A CAD-BEM geometry transformation method for face-based primary geometric input based on closed contour recognition

Performance analysis during the early design stage can significantly reduce building energy consumption. However, it is difficult to transform computer-aided design (CAD) models into building energy models (BEM) to optimize building performance. The model structures for CAD and BEM are divergent. In this study, geometry transformation methods was implemented in BES tools for the early design stage, including auto space generation (ASG) method based on closed contour recognition (CCR) and space boundary topology calculation method. The program is developed based on modeling tools SketchUp to support the CAD format (like *.stl, *.dwg, *.ifc, etc.). It transforms face-based geometric information into a zone-based tree structure model that meets the geometric requirements of a single-zone BES combined with the other thermal parameter inputs of the elements. In addition, this study provided a space topology calculation method based on a single-zone BEM output. The program was developed based on the SketchUp modeling tool to support additional CAD formats (such as *.stl, *.dwg, *.ifc), which can then be imported and transformed into *.obj. Compared to current methods mostly focused on BIM-BEM transformation, this method can ensure more modeling flexibility. The method was integrated into a performance analysis tool termed MOOSAS and compared with the current version of the transformation program. They were tested on a dataset comprising 36 conceptual models without partitions and six real cases with detailed partitions. It ensures a transformation rate of two times in any bad model condition and costs only 1/5 of the time required to calculate each room compared to the previous version.