Human comfort modelling for elderly people by infrared thermography: Evaluating the thermoregulation system responses in an indoor environment during winter

Abstract

Elderly people are vulnerable to cold environments, due to aging’s impact on the density of nerve fibers. Nevertheless, automatic controls of HVAC systems do not consider the user’s real-time thermal sensation and most of algorithms were tested in manikins using climatic chambers or simulated by CFD. Indeed, a standardization of a non-invasive technique as infrared thermography (IRT) for human body responses was not detected in the literature review. This paper proposes a method to determine the indoor thermal comfort of elderly people by IRT. The campaigns took place in a nursing home of the Mediterranean Climate during Winter. A total of 15 old adults were monitored to measure the skin temperature of four face points (nose, forehead, cheekbone and chin) and clothing temperature. A thermal sensation questionnaire and indoor conditions were also collected. The results demonstrated that the IRT model could estimate the thermal exchange from three body-segments (head, back-pelvis, thorax-limbs) to the surroundings by user’s features and environmental parameters. The thermal neutrality was achieved when all facial points reached a skin temperature of 35ºC, the clothing temperature was equal to 31ºC, and the operative temperature and relative humidity were 23.5ºC and 54% respectively. Statistically, 31.70% of the variance of PMV could be attributed to increases of facial skin temperature, while changes in user’s features could have minor influence (from 0.88 to 6.40%). As regards the main contributions of heat losses, they were given by respiration (11-21%), convection (20-32%) and radiation (35-39%). Finally, an innovative HVAC control strategy was posed.