Thermal Discomfort Index Research Articles

Comprehensive spatiotemporal evaluation of urban growth, surface urban heat island, and urban thermal conditions on Java island of Indonesia and implications for urban planning

Urban heat island (UHI) and thermal comfort conditions are among the impacts of urbanization, which have been extensively studied in most cities around the world. However, the comprehensive studies in Indonesia in the context of urbanization is still lacking. This study aimed to classify land use and land cover (LULC) and analyse urban growth and its effects on surface urban heat islands (SUHIs) and urban thermal conditions as well as contributing factors to SUHI intensity (SUHII) using remote sensing in the western part of Java Island and three focused urban areas: the Jakarta metropolitan area (JMA), the Bandung and Cimahi Municipalities (BC), and the Sukabumi Municipality (SKB). Landsat imagery from three years was used: 2000, 2009, and 2019. Three types of daytime SUHII were quantified, namely the SUHII of urban central area and two SUHIIs of urban sprawl area. In the last two decades, urban areas have grown by more than twice in JMA and SKB and nearly 1.5 times in BC. Along with the growth of the three cities, the SUHII in the urban central area has almost reached a magnitude of 6 °C in the last decade. Rates of land surface temperature change of the unchanged urban pixels have magnitudes of 0.25, 0.15, and 0.14 °C/year in JMA, SKB, and BC, respectively. The urban thermal field variance index (UTFVI) and discomfort index (DI) showed that the strongest SUHI effect was most prevalent in urban pixels and the regions were mostly in the very hot and hot categories. Anthropogenic heat flux and urban ratio have positive contributions to SUHII variation, while vegetation and water ratios are negative contributors to SUHII variation. For each city, the contributing factors have a unique magnitude that can be used to evaluate SUHII mitigation options.

Urban Heat Island Assessment in the Northeastern State Capitals in Brazil Using Sentinel-3 SLSTR Satellite Data

The lack of a solid methodology defining urban and non-urban areas has hindered accurately estimating the Surface Urban Heat Island (SUHI). This study addresses this issue by using the official national urban areas limit together with a surrounding areas classification to define three different reference classes: the urban adjacent (Ua), the future urban adjacent (FUa), and the peri-urban (PUa), consequently providing a more accurate SUHI estimation on the nine northeastern Brazilian capitals. The land surface temperature was obtained in this study using the Sentinel-3 satellite data for 2019 and 2020. Subsequently, the maximum and average SUHI and the complementary indexes, specifically the Urban Thermal Field Variation Index (UTFVI) and the Thermal Discomfort Index (TDI), were calculated. The UTFVI expresses how harmful the eco-environmental spaces are, with a very strong SUHI for three capitals. In addition, the TDI, with values between 24.6–28.8 °C, expresses the population’s thermal comfort, with six capitals showing a very hot TDI. These findings highlight the need for strategies to mitigate the effects of the SUHI and ensure the population’s thermal comfort. Therefore, this study provides a better SUHI understanding and comparison for the Brazilian northeastern region, which has diverse areas, populations, and demographic variations.

The impact of meteorological changes on the quality of life regarding thermal comfort in the Amazon region

The meteorological imbalances in Brazil have a strong impact on the lives of the population across the country, especially in the Amazon region. These impacts extend to meteorological phenomena, such as extreme rainfall, droughts, and an increase in temperature in several regions, as well as impacts on health, the economy, and, as the object of this study, the quality of life. This study presents the impact of meteorological changes on the quality of life in the Amazon region, based on (i) the thermal discomfort index (TDI), (ii) the temperature and humidity index (THI), and (iii) the effective temperature index as a function of the wind (TEFW). For this, meteorological data from the years 2003–2021 were used, in which the variables include total precipitation, global radiation, air-dry bulb temperature, the maximum temperature in the previous hour, the minimum temperature in the previous hour, relative humidity, and wind speed. This analysis indicates that for this tropical region, the sensation of mild discomfort was predominant in about 70% of the measurements, indicating a certain level of impact on the population's quality of life, in addition to the fluctuation of levels of discomfort during periods of winter in that there are high rates of precipitation. The data control was performed with the removal of null data and calculation of monthly and annual averages, by using the compression (average) empty data frames in order to receive the values without losing the indexing of dates. At first, it was considered to use the kriging process to fill in the missing data; however, due to the existence of microclimates in the regions, the data could characterize remote regions in a generalized way, which would make it difficult to understand these data in comparison with the data from the National Institute of Meteorology (INMET, in Portuguese).

