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Volume 37, Issue 4 (2022)
GeoRes 2022, 37(4): 557-564 |
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Received: 2022/09/29 | Accepted: 2022/12/1 | Published: 2022/12/16
Received: 2022/09/29 | Accepted: 2022/12/1 | Published: 2022/12/16
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Salem M, Moradkhani A, Ghaedi H. Analysis of Comfort and Thermal User-Perception in Open Urban Spaces of Hot and Humid Regions; a Case Study of Bandar Abbas City, Iran. GeoRes 2022; 37 (4) :557-564
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1- Department of Architecture, Faculty of Technical and Engineering, Mariwan Branch, Islamic Azad University, Mariwan, Iran
2- Department of Architecture, Technical and Engineering Faculty, Technical and Vocational University, Bandar Abbas, Iran
2- Department of Architecture, Technical and Engineering Faculty, Technical and Vocational University, Bandar Abbas, Iran
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Introduction
Bandar Abbas is a major port city in southern Iran that has experienced rapid growth in urban size, population, transportation, and industrial and commercial sectors since 1980, the start of the Iran–Iraq war. This rapid expansion has caused changes in the urban microclimate, negatively affecting human thermal comfort during the hot summer months. Few studies have investigated the impact of climate on urban planning and design in hot and humid climates, particularly in southern Iran and the Persian Gulf region [Thapar, 2008]. Therefore, urban climate studies in these areas are essential for planners and urban designers.
Outdoor thermal comfort has recently gained particular importance within urban microclimate studies for different seasons. Historically, if architecture is not considered simply as the art of providing shelter from climatic elements (protection from wind and rain), human comfort has always been a central goal of architectural design, with thermal comfort being one aspect. Architecture can also be regarded as a “third layer of clothing”: the first being the skin, the second textiles, and the third, the building itself. In outdoor urban spaces, although this “third layer” is partially absent, architecture still exerts influence because it is human-model this is the aspect addressed by the present study.
Microclimate is a crucial factor in determining the quality of outdoor spaces because individuals’ perceptions of spatial quality are strongly influenced by microclimatic conditions. Microclimate also affects human presence in these spaces, as numerous studies have shown that thermal comfort conditions influence both the frequency and duration of outdoor activities [Chen & Ng, 2012; Givoni et al., 2003; Nikolopoulou et al., 2001; Zacharias et al., 2001]. Moreover, indoor thermal conditions are affected by outdoor environments, meaning that improving outdoor conditions can enhance indoor thermal comfort and reduce energy demand for achieving thermal comfort [He et al., 2009; Hoppe & Lin, 2007].
Extensive research over the last decade has examined thermal comfort components along various coastal regions worldwide [Cheng & Ng, 2012; Nikolopoulou, 2011]. Some studies have focused on assessing outdoor thermal comfort zones to evaluate individuals’ thermal perceptions in different climates [Ahmed, 2003; Givoni et al., 2003; Hwang & Lin, 2007; Krüger, 2011; Lin, 2009; Thorsson et al., 2007; Nikolopoulou et al., 2001]. Other studies have indicated that outdoor thermal comfort zones and perception levels vary depending on geographic, physiographic, and cultural differences [Zhao et al., 2016].
Personal parameters have mainly been studied concerning psychological aspects of thermal perception [Lin, 2009; Nikolopoulou et al., 2001; Thorsson et al., 2007]. For instance, a study has focused on age and gender as influential factors on outdoor thermal perception in Tehran [Amindeladar et al., 2017]. Other studies, such as Furgus and Dalman, identified wind speed and clothing as key factors affecting thermal sensation in hot and humid regions [Furgus, 2004; Dalman et al., 2012]. Givoni has emphasized that airflow in outdoor spaces of hot and humid climates often contributes to thermal comfort [Givoni, 1994].
In Iran, outdoor thermal comfort in urban spaces has received limited attention, with only a few field studies conducted, such as Monam’s research on thermal comfort in Tehran’s parks [Monam, 2011]. Given the climatic nature of this topic, each region requires its own focused study.
