Although building designers can use computer software such as DOE-2 and EnergyPlus to evaluate potential energy-saving measures, preparing the input in a way that accurately represents the proposed building and its energy-efficient features is a costly, labor-intensive process. As a result, energy analysis is often postponed to a later point in the design process, resulting in a greatly reduced number of cost-effective options for boosting efficiency than if it had been considered from the start.
Now, building owners and facilities managers (who have a long-term, vested interest in a project) can look to a service that simplifies the process of early energy analysis. Called the Green Building Studio Inc. (GBS) - with funding from the California Energy Commission's Public Interest Energy Research (PIER) program and California utilities (Pacific Gas and Electric Co., Southern California Edison, San Diego Gas & Electric Co., and The Gas Co.) that support Savings By Design, the non-residential new construction program - the Web-based service enables building design teams to integrate whole-building energy analysis into the early stages of the design process to show them the energy impact of early decisions while allowing them to compare alternatives.
The heart of the 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 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).
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 people, and space type - and the gbXML export from BIM feeds an energy model that is automatically developed through the use of regional building standards and codes. This enables 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 to generate estimates for annual energy consumption, costs, and a wide range of data on heating and cooling loads.
GBS is best suited for use in new construction and major renovation of commercial or residential buildings of any size. Interested? Facilities professionals looking to learn more can contact John Kennedy at Green Building Studio Inc. (707-569-7373 or [[email protected]]) or Norman Bourassa at the California Energy Commission (916-654-4581 or [[email protected]]).