Development of a multi-nodal thermal regulation and comfort model for the outdoor environment assessment

The growing need for planning eco-cities is calling on a tool that can give better prediction of the thermal comfort conditions for a specific microclimate. A multi-nodal thermal regulation model can potentially factor in the impacts of the transient and asymmetric thermal conditions on human subjects. In this study, Human subjects were invited to experience various kinds of urban open spaces and to express their thermal feelings, while skin temperatures of 17 local body segments were measured. We tested the multi-nodal thermal regulation model developed by UC Berkeley by comparing its predictions of human body skin temperature, thermal sensation vote (TSV), and thermal comfort vote (TCV) with our onsite human subject measurements and questionnaire survey, in order to identify the causes of the errors between the prediction and measurements. Corresponding to the thermal neutral status, the field-measured data recorded wider local skin temperature ranges than the simulated ones. We proposed using a “null zone” instead of “set-point” in the thermal comfort model to accommodate the possible adaptation of human subjects to the highly fluctuating wind environment in open spaces. It was proposed that the forehead was counted as one of the dominant local body parts when defining the overall thermal sensation. The correlation coefficient R² between the prediction and the field measured TSV improved to 93.7% for the revised model from 76.2% of the original model.