The Role and Impact of Design Elements on the Quality of Thermal Comfort in Urban Open Spaces Case Study: Design of Pedestrian Way in Tamghachiha Pathway in the City of Kashan

Different climate conditions often result in different use of open spaces. The impacts of climate on the use of outdoor spaces in the urban environment are particularly important for quality and quantity of the activities that are carried out in the area. Thermal comfort is one of the most effectual factors on the quality of “place”, and promotion of thermal comfort quality would affect the vitality of the area. Cities significantly modify the meteorological conditions of surrounding areas: overall radiation is higher, except for ultraviolet radiation; the mean annual temperature is higher in cities than in the surrounding areas; wind speed is considerably lower in the cities, being slowed by buildings. As a consequence, relative humidity in cities is lower. Environmental conditions that body is exposed to can, however, be attenuated, filtered or enhanced by architectural means, e.g. a sunshade or vegetation can provide shading. But thermal comfort, especially in outdoor locations is a great challenge to assess, since numerous environmental, personal factors are involved: variation of sun and shade, changes in wind speed, and so on. Thermal comfort, in its basic definition, is the human reaction to the surrounding indoor or outdoor environments. More specific definitions of this term are summarized under three different categories: the psychological, thermo-physiological and energetic definitions. Background of studies about thermal comfort dates back to 1970s, but these studies focus on indoor thermal comfort quality. Attention to outdoor thermal comfort in urban design studies has started in the last decade. Research on outdoor comfort involves different conditions and issues, not encountered in studies on indoor comfort. Surveys in this field emphasized the need for investigating different ways to quantify comfort condition in outdoors. This research is to apply effective urban design techniques, such as shading devices, a selection of surface materials, vegetation and water bodies on the site, evaluating thermal comfort quality of an area and proposing optimum design alternative and modifying thermal comfort. This research is based on simulating thermal comfort quality, using ENVI-met software. This software was chosen because it is the only software where all factors influencing thermal comfort like wind speed and direction , air temperature, etc. are simulated integrally to derive thermal comfort indices. PMV index was also chosen to quantify thermal comfort condition in the area. PMV relates the simple energy balance of the human body to thermal comfort experienced by a person, with normal values between -4 (very cold) and þ4 (very hot). PMV was originally created to measure indoor human comfort, but later adapted to outdoor spaces by Jendritzky. In research process, three differences alternatives, based on various design solutions, were proposed for the area and simulated by ENVI-met software. Impact of each technique was evaluated through comparison of these three alternatives. In conclusion, based on simulation results, shading has a significant influence on thermal comfort, compared with other techniques such as surface materials, vegetation and water bodies, in microclimate scale. Moreover, using a combination of shading with other techniques especially water bodies reinforces reduction of temperature.