A study on a novel photo-bio screen (PBS) used as a shading system in a real building is presented. The green microalgal culture (Scenedesmus obliquus) of the PBS allows a screening of the direct sunlight and a production of biomass containing bioactive compounds. The PBS was tested in a kindergarten classroom at Saint Marcel (Aosta Valley, north-west of Italy) and monitored for 3 weeks (June-July 2016). The visible transmittance T-v of PBS was determined through in situ illuminance measurements, while the daylight amount in the room and the energy demand for lighting ED1 were calculated through Diva-for-Rhino simulations (using the median measured T-v as input). The analysis was split in two phases: (i) the real room (with south-facing windows and external obstructions); (ii) the same room without obstructions, analyzed parametrically by changing the site (Turin, Ostersund, Athens, and Abu Dhabi) and the orientation (south, west, north, and east). For both phases, the results for PBSs were compared to what obtained applying a traditional venetian blind VB of comparable light transmission to the window. From the monitoring campaign, the T-v of the PBS was found to have a quite high variation as a function of the dynamic boundary conditions, so an median value of 0.75 was identified as the reference T-v From simulations, it was found that the daylight amount and the ED1 for PBS and the VB were comparable, with slightly better results for the PBS in Turin and Athens and slightly better results for the VB in Ostersund and Abu Dhabi.