Impact of Passive Cooling on Indoor Comfort in Tropical Office Buildings: An Empirical Study

Thesis Abstract

The study investigates how passive cooling strategies influence indoor thermal comfort, energy use, and perceived productivity in tropical office environments, addressing the gap between theoretical potential and field performance in real-world settings. The aim is to quantify the effectiveness of passive cooling interventions and to elucidate mechanisms through which such strategies affect occupant comfort and work outcomes under tropical climate conditions. Specific objectives include (i) evaluating thermal comfort across office zones with passive cooling features (shading, natural ventilation, thermal mass) and conventional mechanical cooling, (ii) comparing indoor temperatures, humidity, and air velocity with and without passive interventions, (iii) assessing occupant comfort satisfaction and perceived productivity using standardized scales, (iv) estimating energy implications of passive cooling configurations through monitored utility data, and (v) identifying design, operation, and behavioural factors that influence the performance of passive cooling in tropical office buildings. The methodology adopts a mixed-methods, embedded case-study design conducted in three contemporary office buildings in a tropical city, selected for varied facade types and passive cooling implementations. The population comprises office workers and building facilities managers within these buildings. A stratified random sample of 180 occupants (60 per building) is surveyed using a validated thermal comfort questionnaire incorporating ASHRAE/ISO-7730 indices, plus a productivity perception scale. Concurrently, on-site environmental monitoring collects data on indoor air temperature (°C), relative humidity (%), mean radiant temperature (°C), and air velocity (m/s) at 15-minute intervals over six months, complemented by monthly energy consumption records from building management systems. To complement quantitative findings, 20 semi-structured interviews with facilities managers and 12 focus groups (6–8 participants each) with occupants are conducted to explore contextual drivers, behavioural patterns, and perceived trade-offs of passive cooling. Analytical procedures include descriptive statistics and normality tests for environmental and comfort data, repeated-measures ANOVA to compare thermal indicators and comfort scores across passive and conventional zones, and multilevel regression modeling to account for clustering by building and occupant characteristics. The energy impact is analyzed via difference-in-differences estimation between retrofit and non-retrofit zones within the buildings, augmented by time-series decomposition to isolate seasonal effects. Qualitative data are analysed using thematic analysis to identify themes related to design integration, operability, and user acceptance, with triangulation against quantitative results to enhance interpretation. Theoretical framing leverages the Comfort Theory of Environmental Design and the Principle of Thermal Mass Interaction, complemented by the Theory of Planned Behaviour to interpret occupant actions influencing passive cooling effectiveness. Model validation employs cross-validation and sensitivity analyses to assess robustness under alternative parameter specifications. Expected findings include (i) statistically significant improvements in occupant thermal satisfaction and perceived productivity in zones employing passive cooling, without commensurate increases in indoor temperature variability; (ii) reductions in cooling energy use by 25–40% in passive cooling zones during peak heat periods, contingent on envelope performance and occupant behaviour; (iii) identification of optimal combinations of shading, natural ventilation, and thermal mass that maximize comfort while maintaining acceptable air quality; (iv) nuanced understanding of how occupant expectations, perceived control, and routines mediate the relationship between environmental conditions and productivity; and (v) design and operation guidelines emphasizing climate-responsive envelopes, operable skylights, and moisture-appropriate materials. The study contributes to knowledge by providing empirical evidence on the performance of passive cooling in tropical office contexts, clarifying the interaction between building physics, occupant comfort, and productivity, and delivering actionable design, retrofit, and policy guidance for energy-efficient, comfortable offices. It informs building codes and standards for tropical climates and offers a framework for integrating passive cooling with minimal reliance on mechanical cooling. The main conclusion is that well-integrated passive cooling strategies can achieve meaningful comfort and productivity benefits while delivering substantial energy savings, provided that envelope design, ventilation strategies, and occupant engagement are harmonized. Recommendations include adopting climate-responsive façade designs, implementing controllable natural ventilation protocols aligned with indoor air quality targets, incorporating high-thermal-mass materials with nighttime cooling potential, and establishing occupant education programs to cultivate behaviors that enhance passive cooling performance. Further research suggested includes longitudinal studies across diverse tropical climates and exploration of stochastic occupant behaviour models to refine predictive capabilities.