Occupants’ adaptive responses and perception of thermal environment in naturally conditioned university classrooms
Introduction
The interaction between building environment and occupants is complex. People adjust themselves to maintain and improve their wellbeing through physiological, psychological and behavioural reactions to environmental stimuli [1]. It is crucial to understand building occupants’ perceptions of their indoor environment and their adaptive behaviour towards it.
The adaptive theory assumes that people consciously or unconsciously respond to a given thermal environment to which they are exposed in order to restore their own thermal comfort [2]. The recent development of the adaptive theory of thermal comfort explains occupants’ thermal comfort in different environmental contexts, particularly in naturally conditioned (NC) buildings, from the point of view of the adaptive approach [3]. Occupants in a given environment can achieve thermal comfort through adjustments to their personal environmental conditions in the form of taking on/off clothing, drinking hot/chilled water, opening/closing windows, shifting the sun shadow and switching on/off fans, heating or air-conditioners, etc. [4].
Chongqing is a typical hot summer and cold winter city in China. The averages outside temperatures for the hottest and coldest months are 0–10 °C and 25–30 °C, respectively [5]. The city is traditionally called “stove city” which implies the extreme hot summer climate. The classrooms of universities in Chongqing are designed as naturally conditioned spaces without air-conditioners and heating systems. Therefore, occupants’ adaptive responses will play a significant and positive role in the procedure to maintain the indoor environmental parameters at an acceptable thermal environment level or adjust themselves to adapt to the ambient environment. The climatic characteristics in Chongqing provide a great opportunity to examine the effects of the adaptive responses of subjects in NC university classrooms.
The main objectives of this field study are as follows:
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To reveal the real conditions of the thermal environment in NC university classrooms in Chongqing.
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To determine whether the thermal conditions are in the comfort zones specified by ASHRAE Standard 55-2004 [6].
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To reveal subjects’ thermal perceptions in NC classrooms.
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To verify the effects of occupants’ adaptive responses to the hot summer and cold winter weather in NC classrooms in Chongqing.
Section snippets
Brief literature review
The existing thermal comfort standards, such as ASHRAE 55 [14] and ISO 7730 [7], are base on theoretical analysis of the human body heat exchange with the environment as well as experiments conducted in the climate-controlled chamber with ‘paid college-age subjects’ [8], which predict the thermal environment and thermal comfort of human body in air-conditioned (AC) context [4]. The application of such standards in the naturally ventilated (NV) buildings has been challenged by filed
Method
Field measurements and an onsite questionnaire survey have been conducted in this research project. Beginning in April 2005, the survey and experiments were carried out monthly during a complete year in Chongqing, except August due to the summer vacation. Five university lecture buildings located in campuses A and B of Chongqing University have been selected for the study. These were called Lecture Building No. 5 and Lecture Building No. 8 in campus A and Lecture Building No. 1 and Lecture
Indoor physical environment
The statistical summary of indoor environmental parameters in NC classrooms during the year-long survey is shown in Table 3. From Table 3, we can see that the highest temperature in summer reached 38 °C and the lowest temperature was 22.7 °C in summer; and the highest temperature was 15.5 °C and the lowest one was 8.8 °C in winter. The mean air velocity in summer (ceiling fans on) was five times higher than that in winter (ceiling fans off) in order to increase skin evaporation heat exchange. The
Conclusion
From the point of view of the adaptive thermal comfort concept, the relationship between buildings and occupants exhibit extensive interactions. Conversely, occupants in the naturally conditioned buildings can adapt themselves to the ambient environment or adjust the ambient environment to suit themselves for thermal comfort purposes. Particularly in the naturally conditioned buildings where the indoor thermal environment is greatly affected by the outdoor climate, occupants fully utilize the
Acknowledgement
The authors would like to thank Mrs. Jing Wu, Ms. Liang Chen, Ms. Jiaolin Wang, Ms. Hong Wang and all the students from Chongqing University involved in the survey. The authors greatly acknowledge financial support from the Project “nCUBUS – Network for China–UK Building and Urban and Sustainability” funded by the UK Engineering and Physical Sciences Research Council (EPSRC EP/E040748/1) and the finance support from the Chinese National Natural Science Foundation (50838009, 50678179).
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