Contents lists available at ScienceDirect Tunnelling and Underground Space Technology journal homepage: www.elsevier.com/locate/tust Working in underground spaces: Architectural parameters, perceptions and thermal comfort measurements Zheng Tan a,b,c, ⁎ , Adam C. Roberts a,d,e , George I. Christopoulos d,e, ⁎ , Kian-Woon Kwok f , Josip Car g , XiaoZhao Li h,i , Chee-Kiong Soh a a Civil and Environmental Engineering, Nanyang Technological University, Singapore b Institute of Future Cities, The Chinese University of Hong Kong, Hong Kong Special Administrative Region c School of Architecture and Urban Planning, Guangzhou University, China d Culture Science Institute, Nanyang Business School, Nanyang Technological University, Singapore e Decision, Environmental and Organizational Neuroscience Lab, Nanyang Business School, Nanyang Technological University, Singapore f Humanities and Social Sciences, Nanyang Technological University, Singapore g Health Services and Outcomes Research Programme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore h Nanjing University, Institute for Underground Space and Geo-Environment, China i School of Earth Sciences and Engineering, Nanjing University, China ARTICLE INFO Keywords: Underground space Thermal mass Design aspects Human occupants Human-centered Psychology Health Sleep ABSTRACT Rapid economic growth and high urbanization rates create an urgent need for more space in major cities in China. Further development of underground spaces (UGS) is a viable solution that the Chinese government is promoting. For instance, the 13th 5-year Plan for Urban Underground Space Planning suggests that a compre- hensive system for UGS planning and management should be established in at least 50% of Chinese cities by 2020. It is thus imperative to better understand how the architectural and engineering aspects of UGS affect human worker’s performance, well-being, health, and preferences. The present study reports a comprehensive examination of spaces and occupants of UGS in four major Chinese cities (Beijing, Shanghai, Nanjing and Fuzhou). We investigated thermal comfort conditions in UGS without heating and cooling, and estimated the potential of energy saving during transitional seasons. The results indicate that local climate – and especially the humidity level - is a key factor affecting the thermal behaviour of underground structures. In-depth interviews with workers in UGS indicated that immediate access to above ground greenery, indoor plants, and individual control over the environment compensate for a windowless workspace, and those working in UGS did not perceive to have any sleep disturbances. Previous experience with UGS improved the perception of current underground environments. UGS might even be appreciated as working environments with a good acoustic quality. Overall, the present study challenges the uniformity of standards for the construction of UGS, as it suggests that both climatic conditions as well as user preferences should be taken into account. 1. Introduction 1.1. Rapid development of urban underground space Underground space (UGS) is playing an important role in the planning and development of modern urbanization (Delmastro et al., 2016). As an efficient and sustainable infrastructure, UGS shows great economic advantage in coping with dense populations in cities and the high demand for space and mobility (Admiraal and Cornaro, 2016). The demand-driven planning of UGS is common in many major cities worldwide. The massive Toronto underground pedestrian network is 30 km long and can be considered a city by itself (Bélanger, 2007). Japan has investigated the latest technologies in rock caverns and ex- plored deep UGS (Tezuka and Seoka, 2003). In Northern Europe, a significant share of UGS function is for utilities infrastructures due to the energy efficiency of UGS (Bobylev, 2009). In recent years, a rapid and large scale underground space (UGS) development has taken place in different cities in China. In Beijing, there are 3 million m 2 of UGS being constructed each year (Chen et al., 2014). In Shanghai, over 68 million m 2 of UGS had been developed by 2014 (Zhao et al., 2016). The total underground construction area reached 19 million m 2 in Shenzhen in 2013 (Chen et al., 2013b). Guangzhou is building the http://dx.doi.org/10.1016/j.tust.2017.09.002 Received 14 March 2017; Received in revised form 4 August 2017; Accepted 5 September 2017 ⁎ Corresponding authors. E-mail addresses: ttanya@ntu.edu.sg (Z. Tan), aroberts@ntu.edu.sg (A.C. Roberts), cgeorgios@ntu.edu.sg (G.I. Christopoulos), kwkwok@ntu.edu.sg (K.-W. Kwok), josip.car@ntu.edu.sg (J. Car), lixz@nju.edu.cn (X. Li), csohck@ntu.edu.sg (C.-K. Soh). Tunnelling and Underground Space Technology 71 (2018) 428–439 0886-7798/ © 2017 Elsevier Ltd. All rights reserved. MARK