Smart thermostat integration for hvac efficiency and ieq management in Sri Lankan offices

Abstract

This study investigates the energy performance implications of smart thermostat integration within a commercial office building in Colombo, Sri Lanka—a tropical climate context that remains underrepresented in the building energy control literature. A single-case study design was applied using high-resolution five-minute interval HVAC operational data collected across two discrete periods: a pre-intervention baseline (Au-gust–October 2025) and a post-intervention monitoring period (November–December 2025). A multivariable regression-based baseline model was developed in accordance with the International Performance Measurement and Verification Protocol (IPMVP) and validated against the statistical criteria specified in ASHRAE Guideline 14-2020, yielding a CVRMSE of 12.3% and NMBE of −2.8%, both within prescribed thresholds. Post-intervention analysis indicates that HVAC energy consumption decreased from a modelled baseline of 43,724.1 kWh to 38,198.8 kWh under smart thermostat control, representing a gross reduction of 5,525.3 kWh (12.6%). Whole-building peak HVAC demand declined by 7.1 kW (6.3%). Savings were predominantly concentrated during weekend and shoulder-hour periods, indicating that the elimination of unnecessary cooling runtime during un-occupied periods constituted the primary saving mechanism. In the absence of concurrent indoor environmental quality (IEQ) measurements, thermal comfort considerations are addressed through a conceptual operational framework informed by ASHRAE Standard 55-2023 and ISO 7730:2005, explicitly presented as a basis for future empirical validation rather than a confirmed outcome of the present study. The study contributes an empirically grounded, M&V-compliant evaluation framework for facilities managers seeking data-informed HVAC optimisa-tion in tropical commercial office settings.