Building Design

BIM and the U.S. GSA (1-2-3 Revit Tutorial)

1 Jan, 2007 By: AIA ,Rick Rundell

How the IFC is being used to facilitate data exchange for U.S. federal government projects.


In October 2006, the U.S. GSA (General Services Administration) -- the government agency that builds and manages federal facilities -- began requiring the delivery of BIMs for major federal building projects. For those of you unfamiliar with GSA, this is noteworthy because the agency is the U.S. government's "landlord" that meets office and other space requirements of the federal workforce. GSA owns, operates and manages more than 340 million square feet of space in approximately 8,700 owned and leased buildings across the United States. GSA properties include border stations, courthouses, office buildings, laboratories, data processing centers and notable facilities such as the White House.

GSA hires and manages private-sector professionals (architects, engineers, contractors, etc.) to design, renovate and construct its properties. GSA's new rule for BIM delivery applies to all of its major projects receiving design funding in fiscal year 2007 and beyond. For architects and engineers working on one of these projects, this means that their concept design must be submitted to the GSA in both the native format of the BIM authoring application and as an IFC (Industry Foundation Classes) file.

As the largest owner of commercial space in the country, GSA's mandate constitutes a watershed event for the acceptance of IFC as a data exchange standard in the building industry. This month, we take a closer look at the IFC standard and how the GSA is using it to transmit building data.

Many Standards for Data Exchange
A host of vehicles exist to move building data between software applications. There are STEP, IGES, ODBC, XML, DWG, DWF, DXF and PDF, just to name just a few. This alphabet soup of data exchange mechanisms has evolved over time, with various standards developed and advanced by different organizations, vendors and consortiums to suit particular requirements.

For example, in previous articles I explored how ODBC was being used to link BIM with data-centric software solutions for such tasks as specifications management, how DWF was being used to publish space and room data to facility management applications and how XML was being used to pass building data to Internet-based analysis applications.

IFC is an open standard for building data exchange developed by the IAI (International Alliance for Interoperability), a global consortium of commercial companies and research organizations. The IAI was started in 1994 when Autodesk led a group of 12 companies to examine the potential for making different software applications work together. Autodesk is a founding member of the IAI, holds a board-level position in the North American chapter and participates actively in the consortium worldwide.

Data files using IFCs and the other standards mentioned above are mechanisms for moving data from one software application to another, but are not themselves building information models. In turn, BIM is not a file format or data schema. The coordinated, consistent and reliable information delivered by BIM, however, is the foundation for the value these standards have the potential to deliver.

Interoperability and IFC
My recent article on BIM and facilities management cited a 2004 NIST study that estimated the cost of the inefficiencies in the U.S. capital facilities industry -- inefficiencies caused by inadequate interoperability among CAD, engineering and software systems.

IFC strives to increase interoperability by providing a data exchange standard for sharing building data across various applications used for building design, construction and facility management. Unlike some of the generic data standards mentioned above, the IFC standard was specifically created to share building information, and can represent building-specific elements like walls, as well as abstract elements such as spaces.

Its format is open and available to commercial software vendors to build the necessary IFC import and export capabilities into their authoring applications. Applications are deemed IFC-compliant (capable of importing and exporting IFC files) after going through a multi-stage certification process conducted by the IAI.

As a side note: You may start to hear the name BuildingSMART used in conjunction with the IAI and IFC. With the overall architecture of the IFC standard under its belt, the IAI is broadening its scope and is seeking alliances with other organizations to promote the use of BIM and IFC to achieve beneficial change in the building industry. It is branding this initiative BuildingSMART.

Revit, IFC and BIM
Autodesk Revit Building 9.1 software is IFC-certified; having received its stage 1 IFC2x3 (shorthand for IFC2x Edition 3) certification for the Extended Coordination View for both import and export in June of 2006, and full certification for the IFC2x2 Code Checking View (that expands the IFC Coordination View to additionally support architectural code checking) in November of 2005.