Deevi and Chundeli’s study in a hot and humid climate in India, using questionnaires based on lived perceptions, have found a significant relationship between the sky view factor and increased heat tolerance, alongside the influence of mean radiant temperature on street thermal comfort [Deevi & Chundeli, 2020]. Another study in India has indicated that vegetation cover and water presence reduce the temperature–humidity index and improve people’s thermal tolerance [Das & Das, 2020]. Recently, research has also has emphasized emotional dimensions of thermal comfort, such as thermal pleasure and thermal intensity, alongside the traditional four descriptive dimensions (temperature, wind, humidity, and solar exposure) [Liu et al., 2020].
Most studies on thermal comfort focus on indoor spaces, with relatively few field studies in outdoor environments. Majidi et al. have examined thermal comfort in four neighborhoods in Isfahan and concluded that the effective temperature index aligns closely with field observations [Majidi et al., 2018]. Baghai et al. has assessed user perceptions and environmental measurements in traditional courtyards in Yazd, establishing thermal comfort ranges for hot and arid climates [Baghai et al., 2014]. Chehrazi et al. have studied thermal comfort in girls’ primary schools in Isfahan, determining neutral temperature and comfort ranges for females in hot and dry areas [Chehrazi et al., 2021].
A recent emerging topic is the effect of cultural and social homogeneity of neighborhood residents on outdoor thermal comfort ranges and the influence of microclimatic and personal parameters. Results indicated that cultural and social differences among residents can alter thermal comfort ranges and the key influencing factors. For example, Yu-Peng et al. have compared outdoor thermal comfort in two culturally distinct groups in the same climate, finding that temperature and airflow were primary factors for one group, whereas activity enjoyment and psychological expectations have influenced comfort more in the other [Peng et al., 2021]. Mishra et al., in a review of indoor thermal comfort studies, also have observed that culturally and socially homogeneous groups yield more consistent and accurate results [Mishra et al., 2016]. Accordingly, this study selected a homogeneous neighborhood with traditional residents to minimize the effects of heterogeneous groups.
This research examined the effects of microclimatic and personal parameters on perceived temperature in the geography, culture, and climate of Bandar Abbas. Among microclimatic parameters, air temperature, solar radiation, and wind speed (environmental factors) were assessed in combination with clothing and age as personal (human) parameters. The study was conducted in both summer and winter in Bandar Abbas and primarily involves field measurements of microclimatic parameters alongside subjective assessments of thermal perception. This approach aligns with three recent studies conducted in 2021, emphasizing the importance of questionnaires to capture perceived thermal comfort. This research also aims to evaluate personal factors affecting thermal comfort beyond external environmental conditions, which were the primary focus of previous studies.
Methodology
This study employed an experimental approach using field measurements and questionnaires to assess thermal comfort during both hot and cold seasons. Field measurements of air temperature, wind speed, and relative humidity were conducted over 20 days (August 6 to August 26 and February 1 to February 20) at 12 different locations in the coastal neighborhood of Khajeh Ata in Bandar Abbas. This period was chosen as it represents the hottest and coldest days of the year based on Bandar Abbas meteorological data, providing stable weather conditions with similar days. Another reason for this time frame is a comparable study conducted by Thapar in Dubai, where data collection took place over seven days in August and February [Thapar, 2008].
Collected data from in-situ stations and meteorological stations were analyzed using Excel. The software was used to plot dual-axis regression charts and derive mathematical formulas representing relationships between parameters. Field measurements and questionnaire surveys were conducted over 14 days during summer and winter between 17:00 and 19:00, the peak hours of outdoor human activity. Due to the homogeneity of the residents in Khajeh Ata (regarding occupation, local status, religion, and psychological characteristics), respondent conditions were uniform. This social homogeneity helped control confounding parameters, allowing the study to focus on primary climatic parameters (air temperature, wind speed, humidity, and radiant temperature) and personal parameters (age, clothing, activity, etc.).
