comfort with diverse environmental factors or clothing insulation conditions but have not compared SET with different metabolic rates. In this study, the original standard environment was examined using experimental results with different metabolic rates. The results revealed that the original standard environment failed to guarantee the ‘same SET, same TSV’ principle with different metabolic rates. The original standard environment was insufficient in accurately reflecting the effect of the actual activity status on the standard convective heat transfer coefficient and standard clothing insulation. Thus, a new standard environment was developed, incorporating two new variables: the base value of the standard clothing insulation and the convective heat transfer coefficient generated from the actual activities. Through validation of the experimental data, the new standard environment ensured a consistent linear relationship between SET and TSV, in both transient and steady-state conditions, even when the metabolic rate was changed from 1.0 met to 3.8 met. Furthermore, a universal SET was proposed. The universal SET could be applicable to thermal comfort analysis with different metabolic rates in steady-state conditions and activity status transients.

Thermal indices for human biometeorology based on Python

Thermal indices, such as Predicted Mean Vote, Outdoor Standard Effective Temperature, Physiologically Equivalent Temperature, and Universal Thermal Climate Index, are essential for the evaluation of thermal perception, the design of climate sensitive buildings or urban area, and tourism. These thermal indices are built on complicated numeric models. RayMan was developed to calculate thermal indices based on Delphi program language on the Windows 7 operating system. RayMan is not currently under active maintenance or development. Thus, this report describes the development of an innovative Python library named biometeo that includes an innovative thermal index (modified Physiologically Equivalent Temperature) as a next generation program to calculate thermal indices and human biometeorological variables.

Experimental evaluation of thermal adaptation and transient thermal comfort in a tropical mixed-mode ventilation context

Mixed-mode ventilation offers a promising solution for achieving comfortable indoor environments in an energy-efficient manner. However, in the tropics, characterized by a year-round hot and humid climate, opportunities for natural ventilation (NV) are typically limited to specific hours, necessitating operational mode switches on an intraday basis. Much of the thermal comfort research on mixed-mode ventilation relies either on cross-sectional data collected from different subjects or longitudinal data spanning a few seasons. This raises an open question: Can occupants thermally adapt when switching between NV and air-conditioning (AC) modes within a single day? To address the gap, our experimental study engaged 57 tropically acclimatized subjects, exposing them to combinations of five operational modes and four ceiling fan speeds (0.15-1.15 m/s) over an eight-hour timeframe. The results revealed that the subjects preferred a Standard Effective Temperature (SET*) that was 2-3 °C higher when operating in the NV mode compared to the AC modes, indicating thermal adaptation within the same day and in the same space. Specifically, the adaptation process was observed to stabilize between 35 to 45 mins following a mode switch. These findings contribute to the optimization of thermal comfort in mixed-mode controls, considering the dynamic characteristics of thermal adaptation.

Calibrating thermal sensation vote scales for different short-term thermal histories using ensemble learning

The urban heat island effect intensifies, leading to increased thermal exposure for city residents. Variations in thermal sensation are observed among individuals with different short-term thermal experiences, challenging the reliability of Thermal Sensation Vote (TSV) scales. This study investigates TSV disparities in Shanghai, China, between two groups: individuals with Short-Term Air Conditioning Usage Experience (STACUE) and those Lacking Short-Term Air Conditioning Usage Experience (LSTACUE). Through questionnaire surveys and environmental monitoring, the study evaluates the performances of various ensemble learning models for predicting TSV. The selected Random Forest Regressor is employed to calibrate TSV scales for Physiologically Equivalent Temperature, Standard Effective Temperature (SET*), Universal Thermal Climate Index, and Perceived Temperature. Using Shapley values from game theory, we reveal how environmental variables contribute to TSV differences among individuals with varying short-term thermal histories. Results indicate higher Thermal Unacceptable Vote and greater Environmental Expectation Vote for STACUE individuals versus LSTACUE ones. Calibrated TSV scales, particularly SET*, exhibit significant enhancements over original scales: a 35.04 % increase in prediction accuracy percentage and a 0.57 correlation increase. Explainable analysis underscores that air temperature (28.8%) has a stronger impact on TSV among STACUE individuals, whereas mean radiant temperature (32.2%) is the primary factor affecting TSV among LSTACUE. Furthermore, we found gender interacts with thermal environmental parameters concerning TSV. This study sheds light on how short-term thermal history influences TSV among residents, informing customized urban thermal management strategies.

