Thermal Comfort Of People Research Articles

Impact of urban heat islands on the thermal comfort and cooling energy demand of artificial islands—A case study of AMWAJ Islands in Bahrain

Man-made islands, created by reclaiming land from the sea, have become more prevalent in the Gulf Corporation Council countries (GCCC) in recent years as demand for additional land to develop grows. The creation of such islands will affect the landscape, climate and environment through the replacement of sand and water with hard artificial surfaces and buildings. Exposing urban man-made surfaces, such as roads and buildings, to the sun increases the temperatures of their surfaces and the atmosphere, and consequently impacts upon the local weather, building energy consumption and people's thermal comfort through the modification of microclimatic variables such air temperature, relative humidity and wind speed. The current body of work represents the results of field measurements and simulation studies that assessed modifications in urban temperatures of the man-made AMWAJ Islands in the Kingdom of Bahrain, and examined thermal comfort and cooling energy demand on the islands. This work argues that the urban temperatures of AMWAJ Islands were altered in part due to human contributions such as urban geometry, urban surfaces and land use. The modification in temperature could reach almost 5°C. In turn, thermal comfort and cooling demand within AMWAJ islands were affected by the modified temperatures. The increase in urban cooling load was within the range of 14–26% when compared with uninhabited islands. The presence of green surfaces, in conjunction with water bodies that overlap with the infrastructure, help to improve thermal comfort and consequently reduce cooling energy requirements in AMWAJ Islands.

Improvement of Thermal Comfort Conditions in an Urban Space (Case Study: The Square of Independence, Sétif, Algeria)

Several studies all around the world were conducted on the phenomenon of the urban heat island, and referring to the results obtained, one of the most important factors that influence this phenomenon is the mineralization of the cities which means the reducing of evaporative urban surfaces, replacing vegetation and wetlands with concrete and asphalt. The use of vegetation and water can change the urban environment and improve comfort, thus reduce the heat island. The trees act as a mask to the sun, wind, and sound, and also as a source of humidity which reduces air temperature and surrounding surfaces. Water also acts as a buffer to noise; it is also a source of moisture and regulates temperature not to mention the psychological effect on humans. Our main objective in this paper is to determine the impact of vegetation, ponds and fountains on the urban microclimate in general and on the thermal comfort of people along the Independence square in the Algerian city of Setif, which is a semi-arid climate, in particularly. In order to reach this objective, a comparative study between different scenarios has been done; the use of the Envi-met program enabled us to model the urban environment of the Independence Square and to study the possibility of improving the conditions of comfort by adding an amount of vegetation and water ponds. After studying the results obtained (temperature, relative humidity, PMV and PPD indicators), the efficiency of the additions we've made on the square was confirmed and this is what helped us to confirm our assumptions regarding the terms of comfort in the studied site, and in the end we are trying to develop recommendations and solutions which may contribute to improve the conditions for greater comfort in the Independence square. Keywords: microclimate, vegetation, water ponds, simulation, Envi-Met software, comfort.

Designing for an imagined user: Provision for thermal comfort in energy-efficient extra-care housing

Regarded as one solution to the problem of how to enable older people to retain their independence, extra-care housing, where each resident has their own self-contained dwelling and access to communal facilities and to care, has received extensive funding in recent years. Implicit in the concept of specialist housing is the notion of ‘special’ occupants, imagined older people. Adopting a socio-technical approach, this paper considers how ideas about ageing inform those aspects of extra-care-housing-design that relate to thermal comfort. The paper draws on semi-structured interviews with 13 people involved in the design, development and management of UK-based extra-care housing. Participants characterised imagined occupants as vulnerable to cold, at risk from fuel poverty and liable to be burned by hot surfaces or fall from high windows. These user representations were reportedly inscribed into the design of extra-care housing schemes through the inclusion of building features such as communal heating, under-floor heating, restricted window opening and heated corridors. The utilisation of stereotypical user representations of older people raises questions, given that older people's thermal comfort needs can be highly diverse. The paper explores the implications for energy demand.

Shading Effect on Outdoor Thermal Comfort in High-Density City a Case Based Study of Beijing

Shading provided by buildings affects outdoor thermal environments and, therefore, influences the long-term thermal comfort of people in outdoor spaces. This study conducted several field experiments to analyze the outdoor thermal conditions on urban streets in central business district (CBD) of Beijing. The RayMan model was utilized for calculating Sky view factor (SVF) and outdoor thermal comfort using meteorological data of one year period. Analytical results indicate that slightly shaded areas (SVF > 0.5) typically have highly frequent hot conditions during summer, particularly at noon; however, highly shaded locations (SVF < 0.3) generally reduce the intra-urban air temperature in winter; moderately shaded areas (0.3 < SVF < 0.5) show the advantage for balancing the hot conditions in summer and cold conditions in winter throughout whole year. Sky view factor can be used as a comprehensive and practical urban planning index at local scale, i.e. urban canyon street and residential estate. It provides a novelty method on scientific planning and sustainable development of city.

