Thermal Performance of Green Roofs Influenced by Substrate Composition

The selection of materials and substrates is essential for optimizing the thermal performance of green roofs. However, there has been limited research on green roof characteristics under subtropical conditions. Therefore, this study aims to evaluate the internal and substrate temperatures of six green roof prototypes and one control prototype. Prototypes with clay tiles (control), clay substrates with and without vegetation, sandy substrates with and without vegetation, and organic matter substrates with and without vegetation are evaluated. The experimental design involves randomized blocks and the internal and substrate temperatures are monitored. The vegetated sandy substrate prototype exhibits the highest thermal performance, with internal temperatures 0.6 ℃ lower than those of other green roof prototypes and 1.7 ℃ lower than that of the control with clay tiles. This is attributed to the high porosity of the sandy substrate, which enhances thermal insulation. To provide optimal thermal performance, the substrate must have a water retention capacity that is sufficient to guarantee vegetation development, but not excessive so that it constantly increases the thermal conductivity owing to substrate saturation.