SimBuild 2008 Third National Conference of IBPSA-USA Berkeley, California July 30 – August 1, 2008 238 ENERGY DESIGN PLUGIN: AN ENERGYPLUS PLUGIN FOR SKETCHUP * Peter G. Ellis 1 , Paul A. Torcellini 1 , and Drury B. Crawley 2 1 National Renewable Energy Laboratory, Golden, CO 2 United States Department of Energy, Washington, DC * This manuscript has been authored by Midwest Research Institute under Contract No. DE-AC36-99GO10337 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. ABSTRACT This paper describes the Energy Design Plugin, a new software plugin that aims to integrate simulation as a tool during the earliest phases of the design process. The plugin couples the EnergyPlus whole-building simulation engine to the Google SketchUp™ drawing program. Leveraging the powerful SketchUp application programming interface, we developed a plugin that extends the capabilities of SketchUp to allow EnergyPlus building models to be developed in 3-D while taking advantage of all of the native SketchUp capabilities, including intuitive tools, different rendering modes, and realistic shading. The model geometry can be saved to create an EnergyPlus input file. Existing input files can be opened, edited in the SketchUp environment, and saved again. Already well-established as a popular tool among architects and designers, SketchUp offers a familiar, easy-to-use interface that, when coupled with the plugin, could make building energy simulation more accessible for architects, designers, and students during the design process. KEYWORDS energy simulation, EnergyPlus, SketchUp, graphical user interface, design process, conceptual phase INTRODUCTION Although building energy simulation is a useful tool for predicting performance and comparing design options, most energy simulation occurs too late in the design process. In the traditional design process, the energy engineer uses simulation (if at all) as a tool for equipment sizing and code compliance only after the architect has completed the architectural design. Part of the problem is that existing simulation tools are not practical for the design process. Ideally, the design team would use building energy simulations to guide the architectural design from the earliest phases of the project. Experience with real buildings has shown that low-energy design is not intuitive and that simulation should therefore be an integral part of the design process (Torcellini et al. 1999; Hayter et al. 2001). But this is usually not possible because the development of the energy model that describes the building design is time-consuming and requires a skilled specialist. EnergyPlus is a whole-building energy simulation program developed by the U.S. Department of Energy (DOE). EnergyPlus is the next generation of building simulation program and offers many advanced simulation capabilities (Crawley et al. 2004). However, EnergyPlus is a simulation engine only—it does not have its own graphical user interface (GUI). Manually entering detailed, 3-D geometry data can be difficult and prone to errors. Third-party GUIs for EnergyPlus are approaching maturity, but are not necessarily aimed at the earliest phases of the design process. In 2005, we began a task to find ways to integrate simulation into the earliest phases of the design process. Work on the Energy Design Plugin began as a pilot project to explore the coupling of EnergyPlus to a commercially-available 3-D drawing package. The concept was to leverage the capabilities of an established GUI and build on an existing market and user base, instead of developing an entirely new program from scratch. We began further development of the plugin in 2007 with the objective to deploy a version of the Energy Design Plugin for public use. It was decided that the plugin and its source code would be released under an open source license to encourage collaborative development on future versions.