Interoperability: Getting Building Geometry from CAD

The use of energy simulation tools has historically been hampered by the difficulty involved in gathering and accurately entering the myriad building description data required for simulation. There are several activities that support getting building geometry and other data from electronic CAD files into EnergyPlus format including the industry foundation classes (IFC) and Green Building Studio.

CAD Interoperability Data Model

BuildingSMART (formerly International Alliance for Interoperability, IAI) is developing a common data model for the exchange of data between software applications for the Architectural/Engineering/Construction and Facilities Maintenance Industry (AEC/FM). This data model is called Industry Foundation Classes (IFC). Software that implements the IFC data model can easily share input and output data that is stored in IFC data files.

For more information on IFC specifications, visit the buildingSMART technical website.

Green Building Studio Web Service

The Green Building Studio web service (GBS) version 2.0, provided by Green Building Studio, Inc., gives Autodesk Revit, Architectural Desktop, Building Systems, and Graphisoft ArchiCAD users the fastest path from CADD to EnergyPlus IDF. These 3D-CAD/BIM applications all support the gbXML (Green Building XML) schema which can be immediately translated to an EnergyPlus IDF on the GBS. Watch a video of the complete process from 3D-CAD through EnergyPlus simulation.  The gbXML data that is currently translated to an EnergyPlus IDF by the GBS include:

  • DesignDay data
  • Operational Schedules
  • Surface construction and materials
  • Thermal zones
  • HeatTransfer Surfaces and Subsurfaces
  • Interzone surfaces
  • Shading surfaces
  • Internal loads (people, equipment, lights)
  • Exterior loads
  • Compact HVAC Objects

 In essence, the EnergyPlus IDF provided by the GBS is a simulation-ready file that contains all the information used in a GBS simulation including the geometry from the 3D-CAD/BIM application.  The GBS service to create EnergyPlus IDFs is available for a fee.