The BaaS system aims to optimize energy performance in the application domain of "non-residential buildings, in operational stage. In the building operational life-cycle three significant tasks have to be continuously performed: collect information and assessment of the buildings current state (identifying possible faults and inefficiencies if they exist); prediction of the effect that various decisions will have to Key Performance Indicators (KPIs); and optimized operation of systems to achieve high operational performance. A generic ICT-enabled system will be developed to provide integrated services that guarantee harmonious and parsimonious use of available resources.The BaaS system comprises four components:1.\tA data management component to collect, organize, store and aggregate data from various in- and out-of-building sources. An (IFC-based) BIM will act as a central repository for all static building data, and a data warehouse will be used for dynamic data.2.\tA service middleware platform to abstract the building physical devices, support high level services on the cloud and facilitate secure two-way communication between the physical and ICT layers (building) with high level services (cloud).3.\tEnergy models for performance estimation and for control services, looking for a trade-off between prediction accuracy (performance estimation) and computational complexity (fast-model for control design).4.\tAnalytics Serviceso\tfor assessment and prediction services: simulation models, acting as surrogates of the real building, incorporating sensor dynamic data, will be used to assess performance and comprehensively estimate the values of relevant KPIs as well as help perform sensitivity analyses;o\tfor building automatic and control (BAC) services, automatically will generate holistic nearly-optimal control strategies with the goal of achieving operational efficiencies as measured through relevant KPIs and will be imbued with adaptive and re-configurability properties to respond to faults and atypical scenarios.Upon verification of component interoperability, and development of a measurement and verification plan, the BaaS system will be demonstrated in real buildings and will be validated as an Energy Conservation Measure with Energy-Services Companies as the end-user.End-user acceptance will be accomplished by analyzing the replication potential in tandem with the results of a sensibility study.KeywordsEnergy efficiency in buildings, Data Warehouse, Data Interoperability, Middleware Platform, Energy Modelling and Simulation, Automation and Control Systems, Anomaly Identification, Energy Savings M&V Methodology.