Mapping actual thermal properties to building elements in gbXML-based BIM for reliable building energy performance modeling

The ability to import building geometric and construction thermal data from building information models (BIM) has significant potential to reduce the time and uncertainty in building energy modeling process. In today's BIM-based energy modeling practice, thermal properties are mainly derived from generic building construction types in BIM. However, for energy modeling of existing buildings, such assumptions are often inaccurate as they do not account for diminishing thermal resistances of building materials instigated by their deteriorations. To improve the reliability of BIM-based energy modeling, we present a system, together with new methods for automated association and updating of actual thermal property measurements with BIM elements in gbXML schema. By leveraging collections of digital and thermal images and based on environmental measurements, our system first produces a 3D thermal model for the building under inspection and then derives the actual thermal resistances of the building assemblies at the level of 3D vertexes. By associating these measurements with their corresponding elements in gbXML, thermal properties of the BIM elements are automatically updated. Our experiments in real-world residential and instructional buildings show how actual thermal properties can be automatically associated with BIM elements and updated in gbXML. The proposed method shortens the gap between architectural information in BIM and the actual data needed for energy performance simulation, and enables reliable BIM-based energy analysis for retro-commissioning, continuous commissioning, and retrofit.