Air quality and thermal comfort levels under extreme hot weather

Meteorological (T and RH values) and air pollution data (PM10, NO2 and O3 concentrations) observed in Athens, Thessaloniki and Volos were analyzed to assess the air quality and the thermal comfort conditions and to study their synergy, when extreme hot weather prevailed in Greece during the period 2001–2010. The identification of a heat wave day was based on the suggestion made by the IPCC to define an extreme weather event. According to it, a heat wave day is detected when the daily maximum hourly temperature value exceeds its 90th percentile. This temperature criterion was applied to the data recorded at the cities center. Air quality was assessed at three sites in Athens (city center, near the city center, suburb), at two sites in Thessaloniki (city center, suburb) and at one site in Volos (city center), while thermal comfort conditions were assessed at the cities center. Mean pollution levels during the heat wave days and the non-heat wave days were calculated in order to examine the impact of the extreme hot weather on air quality. For this purpose, the distributions of the common air quality index and the exceedances of the air quality standards in force during the heat wave days and the non-heat wave days were also studied. Additionally, the variation of the daily maximum hourly value of Thom's discomfort index was studied in order to investigate the effect of extreme hot weather on people's thermal comfort. Moreover, the values of the common air quality index and Thom's discomfort index were comparatively assessed so as to investigate their synergy under extreme hot weather.

An analysis of influential factors on outdoor thermal comfort in summer

A variety of research has linked high temperature to outdoor thermal comfort in summer, but it remains unclear how outdoor meteorological environments influence people's thermal sensation in subtropical monsoon climate areas, especially in China. In order to explain the process, and to better understand the related influential factors, we conducted an extensive survey of thermally comfortable conditions in open outdoor spaces. The goal of this study was to gain an insight into the subjects' perspectives on weather variables and comfort levels, and determine the factors responsible for the varying human thermal comfort response in summer. These perceptions were then compared to actual ambient conditions. The database consists of surveys rated by 205 students trained from 6:00 am to 8:00 pm outdoors from 21 to 25 August 2009, at Nanjing University of Information Science & Technology (NUIST), Nanjing, China. The multiple regression approach and simple factor analysis of variance were used to investigate the relationships between thermal comfort and meteorological environment, taking into consideration individual mood, gender, level of regular exercise, and previous environmental experiences. It was found that males and females have similar perceptions of maximum temperature; in the most comfortable environment, mood appears to have a significant influence on thermal comfort, but the influence of mood diminishes as the meteorological environment becomes increasingly uncomfortable. In addition, the study confirms the strong relationship between thermal comfort and microclimatic conditions, including solar radiation, atmospheric pressure, maximum temperature, wind speed and relative humidity, ranked by importance. There are also strong effects of illness, clothing and exercise, all of which influence thermal comfort. We also find that their former place of residence influences people's thermal comfort substantially by setting expectations. Finally, some relationships between thermal perception and amount of exercise, thermal experience, mood, clothing, illness and microclimate, etc., are established. Our findings also shed light on how to resist or adapt to outdoor hyperthermic conditions during summer in subtropical monsoon climate areas.

The influence of wind on outdoor thermal comfort in the city of Beirut: A theoretical and field study

This article studies the outdoor comfort in the city of Beirut to improve the quality of open spaces and better explain the people's tolerance and acceptance of outdoor environmental conditions. Field experiments were conducted to develop statistical correlations for thermal sensation and thermal comfort of people in the outdoors to environmental parameters. A transient bioheat model was developed to study the effect of wind speed and frequency in the physiological responses of the human body and its effect on the overall body thermal sensation and comfort state. The model was experimentally validated and simulated for three different wind frequencies of 0.15, 0.25, and 0.35 Hz, representing a range of wind frequencies encountered during an average summer day. For each of these wind frequencies, simulations were performed for two air velocity ranges: V1 = 0.5 m/s to 2.8 m/s (1.64 ft/s to 9.18 ft/s) and V2 = 0.5 m/s to 1.8 m/s (1.64 ft/s to 5.9 ft/s) at air temperatures of 30°C and 34°C (86°F and 93.2°F) and relative humidity of 40% and 70%. The numerical results showed that for velocity range V1, the overall comfort improved from –1.15 to –0.82 with the increase of wind frequency, while at velocity range V2, comfort improved from –1.27 to –0.99 with wind frequency for the same air temperature and relative humidity. It is concluded that the positive effect of wind frequency and velocity amplitude in making people more tolerant of outdoor conditions decreases with the increase in air temperature and relative humidity.

