Impact of Recirculation Rates on Indoor Environment and Occupant Comfort: A Case Study in Norway

The implementation of recirculation of return air has garnered significant attention as a energy-saving strategy in ventilation systems. It has gained widespread utilization in countries like the USA and China due the possibly to reduce energy use for heating and dehumidification. In contrast, Norway’s guidelines recommend its application exclusively during periods of human absence or when ensuring satisfactory indoor air quality (IAQ). The Norwegian winter is characterized by low temperatures which induce low relative humidity (RH) indoor. Although low RH can impact thermal comfort, the implementation of humidification is generally discouraged. This study focuses on a laboratory-based experiences aimed at understanding the effects of varying exhaust air recirculation rates on both room occupants and visitors. For occupants, the investigation delves into comfort perception and typing performance. Visitors’ experiences are assessed by odour perceptions upon smelling the air. The findings highlight that, in comparison to factors like the time of day, room temperature, and RH levels, variations in recirculation rates had a relatively minor influence on occupants’ perception and performance. Therefore, employing this strategy as an energy-saving mechanism while upholding stringent IAQ standards is proposed particularly in cold climates to conserve energy and simultaneously ameliorate indoor RH levels.