Frequently Asked Questions About IFC

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What are IFC and MVD?

The IFC file format is ISO-certified and it was developed by the BuildingSMART (formerly the IAI - the International Alliance for Interoperability). IFC is the only open and standard 3D object-oriented exchange format used by BIM (Building Information Modeling) and it is available free to all software vendors.

IFC provides 3D geometry representation for all project elements and stores standard and custom data about each element, such as materials, profiles, and functions. Applications used by the different disciplines can easily and quickly filter and identify the relevant, discipline-specific information from the IFC database.

The Model View Definition, MVD (or IFC View Definition) is a recommendation for which data and elements the IFC model should include, depending on the purpose of the model exchange. Model View Definitions are either defined within buildingSMART International or by other organizations and interest groups.

IFC data are managed according to the latest worldwide-certified IFC standard, IFC2x3 TC1 (Technical Corrigendum 1). Archicad supports the import and export of both IFC2x3 and IFC4 versions, following the Model View Definitions below:

IFC2x3 Schema

• The Coordination View is currently the most widely implemented view of the IFC Schema. Its main purpose is to allow the sharing of building information models among the disciplines of architecture, structural engineering, and building service. It contains definitions of spatial structure, building, and building service elements. ARCHICAD is certified for both import and export of the latest version: IFC2x3 Coordination View 2.0.
• The IFC2x3 Coordination View (Surface Geometry) is a simplified publishing format (i.e. a subset) of the Coordination View. This format is suitable for viewing (since all IFC viewers support this format), design coordination, clash prevention during design, and clash checking, similarly to IFC4 Reference View. “Coordination View (Surface Geometry)” means that every element will be exported with its BREP (boundary representation) geometry. This method comes closest to reproducing the real shape of the element, together with its specialized sections, connections and solid operations. (However, the element’s parameters are lost, and BREP elements from an imported IFC file are transformed into non-editable elements.)
• The Coordination View, for example, was the first Model View Definition developed by buildingSMART International and is currently the most widely implemented view of the IFC scheme. The main purpose of the Coordination View is to allow the sharing of building information models among the disciplines of architecture, structural engineering, and building services (mechanical). It contains definitions of spatial structure, building, and building service elements that are needed for coordinating design information among these disciplines.
• The IFC2x3 Basic FM Handover View is an extended version of the Coordination View (developed by buildingSMART) that defines the general requirements for design applications to enable the handover of facility management information. The basic scope can be summarized as the space and equipment list for the spatial and technical systems of a facility. Technically, the Basic FM Handover View fulfills the following requirements above and beyond those of the abovementioned Coordination View: the ability to assign furnishing and equipment components to spaces (Space Containment, IFC System), to assign spaces to zones (IFC Zone), to assign a classification to spaces and components (Classification Reference), to assign manufacturer base properties to components (standard and custom IFC Properties), to assign doors and windows to spaces (Space Boundaries), to assign type information for components (IFC Type Product) and to export base quantities for all project components and spatial structures. This MVD is required in various projects defined by buildingSMART and other organizations. An example is the COBie (Construction-Operations Building information exchange), a specification used in the handover of Facility Management information. It is a spreadsheet data format for the delivery of a subset of building model information, rather than geometric model information. ARCHICAD’s BIM-quality models and IFC data exchange capabilities produce data output that is easily converted into COBie documentation, with the help of free or commercial conversion programs.
• There are several other Model View Definitions (generally the extended versions of the Coordination view) specified by organizations or development teams outside of buildingSMART International.

IFC4 Schema

• The IFC4 Schema further divides the Coordination View into two Model View Definitions:
  IFC4 Reference View: Suitable for all BIM workflows based on reference models, where the exchange is mainly one-directional. Requested modifications of the BIM data, mainly of the shape representation, are handled by a change request to the original author.
  • When exporting to IFC4:
    • the relation connections of chained Walls and Beams are omitted
    • Surfaces of Building Materials are omitted
• IFC4 Design Transfer View: Provides building information with support for editing of interconnected elements: inserting, deleting, moving, and modifying physical building elements and spaces, within the limited scope of parametric exchange. An example of a target scenario is an architect providing building design information to an engineer for a particular discipline, where geometric modifications may be needed. Note that the Design Transfer View is not meant for round-trip model exchange scenarios.

NOTE: The IFC4 Schema is not supported by all applications. Use an MVD of the IFC4 Schema only if you are certain that it is supported by the application that will receive IFC data.

All Model View Definitions can be extended by definitions which support additional exchange requirements:

• the Quantity Take-off add-on view adds the ability to transmit base quantities for all spatial and building elements
• the Space Boundary add-on view adds building elements to space relationships to support models in
  thermal and energy analysis
• the 2D Annotation add-on view supports the exchange of additional 2D element representations and
  annotations of building models

Archicad supports all of these additional data types.