The objective climatic parameters measured included air temperature in the shade (Ta, °C), relative humidity (RH%), and wind speed (m/s). Measurements were recorded using a mobile system at 15 test sites. Devices were mounted on tripods at a height of 1.10 m, corresponding to the average center of gravity for adults. To avoid interference from people’s movements, the anemometer (wind sensor) was installed at 2.20 m [Lindberg et al., 2017]. Air temperature, relative humidity, and wind speed were automatically recorded at 2-minute intervals during a 6-minute measurement period.
Alongside environmental measurements, a simultaneous questionnaire study was conducted to collect subjective (perceived) responses. The questionnaire collected data in two sections: the first, completed by the interviewer, included exposure time, sun exposure, activity level, and clothing; the second, completed by the respondent, included personal and demographic information (e.g., age, gender), reason for being outdoors, and duration of stay. Respondents were asked to rate their current thermal comfort and their thermal preference. Thermal sensation was measured using the 7-point ASHRAE thermal sensation scale (TSV): Cold, cool, slightly cool, neutral, slightly warm, warm, and hot. Questions regarding perception of wind and sun exposure provided the necessary subjective data. The entire questionnaire was designed to be completed in under 5 minutes and included personal information such as gender, occupation, local residency status, and age.
The study sample included 163 participants in summer and 151 in winter, randomly selected. For cultural reasons, only male respondents were included; the age range was 8–80 years, with 96% aged 20–56. Female participation in traditional neighborhoods is limited due to cultural norms, as most women remain at home and are unwilling to participate in outdoor surveys.
Findings
A summary of the climatic parameters recorded by instruments, including ranges and standard deviations was provided. Notably, the recorded air temperatures were significantly higher than the official meteorological data for Bandar Abbas. Clothing values, representing physical data, showed a strong impact on thermal comfort. Outdoor air temperatures ranged from 27°C to 41°C in summer and 15°C to 26°C in winter. Average wind speed was 0.28 m/s, and average relative humidity was about 74% in summer and 54% in winter. The mean clothing level was 0.3 clo, ranging from 0.1 to 1.76 clo in summer, and 0.5 clo, ranging from 0.3 to 0.7 clo in winter.
Thermal sensation votes (TSV) were recorded using the 7-point ASHRAE scale: -3 (cold), -2 (cool), -1 (slightly cool), 0 (neutral), +1 (slightly warm), +2 (warm), +3 (hot).
In summer, 41% of respondents reported a neutral sensation (TSV=0), 23% slightly warm (+1), and 28% warm (+2). In winter, 63% were neutral, 22% slightly cool (-1), and 13% slightly warm (+1). Assuming TSVs of -1 to +1 indicate acceptable thermal conditions, over 90% of votes in winter fall within this comfort range, while in summer 90% fall within 0 to +2, consistent with the hot-humid climate of Bandar Abbas. Most summer TSVs lean toward the warm side (+1 to +3), while winter TSVs cluster around neutral (-1 to +1).
Gender, though not analyzed here due to cultural constraints (only male participants), has been shown elsewhere to affect thermal perception, with women generally having smaller comfort zones [Karjalainen, 2012; Krüger & Rossi, 2011]. Age was another personal factor affecting thermal perception. For Bandar Abbas, age showed a weaker correlation with thermal sensation than in northern Iran (Tehran): Correlation coefficients of 0.07 in summer and 0.09 in winter indicated that older residents slightly felt more discomfort in higher summer temperatures but more comfort in higher winter temperatures.
Clothing in Hormozgan varies; men wear long garments such as “kandura,” with variations for work and social occasions, while women wear hats, scarves, long dresses, and veils. Analysis indicated a direct relationship between clothing level and perceived warmth: higher clothing led to warmer TSV ratings (+2, +3). Neutral clothing levels were 0.1 clo in summer and 0.6 clo in winter, showing that even mild winters required extra clothing for comfort.
The study assessed the effect of solar radiation on thermal comfort using mean radiant temperature (MRT) [Thorsson & Honjo, 2007; Thorsson et al., 2007]. The neutral temperature under sun exposure was lower than in shaded conditions, and slope differences indicated varying thermal comfort ranges.
The “acceptable thermal range” for air temperature (Ta) was determined using quadratic regression of TSVs.