An assessment of the impact of passive design variations of the building envelope using thermal discomfort index and energy savings in warm and humid climate

Over the years, the commercial buildings sector has emerged as one of India’s fastest-growing sector and the commercial space is expected to grow four fold between 2015 and 2030. Due to the absence of thermal comfort regulations in India, designers frequently overdesign cooling systems in accordance with international norms, leading to unsustainable practises and energy wastage. The conventional building construction in India’s warm and humid climate make people uncomfortable due to heat gains, forcing the use of cooling equipment that require a lot of energy. Use of passive design options in the building envelope is thought to be a viable strategy for lowering energy usage. The different effects of building exterior components and passive design solutions on the indoor thermal environment can be effectively integrated using the criterion of thermal comfort. A new thermal discomfort index based on adaptive comfort using the numerical method and trapezoidal rule is established and used as a basis of comparison to assess the relative performance of building envelopes. In comparison to the reference building envelope in warm, humid climate, the research shows that careful attention to building envelope design with consideration of various passive options can improve the indoor thermal environment by 5.82 °C, reduce thermal discomfort by 80.75 percent and save energy up to 77 percent.

Influence of green areas on the microclimate of the contiguous urban perimeter

The daily pressures exerted by urban centers, added to the absence of green areas, end up promoting great damage to the quality of life of the resident population. This study aimed to evaluate the influence of a green park in the central area in Dourados, MS, Brazil, on thermal and sound comfort through environmental indicators. The following measurements were taken: air temperature, relative air humidity, light incidence, and noise variation at sampling points in the Arnulpho Fioravante green park and adjacent areas. The thermal discomfort index (TDI), which considers the variables air temperature and relative air humidity, was also adopted. TDI and noise results indicated that the park has little influence on adjacent areas. On the other hand, the park area with the highest plant density showed significant TDI values, classifying it between “feeling comfortable” and “feeling partially uncomfortable.” Areas of the city and the park without vegetation had many “feeling uncomfortable” ratings. Moreover, the vegetation may have acted as a filter to minimize urban noise. Our results indicate that urban green areas are important components in maintaining the population’s quality of life, provided they have good planning and management of available forest resources.

Internet of things and machine learning applied to the thermal comfort of internal environments

The internet of things connects objects to the internet, enabling the dialogue between devices and users, providing new opportunities for applications, such as thermal comfort. In the research, adequate sensors were used to measure the heat index, the thermal discomfort index and the temperature and humidity index based on the temperature and relative humidity of a remote indoor environment. This research evaluated the level of thermal comfort in real-time using tools of storage, processing and analysis of big data information from the collection of IoT devices. With the analysis of the environment, it is possible to intelligently monitor the level of comfort and alert possible hazards to the people present. Machine learning algorithms were also used to analyse the history of stored data and formulate models capable of making predictions of the parameters of the environment. Health researchers, for example, have the necessary knowledge to evaluate clinical data, but they are not used to using data analysis resources and machine learning algorithms. The platform was developed to reduce dependence on data experts and encourage healthcare researchers to develop their own models by automating the steps required for model development, using automated machine learning (AutoML).

Trend analysis of Humidex as a heat discomfort index using Mann-Kendall and Sen’s slope estimator statistical tests

Background: The aim of this research was to assess the Humidex (HD) trends as a thermal discomfort index by analyzing meteorological data during a 30-year period of summertime in Iran. Methods: For this purpose, data regarding average temperature and relative humidity were collected daily from 40 different synoptic meteorological stations during a 30-year statistical period (1985-2014). The HD index was calculated based on temperature and relative humidity according to an equation introduced by Masterton and Richardson. The Mann-Kendall and Sen’s slope tests were performed to analyze the changing trend of the HD. Results: Based on the findings, in 72% of the meteorological stations, the HD followed an upward trend, so that 40% of them was statistically significant. The changing trends in temperature during summertime throughout the studied years fluctuated greatly but generally, in many regions such as the arid, semi-arid, and humid regions, this trend was mostly incremental. Also, the changing trends in relative humidity in all regions was decremental throughout the years under study. Conclusion: The changing trend of the HD, which is based on temperature and humidity, was incremental in arid and semi-arid regions and decremental in the Mediterranean and humid regions.

