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This study examines the use of a Doppler radar occupancy sensor to assess thermal adaptation. Current heating, ventilation, and air-conditioning (HVAC) systems are important for the productivity of employees and the healing of patients; however, their control systems are typically limited to a narrow temperature range, which is usually not comfortable for most occupants. Occupant vital signs can be used to assess thermal comfort, due to the role cardiovascular regulation plays in heat dissipation. This research aims to correlate physiological and thermal adaptation with the goal of optimizing HVAC system operation. A Doppler radar occupancy sensor was used to measure the physiological parameters of ten human subjects under two temperature conditions, and thermal comfort surveys were used to record thermal sensation. The results demonstrate that the Doppler radar occupancy sensor could not only detect heart rate changes due to a significant environmental temperature difference but also detect subtle changes in heart rate during thermal adaptation that were not captured by the surveys. 

Smart buildings promise to adapt environmental conditions to the needs of occupants based on statistical analytics applied to various monitored data. While sensors for accurate monitoring of building parameters such as temperature, lighting, and air-quality abound, currently available occupancy sensors are limited to sensing of presence only, with limited accuracy. Doppler radar sensors have shown great promise for unobtrusive recognition and monitoring of occupant presence, count, activity, and cardiopulmonary vital signs. With such measures, a smart building can optimize operations not only for the most efficient use of energy and space, but also to create healthy and sustainable environments that support occupant wellness, comfort, and productivity. This paper presents an overview of Doppler radar occupancy sensors for smart building applications.