The use of unglazed transpired collector (UTC) facades for air preheating in buildings has been proved to be an energy saving solution for refurbishing old buildings. However, not all climates are appropriate for the installation of this type of facade, and in some cases their benefits in winter can be counterbalanced by the negative effects during summer. There is a risk of overheating and facade cooling load increase if the system is not operated appropriately in summer. In this study, a UTC facade cooling load increase was measured in real weather conditions in four different operating modes. Ambient temperature and solar radiation values were monitored. Surface and air temperatures were measured in the different layers, and the heat flux through the test cell wall was registered in two cases, both with and without UTC. The four operation modes combined mechanical or natural ventilation and air flow direction. Results showed that not ventilating the facade or using natural ventilation increased the facade cooling load by around 45%, whereas outdoor mechanical ventilation produced an increase of 23%. Ventilating with indoor air reduced heat transfer compared to a non-UTC facade but only when it is integrated into an existing ventilation system. Cooling load increase due to overheating in the UTC facade was low in all four modes of operation. UTC facades must be integrated into the building ventilation system to avoid a cooling load increase during summer, or they must be ventilated with outdoor air if there is no ventilation system to reduce the impact of overheating.