For more information, visit:

• http://www.buildingsmart.com/
• MVDs
• Archicad and COBie

Who supports IFC?

With the open IFC platform, Archicad can communicate with a wide range of structural, mechanical and energy analysis applications.

Check the following sites or ask your consultant about the IFC compatibility of any current application:

• buildingsmart-tech.org
• en.wikipedia.org/wiki/Industry_Foundation_Classes
• www.ifcwiki.org

What information does an IFC model carry?

• Building hierarchy (Project, Site, Building, Story, Element)
• Element type (wall, slab, column, beam, roof, stair, zone, etc.)
• Geometry
• Layer-system
• Standard and custom (application-dependent) IFC properties (material, color, cross-sections, fire rating, etc.)
• Connections
• etc.

What does the "Reference Model Concept" mean?

Each discipline is responsible for the creation and development of its own model. The "Reference Model" means that a discipline - for example the structural engineer - uses the architectural model as the initial basis for the structural model. While the structural model will be created as a standalone model, some initial design information will be taken over from the architectural model.

The modeling concepts of the two disciplines differ: for example, the architect designs a two-story column as a single, continuous column element in the architectural design. The structural engineer, on the other hand, cuts two separate structural column members and defines their final structural material and cross-section.

If such differences between the models (and the varying responsibilities of the two disciplines) are to be managed effectively, it is necessary that one discipline's model be locked for editing when viewed in another discipline's environment, yet its elements and data should still be accessible if needed. IFC fulfills this requirement too.

Archicad's IFC user interface has been based on this Reference Model Concept, as well as ease of use. IFC model elements inserted into the architectural model serve as protected reference elements, assigned to layers with different intersection priorities, but all of the associated data can be queried and are accessible. The elements themselves can be added to the architectural model: when you import a model into Archicad using IFC, the imported elements are automatically interpreted as native Archicad elements (Archicad Column, Beam, Slab, Wall, Stair, etc.). Thus, if needed, the imported elements can be edited immediately.

What functions does Archicad support with IFC?

Archicad comes with numerous tools and an easy to use interface to support IFC-based collaboration among disciplines. The most important features are the following.

• Element Classification

For more accurate model mapping, you can classify Archicad elements by their "IFC type". While each Archicad element type has a default counterpart in IFC (which is used if you use the "Automatic" option), you can assign any other IFC type to a particular element – for example, if you have used certain tools to model elements of a different type, such as using the Slab tool to model a ceiling, etc.

In collaborating with structural partners, the "Structural Function" classification can be added to the load-bearing building elements. It also lets you limit the exported IFC model to load-bearing elements only, thereby streamlining the collaboration process.

The "Position" classification lets you sending a model to a partner (e.g. energy analyzer) who is able to differentiate elements by their location (interior or exterior) in the building.

Classification Reference ( IfcClassificationReference ) can be used for the arrangement of IFC elements into categories. You can assign an Item Reference identifier, a classification Name attribute and some other optional parameters to all project elements (such as the building, the stories, the building elements, or the zones). For example, classify building elements by the U.S. GSA standard categories such as OmniClass, UniFormat, etc.

Use IFC Assignments (Groups, Zones, Actors and Space Occupants) to define the relationship between the different project elements. Each assignment type can have its own attributes and standard/custom IFC Properties.

• Handling of IFC data

Easy handling of IFC data can be done both on the element level (in Element Settings) and on the project level (in the IFC Manager), in Teamwork as well as solo projects. Since the IFC properties are native to Archicad, the following functions are available:

• Find & Select command searches for the IFC properties of any element.
• Interactive Element Schedule lists the IFC properties of any element.
• Pick up/Inject Parameters shortcuts and Copy-Paste transfers IFC properties from one element to another.
• The IFC content of Hotlinked Modules can be queried and listed.
• Mapping between Archicad Library Part properties and standard/custom IFC properties is available.
• etc.

• Solutions for different workflows

Archicad offers solutions for different workflows: reference model concept (Merge and Hotlink); open IFC as separate new project (Open); "compare and merge" of imported model versions (Detect IFC Model Changes); and filtered or entire model export (Save as).

Each solution supports all the IFC file versions: IFC, IFCXML and IFCZIP.

Predefined and customizable translators give user-friendly "one-click" IFC import/export and optimized data transfer with major (Tekla Structures, Revit applications, etc.) and local engineering softwares.

• Model export

The entire current Archicad project, or just its filtered content, can be exported in IFC format. Filtration can be done by selection in the current project view, by visible layers, by building stories, by domain types (structural, HVAC or custom), by element types (e.g. columns, beams, etc.), etc. Use "simplified BREP" (boundary representation) geometry export to e.g. IFC viewers, resulting in an accurate geometric display of element intersections and solid operations, without including all element properties.

