Strategies for thermal comfort improvement and energy savings in existing office buildings using occupant feedback

Air-conditioning systems consume between 40 and 50% of the total energy consumption in buildings in Singapore. Set-point scheduling in existing office buildings is challenging as it is necessary to maximize energy savings without causing thermal discomfort to the occupants that can lead to a reduction in productivity. Thermal comfort depends on environmental factors such as air temperature, humidity, air speed, mean radiant temperature and also personal factors such as metabolic rate and clothing. The recent trend is to incorporate direct occupant feedback in Heating ventilation and air-conditioning (HVAC) control to account for the parameters that are difficult to measure or estimate. In this paper, typical office-building rooms with 6-10 occupants in the same thermal zone are considered. A desktop application is developed to collect occupant feedback on thermal sensation, taking into account user's convenience and utilizing the existing Local Area Network (LAN) infrastructure. The temperature and relative humidity is measured by non-intrusive wireless sensor nodes placed as close as possible to the occupant's operating area to minimize errors. Using the sensor data and occupant feedback, various thermal comfort improvement and energy saving strategies are identified without the need for any retrofits.