Working in underground spaces: Architectural parameters, perceptions and thermal comfort measurements

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 comprehensive 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.