Innovative approaches in energy efficiency evaluation of glazed facades in nZEB buildings

Energy evaluation of glass facades by using CFD simulation software is becoming a popular research technique due to the possibility for better approximation of thermal characteristics. Therefore, ability to describe dynamic change of environmental conditions, in spite of constant values used in today standards, can been seen as a step forward in energy efficiency evaluation. In addition to that, specific details, which are not defined by standards, can be researched. For example, airflow through double - skin facades that directly affects heat transfer coefficient, as well as noise isolation parameters according to which curtain wall systems need to be designed. Furthermore, considering the influence of the glass facade on the room, of the observed building, the parameters of thermal comfort, as well as shading effects of glass facade elements with regard to the type of glazing, can be examined. Current methodologies for calculation of thermal properties of glass facades systems are described in this paper. Standards as European (EN ISO 12631:2017) and North American (NFRC 100–2020) describe analysis prescriptions for defining curtain wall thermal properties. These standards mostly use 2D simplification to determine thermal properties with constant boundary conditions and in some cases 3D. Effect of seasonal change of thermal properties as well as change of conditions throughout the day are not described in these standards. CFD tools complement approximations of these standards and allow better design of facade systems, which affects the reduction of annual heat energy demand for the building and improves the energy efficiency. It generally reduces the total energy required which is one of the fundamental assumptions for sustainable development and nZEB designing principles.