Opaque façade areas feature a great potential for generating energy by using PV modules. Their use in the façade sector has so far been limited mainly to cold fronts because the performance of these modules drops with increasing temperatures of the PV cells. In contrast to cold fronts, a rear ventilation to cool the modules is not possible in standard mullion and transom façades. To ensure low module temperatures and thus a high performance, the PV modules are to be combined with rearmounted phase-change materials (PCM). When the temperature in the façade reaches the (freely adjustable) melting point of the PCM, it results in a phase transition from solid to liquid. The material absorbs thermal energy from the PV-module and the rising of the module temperature can be buffered. At night, the thermal energy latently stored in the PCM is released back into the ambient air.