Effect of cold storage backfill on thermal comfort of mine stope based on standard effective temperature

In order to effectively evaluate the thermal comfort during the process of mine cold storage backfill cooling, SET (standard effective temperature) was selected as the evaluation index. According to the actual situation, the physical model and heat transfer model of mine were established. The air temperature distribution was obtained by numerical simulation, and the backfill cooling experiment was carried out. The key factors affecting thermal comfort were analyzed and discussed according to the calculation results of the SET program. The results showed that air temperature has the greatest influence on mine thermal comfort among various environmental factors. Based on the average temperature of stope, the downward backfill can maintain comfort longer than the upward backfill. From the perspective of comfort at different height positions, downward backfill is better than upward backfill. Considering various factors such as cooling effect, rheological characteristics and refrigeration cost, the ratio of ice to water in backfill slurry can be set at 6:4. The research results can provide reference for the reasonable adjustment of thermal environment in mine.

An experimental study of thermal comfort zone extension in the semi-open spray space

Pedestrians will experience different heat stress stages from sunlight to semi-open spray space as they shuttle through stations with spray systems. There are few studies on the influence of thermal experience and thermal history of this specific environment on pedestrian thermal comfort. This study explored the dynamic physiological thermal response and thermal perception of humans in the sunlight to semi-open spray space in Qingdao, China. Meteorological and physiological parameters were measured and questionnaires were conducted. The results showed that from outdoor sunlight to semi-open spray space, thermal sensation and thermal comfort were improved, the mean skin temperature of the whole body decreased by 0.5 °C, the neutral standard effective temperature (NSET*) enhanced by 8.8 °C, and the NSET* range (NSET*R) increased by 7.3–10.2 °C. However, after 10 min in the semi-open spray space, the thermal comfort gradually deteriorated. In addition, the main meteorological factors affecting the thermal sensation in sunlight and semi-open spray space were air temperature and mean radiant temperature, and the main physiological factor was the skin temperature of the right upper arm. This study is helpful for the operation design of spray systems and the evaluation of the thermal environment in semi-open spray in cities.

Assessment of some Bioclimatic Indices using RayMan Model for Baghdad-Iraq

Abstract The evaluation of bioclimatic conditions on a local scale is still an important topic. It might be a key component of the national plan for the sustainable development of various areas under changing climatic conditions. The present study aimed to examine the behaviour of four bioclimatic indices namely physiologically equivalent temperature (PET), Standard Effective Temperature (SET*), Universal thermal climate index(UTCI) and, Predictive mean vote(Pmv) derived from energy budget models for Baghdad city. The monthly means data of air temperature, relative humidity, wind speed, and solar radiation during the period (1981-2021) were used in this study. All calculations of this study were extracted using RayMan Model. The relationship between PET, Pmv, SET, and UTCI indices in addition to meteorological parameters was also conducted in this study. The results indicate that July and August had the highest values of Pmv (4), SET* (39.4), PET (43.9), and UTCI (39.4). For the majority of the studied indices, the comfortable thermal perception occurred only in March, April, and October. PET and UTCI revealed acceptable comparability in terms of temperature perception when compared to other indices for most months of the year. The maximum heat stress was reported for all indices between May and September, with the lowest stress occurring between January and December. April was the most comfortable month of the year, according to the data. Correlations between UTCI and meteorological parameters found a substantial association with air temperature (0.99) and relative humidity (0.98), respectively. The lowest correlation coefficient (R2=0.69) was found with wind speed. All other indicators indicate a substantial association with the UTCI.

半屋外空間における環境グレードが熱的快適性に与える影響

This study aims to clarify effects of various environmental grades on thermal comfort. Field surveys were conducted in five semi-outdoor spaces in Tokyo, consisting of thermal environment measurement, questionnaires about thermal comfort and impression of surveyed spaces and real-time sensation voting. By impression evaluation and comparison of the regression curves of standard new effective temperature (SET*) against percentage of “uncomfortably warm”, the surveyed spaces were classified into two categories: “outdoor tendency” and “indoor tendency”. By regression analysis of real-time sensation voting result using hierarchical Bayesian approach, environmental grade was clarified to affect the correlation between pleasantness/unpleasantness and air velocity.

