Buildings are the single largest energy consumer in Europe. therefore, it’s crucial to increase their energy efficiency. In this context, however, building performance simulations (BPSs) can play an important role in supporting energy-efficient design and operations of buildings. Furthermore, the integration of Internet of Things (IoT) systems into building management can enable significant improvement in energy efficiency strategies. The synergy between BPSs and IoT systems holds great potential for optimizing energy management in buildings, paving the way for a significant reduction in energy consumption. For this vision to come true, BPSs and IoT systems need to interoperate as part of a smart building management system. This paper addresses this interoperability challenge at the semantic level, by introducing the Web of Simulations Ontology (WoSO) as a high-level description of BPSs and IoT system. WoSO focuses on capturing interaction between simulations and IoT systems by extending a reference IoT ontology (SAREF) to include simulations as a component of the extended IoT system. Simulation modeling builds upon the Functional Mock-up Interface (FMI) specification, a widely adopted standard for describing simulation functionalities.