## 1 Introduction
### Building Performance Gap  
The majority of the recent building standards and regulations in different countries have targeted improving the design and the energy performance of newly built energy efficient buildings. In addition, the absence of building continuous commissioning and performance monitoring have been reported as a major challenge facing the building stock and leading to energy performance gaps between the predicted and actual measured performance [6]. In the recent two decades, a large block of research investigations, as well as practical applications, have targeted building performance gaps on various levels and from different perspectives [7; 8; 9; 10]. In this context, a number of frameworks and methodologies have been designed and demonstrated to aid in the proper characterization of such gaps in newly built buildings [11; 12]. When dealing with building performance gaps, one of the major factors to consider is highlighting the causes and the drivers of such gaps. Thus, researchers have classified those causes into three domains that were related to the building major phases: causes originating at the building design stage, causes arising during the construction phase and causes occurring in the building operational phase [13]. When considering this distinction, the main performance gaps causes reported in the literature are related to:  
* Limitations and uncertainties of building energy models [14]. * Mismatch between design and as-built building quality [15]. * Absence or poor initial commissioning [16]. * Changes and modifications throughout the design and construction phases [11]. * Occupants and building users behavior and patterns [17]. * Malfunctioning building devices, equipment and systems [12]. * Poor sizing of energy units and system components [18]. * Unproper building management, automation and control strategies [19]. * No building performance monitoring and absence of proper submetering [20]. Figure 1: Breakdown of the worldwide final energy consumption by sector [1]. Overall, the assessment and evaluation of performance gaps in buildings is generally built up on two key pillars, a reliable and comprehensive baseline and an accessible actual building state [21; 22]. Thus, the comparison between the two pillars provides a clear view on how gaps are defined and where they are located in a building. In their study, [PERSON] et al. [18] demonstrated three building performance gap types: (a) a regulatory gap between predictions from compliance modeling tools and measured data; (b) a static gap between simulation models predictions and measured data; and, (c) a dynamic gap between calibrated dynamic performance model results and measured data. In addition, the authors highlighted that simple modeling and simulation methodologies with a large number of assumptions and generic standard inputs are not useful in fully demonstrating performance gaps in buildings. With compliance modeling tools dominating the majority of buildings assessment framework in EU countries, they stated that comparing compliance tools predictions with actual measured energy data is not the optimal way for highlighting performance gaps and it is often associated with uncertainties and inaccuracies. The accuracy of the employed building energy model is highlighted by many researchers and investigations as a major cause of performance gaps in buildings [23; 24; 25; 26]. [PERSON] et al. [27] delivered a comprehensive review and assessment on the selection and use of building modeling and simulation tools considering the views and needs of various stakeholders. The authors concluded that there is a wide gap between architects' and engineers' priorities and needs in terms of the modelling tool capabilities and specifications, highlighting that dynamic energy models are the most accurate and reliable in terms of building performance depicting and characterization.