Sustainable Urban Environment through Green Roofs: A Literature Review with Case Studies

Abstract

This study conducts a literature review coupled with case-study calculations comparing the thermal contribution of semi-intensive and intensive (deeper) green roofs to non-insulated and insulated building roofs, and enhancing comprehension by validating applied scenarios with published literature-based data. Mitigation of the urban heat island is crucial for reducing energy consumption and enhancing urban sustainability, especially through natural solutions such as green (i.e., planted) roofs. The energy and environmental benefits of green roofs include energy conservation, thermal comfort, noise reduction, and aesthetic improvement. Legal mandates, innovative business models, financial subsidies and incentives, regulations, etc. are all components of green roof policies. Conflicts between private property owners and the public, regulatory gaps, and high installation costs are among the challenges. Green roofs are layered and incorporate interacting thermal processes. Green roof models are either based on the calculation of thermal transmittance (U-values), an experimental energy balance, or data-driven (primarily neural network) approaches. U-values were calculated for eight hypothetical scenarios consisting of four non-insulated and four insulated roofs, with or without semi-intensive and intensive green roofs of various materials and layer thicknesses. While the non-planted, non-insulated roof had the highest U-value, planted roofs were particularly effective for non-insulated roofs. Three of these scenarios were in reasonable accord with experimental and theoretical thermal transmittance literature values. Finally, a non-insulated planted roof, particularly one with rockwool, was found to provide a certain degree of thermal insulation in comparison to a non-planted insulated roof.