In summer, the acceptable thermal range was 23.8–34.4°C with a neutral temperature of 29.1°C. In winter, it ranged from 18–31.1°C with a neutral temperature of 24.5°C. These results reflect the hot-humid climate of Bandar Abbas and the adaptation of residents to local conditions.
Discussion
The aim of this study was to identify the key factors influencing thermal sensation and to determine their optimal ranges for achieving outdoor thermal comfort in the hot and humid climate of Bandar Abbas. To this end, a multivariate analysis was employed to examine the simultaneous effects of these factors on thermal sensation. At the beginning of the discussion, three types or levels of clothing were mentioned; clearly, this study does not address the first type (skin as clothing), but thermal comfort depends on the other two.
The findings indicated that thermal sensation votes were correlated with air temperature and wind speed during both summer and winter. In summer, the parameters of air flow, humidity, and age had inverse effects, meaning increases in these factors shifted thermal sensation toward cooler conditions, while the remaining parameters had direct effects. The greatest influence on thermal sensation was attributed to air flow with a 16.56% inverse effect, followed by clothing insulation with a 41.48% direct effect. Other contributing parameters included: air temperature (2.01% direct effect), mean radiant temperature (0.96% direct effect), humidity (0.23% inverse effect), metabolic rate (0.07%), weight (0.02% direct effect), and finally age (0.01% inverse effect.
In winter, air flow, humidity, and metabolic rate had inverse effects, meaning increases in these factors shifted thermal sensation toward cooler conditions, while the remaining parameters had direct effects. The greatest influence on thermal sensation was attributed to air flow with an 8.46% inverse effect, followed by clothing insulation with a 36.27% direct effect and air temperature with a 16.59% direct effect. Other parameters included: age (0.18% direct effect), weight (0.084% direct effect), mean radiant temperature (0.056% direct effect), humidity (0.05% inverse effect), and metabolic rate (0.001% inverse effect).
Metabolic rate had minimal influence on thermal sensation during both seasons and lies outside the scope of architecture and urban design. Similarly, the effects of age and weight on thermal sensation during both warm and cold periods were negligible overall.
These results show that air flow and wind have a stronger influence on thermal comfort sensation in summer compared to winter (approximately 10%). A similar seasonal asymmetry can be observed for clothing insulation (approximately 5%). Notably, the relative weight of air temperature differs significantly between seasons: in summer, air temperature accounts for approximately 2% of thermal comfort sensation, whereas in winter it accounts for around 16.5%. This difference may seem contradictory when compared to the influence of wind and clothing in summer; however, it can be interpreted that wind and clothing exert the strongest influence on thermal comfort in hot and humid conditions (such as Bandar Abbas in summer). In winter, as heat and humidity decreased and the climate partially shifted away from hot–humid conditions, the influence of air flow and clothing also decreases, while air temperature gained greater significance in determining thermal comfort.
This interpretation is supported by previous research and historical evidence. The results align with Givoni’s findings, which state that air movement in outdoor spaces of hot and humid regions generally improves thermal comfort [Givoni, 1994]. Similarly, Fergus and Dalman also identifiy wind speed and clothing insulation as major determinants of thermal sensation in hot and humid climates [Fergus, 2004; Dalman et al., 2012]. Arena et al. have demonstrated that individuals in cool temperatures (below 23°C) desire up to a 60% reduction in air movement, whereas in warm temperatures (above 26°C) they prefer up to a 70% increase in wind intensity [Arena et al., 1997], reinforcing the current interpretation.
Historical evidence also supports this view. The traditional urban fabric of Bandar Abbas is linear and oriented along the coastline, with streets aligned to maximize exposure to sea and coastal breezes [Ranjbar et al., 2009].
Conclusion
In the hot and humid climate of Bandar Abbas, air flow and wind are the most critical factors for ensuring outdoor thermal comfort in spaces such as squares, streets, and parks. Clothing insulation constitutes the next influential factor. Although other parameters also play a role, wind remains the primary determinant of comfort in this region. The neutral air velocity required to achieve thermal comfort was found to be 0.5 m/s for the warm season and 0.13 m/s for the cold season.
