Infrared Thermography to Evaluate Thermal Comfort under Controlled Ambient Conditions

Infrared thermography (IRT) is often used to assess body temperature and can be useful as a diagnostic tool to detect human diseases. Despite this clear application in medicine, some studies can be found in the literature pointing to the use of IRT to measure body temperature as a parameter to evaluate thermal comfort inside buildings. However, there are still some issues that are understudied that this paper tried to address. For this purpose, an intensive experimental campaign was carried out, in which different combinations of temperature and relative humidity were implemented. Thermal images were taken of the face of a young adult, while the air temperature and relative humidity were assessed, as well as the body temperature, using traditional means. The results confirmed that different IR cameras and different ambient conditions (air temperature) impact the image resolution and definition. A linear correlation between the IRT results and the PMV was found for six subregions of the face. This correlation was higher in the forehead, cheekbones, and chin, and less interesting when measuring the temperature of the nose. However, if the overall temperature of the face is assessed, a good agreement between the PMV and the IRT results can still be found, indicating that the average facial temperature can be used as an indicator for the determination of thermal comfort. A prediction model for PMV based on IRT was proposed, with a root mean square error close to 0.70, when applied in a face temperature range between 28.9 °C and 34.4 °C.