Experimental comparison of summer thermal performance of green roof (GR), double skin roof (DSR) and cool roof (CR) in lightweight rooms in subtropical climate

Subtropical climate is characterized by high solar altitude angle in summer which causes the roof get more heat through solar radiation. GR, DSR, and CR all can decrease solar radiation heat gain of the roof. However, few researches have been done to the comparison of the thermal performance of these three roofs, especially in subtropical climate. In this study, four rooms were built separately with GR, DSR, CR, and ordinary roof (OR). The experiment was done from July 23 to August 4. Results showed that stabilities of the indoor air temperature of the four rooms were: DSR room > GR room > CR room > OR room. The GR, CR, and DSR can reduce the external surface temperature by 13.7°C, 12.0°C, and 4.8°C during the day while bring a temperature rise of 2.3°C, 1.9°C, and 0.9°C at night. Correlation analysis results showed that the internal surface heat flux of GR and DSR were negative correlated with weather factors while internal surface heat flux of OR and CR were positive correlated with weather factors. This study can give support to the selection between GR, DSR, and CR.