Thermal control of an occupied room: investigating the use of carbon dioxide concentration as an auxiliary control variable

This paper details the theoretical and experimental work done in the examination of the relationship between human generated carbon dioxide concentration and temperature rise in an occupied room. Generation of carbon dioxide by humans is linked to metabolic rate and heat generation. Therefore, carbon dioxide concentration may be used as an indicator of occupancy in a room. Typically, a heating control system will react slowly to changes in room occupancy if temperature is used as the process variable. The aim of the work was to establish if carbon dioxide concentration in the space could be used as an auxiliary control variable so as to allow a more rapid temperature control system response. Models of the relationship between room air temperature and occupancy, and carbon dioxide concentration and occupancy are mathematically developed and experimentally validated. The paper concludes that carbon dioxide concentration is an appropriate auxiliary control variable for temperature control when the room, having been occupied, is vacated.