Clima Urbano e Ilhas de Calor no Miolo Urbano na Cidade de Salvador (BA)

O objetivo desta pesquisa foi analisar as ilhas de calor na cidade de Salvador nos bairros do Cabula e Pernambués ambos localizados no miolo urbano da cidade. Foram discutidos a relevância dos fatores geográficos de localização, altitude, influência dos sistemas de brisas marítimas e continentais, assim como o efeito do aquecimento das superfícies devido ao uso do solo urbano. Foi utilizada a concepção teórico-metodológica do Sistema Clima Urbano. Neste contexto, foram gerados mapas de usos dos solos das localidades através do programa Arcview 9.1. Posteriormente, foram efetuadas tomadas das temperaturas de superfície através de termômetros sensores de infravermelho nos diversos tipos de coberturas do solo em visitas técnicas à diversas ruas e avenidas nos bairros. Tais informações subsidiaram a organização do relatório final da pesquisa que se utilizou do Índice de Desconforto Térmico (ID). A utilização do ID detém extrema relevância pois busca estabelecer correlações entre as ilhas de calor e o desconforto físico que detém impacto direto na saúde e qualidade de vida das pessoas. Nos bairros do Pernambués e do Cabula foram identificadas classes de zona de desconforto. Porém, cabe destacar a relevância do fragmento da Mata Ombrófila Densa como elemento fundamental no estabelecimento de ilha de frescor no bairro Cabula.Palavras-chave: ilhas de calor, sistema clima urbano, fatores geográficos, uso do solo, desconforto térmico. Urban Climate, Heat Islands and Thermal Comfort in the Neighborhoods of Cabula and Pernambués in the Urban Center of Salvador (BA) A B S T R A C TThe objective of this research was to analyze the heat islands in the city of Salvador in the neighborhoods of Cabula and Pernambués both located in the urban core area of the city. The relevance of geographic factors of location, altitude, influence of sea and continental breeze systems, as well as the effect of heating of surface areas to urban land use were addressed. The theoretical and methodological conception of the Urban Climate System. In this context, maps of land uses of localities were generated through the arcview 9.1 programa. Subsequently, surface temperatures were made through infrared sensor thermometers through the various types of ground cover through technical visits to several streets and avenues in the neighborhoods. This information supported the organization of the final report of the research that used the Thermal Discomfort Index (ID). The use of ID has extreme relevance because it seeks to establish correlations between heat islands and physical discomfort that has a direct impact on people's health and quality of life. In the neighborhoods of Pernambués and Cabula, discomfort zone classes were identified. However, it is worth highlighting the relevance of the fragment of the Dense Ombrófila Forest as a fundamental element in the establishment of a frescor island in the Cabula neighborhood.Keywords: heat islands, urban climate system, geographic factors, land use, thermal discomfort.

A Thermal Discomfort Index for Demand Response Control in Residential Water Heaters

Demand-response techniques are crucial for providing a proper quality of service under the paradigm of smart electricity grids. However, control strategies may perturb and cause discomfort to clients. This article proposes a methodology for defining an index to estimate the discomfort associated with an active demand management consisting of the interruption of domestic electric water heaters. Methods are applied to build the index include pattern detection for estimating the water utilization using an Extra Trees ensemble learning method and a linear model for water temperature, both based on analysis of real data. In turn, Monte Carlo simulations are applied to calculate the defined index. The proposed approach is evaluated over one real scenario and two simulated scenarios to validate that the thermal discomfort index correctly models the impact on temperature. The simulated scenarios consider a number of households using water heaters to analyze and compare the thermal discomfort index for different interruptions and the effect of using different penalty terms for deviations of the comfort temperature. The obtained results allow designing a proper management strategy to fairly decide which water heaters should be interrupted to guarantee the lower discomfort of users.

Usage of Arduino-based Datalogger for thermal comfort variables monitoring

Environmental monitoring is an effective tool to identify problems in anthropic areas, and the emergence of cyber-physical sensors contributes to technological advances in the area. This paper introduces a device based on the Arduino cyber-physical platform to monitor air temperature and relative humidity in real-time with high efficiency. With the relationship between these two environmental variables, it will be possible to calculate the Heat Index (CI), the Temperature and Humidity Index (ITU), the Effective Temperature Index (ET), and the Thermal Discomfort Index (IDT). The Datalogger developed is easily programmable and easy to assemble and presented stable operation and proper functioning.

Analysis of Outdoor Thermal Discomfort Over the Kingdom of Saudi Arabia.