A Review of methodologies for analyzing thermal comfort in urban pedestrian pathways

According to the ANSI/ASHRAE Standard 55, thermal comfort is a subjective evaluation of thermal environment satisfaction. Therefore, the most challenging issue about thermal comfort is the assessment by subjective evaluation and addressing the case as a mental condition. Hence, The primary goal of the study is to determine which of the well-known thermal comfort indices is most suited for studying urban pedestrian movement. The present research method is based on the study of a wide range of research related to climatic comfort on the scale of urban space. The research has a review character and is set to analyze the different indices comparatively. In the analytical approach, the most significant factors which are compared are 1- PMV (predicted mean vote), 2- P4SR (four-hour predicted transpiration index), 3- HSI (heat stress index), 4- SET (standard effective temperature), 5- E.T.* (new effective temperature), 6- PPD (predicted percentage of dissatisfied) and 7- PET (Physiological Equivalent Temperature). The results show each component's advantages and disadvantages in analyzing thermal comfort in urban pedestrian pathways. The findings also underscored the importance of incorporating mixed methodologies to assist designers in making more accurate selections during urban planning. The most difficult issues that should be reconsidered in order to gain a better understanding of thermal comfort as an "adaptive" issue in urban pedestrian pathways are 1- Resetting the reference temperatures, 2- Readdressing the equations for upper and lower limits, 3- Providing more comprehensive databases (age, weight, gender, and thermal history), and 4- Reprogramming the acceptable temperature ranges based on individual expectations. Controls, layout, airflow, and humidity, among other design considerations, would be better emphasized by urban designers.

Analysis of Thermal Environmental in Buildings with Water and Landscape Elements as Microclimate Modifiers in Hot and Humid Tropical Climates

Thermal conditions in buildings are influenced by climatic conditions and are determined by the thermal performance of the building itself. The thermal condition is caused by the transfer of heat flow between the environment and the building. This study aims to analyze the value of temperature, humidity, solar radiation, and wind speed with the presence of the water element as a modifier of the microclimate in the building as well as thermal comfort for the adaptation of visitor behavior. The research focus is on the water element and the sensation of the thermal environment with public building objects. Field research based on ASHRAE 55 2020 and ISO 7730 standards. Four environmental parameters were measured, namely temperature, humidity, solar radiation, and air velocity. Data were obtained through field measurements using quantitative methods through analysis of the Predicted Mean Vote (PMV) thermal comfort index, Predicted Percentage of Dissatisfied (PPD), and Standard Effective Temperature (SET). The data is processed using a statistical approach and then simulated with 2-dimensional numerical data using the Thermal Comfort Tool (CBE) software after which it is compared with the thermal comfort index. PMV, PPD, and SET are generated and refer to the ASHRAE 55-2020 standard. Meanwhile, the sensation of the thermal environment based on behavioral adaptation was analyzed based on the results of the questionnaire answers using the thermal sensation vote (TSV). The results show that the analysis of the thermal environment in the context of the microclimate in the building, thermal comfort as well as water and landscape elements are important potentials that can provide positive values, improve quality, and maintain microclimate stability at the building scale and regional scale and need to be controlled and taken action. adaptive in buildings such as setting water elements and ventilation systems in buildings to provide a passive cooling effect on buildings.

Can retro-reflective materials replace diffuse highly reflective materials for urban buildings’ wall to improve outdoor thermal comfort?

In recent years, there have been numerous studies on the application of retroreflective (RR) materials to exterior building walls to relieve the urban heat island (UHI) phenomenon and save building energy consumption instead of diffuse highly reflective (DHR) materials. Experimental measurements were undertaken to investigate the impact of applying DHR and RR materials to building exterior walls on the outdoor thermal environment. DHR and RR walls were tested with three canyon aspect ratios (H/ D) of 0.5, 1.0, and 1.5, respectively, with seven environmental indexes recorded and compared, including air temperature (Ta), relative humidity (RH), sol-air temperature (SAT), operative temperature (OT), standard effective temperature (SET*), change in operative temperature (COT), and real-time solar reflectance (ρ). The results show that the RR wall is more effective in improving the outdoor thermal environment, where SAT decreased by 4.5 °C, SET* decreased by 0.5 °C, and COT decreased by 1.2 °C, on average, while it can also improve the real-time solar reflectance (ρ) by 12% on average compared to the DHR wall. Moreover, it gets more effective in scenarios with a higher canyon aspect ratio.

