Posted by: David Scheer - Green Building Studio Product Owner
Who is this for:
- Engineers and energy analysts who want to do more detailed work on their analysis model than the tools in Autodesk® Revit®, Vasari® or Green Building Studio® allow.
- Analysts who want to move seamlessly from an architect's model to DOE2/eQuest or EnergyPlus.
- Modelers who want to create an initial eQuest or EnergyPlus model more quickly than they can with other DOE2 or EnergyPlus UI tools.
- Green Building Studio® (GBS) enables users to seamlessly generate a pre-populated energy simulation models and initial results using the power of Revit and Vasari.
- Green Building Studio®uses the industry standard DOE2.2 (eQuest) engine for high speed at a sufficient level of quality.
- If more advanced energy analysis is needed, GBS allows you to simply export a DOE2/eQuest INP file or an EnergyPlus IDF file for detailed work in those tools.
- Green Building Studio® can also be used as a translator from any tool that creates gbXML model geometry, to a fully-populated energy analysis model that can be simulated in GBS and/or exported to INP or IDF.
Workflows using Revit, GBS, and eQuest/Energy+/gbXML
"I used to use eQuest to create a building model from scratch. After working through 40-plus screens of input, I wondered if there is a simpler way to model energy performance."
eQuest, EnergyPlus and other engineering software such as Carrier HAP, Trane Trace and IES are powerful, complex programs that are used by engineers to carry out detailed energy analyses and equipment sizing. These tools have great input flexibility which, as a result require more specialized knowledge and detailed inputs.
Revit is a tool that creates building information models (BIM) which contain a wealth of building and design-specific information. The exact information that is contained in the model varies depending upon the tool used to create it and the user-inputted level of detail. At a minimum, the Revit model should contain information about building surfaces, openings, and simplified room, space and/or HVAC representations. Depending on the tool, information may also exist about lighting power loads, internal loads and schematic HVAC requirements. For early stages of design, when decisions about massing, glazing amounts, orientation and site placement are being made, Revit models should be kept simple.
Green Building Studio is geared toward serving a seamless workflow from authoring tools that generate gbXML format model data, such as Revit and Vasari. Coupled with Revit and Vasari, GBS provides a one-step simulation workflow by generating a sophisticated energy model with a minimum set of inputs. This means that an architect or engineer or analyst can quickly generate reasonable energy simulation results from their existing Revit model by specifying as little as just the building type and the location. Like eQuest, GBS uses the DOE 2.2 simulation engine to run simulations when initiated from a Revit model. Not only does GBS takes care of most of the tedious work of filling in the missing pieces of the energy model, and it also carries out these simulations on remote servers so it doesn't take local resources, and it can run many simulations at the same time.
How Can I Carry Out Energy Simulations When So Little is Known About the Building?
An energy model run in a sophisticated modeling engine like DOE2.2 requires a minimum set of data to create a reasonable simulation. All simulation tools, including eQUEST and GBS, make assumptions that can later be changed by the user. The assumptions include envelope and equipment performance, occupancy levels and schedules, internal gains, etc.
Filling in all this data and more is very time-consuming and fraught with opportunities for errors and typos. GBS smooths out the process by 'filling in the blanks' with reasonable assumptions based on the users input and normal conditions found on buildings of the type and configuration and in the location the user has specified. GBS assumes that unknown or unspecified design parameters will meet ASHRAE 90.1 levels of performance. If the modeler has specified any detailed information through the authoring tool (eg Revit, Vasari), that information is used by GBS, and only the missing data is added. In this way, the modeler can quickly move from architectural model to complete energy model to energy simulation to results viewing, adding only the information they know about.
But while the Revit-GBS pair is quite powerful, many of the knobs and levers that energy modelers and engineers want may not be available. GBS recognizes these limitations and offers export in INP format for eQuest and DOE2, IDF format for EnergyPlus, and gbXML for other tools like Trace700 that support that standard.
Export from GBS
When the architect or analyst has exhausted the capabilities of Green Building Studio for collaboration and iteration on their project design, they can move on to other tools using the Export Data Files feature.
The process is simple:
- If you do not currently have GBS entitlement on your Autodesk360 account, go to gbs.autodesk.com to sign up for a full or trial subscription entitlement.
Note that a trial account will give you the ability to run unlimited simulations on up to 2 projects.
- If you are not working in Revit or Vasari, skip to Step 4 and submit a gbXML model directly to GBS (wiki help).
From Revit or Vasari, create or open a RVT model and sign in to Autodesk 360.
- From the Analyze toolbar, click on Run Energy Simulation, which will kick off a simulation in Green Building Studio.
- Sign on to GBS (gbs.autodesk.com) and navigate to the project where you submitted the simulation request.
- From the project Run List, click on the model, or 'base run' that you would like to export.
- Navigate to the "Export and Download Data Files" tab.
- Choose the file format you would like to export, right-click and save to your local drive.
- Open the file in eQuest, EnergyPlus or any tool that recognizes the IDF, INP or gbXML format.
eQuest (DOE2) vs EnergyPlus vs gbXML
Like eQuest, Green Building Studio uses the latest release of DOE2.2 as its simulation ‘engine’. When a model is submitted for analysis to GBS either directly from Revit or Vasari, or as a gbXML upload to the GBS Web UI or through the REST API, a new gbXML is created that includes the complete information needed for an energy simulation. Then using an XSLT style sheet, the gbXML file is transformed into an INP file that is run directly with the DOE2 engine.
Because DOE2 is the native simulation engine of GBS, the process of populating and transforming the gbXML model has been optimized and validated for use with DOE2. For this reason, the highest quality export is the INP file for eQuest, and an eQuest simulation should yield the same results as the GBS simulation.
Trace700 imports gbXML format directly, and users of Autodesk Revit MEP have commonly used that tool in conjunction with Trace700. Using the gbXML with Trace700 is also a high quality method for continuing energy modeling outside of GBS.
GBS also provides a transform to the EnergyPlus IDF file format, though these EnergyPlus models are not currently simulated in GBS primarily due to the long simulation times. EnergyPlus offers some advanced capabilities that are not available with DOE2 and other older simulation engines, such as physical modeling of thermal mass and airflow, comfort calculations and radiant energy transfer, and as the EnergyPlus engine becomes more reliable and user interface tools begin to mature, the industry is starting to move toward taking advantage of these capabilities. In GBS, the IDF format is validated for geometry and model content and tested to ensure a successful running model, but the results have not been as rigorously tested as the standard DOE2-based GBS runs. Stay tuned for more advances in this area in the near future, and in the meantime please share your experiences with this feature.
More information can be found at the following links
(Note: though still helpful, some of the information in these links may be out of date due to new software developments)
- Using Green Building Studio with eQUEST, the Freeware DOE 2.2 Interface
- Detailed Energy Analysis
- Energy Analysis Workflow for Sustainability
- Trane Trace 700 GBXML Integration
- Engineers Can Save Time Using Green Building Studio (GBS)
Tell us about your experiences
Share your experiences with us..Have you used the export capabilities of Green Building Studio? What external tools are you using? Are there other export formats you think would be useful? Want more information about the issues discussed in this post?