Improving the analysis of radiant thermal effects on children

Abstract

Children’s thermal comfort is an important consideration in schools and daycares due to its impact on their concentration, attendance, and overall happiness. Recent research has shown that children are not thermally comfortable in schools and that adults are unable to correctly predict and adjust the environment to meet their thermal preferences. Yet, these spaces are typically designed according to the heat loads of adult occupants, and their comfort is assessed using methods developed for adults. However, most of the design parameters and evaluation approaches applied in this field have not been validated for children. One of these parameters is the view factor, which are used to calculate the mean radiant temperature, an index that quantifies the radiant thermal exchange between the occupant and its surroundings. This thesis aims to rectify this gap by analyzing the methods used for the prediction and evaluation of children’s thermal comfort, with a focus on the radiant aspect of their heat exchange. In light of the stated goals, detailed numerical manikins of adults, representative of the subjects found in Fanger’s seminal experiments, are generated and used to evaluate various methodological assumptions. Raytracing and hemicube numerical calculation methods are compared for accuracy. The effect of manikin pose is investigated in the standing posture, and found to significantly influence data match with literature. The adult manikin pose is thus calibrated to ensure results closely match those of the average male from Fanger’s experiments. Through a thorough comparison between three seating configurations, it is demonstrated that a seat’s blocking of radiation from the floor is significant in all cases. The presence of a seat is found to lower the mean radiant temperature by up to 2 °C in the two scenarios simulated with office and school chairs. The Anterior/Posterior symmetry assumption, currently accepted in the literature and used in all thermal comfort standards, is debunked in the presence of seats, requiring an important methodological change in all future investigations of human radiation data in the seated posture. The rigorous method developed addresses several gaps found in view factor literature, allowing for numerical calculation of projected area factors and view factors of numerical manikins for any population investigated. This novel method is then applied to a numerical manikin of a 5-year-old boy in order to investigate whether children’s radiation data is significantly different from that of adults. A 5- year-old boy manikin is retained to represent the lower end of the child population found in schools. Both child and adult manikins are generated in the standing and the seated posture combined with three different seating configurations. In the seated posture, the difference between the adult and child is found to be insignificant. The smaller size and reduced shading by school chairs when compared to office chairs explains the majority of the differences found when comparing the child and adult radiation data. The results indicate however that children have distinct radiation data than adults in the standing posture. In the two test scenarios considered, one with radiant floor heating, and another with a chilled ceiling, the child’s different projected area factors lead them to experience a mean radiant temperature up to 1 °C greater than the adults’, affecting their thermal comfort. The thesis concludes that children’s particular characteristics warrant a special consideration in thermal comfort standards. In the standing posture, child specific radiation data should be used for the design and evaluation of spaces where occupants are primarily children. In the seated posture, the radiation data used for both adults and children should be revised to account for the shading effect of seats that will inevitably be present, and the Anterior/Posterior symmetry assumption should be disposed of in favour of a complete accounting of radiant exchange of the human body with its environment. More research must be done on children’s thermal comfort, particularly on the applicability of the predicted mean vote equations currently in use for the evaluation of children’s thermal comfort, and to evaluate the particularity of children in other modes of heat exchange.

Date	18 Dec 2025
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Katherine D'Avignon (Supervisor)