Evaluation of thermal environment and human thermal comfort in 8 types of public places from 2019 to 2021

Objective: To evaluate the thermal environment of different types of public places and the thermal comfort of employees, so as to provide scientific basis for the establishment of microclimate standards and health supervision requirements. Methods: From June 2019 to December 2021, 50 public places (178 times) of 8 categories in Wuxi were selected, including hotels, swimming pools (gymnasiums), bathing places, shopping malls (supermarkets), barber shops, beauty shops, waiting rooms (bus station) and gyms. In summer and winter, microclimate indicators such as temperature and wind speed were measured in all kinds of places, combined with the work attire and physical activity of employees in the places. Fanger thermal comfort equation and center for the built environment (CBE) thermal comfort calculation tool were used to evaluate the predicted mean vote (PMV), predicted percent dissatisfied (PPD) and standard effective temperature (SET) according to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 55-2020. The modification effects of seasonal and temperature control conditions on thermal comfort were analyzed. The consistency of GB 37488-2019 "Hygienic Indicators and Limits in Public Places" and ASHRAE 55-2020 evaluation results on thermal environment was compared. Results: The thermal sensation of hotel, barber shop staff and the gym front-desk staff were moderate, while the thermal sensation of swimming place lifeguard, bathing place cleaning staff and gym trainer were slightly warm in summer and winter. Waiting room (bus station) cleaning and working staff, shopping mall staff felt slightly warm in summer and moderate in winter. Service staff in bathing places felt slightly warm in winter, while staff in beauty salons felt slightly cool in winter. The thermal comfort compliance of hotel cleaning staff and shopping mall staff in summer was lower than that in winter (χ(2)=7.01, 7.22, P=0.008, 0.007). The thermal comfort compliance of shopping mall staff in the condition of air conditioning off was higher than that in the condition of air conditioning on (χ(2)=7.01, P=0.008). The SET values of front-desk staff in hotels with different health supervision levels were significantly different (F=3.30, P=0.024). The PPD value and SET value of the front-desk staff, and the PPD value of cleaning staff of hotels above three stars were lower than those of hotels below three stars (P<0.05). The thermal comfort compliance of front-desk staff and cleaning staff in hotels above three stars was higher than that in hotels below three stars (χ(2)=8.33, 8.09, P=0.016, 0.018). The consistency of the two criteria was highest among waiting room (bus station) staff (100.0%, 1/1) and lowest among gym front-desk staff (0%, 0/2) and waiting room (bus station) cleaning staff (0%, 0/1) . Conclusion: There are different degrees of thermal discomfort in different seasons, under the condition of air conditioning and health supervision, and the microclimate indicators can not fully reflect the thermal comfort of human body. The health supervision of microclimate should be strengthened, the applicability of health standard limit value should be evaluated in many aspects, and the thermal comfort of occupational group should be improved.

Climate chamber investigation of the effect of indoor thermal histories on thermal adaptation in different seasons

The indoor thermal history of residents in the hot summer and cold winter climate zone in China have undergone a significant change in recent years, which also changes their seasonal thermal adaptations and this has formed feed-back effects to the increasing usage of air conditioning units in this area. To study the seasonal variations of thermal adaptation, the thermal comfort experiments were conducted on two groups of participants. Each groups included 20 participants who had indoor history mainly with natural ventilation (NV group) and air-conditioning (AC group), respectively. The results demonstrated that the thermal sensation vote (TSV) in warm environments did not differ between AC and NV subjects in summer. However, the TSV of AC subjects were much lower than that of NV subjects in the same standard effective temperature and skin temperature in a cold environment in winter. Overall, the participants who spent most of their time in AC space in winter showed a low level of thermal adaptation with a narrower acceptable skin temperature range of 32.6 – 33.5 °C. Thus, this study presents the basic information regarding the seasonal effects on human thermal adaptation due to different long-term indoor thermal histories.

Assessing thermal resilience of an assisted living facility during heat waves and cold snaps with power outages

Extreme hot and cold weather events are becoming more frequent, intense, and longer due to climate change. When these events occur coincidentally with power outages, the resulting extreme indoor temperatures pose a severe health hazard for occupants. This study conducted a holistic modeling and analysis of an assisted living facility, where senior residents live, to assess its thermal resilience performance under a six-day heat wave in 2015 and a three-day cold snap in 2021 with power outages. Impacts of 13 energy efficiency measures on thermal resilience and backup power capacity of the facility were evaluated. Three thermal resilience metrics: the SET (standard effective temperature) degree-hours, the Heat Index, and the Hours of Safety, were used and calculated from the EnergyPlus simulation models. Major findings are: (1) the facility would suffer from extreme temperatures during the cold and hot events without a power supply, not meeting the passive survivability requirements; (2) most passive envelope measures improve thermal resilience for both hot and cold events, but making the building envelope airtight results in conflicting performance between the hot and cold events; (3) natural ventilation is an effective measure to mitigate summer indoor overheating; and (4) the energy efficiency package can reduce backup power capacity by 19% for the three-day cold snap. It is recommended that building technologies and design strategies be evaluated to consider co-benefits of energy use, thermal resilience, and backup power needs through building energy codes or policies for existing and new buildings, which are transitioning for decarbonization and climate resilience.

