Elsevier

Energy and Buildings

Volume 140, 1 April 2017, Pages 9-18
Energy and Buildings

Full Length Article
Seasonal variation of thermal sensations in residential buildings in the Hot Summer and Cold Winter zone of China

https://doi.org/10.1016/j.enbuild.2017.01.066Get rights and content

Highlights

  • A large-scale thermal comfort survey in residential buildings in the HSCW zone is presented.

  • There are different adaptive responses and thermal sensations with air temperature in different seasons.

  • Significance of seasonal variations of neutral temperatures due to thermal experience has been revealed.

  • Dynamic evaluation for thermal comfort is suggested.

Abstract

Seasonal variation of thermal comfort demands directly affects the energy needs for heating or cooling purpose. In previous studies, the differences of neutral temperatures between summer and winter were revealed, but the studies on the difference of human thermal adaption in transitional seasons are insufficient. To clarify this, this paper presents a year-long survey which was carried out in 505 residential buildings in six cities located in the Hot Summer and Cold Winter (HSCW) zone of China involving 11,524 subjects. Results show a significant difference of adaptive responses in different seasons, and a lag of behavioral responses behind climate change in transitional seasons is observed. Occupants not only adjust clothing insulation according to air temperature in different seasons, but also actively control indoor air movement, including closing/opening windows and using fans. The seasonal, monthly and daily neutral temperatures are studied, implying that occupants’ thermal experience has significant effect on their thermal comfort by behavioral, physiological and psychological paths. According to the comparative study, the running mean air temperature method and aPMV model are recommended in free-running space. The findings provide scientific evidence to the concept that dynamic thermal comfort temperature range should be considered in evaluation of indoor thermal environment.

Introduction

The existing building stock in cities in China’s Hot Summer and Cold Winter (HSCW) climate zone covers some 9 billion m2 of which residential buildings accounted for 66% in 2012 [1]. The HSCW zone has unique climate characteristics, i.e. hot long summers, cold wet winters, a rainy climate with monsoon, and so on, as described in reference [2]. Due to economic growth, there has been a continued and growing demand for the improvement of the indoor thermal environment and consequently the growth of energy demand for both heating and cooling [1], [3]. Such situations have a considerable adverse impact on the nation’s energy reduction target [4].

In residential buildings, besides the building design [5], occupants’ behavioral habits, varieties of thermal sensation and comfort requirements [6] significantly impact on energy consumption. There would be a potential waste of energy [7] to maintain the indoor thermal environment within the thermal comfort thresholds using the thermal comfort standards if there is not a full understanding of the different thermal sensation characteristics in different seasons in free-running buildings. Our previous study in naturally ventilated classrooms demonstrates that occupants’ thermal sensations dynamically respond to the outdoor climate [8]. Because of adaptions to the natural climate using available facilities, occupants have a wider acceptable temperature range in NV (Naturally ventilated) buildings than that in AC (Air-conditioned) buildings [9], [10], [11]. Many studies [12], [13], [14], [15], [16], [17], [18], [19], [20] also conclude that differences exist in occupants’ thermal sensations between summer and winter, due to the obvious differences in outdoor climates between these two seasons.

China has a diverse climate and consequently is divided into five climate zones for building thermal design purposes [21]. Among the five zones, the HSCW zone has unique climatic characteristics and the residents have diverse adaptations for ensuring thermal comfort [22], [23], [24], [25], [26] in free-running space. This has attracted many scholars to engage in this research. Some previous studies were concentrated in a specific city for year-long study [26], [27], whilst some studies focused on a specific season (e.g. summer) in this area [28], [29]. However, most studies [30], [31], [32], [33] were only conducted during a specific season in one city/province.

The aim of this study is to obtain a sophisticated understanding of residents’ thermal sensations and their dynamic responses to the variation in outdoor climates for different seasons in free-running space. This will provide a fundamental knowledge of the thermal comfort demand for residential buildings in this region. Consequently, a dynamic solution to achieve indoor thermal comfort in residential buildings will possibly be developed to meet the requirements for both thermal comfort and energy efficiency.

Section snippets

Methods

Onsite field measurements and a questionnaire survey have been conducted in this research. Statistical regression methods are used for the analysis of data.

Thermal environments

The monthly thermal environment parameters including air temperature, relative humidity and air velocity all around the year are illustrated in Fig. 2. The twelve months in a year are traditionally divided into four seasons: winter (including December, January and February), spring (including March, April and May), summer (including June, July and August) and autumn (including September, October and November). The environmental parameters of the survey are summarized in Table 2. It can be seen

Variation of thermal sensation between spring and autumn

There is strong evidence that thermal sensations vary in different seasons. There are several possible reasons to explain the difference of thermal sensation between spring and autumn. The thermal environments in real buildings are dynamic ones (i.e. not steady-state). It is complex to predict occupants’ thermal sensations by physical parameters in dynamic environments [42], [43], [44], [45], [46], especially considering their adaptation to the dynamic thermal environment in real buildings [47].

Conclusions

This paper presents research into thermal sensation variation according to the changing of seasons based on the data collected in 505 free-running mode residential buildings involving 11,524 subjects in six cities in the HSCW Zone in China. A significant difference of human thermal adaption at different seasons has been demonstrated. The main conclusions are drawn as follows:

  • (1)

    Behavioral responses show variety in different seasons.

    • Air temperature is found to be the most significant driver to

Acknowledgements

The authors would like to thank the Natural Science Foundation of China (NSFC 51561135002) and the International Science & Technology Cooperation Program of China (No.2014DFA62970), and the Graduate Scientific Research and Innovation Foundation of Chongqing, China (No. CYS16006), and the 111 Project (No.B13041) for their financial support.

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