Who is this for? Architects, Engineers, and other building professionals performing energy analysis using Vasari, Revit, or Green Building Studio who want more information on the energy settings applied to their models.
Takeaway: Autodesk Building Performance Analysis (BPA) products give you the ability to begin performing energy and carbon analysis on your building project at the earliest schematic design phase. The BPA products rely on Green Building Studio’s extensive and continually updated database of building parameters, such as constructions, schedules and equipment to supply the assumptions needed to perform whole building energy and carbon analysis. These assumptions are taken from several industry-recognized organizations and are continuously revised, as the industry standards evolve. The appropriate input assumptions are applied to your schematic model, based upon your building project size, height, location, and building type. This powerful Energy Analysis feature in Vasari and Revit allows you move toward more energy-efficient and sustainable designs before details that will impact energy usage have been decided upon.
Author: Marjorie Stein - Product Manager, Building Performance Analysis, Autodesk, Inc.
Many of you who use our Energy Analysis features in Vasari and Revit have starting asking us what are the default inputs used for the energy analysis of my model, and what are these defaults based upon?
As you may already know, Autodesk Green Building Studio is the cloud-based tool used by the Energy Analysis feature in Vasari and Revit. Green Building Studio has a rich and extensive database of intelligent defaults for building constructions, schedules, internal loads, HVAC equipment, and other inputs needed for the energy and carbon analysis.
The Revit and Vasari inputs that are exposed in the Energy Settings dialogue box are primarily based upon Commercial Buildings Energy Consumption Survey (CBECS) characteristics, and standard practices in the construction industry. You can make edits to these energy settings within the Energy Settings dialog box in your Revit or Vasari project.
Conceptual Constructions Descriptions of the thermal characteristics of the walls, floors, roofs, windows, and skylight.
Building Operating Schedule Defaults Descriptions of the default operating schedule applied to your model, based upon the project’s building type.
Building Operating Schedule Drop-down options Descriptions of the operating schedule options that may be applied to your model.
HVAC System Details of the HVAC system options.
The Outdoor Air value defaults to 15 cfm/person. You can edit this value using Outdoor Air per Person; Outdoor Air per Area; or Air Changes per Hour. Note: Due to limitations with the DOE-2 energy simulation engine used by Green Building Studio for Revit and Vasari, the Outdoor Air inputs are not additive values—DOE-2 will use the largest calculated value for the energy analysis.
Additional input defaults used in the energy analysis, but not exposed in the Revit or Vasari Energy Settings, are based upon ASHRAE Standards. You can view these input assumptions by logging in directly to the Green Building Studio website. Navigate to your project, choose the project, click on the specific simulation run you wish to review, and navigate to the Building Assumptions and Details section of the Energy and Carbon Results. These defaults can be edited using the Green Building Studio Project Template, Project Default, and Design Alternative features. For the more experienced users, you can download even more detailed inputs from the Green Building Studio website by going to the Export and Download Data Files tab associated with each energy analysis run. There you can download files such as the gbXML file (which is populated with the default analysis inputs), the DOE-2 input file, the EnergyPlus file, and/or the Weather Data file.
Green Building Studio also supports a workflow which allows you to upload gbXML files directly to the Green Building website. In cases where the energy setting parameters are not already defined in the gbXML files, defaults are applied which, in some cases, differ from the defaults used within Revit and Vasari. These defaults are primarily based upon the ASHRAE 90.1, ASHRAE 90.2, ASHRAE 62.1 and CBECS data, and vary with building type, location, size, and number of floors. These building assumptions and details can be viewed from the Autodesk Green Building Studio wiki help page.
For energy settings where ASHRAE baselines do not exist, regional code baselines, or building survey findings are applied as a reasonable starting point for new construction projects:
- Schedules: California Non-residential New Construction Baseline Study 1999
- Envelope thermal characteristics, LPD, HVAC efficiency: ASHRAE 90.1 2007 and ASHRAE 90.2 2007
- Equipment power density & DHW loads: California 2005 Title 24 Energy Code
- Occupancy density, ventilation: ASHRAE 62.1-2007
- HVAC system type default for building type/size & other miscellaneous building characteristics: 2003 Commercial Buildings Energy Consumption Survey
We’d like to hear from you: Is this information helpful, and what other relevant data would be useful to you?