A critical review and simulation-based evaluation of green roof’s energy savings
Saini, Deva Shree
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Green roofs are often identified as energy-efficient techniques which, through their various mechanisms, contribute to a comfortable indoor environment. A significant number of published literature has investigated the thermal performance of a green roof under various climatic conditions and building parameters. A comprehensive literature review carried out in this research shows significant energy saving figures ranging from 12-60%. On the contrary, a simulation study on green roofs conducted in this research presents marginal energy-saving figures. The results of this research give a major insight into the thermal performance of the green roof based on the insulation thickness. It was observed that the insignificant results were due to comparable R-values of the original roof with the installed green roof assembly. This study, therefore, performs optimization to obtain the best set of design variables that could maximize the energy savings by green roofs on a well-insulated conventional roof. But the optimization was only able to achieve maximum energy savings ranging from -0.17-5.77%. With marginal energy savings figures, green roofs might look like a costly investment with high installation & operation costs. However, a cost-benefit analysis of green roofs shows that the other numerous benefits of green roofs such as carbon sequestration, improved air quality, reduction of noise pollution, pleasing views & aesthetics, increase in property value, etc. contribute significantly to the less known economic benefits. These several benefits of green roofs can outweigh the initial investment cost by approximately 110 million USD over its life cycle for a case-specific study undertaken in this thesis. This research thus presents the other more beneficial aspects of green roofs as key factors in establishing it as a sustainable measure. It discusses an outlook beyond the cost comparison, as green roofs can outperform conventional roofs from an ecological and social point of view.