In this study, the variability and trends of the outdoor thermal discomfort index (DI) in the Kingdom of Saudi Arabia (KSA) were analyzed over the 39‐year period of 1980–2018. The hourly DI was estimated based on air temperature and relative humidity data obtained from the next‐generation global reanalysis from the European Center for Medium‐Range Weather Forecasts and in‐house high‐resolution regional reanalysis generated using an assimilative Weather Research Forecast (WRF) model. The DI exceeds 28°C, that is, the threshold for human discomfort, in all summer months (June to September) over most parts of the KSA due to a combination of consistently high temperatures and relative humidity. The DI is greater than 28°C for 8–16 h over the western parts of KSA and north of the central Red Sea. A DI of >28°C persistes for 7–9 h over the Red Sea and western KSA for 90% of summer days. The spatial extent and number of days with DI > 30°C, that is, the threshold for severe human discomfort, are significantly lower than those with DI > 28°C. Long‐term trends in the number of days with DI > 28°C indicate a reduced rate of increase or even a decrease over some parts of the southwestern KSA in recent decades (1999–2018). Areas with DI > 30°C, in particular the northwestern regions of the Arabian Gulf and its adjoining regions, also showed improved comfort levels during recent decades. Significant increases in population and urbanization have been reported throughout the KSA during the study period. Analysis of five‐years clinical data suggests a positive correlation between higher temperatures and humidity with heat‐related deaths during the Hajj pilgrimage. The information provided herein is expected to aid national authorities and policymakers in developing necessary strategies to mitigate the exposure of humans to high levels of thermal discomfort in the KSA.

Retrofitting post-war office buildings: Interventions for energy efficiency, improved comfort, productivity and cost reduction

Within the UK non-domestic building stock, offices built between 1940 and 1980, are especially in need of retrofit, they can suffer from high energy consumption and thermal discomfort. Many post-war offices will still be in use throughout the first half of this century. This paper evaluates retrofit strategies for post-war office buildings accounting for the improved energy efficiency, thermal comfort and hence productivity, and reduction of capital and running costs. The aim of the paper is seeking optimal, generic retrofit strategies to provide guidance to building owners, occupiers and other decision makers. Dynamic thermal modelling is used to compare retrofit outcomes for existing building standards (PartL2B) and higher standards (Passivhaus retrofit: EnerPHit). The effects of location and orientation and both current and future UK weather conditions (2050) are considered. Multiple combinations of heating and cooling strategies and retrofit measures are assessed. The analysis methodology uses a sophisticated comfort, productivity and cost assessment. An Overall Building Thermal Discomfort (OBTD) index is introduced which enriches the current CIBSE overheating criterion 1 by including the number of occupants. Productivity improvements as a result of better comfort are included in cost calculations. Cost benefits are calculated both for buildings used by the owner (CBO) and for buildings let to a tenant (CBT). On cost and energy grounds, UK building regulation compliant retrofit is optimal provided that passive summertime overheating controls, such as night ventilation, blinds and/or overhangs, are installed. The EnerPHit standard retrofit provides resilience as the climate warms provided summer cooling is available, for example through mixed-mode ventilation.

URBAN MICROCLIMATE IN VEGETATED AND NON-VEGETATED AREAS IN RAINY AND SUNNY CONDITIONS

Cuiabá city is nationally known as "green city" because of to its large afforestation, has experienced progressive urban expansion for years, with deforestation possibly causing a rise in temperature and the development of heat islands In this context the afforestation can be an alternative for the improvement of the thermal comfort of the residents of this city. So the study objective was to analyze the microclimate differences of vegetated and non-vegetated urban areas in rainy and sunny conditions, analyzing also the heat index and the thermal discomfort index. The sampling took place at a public place and great flow of pedestrians. Data on the air temperature (T air ), soil temperature (T s ), and relative air humidity (R h ) were recorded using two linear transects, starting at 7 am and ending at 7 pm, in two-hour intervals. Due to the seasonality of the city's climate, measurements were taken in the dry and humid period of the year. There was a statistical difference for soil temperature between the sites (p-value < 0.001) and an increase of approximately 10°C in both periods in non-vegetated areas. There was no statistically significant difference for the heat index and thermal discomfort index among the analyzed transects, especially in the wet season, periods of discomfort occurred. Was verified that for open sites vegetation decreased air and soil temperature, increased relative humidity, but it was not enough to have thermal comfort at all times of the day.

