Due to its multifaceted benefits, building information modelling (BIM) is rapidly gaining traction in the AEC industry as the key pre-construction planning, construction management, and post-construction facilities management tool. Whilst many firms have transitioned to this ‘intelligent’ model-based process, the ‘real’ potential of BIM can only be achieved by open exchange of design and non-design project information amongst key project stakeholders: architects, structural engineers, MEP design consultants, MEP engineers, and other trade subcontractors.

A common challenge faced by mid-sized to large projects is that not all project participants use the same BIM application. This is where the concept of closed BIM and open BIM comes into play. The above two approaches are fundamentally different ways of looking at 3D BIM modelling.

Closed BIM, also known as ‘lonely BIM’, is a BIM environment wherein the same version of a BIM application is used by all key project stakeholders. This approach may also include different trades using the BIM-compatible applications from the same vendor. As a case in point, the lead architect uses Revit Architecture to model architectural elements. The structural engineer uses Revit Structure to take the architectural BIM model as the reference and define the building’s structure whilst the MEP design consultant uses Revit MEP to model building services. Although no file conversion is required in the closed BIM approach, the process is restrictive in the sense that it only allows project participants well-versed with certain BIM tools to collaborate, thereby not allowing ‘true’ integration.

On the other hand, open BIM is a workflow wherein all participants can collaborate and exchange project information with each other using non-proprietary, neutral file formats irrespective of the BIM tools and applications they use. The information exchanged is not only limited to the BIM model’s geometric data but also includes other parametric data, such as specifications, quantity take-offs, material procurement, cost estimation, and construction phasing. Most common open BIM protocols currently in use include Industry Foundation Classes (IFC) and Construction Operations Building Information Exchange (COBie).

Whilst IFC allows exchange of both geometric and non-design data amongst different applications that support open BIM, COBie only allows facilities management data to be exchanged. Using IFC, the architectural BIM model created by the lead architect’s design team in Graphisoft ArchiCAD can be opened and manipulated by the structural engineer when his/her team works in Tekla Structures. Similarly, the integrated architectural and structural BIM model can be imported into Revit MEP platform by the lead MEP consultant. Once the detailed MEP design is complete, the federated model can be taken into a clash detection and 3D BIM coordination tool, such as Navisworks again using IFC format. This leads to workflow-level collaboration amongst key project members which is the essence of BIM compared to the conventional 2D CAD workflows.

At XS CAD, we have an extensive know-how of both open BIM and closed BIM methodologies due to the fact that we have provided 3D BIM modelling and 3D BIM coordination support to architects, MEP engineers, and contractors in the US, the UK, Canada, Australia, and India. To find out more about how your project can benefit from our BIM modelling services, contact us.