Green roof and energy – role of climate and design elements in hot and temperate climates

In the past few decades, the air temperature of built environment and energy demand of buildings has been increased, particularly in summer. As a consequence, the number of heat waves, heat-related mortality and morbidity have increased. The wide application of air conditioning and high level of energy use are inevitable to save people's lives, particularly in hot and temperate climates. Under these circumstances, this study offers a scoping review of the articles published between 2000 and 2020 to evaluate the role of green roofs in building energy use in hot and temperate climates. Given the ongoing trend of urban overheating, the scope of this review is limited to hot–humid, temperate and hot–dry climate zones. This scoping review shows the benefits of green roofs for reducing the demand of building energy in different climate zones and highlights the higher magnitude of energy saving in temperate climates than hot-humid or hot-dry climates provided that the green roofs are well-irrigated and uninsulated. According to the review of the articles published between 2000 and 2020, the reduction in cooling load is maximum (mean 50.2%) in temperate climate zones for well-irrigated green roofs. The effectiveness in saving cooling load reduces in hot–humid and hot-dry climate zones with means of 10% and 14.8% respectively. Green roof's design elements also strongly influence the potential in saving energy, and the effectiveness is heavily influenced by background climatic conditions. The findings of this study assist building designers and communities to better understand the amount of energy savings due to green roofs and present the results in different climates quantitatively.