• Model import

The IFC model obtained from another application is always transformed into native Archicad elements. At the same time, it is possible to use the imported elements as a reference, since they can be automatically placed onto their own, protected layers (which are locked to prevent editing). Since the incoming elements or modifications are converted into a native format, they become an active part of the architectural model, while retaining their properties (e.g. material, profile) assigned in e.g. the received structural model.

• Detect IFC model version changes

As part of an IFC model-based data exchange workflow, Archicad enables you to compare two subsequent versions of an IFC model, to insert and to list the detected changes into the current Archicad model (using Mark-Up tool).

Which methods can I use to import an IFC file into Archicad?

Archicad provides three methods for importing an IFC model into it: Open, Merge, and Hotlink.

Open

The Open command launches an IFC model as a separate Archicad file, independent of any other project currently open in Archicad.  Archicad will transform the imported elements into corresponding Archicad elements, based on settings in the chosen IFC Translator for Import. This imported file (or a part of it) can be added later as a reference to the appropriate part of another Archicad project as a Hotlinked Module.

Merge (File > Interoperability > Merge):

Available only in Floor Plan view. Inserts an IFC model in whole or
in part into a running Archicad project. Merge preserves your running project, without overwriting its data (this is the “Reference model” concept). However, even in this “Reference model”, the merged
elements are real Archicad elements based on the IFC-ARCHICAD mapping convention.
In the Merge process, Archicad automatically generates new IFC GlobalId (Archicad IFC ID) values for all imported elements to avoid overwriting the IFC GlobalIDs of the host project. For the purposes of listing and searching, the elements’ original GlobalId values are also retained, in the form of a parameter
called “External IFC ID”.

Hotlink (File > External Content > Place Hotlink)

Place IFC files as hotlinks directly into the currently open Project as protected reference content. You can place this hotlink as many times as needed. Thus, in a project using repeated building blocks/parts, you do
not need to request a huge IFC file based on the entire project - a smaller IFC file that contains just the module is enough.

What does the “detect IFC model version changes” function mean?

With the so-called "Detect IFC Model Changes" function, Archicad detects the differences between two IFC that reflect two different versions of a project model according to the elements' IFC global unique identifiers, and  it finds the new, deleted and modified elements. The elements affected by the modifications are generated and merged into the currently running project (that project can also be an empty one). Modifications can be viewed and managed using Archicad's Mark-Up tool in both 2D and 3D views.

NOTES: Only 3D elements will be considered, and will be paired by their unique ID; Change Detection is available for IFC2x3 files only.

What IFC versions does Archicad support?

Industry Foundation Classes (IFC) are the open and neutral data format for openBIM. Archicad supports the import and export of both IFC2x3 and IFC4 versions. IFC data are managed according to the latest worldwide-certified IFC standard, IFC2x3 TC1 (Technical Corrigendum 1).

Note: IFC2x3 is recommended - this is the most widely used version. Choose IFC4 for exporting, only if you are certain that it is supported by the application that will receive IFC data using this Translator.

What are the differences between the various IFC formats?

• .ifc: the default IFC exchange format using the STEP physical file structure
• .ifcXML: IFC data file using the XML document structure. This format is recommended for architects whose partners’ applications cannot read the original .ifc format, but can manage XML databases (such
  as budget, energy calculations, etc.). This format delivers the same model information as the plain .ifc format, but the elements and their properties are stored in a more informative structure. An .ifcXML file is normally 300-400% larger than an .ifc file.
• .ifcZIP: IFC data file using the ZIP compression algorithm. It is the compressed version of .ifc or .ifcXML.
  An .ifcZIP file usually compresses an .ifc down by 60-80% and an .ifcXML file by 90-95%.

NOTE: .ifcZIP is compatible with e.g. Windows compressed folders, WinZip, etc. So if the recipient cannot read .ifcZIP, then a ZIP extractor application can open the file into .ifc or .ifcXML format.

Does Hotlink work with IFC files?

You can place IFC files as hotlinks directly into the Archicad Project as protected reference content. See details on how to Hotlink IFC Files.

How can I check the result of my IFC model export?

After exporting an IFC model, it is good practice to check the IFC model by reopening it in Archicad or opening it in an IFC viewer. There are many free IFC viewers on the market that can be readily downloaded, for example:

• Tekla BIMsight: http://www.teklabimsight.com/
• Solibri Model Viewer: http://www.solibri.com
• DDS-CAD Viewer: http://www.dds-cad.net

Additional information can be found at the following Wiki address: http://www.ifcwiki.org

Where can I read more about IFC and the suggested data exchange workflow with other disciplines?

A dedicated chapter (called Interoperability) of the Archicad Help gives a detailed description of the collaboration-related topics including the suggested and effective workflow between the architects and the structural/MEP/energy analysis engineers, the Archicad features that can be used to prepare a model for later data exchange, as well as the IFC-related concepts, skills and all functions.

More detailed information can be found in the IFC Reference Guide for Archicad 24 as well, available here.