Acknowledgments: No acknowledgments were reported by the authors.
Ethical Permission: No ethical approvals were reported by the authors.
Conflict of Interest: The authors declare no conflict of interest.
Authors’ Contributions: Salem MD (First Author), Introduction Writer/Main Researcher/Discussion Writer (50%); Moradkhani A (Second Author), Data Analyst (30%); Ghaedi SH (Third Author), Methodologist (20%)
Funding: No funding was reported by the authors.
Bandar Abbas is a major port city in southern Iran that has experienced rapid growth in urban size, population, transportation, and industrial and commercial sectors since 1980, the start of the Iran–Iraq war. This rapid expansion has caused changes in the urban microclimate, negatively affecting human thermal comfort during the hot summer months. Few studies have investigated the impact of climate on urban planning and design in hot and humid climates, particularly in southern Iran and the Persian Gulf region [Thapar, 2008]. Therefore, urban climate studies in these areas are essential for planners and urban designers.
Outdoor thermal comfort has recently gained particular importance within urban microclimate studies for different seasons. Historically, if architecture is not considered simply as the art of providing shelter from climatic elements (protection from wind and rain), human comfort has always been a central goal of architectural design, with thermal comfort being one aspect. Architecture can also be regarded as a “third layer of clothing”: the first being the skin, the second textiles, and the third, the building itself. In outdoor urban spaces, although this “third layer” is partially absent, architecture still exerts influence because it is human-model this is the aspect addressed by the present study.
Microclimate is a crucial factor in determining the quality of outdoor spaces because individuals’ perceptions of spatial quality are strongly influenced by microclimatic conditions. Microclimate also affects human presence in these spaces, as numerous studies have shown that thermal comfort conditions influence both the frequency and duration of outdoor activities [Chen & Ng, 2012; Givoni et al., 2003; Nikolopoulou et al., 2001; Zacharias et al., 2001]. Moreover, indoor thermal conditions are affected by outdoor environments, meaning that improving outdoor conditions can enhance indoor thermal comfort and reduce energy demand for achieving thermal comfort [He et al., 2009; Hoppe & Lin, 2007].
Extensive research over the last decade has examined thermal comfort components along various coastal regions worldwide [Cheng & Ng, 2012; Nikolopoulou, 2011]. Some studies have focused on assessing outdoor thermal comfort zones to evaluate individuals’ thermal perceptions in different climates [Ahmed, 2003; Givoni et al., 2003; Hwang & Lin, 2007; Krüger, 2011; Lin, 2009; Thorsson et al., 2007; Nikolopoulou et al., 2001]. Other studies have indicated that outdoor thermal comfort zones and perception levels vary depending on geographic, physiographic, and cultural differences [Zhao et al., 2016].
Personal parameters have mainly been studied concerning psychological aspects of thermal perception [Lin, 2009; Nikolopoulou et al., 2001; Thorsson et al., 2007]. For instance, a study has focused on age and gender as influential factors on outdoor thermal perception in Tehran [Amindeladar et al., 2017]. Other studies, such as Furgus and Dalman, identified wind speed and clothing as key factors affecting thermal sensation in hot and humid regions [Furgus, 2004; Dalman et al., 2012]. Givoni has emphasized that airflow in outdoor spaces of hot and humid climates often contributes to thermal comfort [Givoni, 1994].
In Iran, outdoor thermal comfort in urban spaces has received limited attention, with only a few field studies conducted, such as Monam’s research on thermal comfort in Tehran’s parks [Monam, 2011]. Given the climatic nature of this topic, each region requires its own focused study.
Deevi and Chundeli’s study in a hot and humid climate in India, using questionnaires based on lived perceptions, have found a significant relationship between the sky view factor and increased heat tolerance, alongside the influence of mean radiant temperature on street thermal comfort [Deevi & Chundeli, 2020]. Another study in India has indicated that vegetation cover and water presence reduce the temperature–humidity index and improve people’s thermal tolerance [Das & Das, 2020]. Recently, research has also has emphasized emotional dimensions of thermal comfort, such as thermal pleasure and thermal intensity, alongside the traditional four descriptive dimensions (temperature, wind, humidity, and solar exposure) [Liu et al., 2020].