Indoor thermal comfort assessment using PCM based storage system integrated with ceiling fan ventilation: Experimental design and response surface approach

The integration of Phase Change Materials (PCMs) in buildings as a potential method to improve indoor thermal comfort can be achieved via free cooling/heating approach. This paper presents the results of a study on indoor thermal comfort and energy efficiency regarding the PCM's positive role when applied to the new constructive solutions, inside a building with a ceiling fan-assisted ventilation system. The scope was driven to investigate the potential of the solution for overheating/overcooling mitigation. The thermal performance of the proposed system was experimentally evaluated by comparing the behaviour of a prototype test room (including PCM panel), with the behaviour of a similar prototype test room, in which no PCM was added. First the experiments are conducted in an artificial climate inside a laboratory environment chamber which was controlled by harmonic and linearly rising/falling temperature changing processes. Experiments were performed based on 5 level RSM CCD method to quantify the potential effects of using PCM panels and to determine individual/interactive effect of parameters on thermal discomfort index, PPD. Results indicate that minimum discomfort level can be achieved when inlet air temperature and humidity, fan rotating speed and PCM slab height and thickness were set to 29, 48%, 115 rpm, 31 cm and 2.6 cm, respectively. PPD was obtained 4.1% in the optimized condition. Then optimised tests rooms were subjected to realistic daily temperature profiles during winter and summer. In summer case, the experiments proved that the PCM application in one of the rooms lead to an overheating reduction of 13.83% representing a PCM efficiency of 56%. Under the winter condition during two months, the experiments showed proposed hybrid system can averagely reduce discomfort level around 2.61% corresponding a PCM efficiency of about 35.49%. Based on the results, proposed system have the potential to shift cooling/heating energy demand away from peak hours.

Valuation of the human thermal discomfort index for the five Brazilian regions in the period of El Niño-Southern Oscillation (ENSO).

Brazil is an extensive country with five administrative regions that have different climates, mainly due to their geographic locations. The El Niño-Southern Oscillation influences the regime of temperature and precipitation of the Brazilian regions, which can directly affect the thermal discomfort of the population. The objective of this study was to evaluate the human thermal discomfort index (HDI) in the five regions of Brazil for El Niño, La Niña, and neutral years from 1979 to 2017, as well as the influence of the degree of intensity of the Pacific Ocean anomaly in the thermal conditions of the Brazilian regions. Monthly data on air temperature and dewpoint temperature obtained from the ERA-Interim reanalysis were used. The HDI was calculated using specific equations. The results were analyzed by means of composition fields. From the results, it was possible to conclude that the El Niño and La Niña phenomena influence the HDI of the Brazilian regions. El Niño increases the discomfort due to the heat and the La Niña causes them to decrease. This study is important since these phenomena, by influencing thermal conditions, directly affect the well-being and health of the Brazilian population.

Thermal Comfort Level Assessment in Urban Area of Petrolina-PE County, Brazil

Abstract This study evaluated the thermal conditions of urban areas in Petrolina-PE, from continuous data collected in urban and rural areas for the year of 2012. The results characterized urban heat islands (UHI) with varying intensity in urban areas, especially UHI = 5.3 °C (high intensity) occurred on April 28, 2012. It was evident that the constituent elements of urban areas contribute to the formation and expansion of UHI bringing thermal discomfort for its inhabitants. An adaptation to Thom’s equation for calculating the Thermal Discomfort Index (DIT), was used to obtain the maximum (DITx) and minimum (DITm) thermal discomfort. In the urban area, the DITm indicated thermal comfort in 23.0% of the days and partial comfort in 77.0% of days surveyed. Already, the DITx characterized 71.6% of days with partial comfort and 28.4% of days with thermal discomfort. In the rural area, The DITm indicated that 41.5% of days were thermally comfortable and 58.5% of days had partial comfort. However, the DITx pointed 87.7% of the days of this environment with partial thermal comfort and 12.3% of thermally uncomfortable days. Finally, the results showed that afforestation of urban area constitutes to an effective and efficient way to mitigate thermal discomfort.

