A significant amount of global energy consumption takes place in the built environment, with as collateral effect CO2-related climate change. One of the strategies to realize a significant CO2 reduction is by integrating photovoltaic modules in the building envelope (BIPV). Disadvantages of BIPV include a possibly lower energy output and a possibly decreased life span due to the lack of optimal cooling of the PV modules. Currently, cooling of PV modules is usually realized by passive back-string ventilation, which is under strain when integration PV modules in the building envelope. In this study, a comparative field study of BIPV is conducted in the field lab ‘The District of Tomorrow’ to generate insight into BIPV efficiency as a function of back-string ventilation. This paper presents a selection of the monitoring results of the realized system, consisting of 24 PV modules in 4 segments with a total of 6000 Wp output with different amounts of back-string ventilation. The measurements indicate that in a moderate climate BIPV solutions without back-string ventilation result in increased operating temperatures, lower electricity output and condensation between PV modules and rooftop surface. To decrease relative humidity levels and operating temperatures to acceptable values, back-string ventilation is seen as an effective cooling medium in the presented field case.