Most studies on thermal comfort focus on indoor spaces, with relatively few field studies in outdoor environments. Majidi et al. have examined thermal comfort in four neighborhoods in Isfahan and concluded that the effective temperature index aligns closely with field observations [Majidi et al., 2018]. Baghai et al. has assessed user perceptions and environmental measurements in traditional courtyards in Yazd, establishing thermal comfort ranges for hot and arid climates [Baghai et al., 2014]. Chehrazi et al. have studied thermal comfort in girls’ primary schools in Isfahan, determining neutral temperature and comfort ranges for females in hot and dry areas [Chehrazi et al., 2021].
A recent emerging topic is the effect of cultural and social homogeneity of neighborhood residents on outdoor thermal comfort ranges and the influence of microclimatic and personal parameters. Results indicated that cultural and social differences among residents can alter thermal comfort ranges and the key influencing factors. For example, Yu-Peng et al. have compared outdoor thermal comfort in two culturally distinct groups in the same climate, finding that temperature and airflow were primary factors for one group, whereas activity enjoyment and psychological expectations have influenced comfort more in the other [Peng et al., 2021]. Mishra et al., in a review of indoor thermal comfort studies, also have observed that culturally and socially homogeneous groups yield more consistent and accurate results [Mishra et al., 2016]. Accordingly, this study selected a homogeneous neighborhood with traditional residents to minimize the effects of heterogeneous groups.
This research examined the effects of microclimatic and personal parameters on perceived temperature in the geography, culture, and climate of Bandar Abbas. Among microclimatic parameters, air temperature, solar radiation, and wind speed (environmental factors) were assessed in combination with clothing and age as personal (human) parameters. The study was conducted in both summer and winter in Bandar Abbas and primarily involves field measurements of microclimatic parameters alongside subjective assessments of thermal perception. This approach aligns with three recent studies conducted in 2021, emphasizing the importance of questionnaires to capture perceived thermal comfort. This research also aims to evaluate personal factors affecting thermal comfort beyond external environmental conditions, which were the primary focus of previous studies.
Methodology
This study employed an experimental approach using field measurements and questionnaires to assess thermal comfort during both hot and cold seasons. Field measurements of air temperature, wind speed, and relative humidity were conducted over 20 days (August 6 to August 26 and February 1 to February 20) at 12 different locations in the coastal neighborhood of Khajeh Ata in Bandar Abbas. This period was chosen as it represents the hottest and coldest days of the year based on Bandar Abbas meteorological data, providing stable weather conditions with similar days. Another reason for this time frame is a comparable study conducted by Thapar in Dubai, where data collection took place over seven days in August and February [Thapar, 2008].
Collected data from in-situ stations and meteorological stations were analyzed using Excel. The software was used to plot dual-axis regression charts and derive mathematical formulas representing relationships between parameters. Field measurements and questionnaire surveys were conducted over 14 days during summer and winter between 17:00 and 19:00, the peak hours of outdoor human activity. Due to the homogeneity of the residents in Khajeh Ata (regarding occupation, local status, religion, and psychological characteristics), respondent conditions were uniform. This social homogeneity helped control confounding parameters, allowing the study to focus on primary climatic parameters (air temperature, wind speed, humidity, and radiant temperature) and personal parameters (age, clothing, activity, etc.).
The objective climatic parameters measured included air temperature in the shade (Ta, °C), relative humidity (RH%), and wind speed (m/s). Measurements were recorded using a mobile system at 15 test sites. Devices were mounted on tripods at a height of 1.10 m, corresponding to the average center of gravity for adults. To avoid interference from people’s movements, the anemometer (wind sensor) was installed at 2.20 m [Lindberg et al., 2017]. Air temperature, relative humidity, and wind speed were automatically recorded at 2-minute intervals during a 6-minute measurement period.
