Thermal characteristics of green roof in natural climate

A long-term experiment measurement in an existing building roof of a construction with natural ventilation layer was carried out in the city of Chongqing, China. Internal surface temperatures of the roof with and without green were measured every hour by data loggers for five months continuously in summer, 2005. Climate parameters, such as solar radiation, air temperature, wind speed, relative humidity, rainfall were measured at the same time by weather station. Thermal characteristic of green roof was studied by statistic analysis method. Thermal effect of green roof was evaluated for the whole summer time. The result shows that solar radiation, air temperature and wind speed have positive effect on the reduction of internal surface temperature, while relative humidity, rainfall and its frequency have negative effect on the reduction of internal surface temperature. Internal surface temperature reduction with and without green in daily maximum is greater than that in daily average. Delayed times of thermal response with and without green to solar radiation are determined about 26 h and 6 h respectively. Green roof has a great thermal inertia.