Rooftop Gardening. A Solution for Energy Saving and Landscape Enhancement in Mediterranean Urban Areas

Abstract

Urban green areas are losing their exclusively aesthetic and scenic significance and are increasingly acquiring a social value related to a return to the ancient rural traditions characterizing the history of peoples. Rooftop gardening is therefore an opportunity to grow agricultural crops rather than decorative plants. However, according to the scientific literature, it is also an optimal solution for the passive control of indoor microclimate conditions, above all in hot climate areas. The shade contribution, the evapotranspiration effect of plants and the thermal inertia of the growing medium allow limiting the summer solar load in the building. The goal of this study is to evaluate the effects of a rooftop garden in an urban area. After choosing a horticultural crop suitable for rooftop gardening, the need for biomass thermal energy for the building air conditioning was evaluated in two different configurations: the one with a traditional flat roof, the other with a rooftop lettuce garden. The energy analysis of the building with the traditional roof showed that the consumption of the total biomass energy produced annually to keep the required indoor thermal conditions was about 15304kW. That analysis also showed that, in the case of the rooftop lettuce garden, energy could be limited to about 12592kW, which corresponds to a reduction of some 18% of the total annual energy.