The integration of volatile, decentralized energy into building energy systems requires intelligent algorithms that are capable of controlling the augmented complexity and the interactions of subsystems efficiently. Not only do the algorithms require computing capacity, but also a feasible information and communication infrastructure. One possibility to provide computing power on demand is cloud computing that forms together with an extended connectivity of physical devices the Internet of Things (IoT). We present a customizable open-source IoT platform setup using FIWARE. For the integration of existing building automation networks, we extend an OpenMUC gateway with BACnet functionality and connect it to our platform via MQTT. We successfully demonstrate the overall setup with a web-based visualization of high resolution energy monitoring and a control loop as basic requirements for the integration of more advanced control algorithms in future building energy management systems. We find our setup generally feasible for both use cases and, hence, will aim for the integration of more advanced control algorithms in the future using the presented platform components.