Optimal Overhang Depths in the Mediterranean Basin: Climate Subtypes and Envelope Retrofitting Impacts for Bioclimatic Sustainable Buildings

This paper introduces an innovative, environmentally sustainable, and climatic study analysing the impact of overhang depths on heating and cooling building energy demands in the Mediterranean Basin via dynamic energy simulations of a south-oriented reference residential building zone. The adopted bioclimatic approach aims at increasing building sustainability and suggests, for representative Köppen–Geiger climate subtypes, optimal overhang depths and climate-correlated depth domains. The definition of a large geoclimatic study based on 80 locations and the classification of results based on climate subtypes are two novelties introduced in this work. From the energy point of view, overhangs can reduce local building cooling needs by, on average, 27%, while decreasing the total final energy needs (QTOT) by 17%. A new approach is also introduced: comparing the energy reduction due to the addition of an overhang to commonly applied envelope retrofitting solutions, such as wall insulation or window substitutions. Overhangs show great potential in sites with arid climate subtypes and are more effective than other solutions in several locations. This study underlines the need to increase the adoption of passive cooling solutions by local retrofitting regulations in places with a Mediterranean climate, following a bio-regionalist approach able to increase the local buildings’ sustainable development.