With the intensification of global aging, a comfortable indoor environment is crucial for the well-being of the elderly. However, research on the thermal effect of solar radiation, i.e., infrared radiation, remains scarce. This study innovatively used infrared heaters to simulate the thermal effect of solar radiation and conducted a comprehensive thermal comfort experiment involving subjective evaluations and electroencephalogram (EEG) measurements on 30 elderly participants and 30 young participants in an artificial climate laboratory. The results showed that there were significant age-related differences in the subjective ratings and EEG power under different infrared radiation levels. Under low radiation conditions, as the irradiated area increased, the elderly participants’ thermal sensation ratings were 0.5 points higher than those of young participants, and their evaluation results in terms of comfort, relaxation, and alertness were also higher. The logarithmic EEG power of both age groups decreased, but the overall power level of the elderly was consistently lower. Notably, under high radiation conditions, the comfort level of both groups decreased, with a more significant decline in young people. Interestingly, when the EEG power of young people decreased, that of the elderly increased, indicating that despite the elderly’s better subjective evaluations, they are more susceptible to heat stress. In addition, this study shows that under the action of infrared radiation, the logarithmic EEG power of young participants is approximately 1.0% to 1.5% higher than that of elderly participants. This study found that the frontal alpha band is a key indicator for predicting thermal comfort in people of different ages, which highlights the innovative contribution of this research. To fill the gap in the field of thermal comfort research, this study explored the elderly’s response to infrared radiation, an aspect that has not been fully studied before. These insights can provide references for the design of more comfortable environments in facilities for the elderly, thereby significantly improving the quality of life of this population.

In research related to cognitive performance, temperature is often regarded as a core influencing factor and has received significant attention. However, as a key component of the building thermal environment, solar radiation and its mechanism of action on cognitive performance have rarely been studied. This paper conducts a laboratory study, using an infrared radiation heater to simulate the thermal effect of solar radiation, and explores the age-related differences between the elderly and the young in thermal comfort, electroencephalogram (EEG) activity, and cognitive ability under three radiation intensities (0 W, 500 W, and 1000 W). The results show that age has a relatively small impact on subjective thermal responses but a significant impact on mental state and cognitive performance. In the infrared radiation environment, the alertness (ALV score) of the elderly remains more stable, while young people show an increased sense of drowsiness. EEG analysis indicates that the frontal lobe logarithmic power of both groups of subjects is 4.55–6.79% higher than the average of other brain regions. High radiation (1000 W) inhibits the EEG activity of young people but triggers compensatory activation in the elderly, thus reducing age-related neural differences. Cognitive tests show that compared with the non-radiation condition, high infrared radiation (1000 W) significantly improves the cognitive levels of the elderly in terms of attention (CPT: +1.53%), response ability (DLT: +0.78%) and visual search ability (VST: +2.04%), while these abilities decline in young people (CPT: −2.78%, DLT: −1.21%, VST: −3.82%). The correlation analysis between EEG and cognitive tests identifies that the right frontal electrodes (F4, F8) and the occipital O1 may be potential candidate electrodes for evaluating the cognitive performance of the elderly and young people. This study provides crucial objective physiological evidence for clarifying the relationship between heat sources such as the thermal effect of solar radiation, which “acts directly on the human body”, and human thermal comfort and cognitive performance.