Thermal environment of rural residential buildings in Hengyang, China: A two-year on-site study

Epidemiological evidence suggests that outdoor climate strongly influences human health. However, since people spend 90% of their time indoors, the indoor environment may be a better indicator of epidemiological diseases and infections. Despite previous studies exploring the relationship between indoor and outdoor thermal environments, little is known about this relationship in China's subtropical countryside. This study aims to investigate the indoor-outdoor relationship of air temperature and relative humidity, examine the spatial and temporal variation characteristics of the indoor thermal environment, and estimate indoor thermal comfort. We monitored outdoor and indoor air temperature and relative humidity for two years using wireless IoT temperature/humidity button sensors in fourteen residential buildings. Our results show that the average vertical spatial variance range of air temperature was largest in summer (2.11 °C) and smallest in fall (1.23 °C), while horizontal spatial variation was negligible. The average daily temporal variation range was largest on the third floor (2.3 °C) and smallest on the first floor (1.5 °C). Indoor air temperatures were highly correlated with outdoor air temperatures, with a linear correlation coefficient greater than 0.9. The relationship between indoor and outdoor relative humidity was moderate, with an average correlation coefficient of 0.54. Furthermore, we found that almost all uncomfortable indoor air temperature points were lower than the lower temperature limit of the adaptive comfort band in all seasons, and almost no indoor temperatures in summer and winter were within the PMV comfort band.