Building integration of innovative photovoltaic technologies, defined by high efficiency and optical properties allowing their use as a replacement of solar control films, offers new opportunities for energy saving. In order to estimate this potential under real world conditions, we have carried out simulations for this scenario based on an existing office building located in Bari (Italy). The building has a significant amount of transparent surfaces combined with transparent shades, while office layout corresponds to a typical Mediterranean configuration with several single/double offices (2.9 m by 6.6 m). We investigate the effect of the replacement of standard clear glass windows with new windows integrating perovskite-based semi-transparent photovoltaic modules, and the replacement of the original transparent shading system with high performance opaque perovskite-perovskite tandem cells. In particular, the attributes that were directly influenced by the proposed modifications were investigated in detail, including overall energy consumption for heating, air conditioning, and artificial lighting, evaluated against the overall energy yield given by building-integrated photovoltaic modules. Results showed that under ideal conditions (no obstructing buildings) yearly savings up to 18% could be obtained. In presence of nearby buildings savings dropped to 14%. Considering that fabrication costs for this technology are promisingly low and that this is currently the only neutral colored semi-transparent photovoltaic, the above results are promising, particularly for buildings with large window-to-wall ratios.