Green occupants for green buildings

Given contemporaneous concerns of climate change and increasing fossil fuel prices, architects and building designers are exploring mixed-mode (MM) ventilation as a way of combining the best features of air-conditioned (AC) and naturally-ventilated (NV) buildings. MM or ‘hybrid’ buildings utilise a ‘free-running’ NV mode whenever outdoor weather conditions are considered favourable, but revert to mechanical systems for heating, ventilation and air-conditioning when external conditions are deemed less favourable for occupants. This thesis explores how occupant expectations and environmental attitudes may influence thermal comfort and occupant satisfaction within the context of the indoor thermal environment. In doing so, it evaluates the potential for climate change mitigation in NV and MM buildings through occupant behavioural adaptations. Two academic office buildings with different ventilation strategies (i.e. MM and NV) from a university in Sydney, Australia were used as case studies for this research. Post-occupancy evaluations (POEs) supplemented with the 15-item New Ecological Paradigm (NEP) questionnaire, measuring strength of endorsement (from low to high) of an ecological worldview, were conducted in both buildings to examine how environmental attitudes caninfluence occupants’ tolerance of the indoor environmental performance of green buildings. Parallel thermal comfort studies, along with continuous indoor and outdoor climate measurements, were also conducted to investigate the differences in occupant satisfaction and comfort perceptions between each building and between the POE and comfort questionnaires.The POE ‘forgiveness factor’ attempts to quantify the users’ tolerance of a building’s environmental conditions by taking into account the user’s scores for thermal, acoustic and visual comfort. This study found a possible association between environmental beliefs and occupants’ forgiveness factor, which suggests that despite having less-than-ideal thermal conditions, occupants with higher NEP scores were more tolerant of their building’s shortcomings compared to occupants with lower NEP scores. Analyses of subjects’ thermal sensation within the MM building indicated that observed comfort votes (Actual Mean Vote – AMV) measured in AC mode were congruent to those predicted using the Predicted Mean Vote (PMV) equation. During NV mode, however, observed AMV values did not conform to the PMV values, suggesting that occupants were more adaptive to indoor operative temperatures during NV mode as opposed to when the building was in AC mode. In comparison, whilst occupants experienced significantly warmer operative temperatures in the NV building, observed thermal sensations were also found to differ from the predicted values, suggesting adaptive behaviours of the occupants. Thermal satisfaction and acceptability, along with participant comments and anecdotal evidence from each building, were analysed to investigate the effectiveness of POE methods in evaluating building performance. Results from this study suggest occupants can and do use POE as a vehicle for complaint about general workplace issues, unrelated to their building. This thesis underscores the importance of occupant expectations and attitudes within the indoor thermal environment. Each study highlights significant differences between occupants’ thermal responses under different indoor environmental conditions, suggesting people’s environmental attitudes and expectations affect their perception of comfort and satisfaction within MM and NV buildings. Furthermore, the complexity of thermal perception and the inadequacy of static models to describe occupant comfort in MM buildings are discussed in the context of whether such design approaches fall within the scope of international adaptive comfort standards. This research provides evidence to support extending the psychological dimensions of thermal comfort and building performance studies to account for the contextual influences at play in green buildings, such as environmental attitudes, expectations and personal control.