Life cycle cost analysis of rooftop gardens in Singapore

Since the 1960ʹs green movement, green roofs have ‘re-emerged’ as a viable solution to address pressing environmental issues like increased storm water runoff, the urban heat island effect, deterioration of air and water quality, and loss of habitat and biodiversity facing urban centres. Increasingly becoming popular worldwide, green roofs are still not an area local builders are keen to take on. Despite the availability of materials and suitability of climate here, they are held back partly by concerns pertaining to costs. The objectives of this study are to highlight the economic benefits of green roofs that can offset the initial costs; to examine the initial cost implications of having a green roof as compared to a conventional flat roof; to compute and compare the life cycle costs of roof gardens and average flat roofs; and to incorporate economic benefits by incorporating energy costs into life cycle costs. It is observed that life cycle costs of extensive green roofs with or without consideration for energy costs, are lower than that of exposed flat roofs, despite its higher initial costs. However, for accessible rooftops, even life cycle (energy) costs of intensive system are not less than the normal build-up flat roof.