Transforming BIM to BEM: Generation of Building Geometry for the NASA Ames Sustainability Base BIM

Abstract

Executive SummaryTypical processes of whole Building Energy simulation Model (BEM) generation are subjective, labor intensive, time intensive and error prone. Essentially, these typical processes reproduce already existing data, i.e. building models already created by the architect. Accordingly, Lawrence Berkeley National Laboratory (LBNL) developed a semi-automated process that enables reproducible conversions of Building Information Model (BIM) representations of building geometry into a format required by building energy modeling (BEM) tools. This is a generic process that may be applied to all building energy modeling tools but to date has only been used for EnergyPlus.This report describes and demonstrates each stage in the semi-automated process for building geometry using the recently constructed NASA Ames Sustainability Base throughout. This example uses ArchiCAD (Graphisoft, 2012) as the originating CAD tool and EnergyPlus as the concluding whole building energy simulation tool. It is important to note that the process is also applicable for professionals that use other CAD tools such as Revit ("Revit Architecture," 2012) and DProfiler (Beck Technology, 2012) and can be extended to provide geometry definitions for BEM tools other than EnergyPlus. Geometry Simplification Tool (GST) was used during the NASA Ames project and was the enabling software that facilitated semi-automated data transformations. GST has now been superseded by Space Boundary Tool (SBT-1) and will be referred to as SBT-1 throughout this report.The benefits of this semi-automated process are fourfold: 1) reduce the amount of time and cost required to develop a whole building energy simulation model, 2) enable rapid generation of design alternatives, 3) improve the accuracy of BEMs and 4) result in significantly better performing buildings with significantly lower energy consumption than those created using the traditional design process, especially if the simulation model was used as a predictive benchmark during operation.Developing BIM based criteria to support the semi-automated process should result in significant reliable improvements and time savings in the development of BEMs. In order to define successful BIMS, CAD export of IFC based BIMs for BEM must adhere to a standard Model View Definition (MVD) for simulation as provided by the concept design BIM MVD (buildingSMART, 2011). In order to ensure wide scale adoption, companies would also need to develop their own material libraries to support automated activities and undertake a pilot project to improve understanding of modeling conventions and design tool features and limitations.3

Making SimModel information available as RDF graphs

“…Simergy is a comprehensive graphical user interface (GUI) for the US Department of Energy's (DOE) building energy simulation program EnergyPlus (LBNL 2013, O'Donnell et al 2013. The application provides an intuitive schematic editor for HVAC systems.…”

Automatic generation of second-level space boundary topology from IFC geometry inputs

“…The resulting IDF file contains all information related to building geometry and constructions needed to run an EnergyPlus simulation. IDF Generator is proposed as a semi-automated process, since for complex building geometries a manual manipulation of IDF geometry is required, including some corrections to windows in curtain walls, missing floors and ceilings [13]. The RIUSKA [14], developed by Granlund, uses the DOE-2.1 [15] thermal simulation engine and imports the building geometry from an IFC file, utilizing the BSPro server middleware ( [16]).…”

“…Concerning the building geometry, IFC can provide static building information that include geometric configuration and material properties, but in a form that might not be directly usable for the generation of thermal simulation models due to the absence of 2 nd -level space boundary information [13]. Hence, a consistent approach is required to extract building geometry information, contained in an IFC file, and subsequently to correctly identify the 2nd-level space boundary information.…”

A Performance Evaluation of the BIM-Based Object-Oriented Physical Modeling Technique for Building Thermal Simulations: A Comparative Case Study

“…While these tools have been developed to facilitate the energy model generation processes through BIM, separate analysis models still need to be prepared to satisfy each simulation engine. Moreover, while a BIM-based energy model creation tool can simplify the energy model creation process, reliable energy model creation is still labor intensive, time consuming, and error prone [12]. In this context, in order to efficiently provide comprehensive building performance analyses from a single BIM model, the integration of multi-domain simulations is necessary and a seamless model translation between BIM and multi-domain simulations must be achieved.…”