Thermal load at workstations in the underground coal mining: Results of research carried out in 6 coal mines

Statistics shows that almost half of Polish extraction in underground mines takes place at workstations where temperature exceeds 28°C. The number of employees working in such conditions is gradually increasing, therefore, the problem of safety and health protection is still growing. In the present study we assessed the heat load of employees at different workstations in the mining industry, taking into account current thermal conditions and work costs. The evaluation of energy cost of work was carried out in 6 coal mines. A total of 221 miners employed at different workstations were assessed. Individual groups of miners were characterized and thermal safety of the miners was assessed relying on thermal discomfort index. The results of this study indicate considerable differences in the durations of analyzed work processes at individual workstations. The highest average energy cost was noted during the work performed in the forehead. The lowest value was found in the auxiliary staff. The calculated index of discomfort clearly indicated numerous situations in which the admissible range of thermal load exceeded the parameters of thermal load safe for human health. It should be noted that the values of average labor cost fall within the upper, albeit admissible, limits of thermal load. The results of the study indicate that in some cases work in mining is performed in conditions of thermal discomfort. Due to high variability and complexity of work conditions it becomes necessary to verify the workers' load at different workstations, which largely depends on the environmental conditions and work organization, as well as on the performance of workers themselves. Med Pr 2016;67(4):477-498.

Two Stage Assessment of Thermal Hazard in An Underground Mine

Abstract The results of research into the application of selected thermal indices of men’s work and climate indices in a two stage assessment of climatic work conditions in underground mines have been presented in this article. The difference between these two kinds of indices was pointed out during the project entitled “The recruiting requirements for miners working in hot underground mine environments”. The project was coordinated by The Institute of Mining Technologies at Silesian University of Technology. It was a part of a Polish strategic project: “Improvement of safety in mines” being financed by the National Centre of Research and Development. Climate indices are based only on physical parameters of air and their measurements. Thermal indices include additional factors which are strictly connected with work, e.g. thermal resistance of clothing, kind of work etc. Special emphasis has been put on the following indices - substitute Silesian temperature (TS) which is considered as the climatic index, and the thermal discomfort index (δ) which belongs to the thermal indices group. The possibility of the two stage application of these indices has been taken into consideration (preliminary and detailed estimation). Based on the examples it was proved that by the application of thermal hazard (detailed estimation) it is possible to avoid the use of additional technical solutions which would be necessary to reduce thermal hazard in particular work places according to the climate index. The threshold limit value for TS has been set, based on these results. It was shown that below TS = 24°C it is not necessary to perform detailed estimation.

Characterization of human thermal comfort in urban areas of brazilian semiarid

ABSTRACT Experimental studies were conducted aiming to characterize the thermal conditions in urban areas of the Brazilian semiarid for identifying the level of human thermal comfort in urban areas of the municipalities of Mossoró-RN, Serra Talhada-PE, Petrolina-PE and Juazeiro-BA. The results showed that the constituent elements of urban areas contribute to human thermal discomfort index (DIT). Both the wet and dry seasons showed up an uncomfortable condition in Mossoró on May 15th and on 23rd, 2008 (rural area) and on May 25rd, 2008 (urban area). By applying Thom's equation for obtaining the DIT, it was observed that the urban areas reported thermal comfort conditions always inferior to those observed in the rural areas. The results indicate conditions of partial comfort for the all areas surveyed. However, the incidence of human thermal discomfort related to the minimum, average and maximum air temperatures are, probably associated to the formation of urban heat islands. In addition, the afforestation is an effective mechanism of mitigating the adverse effects of these structures with better quality of life to the population. Therefore, it can be stated that the Brazilian semiarid region has specific urban climate, which is influenced by the design characteristics of the urban structure and buildings.

Effects of return air vent height on energy consumption, thermal comfort conditions and indoor air quality in an under floor air distribution system

In this article, an under floor air distribution (UFAD) system with separate return and exhaust air vents is investigated. The proper angle of the swirl inlet diffuser is selected by comparing the general thermal comfort conditions obtained from three different inlet angles. At this proper inlet angle, the effects of return air vent height on energy consumption, thermal comfort conditions, and indoor air quality (IAQ) are investigated. To this end, thermal comfort indices (PMV–PPD), local thermal discomfort index (temperature gradient in vertical direction), and IAQ index (mean local age of air) are probed by CFD methods. Energy consumption reduction in an UFAD system equipped with a return air vent compared to MV system is 10.9, 15.3, 18.9, and 25.7% when the return air vent height is set at 2.0, 1.3, 0.65, and 0.3m, respectively. Reducing the height of return air vent from ceiling to floor leads to an increase in exhaust air temperature and temperature gradient at the vertical direction. It is found that selection of the 1.3m height from floor (upper boundary of occupied zone in seated mode) for return air vent height will cause a 15.3% reduction in energy consumption and would maintain the thermal comfort and IAQ in the specified range.