IFC format and Open BIM, all you need to know

What is it, why is it so important, how does it work, the connection with BIM, the advantages and the list of all certified software: here is the complete guide to the IFC format

One of the main requirements for you when working with a BIM software is to ensure that you have maximum freedom to share data relating to the design model and, above all, being able to work in a truly open system.

It is known that, proprietary file formats are those that can only be read by your own software and by other authorized software. Consequently, when project team members work with different software solutions, the use of proprietary formats can prevent interoperability, i.e. the ability of a product or system to interact and work with other products or systems, without any restrictions on access or implementations.

On the contrary, open file formats can be read and edited by anyone. The IFC – Industry Foundation Classes, format has been created to meet these needs, being a particular open file format that allows the interchange of an information model, without loss or distortion of data and/or information.

IFC Industry Foundation Classes logo

BIM and the IFC

To better answer the question “what is IFC”, it is necessary to take a step back and first explain the concept of BIM.

BIM stands for Building Information Modelling. It has been defined by NIBS – National Institutes of Building Science as the “digital representation of physical and functional characteristics of an object”.

First of all, BIM is an operational methodology and not a tool. It must be identified as a process of building digitization that uses a digital information model containing all the information relating to its entire life cycle: design, construction, management, maintenance and dismission.

One of the substantial characteristics of the BIM methodology is the easier cooperation among the actors involved during the phases of a building’s life cycle, to insert, extract, update or modify the model information, such as for example:

the architectural designer defines functions, shapes and geometries to generate the 3D model
the structural designer specifies and calculates the structural elements
the safety manager analyses and forecasts possible critical issues during the operational phases
the maintenance manager outlines and investigates the building’s technical aspects to be monitored during its lifetime.

All this requires a standard format that allows interoperability and data exchange in a secure way, without errors and/or loss of information: this is the aim of the IFC format.

In short, the IFC is an open format, established as an international standard, it is necessary for the exchange of models and information contents. It is also intended for the exchange of information internally within a project team and between different software, during the development of the design, construction, operation and maintenance phases.

Interoperability in a closed and open system

The history of the IFC

In 1994 an industrial consortium invested in the development of a computer code (a set of C++ classes) that was able to support the development of integrated applications.

Twelve US companies joined the consortium, which took the name “Industry Alliance for Interoperability”. In September 1995 the consortium opened its membership to all interested parties and in 1997 changed its name to “International Alliance for Interoperability”.

The new alliance was reconstituted as a non-profit organisation, with the aim of developing and promoting the Industry Foundation Classes (IFC) as a neutral data model, containing information relating to the entire life cycle of a building and its installations. Since 2005, the alliance has been carrying out its activities through BuildingSMART.

BuildingSMART is currently an organization whose objectives include improving the exchange of information between software applications that are used in the construction industry and developing an international standard for tools and training to support the extensive use of BIM.

BuildingSmart International logo

The IFC format characteristics

As already mentioned, the IFC format is an open and neutral file format, designed by buildingSMART International to support interoperability between individual applications operating within the construction industry and registered as an official international standard ISO 16739:2013.

The IFC, originally created as an open, interoperable and interchangeable file format, is able to meet a variety of needs. Strictly speaking, IFC is not just an exchange format, but a schema, i.e. a data structure or specification. The IFC schema can be thought of as a “storage system” to organize and carry digital data.
Let’s see in detail the specifications of such schema.

Interchange files

It is possible to consider the IFC as an interchange file because it allows to transfer geometries and information keeping unchanged the structure of the whole and of the single parts. Objects will have a precise position in space and will be distinguished by categories, characteristics and function.

Data model

By data model it is meant the theoretical structure associated with the model that enables its management, i.e. the ability to break it down and assemble it in different ways, depending on a specific use.

The basic criteria for the data model structure are the following:

with data filter we can choose which components to interchange, since only essential information and geometries will have to be incorporated for a given objective
through properties we can report what information will flow into the model objects and what relationship will be arranged among them
with attributes we can identify the characteristics that the objects involved should have.

Archive element

Data must be usable by several operators and over a fairly long period of time. For this reason, the IFC format, being an open format, is accessible by anyone anytime, regardless of the software adopted and its version. The IFC file archiving and preservation, must always guarantee easy consultation. Therefore, model data must be structured and the same models will be identified according to their use and function.

