Introducing the Green Building Studio

September 04, 2007
September/October 2007
A version of this article appears in the September/October 2007 issue of Home Energy Magazine.
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Building designers can use computer software, such as DOE-2 and EnergyPlus, to evaluate potential energy-saving measures. However, preparing the input in a way that accurately represents the proposed building and its energy-efficient features is a costly, labor-intensive business. As a result, designers often postpone energy analysis until late in the design process.  This leaves them with far fewer cost-effective options for boosting efficiency than would be the case if they had considered analysis from the start.

The Green Building Studio (GBS) is a Web-based service that enables building design teams to integrate whole-building energy analysis into the early stages of the design process. Architects and engineers use their existing-building-information-modeling (BIM) systems to communicate the project’s building geometry to the GBS Web site, which conducts an energy analysis of the building design.

Features and Benefits

GBS enables the design team to look at the energy impact of early decisions, compare alternatives, and share information more broadly than is possible with conventional design practices.

Building energy model. The heart of the GBS system is an open-data format called Green Building XML (gbXML), a simple means of sharing data between BIM and energy simulation software. Designers construct their early building design model from their own BIM system, and then use gbXML and some simple user inputs to export a building energy model. Before conducting a simulation, GBS will error check the submitted gbXML file to ensure that all the building spaces are properly defined. Most commonly used BIM systems are compatible with gbXML, which is based on Extensible Markup Language (XML).

Compatible systems include Autodesk Revit Building and Revit Systems; Autodesk Architectural Desktop (ADT) 2004, 2005, and 2006; Autodesk Building Systems (ABS); and Graphisoft ArchiCAD 9 and 10. In addition, major HVAC manufacturers accept gbXML input directly into their energy and load analysis packages. GBS uses the internal load information—such as lighting, equipment, number of occupants, and space type—at the room level from Revit Systems, ArchiCAD, ADT, or ABS.

Energy analysis. The gbXML export from BIM feeds an energy model that is automatically developed through the use of regional building standards and codes, which enable the GBS system to make intelligent assumptions about items such as insulation and lighting levels. The resulting building description then goes through a DOE-2.2 hourly simulation using typical-year weather data for the building’s location. The simulation generates estimates for annual energy consumption, costs, and a wide range of data on heating and cooling loads.

Comparing alternatives. Designers can use a new Design Alternative feature to modify their GBS runs to compare the energy impact of design options such as window types, glazing types and orientation, lighting efficiency and controls, HVAC systems, wall insulation levels, building orientation, multilevel versus single-level designs, and other building geometry considerations that come up early in the design process. GBS offers five free simulations for each project. After the five free runs are used, each additional simulation requires a nominal fee based on the number of spaces being analyzed. In addition, GBS allows manufacturers to place their products in GBS so that users can apply the product to their design to evaluate its potential energy savings.

Information sharing. The GBS system also facilitates direct sharing of detailed project and building data with engineering firms, which can then run the information through detailed design software, use it to specify equipment, and share it with other parties, such as bid preparers and manufacturers of building products.

Saving time on plan takeoff. GBS makes it easy to go to the next step by creating detailed input files for more comprehensive energy analysis by DOE-2 and EnergyPlus. The files are created in minutes—a process that could take one to two weeks using plan takeoff or engineering services. Using this capability can reduce the cost of preliminary and downstream building design by $5,000–$10,000 or more.

Product Advisor. The GBS system also features a Product Advisor that enables the building designer to continue to offer the service relatively inexpensively. Each building project that goes through GBS provides the design team with relevant product information as early in the process as the planning and schematic design stages. Using a Web-style bidding and paid-placement approach, as well as a building relevance filter, the system sends highly targeted building component advertisements to the building designer’s desktop in the GBS Product Advisor screen. These advertisements are linked to building product libraries online, providing targeted advertising placement for product manufacturers and project-appropriate information for the design team.

GBS is best suited for use in new construction and major renovation of commercial or residential buildings of any size, including single-family homes. It is currently enabled only for buildings located in the United States.

California Codes and Standards

GBS analysis helps ensure that the basic building design meets local codes. For buildings in California, the system also performs an analysis using building equipment assumptions based on the Savings By Design program—a utility-run effort to improve building efficiency. This option can be used to compare a Title 24–compliant building and a high-efficiency alternative.

What’s Next?

In early 2007, GBS will be expanded to the United Kingdom (UK), when Greenspace Research, a GBS partner, launches GBS UK. This will allow UK customers to analyze their buildings more accurately.

John Sustar is a research associate at E Source, which provides research and advisory services for energy service providers, major energy users, and the other key players in the retail energy marketplace.

GBS was developed by Green Building Studio, Incorporated, with funding from the California Energy Commission’s Public Interest Energy Research (PIER) program, and from the California utilities that support the nonresidential new-construction program Savings by Design. These utilities include Pacific Gas and Electric Company, Southern California Edison, San Diego Gas and Electric Company, and the Gas Company.

For more information:

Reports documenting this project and providing more details may be downloaded from the Web at final_project_reports/500-02-038f.html.

The California Energy Commission’s Public Interest Energy Research (PIER) program supports public interest energy research and development that helps improve the quality of life in California by bringing environmentally safe, affordable, and reliable energy services and products to the marketplace. For more information, go to

This article was based on a PIER Technical Brief. To read Technical Briefs on other topics, visit public/products/cec_form.asp.

To learn more about Green Building Studio, Incorporated, contact John Kennedy. Tel:  (707)569-7373; E-mail:;  or visit

To learn more about the California Energy Commission, contact Norman Bourassa. Tel:(916)654-4581; E-mail:; or visit
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