# Interoperability between Building Information Modelling (BIM) and Building Energy Model (BEM)
## 4 Conclusions  
The lack of BIM-BEM interoperability is one of the existing gaps between digitalisation and the construction area. As BEMs are the basis of energy performance certificates (EPCs), they should present accurate results, in order to guarantee the confidence of investors in the energy efficiency sector.  
It was observed that there exists a semi-automated workflow between BIM and BEM. First of all, at the moment of exporting the gbXML and IFC files, some parameters must be activated in Revit. Secondly, it is necessary to set the BEM tool appropriately for the model schema data import, with respect to the building typology, ideal loads, occupation schedule, and weather file.  
However, their configuration was not sufficient to ensure adequate interoperability, as many of the problems encountered in the BEM softwares were consequences of errors from transfer of the BIM authoring tool data to gbXML and IFC files. Neither the energy models created with gbXML nor IFC can be trusted as a reference for the BIM, as they presented thermal properties and geometry values different from the baseline model, which led to distinctive and erroneous simulation results.  
In addition, the BIM-BEM interoperability does not work for all types of buildings. It was shown that the bigger and more complex the building is (related to its shape and constructive systems), the less reliable the data transferred is and, so, the greater the problems in creating the model in the BEM software. These geometry issues resulted in fatal errors and made the energy simulations impossible.  
In summary, BIM-BEM interoperability still has many shortcomings. We generated simulation results for the residential building, but they were not reliable. On the other hand, the warehouse could not even be simulated. For these reasons, it is possible to conclude that greater confidence can be had when recreating the model in a native BEM tool, in order to guarantee the better quality of results without geometric or construction component errors. Therefore, it is understood that the BIM to BEM interoperability is not ready to save time and costs in the design process, under the current state-of-the-art. A bigger effort should be made by standardization bodies, in order to increase the confidence of stakeholders.  
conceptualization, G.B.P., C.F.B., K.D.V.d.L. and A.S.-O.G.; methodology, G.B.P., C.F.B., K.D.V.d.L. and A.S.-O.G.; software, G.B.P. and K.D.V.d.L.; validation, G.B.P., C.F.B. and K.D.V.d.L.; investigation, G.B.P. and K.D.V.d.L.; resources, C.F.B.; writing--original draft preparation, G.B.P.; writing--review and editing, G.B.P., C.F.B., K.D.V.d.L. and A.S.-O.G.; supervision, C.F.B. and A.S.-O.G.; project administration, C.F.B.; funding acquisition, C.F.B. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Government of Navarra (Spain) under the project \"From BIM to BEM: B&B\" (ref. 0011-1365-2020-000227).  
Not applicable.  
We would like to thank Fundacion Saltoki for making its warehouse BIM model available, which served as a case study for this research. We also thank CYPE Ingenieros for their support and collaboration during this study.