Data schema

IFC is a data schema that assigns a name and relationships between objects that will serve, in addition to optimizing the storage system itself, to make the objects readable by different software.

To sum up:

IFC models include geometric and non-geometric entities
IFC models contain the building geometry and data associated with its elements
by exporting data from a project carried out with BIM methodology using an IFC file, data are transferred from one application to another
the IFC format is open, free and well documented. By providing an IFC export and import interface, compliant with the IFC standard, software application providers are able to ensure interoperability with hundreds of other BIM tools and applications.

How does the IFC work?

The IFC format is a standardized data model that describes:

identity and semantics: object, name, function
characteristics: material, colour, properties
relationship between:
- objects (e.g. walls, slabs, windows)
- abstract concepts (e.g. performance, costing)
- processes (e.g. installation, assembly)
- people (e.g. owners, designers, contractors, managers).

The IFC schema is able to define building elements, pre-fabricated products, mechanical/electrical systems, and even the most abstract models for structural analysis, energy analysis, cost allocation, work planning and much more. The IFC schema defines classes of objects and their relationships.

Moving on to a technical analysis we can say that classes are designed to describe the building’s components – system installations, spaces, areas, furniture, structural elements – including the specific properties of each individual object, such as: position, shape, physical and mechanical characteristics, connections with other objects, energy performance, safety, cost, maintenance requirements.

Let’s make a practical example:

the window is a class that can be split into various window types
the window belongs to the building domain
the type definition recognizes the window, its set of properties and general attributes in the project
instances that represent the modelled entity, can correspond to each type
we can associate attributes and properties to instances.

The IFC also defines the relationships between the building elements and therefore:

reports describing how components are part of buildings
the relationships that enclose the spatial configuration, for example how the site is composed of buildings, floors, spaces and how spaces are grouped into functional zones
other reports linking the position of elements in systems, useful for operation and maintenance.

The IFC schema itself can be expressed in various file formats, most commonly in STEP such as IFC-SPF but also as XML or a ZIP file.

IFC-SPF is a text format in the modelling language of express data. It has compact dimensions and is the most used IFC format
IFC-XML is a format in the extensible markup language, XML. Although XML is a more common programming language, IFC-XML has a larger file size than IFC-SPF and is less used
IFC-ZIP is a ZIP compressed format of the IFC-SPF file. A. ifcZIP file usually compresses a 60-80% .ifc and a 90-95%. ifcXML.

The IFC specification has undergone multiple development cycles since its kickoff in 1995. There have been more than a dozen iterations from IFC1 to the current IFC4 version (including the ifcXML and IFCzip versions). IFC4 was officially released in March 2013. However, it took a few years for this current version to be implemented in the industry software.

Since 2018 buildingSMART is engaged in the certification of the software for the implementation of IFC4, testing and certification of the import and export capacity.

The evolution of the IFC

The advantages of the IFC

As illustrated, it is clear that the main advantage offered by the IFC format is to allow collaboration between the various figures involved in the construction process, allowing to exchange information through a standard format. This entails greater control and quality, reduction of errors, reduction of costs, time saving, with consistent data and information in the design, execution, management and maintenance phase.

openBIM IFC

According to the buildingSMART International website, the term openBIM refers to “a universal approach to the collaborative design, realization and operation of buildings based on open standards and workflows”.

The fundamental objective of the openBIM is to facilitate data exchange between all actors involved in the creation of a BIM model covering all possible fields of application: from design to construction, from building operations to its demolition and recycling of components and materials at the end of the building’s life cycle.

An essential requirement for the openBIM is the use of open and neutral data formats while the IFC format is the most common solution for the openBIM.

IFC certification and software compliance warranty

BuildingSMART International has defined a certification process that ensures the correct import and export of its IFC data, guaranteeing standards compliance. Therefore, it is essential for a software to provide the warranty that it is able to read, write and exchange information with other programs.

You can check the list of certified software by bSI by accessing this link.

ACCA is the software house with the largest number of certified software in the world. To date, ACCA software has obtained 19 IFC certifications relating to 16 software solutions:

In February 2022 ACCA software became multinational member of buildingSMART International.