راحتی در فضای باز و فعالیت های حرارتی فضای باز : بررسی مجدد تحقیقات در دهه گذشته

Outdoor spaces are important to sustainable cities because they accommodate pedestrian traffic and outdoor activities, and contribute greatly to urban livability and vitality. In the global context of climate change, outdoor spaces that provide a pleasurable thermal comfort experience for pedestrians effectively improve the quality of urban living. The influence of thermal comfort on outdoor activities is a complex issue comprising both climatic and behavioral aspects; however, current investigations lack a general framework for assessment. This paper presents a review of research over the past decade on the behavioral aspects of outdoor thermal comfort. The article focuses on perceptions of outdoor thermal comfort and the use of outdoor space in the context of urban planning. We further discuss a general framework for assessing outdoor thermal comfort based on behavioral aspects and the need for predicting tools in the design and planning of outdoor thermal comfort.

Outdoor spaces are important to sustainable cities because they accommodate daily pedestrian traffic and various outdoor activities and contribute greatly to urban livability and vitality. Encouraging more people on the streets and in outdoor spaces will benefit cities from various perspectives, including physical, environmental, economical, and social aspects (Hakim et al., 1998, Hass-Klau, 1993, Jacobs, 1972 and Whyte, 1988). With more than half of the world’s population now living in cities (Population Reference Bureau, 2009), downtown areas are particularly vulnerable to extreme weather conditions in the global context of climate change. Under these circumstances, ensuring that pedestrians are well served by outdoor spaces is essential to high-quality urban living. Over the past few decades, making outdoor spaces attractive to people, and ultimately used by them, has been increasingly recognized as a goal in urban planning and design (Carr et al., 1993, Gehl and Gemzøe, 2004, Marcus and Francis, 1998 and Maruani and Amit-Cohen, 2007). Among many factors that determine the quality of outdoor spaces, the outdoor microclimate is an important issue. In contrast with car commuters, pedestrians are directly exposed to their immediate environment in terms of variations of sun and shade, changes in wind speed, and other characteristics. Thus, people’s sensation of thermal comfort is greatly affected by the local microclimate. The microclimate also influences decisions on whether to use the space. For example, in his seminal work, “Life Between Buildings: Using Public Space,” Gehl (1971) first studied the influence of microclimate on outdoor activities by counting people sitting on sunny and shady benches. He showed that local sunny or shady conditions significantly impact the desire of people to either stay or leave. In the past decade, broad applications in urban studies of concepts and equipment used in biometeorology and urban climatology have yielded a vast number of research projects on outdoor thermal comfort in various climates around the world (Ahmed, 2003, Ali-Toudert and Mayer, 2006, Cheng and Ng, 2006, Cheng et al., 2010, Givoni et al., 2003, Gulyas et al., 2006, Höppe, 2002, Nikolopoulou and Lykoudis, 2006, Spagnolo and De Dear, 2003, Stathopoulos et al., 2004 and Tseliou et al., 2009). Some studies have focused on modeling and assessment methods from a thermophysiological perspective (e.g., Gulyas et al., 2006 and Höppe, 2002), whereas others have conducted detailed investigations of the climatic parameters that determine the thermal comfort level of humans (e.g., Cheng and Ng, 2006 and Spagnolo and De Dear, 2003). In the context of urban planning, how the thermal sensations of people influence their behavior and use of outdoor spaces is of utmost interest. Given the range of literature along these lines, a general framework for assessing the behavioral aspects of outdoor thermal comfort conditions will be beneficial for both researchers and planning practitioners. Such a framework has yet to be discussed in great depth. The focus of this review is twofold. First, we provide a brief introduction to the most widely used models and indicators in outdoor thermal comfort assessment. Second, we present a comprehensive literature review of outdoor thermal comfort research over the past decade from a behavioral perspective, with a focus on the link between outdoor thermal comfort and outdoor activity and the use of outdoor space in the context of urban planning. Subsequently, we discuss a general framework for assessing the behavioral aspects of outdoor thermal comfort and identify the need for predicting tools in design and planning that address outdoor thermal comfort.

According to the literature reviewed above, outdoor spaces are important in promoting the quality of life in cities. However, outdoor thermal comfort in an urban environment is a complex issue with multiple layers of concern. The environmental stimulus (i.e., the local microclimatic condition) is the most important factor in affecting the thermal sensations and comfort assessments of people. These assessments are both dynamic and subjective: dynamic in the sense that adaptation to an ambient thermal condition is progressive, and that thermal sensation is primarily affected by previous experience, and subjective in the sense that the evaluation of a thermal comfort condition is not always consistent with the objective climatic or biometeorological condition. In addition to the climatic aspects of thermal comfort, a variety of physical and social factors that influence perceptions of urban space come into play when people are outdoors. For example, they are often engaged in activities, either alone or with other people, and those activities might be associated with physical amenities such as street furniture, shelter, seating, or kiosk stands. Thus, the use of outdoor space is determined not only by the “state of body” but also by the “state of mind.” This suggests that, to assess the perception of outdoor thermal comfort in terms of behavioral aspects, an assessment framework should work on at least four levels: physical, physiological, psychological, and social/behavioral (Fig. 4). This framework should allow the local microclimatic condition to be linked with human sensations as well as with the use of space in both spatial and temporal terms. In other words, static and objective aspects (i.e., physical and physiological characteristics) should be measured and modeled effectively to provide “climatic knowledge,” and dynamic and subjective aspects (i.e., psychological and social/behavioral characteristics) require comprehensive field interviews and observations to provide “human knowledge.”