Comparative evaluation of measured and perceived indoor environmental conditions in naturally and mechanically ventilate

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Comparative evaluation of measured and perceived indoor environmental conditions in naturally and mechanically ventilated office environments

Low Carbon Building Research Group, Oxford Institute for Sustainable Development, School of Architecture, Oxford Brookes University, Oxford, UK

Abstract

Keywords

This paper uses a case study-based approach to comparatively evaluate the relationship between measured and perceived indoor environmental conditions in two office buildings, one naturally ventilated and one mechanically ventilated, located in south England. Environmental parameters (indoor and outdoor temperature and relative humidity, and indoor CO2 concentration) were continuously monitored at 5-minute intervals over a 19-month period (March 2017 to September 2018). During this time, occupant satisfaction surveys (both transverse and longitudinal) recorded occupant perceptions of their working environment, including thermal comfort, resulting in approximately 5700 survey responses from the two case studies combined. In the NV office, CO2 levels were high (often >2000 ppm) and indoor temperature was both high (>27 °C) and variable (up to 8 °C change in a working day). In contrast, the MV office environment was found to operate within much narrower temperature, RH and CO2 bands. This was particularly evident in the little seasonal variation observed in the CO2 levels in the MV office (rarely above 1200 ppm); whereas in the NV office, CO2 concentrations exceeded 2000 ppm on 12% of working days during the heating seasons and less than 1% in the non-heating season. Despite these differences in measured indoor environmental conditions, occupants’ overall satisfaction with their environment was similar in both buildings. Occupants of the NV building were found to be more tolerant of higher indoor temperatures while neutral thermal sensation corresponded to a higher indoor temperature, indicating the role of adaptation. This has important implications for energy use in managing the indoor environment.

indoor environment,

Introduction

The UK has a service-based economy, with 71% of GDP coming from the service sector and 18% from industry (Plecher 2020). A substantial proportion of service and industry based employees are office based, accounting for a significant proportion of the UK workforce. A UK-based survey revealed that office workers spend more time per day at their desk or workstation (6.8 hours) than they do in bed (6.4 hours), relaxing at home (3.5 hours) or outdoors (37 minutes) (Bean 2018). The workplace environment therefore has an important role to play in the health and wellbeing of its occupants, as well as having an impact, E-mail: [email protected]

occupant perception, thermal comfort, monitoring, occupant survey

Article History Received: 06 February 2020 Revised: 19 May 2020 Accepted: 08 June 2020 © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020

whether positive or negative, on their productivity (Gupta et al. 2020). A number of studies have investig