Effects of various environmental grades on thermal comfort in semi‐outdoor spaces

AbstractThe introduction of semi‐outdoor spaces to urban spaces and offices has increased in recent years. In previous studies, environmental grade has been defined as the level of control for the thermal environment set for an architectural space based on the use, where “semi‐outdoor environment” is an environmental grade division that exists as a gradation between indoors and outdoors. This study aims to clarify effects of various environmental grades on thermal comfort. Field surveys were conducted in five semi‐outdoor spaces in Tokyo from 9 to 25 September 2021, consisting of thermal environment measurement, questionnaires about thermal comfort and impression of surveyed spaces and real‐time sensation voting. By impression evaluation and comparison of the regression curves of standard new effective temperature (SET*) against percentage of “uncomfortably warm,” the surveyed spaces were classified into two categories: “outdoor tendency” and “indoor tendency.” The difference in thermal comfort for the diverse semi‐outdoor environment could be evaluated by the difference in spatial characteristics such as “sense of weight” of the top surface in addition to the difference in environment control. By regression analysis of real‐time sensation voting result using hierarchical Bayesian approach, environmental grade was clarified to affect the correlation between pleasantness/unpleasantness and air velocity.

The other side

Building occupants are either used or compelled to live in overheated indoors in buildings, particularly in urban environments in the tropics. It doesn’t mean that they are acclimatized to overheated indoors. This scenario has become a normalcy in the current building design and operational practice. The fail- ure of building design to control heat transfer from outside to inside and remove indoor heat generat- ed by occupants and equipment in buildings to the outside is seen as a major reason for indoor over- heating. This normalcy is problematic for the occu- pants in particular and to the environment at large. It is problematic because of its negative effect on the indoor comfort level on one hand and associated emissions due to wasteful (or rather extensive) use of energy for cooling on the other hand. Overheating elevates the indoor thermal environment particu- larly the standard effective air temperature higher than the preferred thermal comfort range. Similarly, the dramatic effect of daylighting that could be gen- erated from architectural space is seen as least re- garded and not taken into the indoors meaningfully in today’s average building design and practice, thus largely depending on active systems. Lack of opti- mum balance in daylight, artificial or mixed mode visual environments demands more energy either to maintain indoor visibility or to combat glare and heat stress associated with tropical daylighting, or both. This overall practice uses extensive amounts of ac- tive energy to maintain indoor comfort (both thermal and visual) contributing to emissions and weakening the demand side efficiency of operational stage.

Indoor Environmental Quality assessment of mixed-mode ventilation with ceiling fans in the tropics

Mixed-mode ventilation in buildings has a potential for significant energy savings. However, previous attempts in the tropics were unsuccessful due to the hot and humid weather. Indeed, there is little to no natural ventilation potential in tropical climates if conventional air conditioning systems are used. Additionally, existing studies typically do not consider the noise and air quality constraints while the performance of mixed-mode buildings is susceptible to outdoor conditions. Using elevated air movement has proven to be an effective strategy to offset the rise in the room temperature setpoint without sacrificing occupants’ thermal comfort as it helps dissipate body heat through the convective cooling effect. Hence, this study aims at investigating the total indoor environment quality (IEQ) performance of mixed-mode ventilation operations with various air speeds based on tropically acclimatized subjects. To this end, a testbed was designed and constructed in Singapore, consisting of a variable air volume (VAV) system, ceiling fans with continuous speed control, personal ventilation (PV) desks, and plenum acoustic windows. Five operating modes have been tested: fully air-conditioned (AC) mode using VAV alone, hybrid air conditioned (AC+PV) mode using VAV and PV desks, concurrent ventilation (CV) mode using PV desks with the windows partially opened, natural ventilation (NV) mode with the windows fully opened, and acoustic natural ventilation (Acoustic NV) mode with the windows partially opened. 57 subjects were invited to the experiment and asked to complete a comprehensive IEQ survey under 16 different indoor conditions, which are combinations of these operating modes and air speeds ranging from 0.10 to 1.15 m/s. Experiment results show that NV and CV in Singapore can achieve more than 90% thermal acceptability with adequate air movement. More importantly, the median standard effective temperature (SET*) for thermal neutrality is approximately 3°C higher when operating in NV as compared to AC+PV or CV modes, indicating adaptation even when the modes switches are within the same day.