Paper Conference

Proceedings of BSA Conference 2015: Second Conference of IBPSA-Italy


BIM-generated data models for EnergyPlus: A comparison of gbXML and IFC Formats

Ira Ivanova, Kristina Kiesel, Ardeshir Mahdavi

Abstract: Building Information Modelling (BIM) aims to promote collaboration between project partners by providing a single model with the required relevant information. BIM data is meant to be provided to multiple domain-specific applications in an effective manner. We consider two data formats used to facilitate this interoperability: (i) gbXML format, developed by Green Building Studio and (ii) IFC format, developed by buildingSMART. Both of these formats can be used to provide geometry information and other data to Building Performance Simulation (BPS) applications. However, gbXML and IFC have unique data structures, which has consequences for how the original geometrical and spatial data from the BIM model is translated. In this context, the present contribution aims to assess and compare the usage of IFC and gbXML data formats in separate workflows, thereby observing consistency of building data and efficiency of the process. First, the main differences and specifics of the two formats are investigated and several case models are developed. Using a BIM authoring tool both formats are then tested in a typical workflow including the use of a BPS tool. To explore the implications of the quality of the BIM model, a second workflow (with the same case models) was set up in a different BIM authoring tool. These workflows and their outcome with regard to BPS were analyzed and the capabilities and differences of the two formats were studied in detail. The results of this study show that both data formats are capable of extracting and transferring geometrical information from BIM models. However, the successful transfer of this information is strongly related to the quality of the BIM representation. Demonstrative simulation runs show that incorrect BIM-based building geometry data can produce misleading results. Moreover, the overall approach to using gbXML and IFC to perform BPS is currently rather cumbersome and difficult to validate.
Pages: 407 - 414