Obtaining the NZEB target by using photovoltaic systems on the roof for multi-storey buildings

Photovoltaic (PV) systems are often used for the attainment of the NZEB (Net Zero Energy Building) target. The lack of sufficient roof area for the plant installation is, however, a common issue that limits the spread of this technology mainly in urban areas characterized by high density of buildings. This work evaluates the possibility of obtaining the NZEB target for residences and offices in Mediterranean area, using only “on site” PV systems, i.e., on the roof slab, considering different typologies of building. An in-depth analysis is provided for obtaining the building geometric parameters that would allow to establish, in the first stages of the design process and avoiding dynamic energy simulations, whether it is possible to achieve energy self-sufficiency for a certain building, taking into consideration the characteristics of the plans and the number of floors. The results show that, for the investigated square-based residential building, the energy self-sufficiency, and therefore the NZEB target, is obtainable up a maximum of 7 levels (6 levels for rectangular shape building, 5 for L and courtyard shapes), while, for another case study building intended for offices, the energy self-sufficiency is obtainable up to a maximum of 7 levels. For early design analyses about geometric characteristics and intended use of new buildings, it would be possible to use the results reported in this study to achieve a first evaluation of NZEB target attainment.