The influence of radiation intensity and wavelength on thermal perception

Thermal radiation is considered a fundamental factor of human thermal perception, however the effect of specific radiation spectra has not yet been explored comprehensively. This study investigates the influence of different radiation types, short-wave infrared A and long-wave infrared C radiation, on thermal sensation and thermal comfort. 29 participants were exposed to these two radiation types at two irradiance levels, 100 W/m2 and 200 W/m2, and at two air temperatures, 16 °C and 22 °C. The results confirm the well-established observation that additional irradiation induces a warmer thermal sensation. For an otherwise cold environment, a certain level of irradiation did also improve thermal comfort. When it comes to moderate thermal environments, we found that comparable amounts of infrared C irradiation are perceived substantially warmer than their infrared A counterparts. This significant outcome can potentially be explained by the radiative properties of human skin, which greatly depend on the irradiation spectrum. Current thermal perception models do not fully account for such differences. Thereby our findings contribute to a better understanding of thermal perception in environments as buildings or outdoors. •This study investigates human perception of different radiation kinds and intensities.•Various types of infrared irradiation promptly induce a warmer thermal sensation.•IR-C radiation is perceived warmer than IR-A radiation in moderate environments.•Models as the PMV do not account for all radiation effects on thermal sensation.