Alongside environmental measurements, a simultaneous questionnaire study was conducted to collect subjective (perceived) responses. The questionnaire collected data in two sections: the first, completed by the interviewer, included exposure time, sun exposure, activity level, and clothing; the second, completed by the respondent, included personal and demographic information (e.g., age, gender), reason for being outdoors, and duration of stay. Respondents were asked to rate their current thermal comfort and their thermal preference. Thermal sensation was measured using the 7-point ASHRAE thermal sensation scale (TSV): Cold, cool, slightly cool, neutral, slightly warm, warm, and hot. Questions regarding perception of wind and sun exposure provided the necessary subjective data. The entire questionnaire was designed to be completed in under 5 minutes and included personal information such as gender, occupation, local residency status, and age.
The study sample included 163 participants in summer and 151 in winter, randomly selected. For cultural reasons, only male respondents were included; the age range was 8–80 years, with 96% aged 20–56. Female participation in traditional neighborhoods is limited due to cultural norms, as most women remain at home and are unwilling to participate in outdoor surveys.
Findings
A summary of the climatic parameters recorded by instruments, including ranges and standard deviations was provided. Notably, the recorded air temperatures were significantly higher than the official meteorological data for Bandar Abbas. Clothing values, representing physical data, showed a strong impact on thermal comfort. Outdoor air temperatures ranged from 27°C to 41°C in summer and 15°C to 26°C in winter. Average wind speed was 0.28 m/s, and average relative humidity was about 74% in summer and 54% in winter. The mean clothing level was 0.3 clo, ranging from 0.1 to 1.76 clo in summer, and 0.5 clo, ranging from 0.3 to 0.7 clo in winter.
Thermal sensation votes (TSV) were recorded using the 7-point ASHRAE scale: -3 (cold), -2 (cool), -1 (slightly cool), 0 (neutral), +1 (slightly warm), +2 (warm), +3 (hot).
In summer, 41% of respondents reported a neutral sensation (TSV=0), 23% slightly warm (+1), and 28% warm (+2). In winter, 63% were neutral, 22% slightly cool (-1), and 13% slightly warm (+1). Assuming TSVs of -1 to +1 indicate acceptable thermal conditions, over 90% of votes in winter fall within this comfort range, while in summer 90% fall within 0 to +2, consistent with the hot-humid climate of Bandar Abbas. Most summer TSVs lean toward the warm side (+1 to +3), while winter TSVs cluster around neutral (-1 to +1).
Gender, though not analyzed here due to cultural constraints (only male participants), has been shown elsewhere to affect thermal perception, with women generally having smaller comfort zones [Karjalainen, 2012; Krüger & Rossi, 2011]. Age was another personal factor affecting thermal perception. For Bandar Abbas, age showed a weaker correlation with thermal sensation than in northern Iran (Tehran): Correlation coefficients of 0.07 in summer and 0.09 in winter indicated that older residents slightly felt more discomfort in higher summer temperatures but more comfort in higher winter temperatures.
Clothing in Hormozgan varies; men wear long garments such as “kandura,” with variations for work and social occasions, while women wear hats, scarves, long dresses, and veils. Analysis indicated a direct relationship between clothing level and perceived warmth: higher clothing led to warmer TSV ratings (+2, +3). Neutral clothing levels were 0.1 clo in summer and 0.6 clo in winter, showing that even mild winters required extra clothing for comfort.
The study assessed the effect of solar radiation on thermal comfort using mean radiant temperature (MRT) [Thorsson & Honjo, 2007; Thorsson et al., 2007]. The neutral temperature under sun exposure was lower than in shaded conditions, and slope differences indicated varying thermal comfort ranges.
The “acceptable thermal range” for air temperature (Ta) was determined using quadratic regression of TSVs.
In summer, the acceptable thermal range was 23.8–34.4°C with a neutral temperature of 29.1°C. In winter, it ranged from 18–31.1°C with a neutral temperature of 24.5°C. These results reflect the hot-humid climate of Bandar Abbas and the adaptation of residents to local conditions.
