Influence of green roof systems on the energy performance of buildings and their surroundings

The thermal behavior of green roofs may vary according to climate and substrate and plant characteristics. This study aimed to analyze the influence of green roof systems on the energy performance of buildings and their surroundings under three different Brazilian climates. For this, 1944 combinations of green roof parameters were simulated. An initial validation of the thermal balance model was performed reaching RMSE of 2.17 °C and 2.85 °C, for substrate and vegetation temperature, respectively. It was obtained that, in temperate climate, low leaf area index (LAI), combined with high substrate thickness and low thermal transmittance, provided 5.6% of reduction with climatization when compared with cool roofs, and high transfer of latent heat to the exterior. In semi-humid tropical climate, 4.9% of savings was achieved with high LAI, intermediate substrate thickness, and high thermal transmittance. In equatorial climate, although there was high transfer of humidity, green roofs resulted in higher energy consumption than cool roofs, indicating that low thermal mass systems are more favorable for climates with low temperature fluctuations. The results showed that green roofs play a fundamental role in improving energy efficiency and outdoor air quality. However, an inadequate system may produce detrimental effects depending on climatic conditions.