The human thermal sensation inside a semi-outdoor space enclosed by a semi-transparent pitched roof, located in Parma, north of Italy, is compared with the outdoor sensation under the same climate conditions. The assessment of the semi-outdoor setting was performed using the Physiological Effective Temperature (PET) thermal sensation index. With the aim of mitigating the semi-outdoor climate, some natural means were considered at the design stage, namely, the solar radiation absorptivity of the glass sheet roof, natural airflow, space thermal capacity and roof evaporative cooling. The dynamic thermal simulation of the semi-outdoor space was performed for three representative weeks of the months of January, March and July by accounting for the actual climate of the location. The results show that the semi-transparent roof can improve the human thermal sensation inside the semi-outdoor space with respect to that of the outdoor space. The results also demonstrate the effect of each design parameter on the PET index.