Discussion
The aim of this study was to identify the key factors influencing thermal sensation and to determine their optimal ranges for achieving outdoor thermal comfort in the hot and humid climate of Bandar Abbas. To this end, a multivariate analysis was employed to examine the simultaneous effects of these factors on thermal sensation. At the beginning of the discussion, three types or levels of clothing were mentioned; clearly, this study does not address the first type (skin as clothing), but thermal comfort depends on the other two.
The findings indicated that thermal sensation votes were correlated with air temperature and wind speed during both summer and winter. In summer, the parameters of air flow, humidity, and age had inverse effects, meaning increases in these factors shifted thermal sensation toward cooler conditions, while the remaining parameters had direct effects. The greatest influence on thermal sensation was attributed to air flow with a 16.56% inverse effect, followed by clothing insulation with a 41.48% direct effect. Other contributing parameters included: air temperature (2.01% direct effect), mean radiant temperature (0.96% direct effect), humidity (0.23% inverse effect), metabolic rate (0.07%), weight (0.02% direct effect), and finally age (0.01% inverse effect.
In winter, air flow, humidity, and metabolic rate had inverse effects, meaning increases in these factors shifted thermal sensation toward cooler conditions, while the remaining parameters had direct effects. The greatest influence on thermal sensation was attributed to air flow with an 8.46% inverse effect, followed by clothing insulation with a 36.27% direct effect and air temperature with a 16.59% direct effect. Other parameters included: age (0.18% direct effect), weight (0.084% direct effect), mean radiant temperature (0.056% direct effect), humidity (0.05% inverse effect), and metabolic rate (0.001% inverse effect).
Metabolic rate had minimal influence on thermal sensation during both seasons and lies outside the scope of architecture and urban design. Similarly, the effects of age and weight on thermal sensation during both warm and cold periods were negligible overall.
These results show that air flow and wind have a stronger influence on thermal comfort sensation in summer compared to winter (approximately 10%). A similar seasonal asymmetry can be observed for clothing insulation (approximately 5%). Notably, the relative weight of air temperature differs significantly between seasons: in summer, air temperature accounts for approximately 2% of thermal comfort sensation, whereas in winter it accounts for around 16.5%. This difference may seem contradictory when compared to the influence of wind and clothing in summer; however, it can be interpreted that wind and clothing exert the strongest influence on thermal comfort in hot and humid conditions (such as Bandar Abbas in summer). In winter, as heat and humidity decreased and the climate partially shifted away from hot–humid conditions, the influence of air flow and clothing also decreases, while air temperature gained greater significance in determining thermal comfort.
This interpretation is supported by previous research and historical evidence. The results align with Givoni’s findings, which state that air movement in outdoor spaces of hot and humid regions generally improves thermal comfort [Givoni, 1994]. Similarly, Fergus and Dalman also identifiy wind speed and clothing insulation as major determinants of thermal sensation in hot and humid climates [Fergus, 2004; Dalman et al., 2012]. Arena et al. have demonstrated that individuals in cool temperatures (below 23°C) desire up to a 60% reduction in air movement, whereas in warm temperatures (above 26°C) they prefer up to a 70% increase in wind intensity [Arena et al., 1997], reinforcing the current interpretation.
Historical evidence also supports this view. The traditional urban fabric of Bandar Abbas is linear and oriented along the coastline, with streets aligned to maximize exposure to sea and coastal breezes [Ranjbar et al., 2009].
Conclusion
In the hot and humid climate of Bandar Abbas, air flow and wind are the most critical factors for ensuring outdoor thermal comfort in spaces such as squares, streets, and parks. Clothing insulation constitutes the next influential factor. Although other parameters also play a role, wind remains the primary determinant of comfort in this region. The neutral air velocity required to achieve thermal comfort was found to be 0.5 m/s for the warm season and 0.13 m/s for the cold season.
Acknowledgments: No acknowledgments were reported by the authors.
Ethical Permission: No ethical approvals were reported by the authors.
Conflict of Interest: The authors declare no conflict of interest.
Authors’ Contributions: Salem MD (First Author), Introduction Writer/Main Researcher/Discussion Writer (50%); Moradkhani A (Second Author), Data Analyst (30%); Ghaedi SH (Third Author), Methodologist (20%)
Funding: No funding was reported by the authors.
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