The support for IFCs in Revit enables compliance with the GSA's IFC delivery requirements. In fact, Autodesk is currently working with GSA to develop best practices and BIM guidelines for architectural and engineering firms conducting federal civilian design and construction projects.

All of this boils down to the ability to export IFC files from Revit and import IFC files into Revit. In the near term, exporting IFC files is more typical. Design information created in an authoring application such as Revit is exported to an IFC file for building data consumers (owner/operators, municipalities, construction firms) to use in other applications.

For example, the initial goal of GSA's BIM requirement is to better manage its space by automating spatial validation of A/E designs. In the past, GSA validated space requirements using manually created 2D polygons in plan drawings during early design stages. This process was time-consuming and led to discrepancies when the GSA team measured and reported on the actual building spaces (the basis for their rent calculations). By requiring building data to be delivered in IFC files for all future projects, GSA can import the data directly into a checking program that calculates rentable and usable areas and ensures that all designs adhere to their spatial requirements.

With the goal of easing of interoperability between software platforms, several other federal and municipal government agencies (notably Denmark and Norway) require or will soon require IFC data exchange for publicly funded building projects. The Singapore Building and Construction Authority already uses IFC-based building data to automate the checking of building plans for code compliance. No doubt, as the use of BIM grows and the maturity of the IFC standard is established, there will be many more examples of real-world IFC-based data exchange.

Sample IFC Export Workflow for GSA Submission
• A GSA spatial BIM model is created in Autodesk Revit Building with custom GSA spatial project parameters assigned to room objects, including GSA STAR Space Type.

figure
GSA requires spaces greater than nine square feet to have a specific set of non-graphic data attributes (described in Section 2.1.1 of the GSA BIM Guide For Spatial Program Validation).

• In this model, Mechanical Room 2306 is modeled as a room in Revit (bounded by walls) and assigned several GSA-specific nongraphic data attributes. Within Revit these attributes are implemented as project parameters using schedule keys that provide automatic lookup tables for entering the data automatically.

figure
Revit schedule keys provide automatic lookup tables for entering GSA-specific attribute data automatically.

• A further examination of the parameters in Revit assigned to this Mechanical Room 2306 illustrates the kind of GSA Spatial data that is being tracked with these rooms. Parameters in gray (show below) were automatically populated using Revit schedule keys.

figure
Parameters in gray were automatically populated using Revit schedule keys.

• You can export the Revit BIM as IFC using the built-in IFC Import/Export capability of Revit (shown below). The IFC export in Revit Building 9.1 was enhanced to export GSA-specific non-graphic spatial data to the IFC file.

figure
Revit provides built-in IFC import and export capability.

• Revit Building 9.1 can export IFC version 2X2, 2X3 and the BCA ePlan Check view (as required by the Singapore government code checking initiative). For the GSA IFC export requirements, 2X2 is the minimum requirement -- but the other versions export the GSA-specific IFC space parameters as well.

figure
Revit has been validated against GSA's BIM and IFC delivery requirements.

• If you open the exported IFC file using Notepad, you can see the format of an IFC file. A room in Revit is exported as an IFCSPACE with its Revit Project Parameters assigned as IFC Property Sets to the IFC Space. GSA-specific spatial data can also be exported to the IFC file.

figure
Format of sample IFC files.

• There are a variety of viewers, such as the one shown below from Data Design Systems, capable of viewing IFC files directly.

figure
Revit Building 9.1 IFC file, displayed by an IFC viewer (from DDS).

• From within the viewer, clicking on Mechanical Room 2306 displays the IFC property sets resident in the IFC file.

figure
Attributes of Mechanical Room 2306, transferred from the Revit model to the IFC file, can be displayed by the IFC viewer.

BIM Growth
GSA's new requirement for BIM is one more (very prominent) example of the growing acceptance and importance of BIM within the building industry. In parallel, Revit IFC certification is the latest example of Autodesk's commitment to open, standards-based data exchange mechanisms in its products. Combined, they are especially good news for firms using Revit on federal building projects funded by the GSA.


About the Author: AIA


About the Author: Rick Rundell

Rick Rundell

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