A Study of the Ventilation and Thermal Comfort of the Environment Surrounding a New University Building under Construction

The purpose of this study was to investigate the effect of a new building which can impose on its immediate ambient environment, on air movement and thermal comfort of people using the area. The effect of eight prevailing wind directions around the building was simulated using computational fluid dynamics (CFD). The CFD simulation was validated by two wind tunnel experiments. The CFD results were used to conduct an air ventilation assessment using velocity ratio (VR) indicator and to assess thermal comfort by an extended predicted mean vote (PMV) evaluation. An analysis of the relationship of VR and PMV with the to-be-built building (the front area index λf and plan area density λp) was also conducted. The result indicates that the PMV trend was generally opposite to the VR trend. The λp would increase due to the new building and the λf would increase in all wind directions except East-South-East and South-East. There could be a significant change in thermal comfort when the λf became smaller than 12% and a significant change in ventilation efficiency if the λf was smaller or larger than 12%. It means that λf can be used as an urban planning parameter for the thermal comfort study in the natural ventilated urban environment.

Field Studies of Indoor Thermal Comfort and the Progress of the Adaptive Approach

The experimental basis of the adaptive approach to thermal comfort is the field study. Since the publication of Bedford's study in 1936, many researchers have collected data on people's thermal comfort in everyday conditions. The principal assemblages of data are those of Humphreys (1975; 1978; 1981), de Dear et al (1997), de Dear (1998), de Dear and Brager (1998) and McCartney and Nicol (2001). In addition there exist numerous studies not included in any assemblage. The data come from a variety of climates and countries, from people in buildings that are heated or cooled mechanically, and from buildings operating without either heating or cooling. This paper compares the more recent data with the early patterns revealed by Humphreys' 1975–1981 analyses of the worldwide data. The comparison is made for indices of thermal comfort, mean warmth response, temperatures found to be comfortable, sensitivity to temperature change, interpersonal variation, distribution of comfort with temperature, and the influence of outdoor temperature in the presence or absence of heating and cooling. The empirical findings are compared with predictions from the predicted mean vote (PMV) model of comfort. The role of the adaptive approach in the formation of standards and guidelines is discussed.

Predicting thermal comfort in Shanghai's non-air-conditioned buildings

The thermal comfort of people in naturally ventilated environments was examined in a field study in Shanghai, China, in which over 1814 office workers responded to a questionnaire while simultaneous physical measurements were taken. The paper explores whether it is justifiable to use the predicted mean vote (PMV) model to predict inhabitants' thermal sensations. Participants cast votes on standard subjective thermal rating scales and these were correlated with temperature indices that variously account for the thermal impacts of humidity, radiant temperature, air velocity and clothing levels. It was found that the actual mean thermal sensation is lower than the PMV, i.e. about 0.64PMV. The upper boundary of operative temperature is about 29°C which is outside of the current American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standard comfort zone (ASHRAE 55-2004), but lower than the temperature of the upper 80% acceptable limit calculated using an adaptive model (30.1°C). This suggests that people residing in this hot area have adapted to its climate and their expectations for comfort allow them to endure heat better than expected. Le confort thermique des personnes travaillant et vivant dans des environnements ventilés naturellement a été examiné dans le cadre d'une étude de terrain menée à Shanghai (Chine). Mille huit cent quatorze employés de bureau ont répondu à un questionnaire pendant que dans le même temps on relevait des mesures physiques. L'auteur de cet article se demande s'il est justifié d'utiliser le modèle du vote moyen prévisible (PMV) pour prévoir les sensations thermiques des habitants. Les participants ont voté sur la base d'échelles de classement thermique subjectives standard et les résultats ont été comparés aux indices thermiques qui, de manière variable, entrent en ligne de compte dans l'impact thermique de l'humidité, de la température rayonnante, de la vitesse de l'air et des niveaux d'habillement. Il s'est avéré que la sensation thermique moyenne réelle est inférieure au PMV, c'est-à-dire environ 0,64 PMV. La limite supérieure de la température opérative est d'environ 29°C, c'est-à-dire en dehors de la zone de confort standard de la norme de l'American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE 55-2004), mais inférieure à la température de la limite supérieure acceptable à 80% calculée au moyen d'un modèle d'adaptation (30,1°C). Cela laisse à penser que les personnes résidant dans une région chaude s'adaptent au climat et que leurs attentes en matière de confort leur permettent de mieux résister que prévu à la chaleur. Mots-clés: comportement adaptatif, attente, ventilation naturelle, vote moyen prévisible (PMV), confort thermique