Thermostat Control and Window Opening: Impact on Indoor Environmental Conditions and Building Performance

This paper investigates thermostat interventions and window openings across 77 offices during the heating and transition seasons of 2023. A cloud-based heating controller, that takes user preferences and anticipated presence schedules, was evaluated in two buildings of the Living Lab Energy Campus (LLEC) at Forschungszentrum Jülich, Germany. Occupants adjust the setpoint via a web-based interface or local interaction. Data on indoor and outdoor environmental parameters, occupancy and occupant behavior, and heating consumption were collected. Additionally, a web-based survey was conducted in March 2024 for further insights. The results indicate that the heating controller effectively adapts to user preferences and occupancy patterns, significantly influencing heating consumption, alongside the impact of building construction age. Besides, an initial economic evaluation revealed that the implemented measures resulted in approximately 18.5% energy savings. The heating controller combined with window openings maintained indoor thermal comfort, with 63.7% of occupants preferring no change in the indoor temperature, and 83.5% reported acceptance of the indoor thermal conditions. About 69% of respondents attributed their satisfaction with room control to their accessibility to different control options. Space orientation was found to be an important factor affecting temperature setpoints and window opening duration.