The impacts of occupant behaviours on energy consumption in New Zealand office buildings : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Construction at Massey University, Albany, New Zealand
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Date
2023
DOI
Open Access Location
Authors
Weerasinghe, Achini
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Massey University
Listed in 2023 Dean's List of Exceptional Theses
Listed in 2023 Dean's List of Exceptional Theses
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Abstract
The building and construction sector consumes 36% of the global energy and produces 39% of energy-related CO2 emissions. Building energy consumption is influenced by various factors, including climate, building-related characteristics, building services, and occupant behaviours. In return, occupant behaviours significantly impact building energy consumption, with the difference between simulated and actual energy use due to how occupants behave and interact within the building. Numerous direct and indirect factors may influence occupant energy behaviours, with physical environmental, contextual, and social-psychological factors being the most widely recognised categories. Research on occupant behaviour in buildings is expanding, but only about 7% of those studies explore the determinants of behavioural change. Also, behavioural models and tools are becoming more complex to represent the human component better. As such, there is a need for further research on energy conservation approaches and drivers of occupant behaviour change in commercial buildings, especially in the New Zealand context, and a need for models that consider both subjective and objective aspects and an ontology that explicitly addresses the subjective aspects. Thus, this research focuses on creating an ontology that specifies occupant behaviour-related data monitoring and collection to optimise the energy performance of New Zealand office buildings. This research followed a narrative and systematic literature review, a preliminary study, and two primary data collection rounds to fill the above research gap and achieve the research aim. The research used a mixed methods approach consisting of grounded theory, survey, and qualitative and quantitative data collection and analysis techniques, with critical realism philosophy and an abductive approach as the underlying theoretical framework.
The narrative and systematic literature reviews focused on identifying the prevalent occupant energy behaviours and the significant drivers that influence these behaviours in the New Zealand and international contexts. The narrative review of academic articles defines occupant behaviours and highlights the importance of considering indoor environmental quality (IEQ) parameters and other factors influencing occupant behaviours. Also, it identifies the main factors influencing occupant behaviours. The narrative review further suggests that energy research practices based purely on objective factors of occupant behaviours may not highlight valuable insights from subjective aspects. Therefore, a systematic review of research articles on the social-psychological drivers of occupant behaviours is conducted to determine previous research patterns and trends and identify gaps for future investigation. The systematic review highlights the influence of social-psychological theories and constructs on occupant energy behaviours and discusses the application of theories in different occupant behaviours and future research trends and implications. In the following stages of the research, these identified prevalent occupant energy behaviours and the significant drivers that influence these behaviours are preliminarily and primarily investigated in the New Zealand context.
Accordingly, the preliminary research investigates the attitudes and approaches of building managers towards occupant energy behaviours in New Zealand tertiary education office buildings and how organisational energy culture affects their strategies for addressing occupant preferences. The research used grounded theory analysis, with 25 participants from a university being interviewed through semi-structured interviews with facilities managers, sustainability managers, and building occupants. The study found that building managers often oversimplify the complex relationship between discomfort, energy consumption, and the influence of social-psychological factors on occupant behaviour. To improve the organisational energy culture, the study suggests increasing occupant knowledge and awareness of energy consumption, providing energy feedback, and giving occupants more responsibility to meet energy targets. The preliminary study also evaluates the relationship between occupant energy behaviours, IEQ satisfaction, user control, and social-psychological factors. The study collected data from 52 occupants in five office spaces at a university in Auckland, New Zealand, and analysed using descriptive and binary logistic regression analysis. The study found that thermal and air quality conditions are the primary sources of IEQ discomfort, and occupant satisfaction is linked to their comfort preferences. The preliminary study showcases how organisations rationalise occupant energy behaviours and comfort preferences in New Zealand office buildings while highlighting the importance of considering occupant comfort and behaviours when implementing energy-saving measures and preparing occupant-centred energy policies.
Subsequently, the primary data of the research focuses on evaluating how occupants perceive decision-making regarding their energy behaviours in New Zealand office buildings to enable informed decisions for building managers. The primary research explores the influence of social-psychological factors on occupant energy behaviours in office environments. It utilises a combination of questionnaires distributed to 294 office occupants in New Zealand and PLS-SEM analysis to assess the impact of motivation, opportunity, and ability on these behaviours. The results indicate that improving energy-saving opportunities through subjective norms, organisational support, behavioural interventions, and individual control capability leads to increased perceived behavioural control and knowledge, motivating occupants to engage in energy-saving behaviours. As the subjective factors are clearly identified, the research next investigates the influence of subjective and objective factors on occupant behaviours in New Zealand office buildings. The study collected data on indoor environmental comfort, control availability, and social-psychological factors through online surveys of 99 occupants and analysed the data using machine learning techniques. The study found that the availability of user controls is the main predictor of most occupant behaviours, followed by social-psychological factors and indoor environmental parameters. Demographic factors such as gender, work duration, and workspace permanence are also important. These primary research findings then contributed to developing an ontology for effectively monitoring and collecting occupant energy behaviour-related data to optimise the energy performances of New Zealand office buildings.
The proposed ontology effectively describes and captures the complex interplay of drivers affecting occupant energy behaviours in offices, including environmental factors, user control, social-psychological factors, and demographic information. The subject matter experts agreed that the ontology provides a comprehensive and structured representation of occupant energy behaviours and could be helpful in building performance simulation and energy management systems. They also emphasised the importance of considering occupant behaviour-related data in building energy management strategies and audits. Accordingly, this study provides a new approach to assessing the combined impact of comfort preferences, energy behaviour, and various environmental, building, and social-psychological factors for modelling occupant energy behaviours in office buildings. The study provides a practical and valuable contribution to building energy efficiency, supporting the integration of occupant energy behaviours into building performance simulation, energy management, and sustainability strategies.
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Keywords
Office buildings, Energy consumption, Social aspects, New Zealand, Dean's List of Exceptional Theses