Bunn, Roderic; (2018) Towards a theory of carrying capacity, evidence from long-term longitudinal case studies of occupant satisfaction in non-domestic buildings. Doctoral thesis (Eng.D), UCL (University College London).

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Abstract

This thesis presents research into the longitudinal comfort performance of six office buildings and one educational building in their normal, everyday modes of operation. The aim of the research was to determine whether changing patterns in occupant comfort perceptions in longitudinal occupant surveys can be identified, and whether such patterns can be linked reliably to morphological, physical and operational factors. Statistical and qualitative analysis sought to determine whether changes in physical and operational contexts could be reliably associated with discernable changes in occupant satisfaction. The ultimate objective was to inform policies and decisions made by designers and operators. It also aimed to aid decision-making during interventions carried out during a Soft Landings process of feedback and professional aftercare (Bordass, W.; Bunn R.; Leaman, A. and Way, M. 2014). The research relied primarily on quantitative measurements, descriptive statistics, and the numerical comfort scores and qualitative feedback obtained from the Building Use Studies (BUS) survey, in common use in its current form since 1998. Such surveys are becoming a staple tool in post-occupancy building performance assessments, and occupant health and wellbeing assessments. The longevity of the BUS survey, plus its consistency over time, facilitated the research project. The research involved multiple longitudinal surveys of seven non-domestic buildings using a grounded theory, case-study based approach. The database of surveys amounted to over 2300 individual occupant responses, with three to 21 years between BUS surveys. Data obtained was mapped against the morphological and physical changes in the buildings over time, with details of changes captured in a contextual framework developed for the project, called context nesting. Movement in BUS occupant satisfaction scores were tested statistically. Longitudinal statistical change in the perceptionsof building occupants were triangulated with measured and calculated contextual information to determine potential causal factors, with the strength of causality based on the weight of evidence.The research revealed a consistency in each building’s main comfort and satisfaction scores over time, unless contextual or population changes had occurred to alter occupants perceptions, and thereby their scoring. This finding motivated a theoretical concept termed ‘building comfort signatures’, i.e.that a building’s comfort profile will be determined by its design and initial operation and captured inthe first occupant survey. The research also explored relationships between occupant numbers (i.e.density) and satisfaction. Some relationships were found between higher densities over time and declines in occupant satisfaction for a range of comfort variables. The research failed to find consistent relationships between changes in seasonal, functional, and environmental control variables and what were treated as the ‘outcome’ variables of perceived comfort, health and productivity. It is postulated that the lack of repeated relationships between perceived productivity, comfort and health across the buildings were due to survey respondents’ ability to cope, tolerate and adapt to prevailing conditions. The research project concludes by reconsidering how occupant satisfaction metrics may be better applied through the adoption of ‘carrying capacity’ theory, defined as the ability of a given office workspace to enable people to perform tasks without detriment to their perceived comfort, health and productivity. It is suggested that a baseline for determining carrying capacity should be based on a thorough and detailed mapping of a building’s context(s), alongside the results from occupant satisfaction surveys, and that these dual characteristics be used as baselines against which occupant satisfaction can be efficiently and effectively monitored and managed over time.

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