Energy consequences of Comfort-driven temperature setpoints in office buildings

Abstract

The diversity in occupants’ thermal comfort preferences is usually overlooked in the operations of centralized-HVAC buildings and room temperatures are maintained within a narrow temperature range. In this study, we first created total of 400 comfort profiles for four major climate zones and for two seasons (winter and summer), using the RP884 database. We then systematically simulated and quantified the impact of using zone level setpoints (based on the generated comfort profiles) on energy consumption in office buildings. We also evaluated the consequences of using comfort-driven zone level setpoints on occupant satisfaction. The results indicate that using comfort-driven zone level setpoints can lead to an average increase in occupant satisfaction of 25% compared to the fixed building level setpoint of 22.5 °C, and 40% increase in occupant satisfaction compared to the DOE reference cooling setpoint of 24 °C and heating setpoint of 21 °C. Using comfort-driven zone level setpoints can also lead to average energy savings of 2.1% when compared to the fixed building level setpoint of 22.5 °C or average increase in energy consumption of 6.2% when compared to DOE reference setpoints, depending on the building size, construction and climate type. The variation in energy consumption caused by diverse occupant preferences is less than 2% of the annual building energy consumption. Furthermore, we demonstrated that even with the zone level setpoints, it is quite difficult to meet the ASHRAE requirement of 80% occupant satisfaction, which supports the use of personalized comfort systems to improve occupant satisfaction in buildings.