Human Thermal Load in Warm Season Weather Conditions of Temperate, Lowland, Continental Climates Based on the Results of the New Clothing Model

Abstract

We used a new IREQ-type (Required Insulation) model to estimate the heat excess caused by weather in the warm season of the temperate, lowland, and continental climates. The model we developed estimates heat excess by calculating both the “compensatory sweating”, λE_sw^comp, and the “clothing thermal resistance”, r_cl,t. The model is very simple and can be used to estimate thermal load under any weather condition. It can be applied to individuals and all activity types (lying, standing, walking, running). Longitudinal data collection method was used, with 240 observations conducted for the period 2023–2025 in the Hungarian lowland, measuring sweating (referred to as “regulatory sweating”, λE_sw) and comparing it to “compensatory sweating”. The λE_sw^comp and r_cl,t values were also compared to the estimated UTCI (Universal Thermal Climate Index) values. The main results are as follows: (1) λE_sw^comp values registered when running changed between 80 and 650 W m⁻² in the warm season in the Hungarian lowland, (2) observations revealed that λE_sw < λE_sw^comp in general, (3) during extreme loads, the upper limit of physically interpretable r_cl,t values is around 4 clo-t. These high r_cl,t values occur when λE_sw^comp is high (above 500 W m⁻²), the λE_sw is low (around 100 W m⁻²) and (4) the model is very sensitive to changes in irradiance and regulatory sweating values in situations with high heat excess. One of our most important future tasks is to parameterize sweating as simply as possible, which would have acceptable accuracy for as many people as possible.