Exploring the impact of variable physical parameters of human body on the assessment of energy demands in smart buildings toward a novel dynamic thermal comfort approach

Indoor thermal comfort represents a key aspect of building design. The reference standards do not consider the thermal adaptability of the human body, and HVAC system control strategies are based on a steady-state assumption that returns an incorrect estimate of occupants’ thermal demand with a consequential overestimation of the building energy consumption. To overcome these issues, a physiological thermal comfort model for the human body thermal behaviour evaluation is developed in MatLab environment. In the present work, heart rate and skin temperature are considered as input for the model that can be measured with thermo-scanner and wearable devices. Thus, the developed model allows to determine the dynamic variation of the physiological aspects, such as skin temperature, and to characterize the occupants’ thermal sensation. Finally, the developed physiological thermal model is implemented in a building energy simulation tool (called DETECt 2.4) to perform suitable energy analyses on thermal comfort models impact. To show the potentiality of the developed model, a suitable case study consisting of an office space is considered. Here, space heating and cooling demands obtained by applying the novel developed model are compared to those obtained through standard thermal comfort models based on Fanger’s theory. By the comparison, between the proposed model - which considers the occupant in thermal evolution – and the reference ones – considering the occupant heat exchange in steady state - , interesting results are obtained. The same HVAC system control strategy is used in the investigated models however, the results in thermal energy demands are different due to the dynamic variation of occupant thermal load gain. The annual heating and cooling demand in the reference case with the assumption of steady state are respectively 18.2 and 46.4 kWh/m2∙y whereas, assessing an occupant dynamic thermal evolution they are respectively equal to 20.4 and 44.8 kWh/m2∙y (+12% in heating and −3.5% in cooling). Furthermore, the comfort analysis highlights the difference in considering the physiological parameters of the person dynamically variable and not constant.