Integration: BIM design

Building information modeling (BIM) is used frequently when working across multiple disciplines, including mechanical, electrical, plumbing, and fire protection engineering, and also with other stakeholders such as architects and contractors.


This article has been peer-reviewed.Learning objectives

  • Understand the requirements for a BIM model.
  • Learn the key components of a BIM execution plan.
  • Understand the nuances of smart data, content, and other details within a model.

Is it possible for BIM to be done correctly for mechanical, electrical, plumbing, and fire protection (MEP/FP) design? Numerous factors come into play when integrating BIM into the MEP/FP engineering and design process. It is up to the design team to take the best from each variation of modeling and apply the appropriate elements to create a successful process.

Expectations are never the same on any engineering project. Everyone has various ideas of how BIM will be incorporated, and quite a few of them are unrealistic. The MEP/FP engineering team needs to set appropriate expectations with the architect and owner at the onset of the project. Before defining these expectations, we need to understand why divergent expectations exist.

Figure 1: An overall view of a building shows a single mechanical, electrical, plumbing, and fire protection (MEP/FP) design model representing accurate location and overall dimensions of equipment and systems. This image is rendered from a single Revit mWhen we say or hear BIM, it is often interpreted to mean 3-D modeling using Autodesk Revit. While other platforms are available, most architects use Revit, which sets the expectation that MEP/FP models will also use Revit. The main concern is related to the detail and accuracy that an architect or owner might expect because he or she doesn't completely understand the MEP/FP software or process. Architectural models are detailed and dimensioned to a high level of accuracy, and it is expected that MEP/FP models will match that accuracy, an attitude also shared by the client/owner. This sets the precedence in architectural and structural models, which are required to provide dimensional control for the contractor as an element of design. MEP/FP design work rarely, if ever, has the same level of detailing. However, as MEP modeling software became mature enough to be used on major projects, expectations were already set for similarly detailed MEP/FP models.

Contractors have also become accustomed to using architectural/structural models directly to create their 3-D coordination models; increasingly, they expect the MEP/FP models to have the same detail and accuracy. For example, a general contractor was completely surprised by my "negative" response when he asked about modeling all the conduit runs in the electrical model. MEP/FP design models are created primarily to show design intent. While support modeling and constructability are secondary drivers, they are still important, as the subcontractors make a substantial investment in the trade coordination exercises and rely on that information from the design models.

Keeping this in mind, the MEP/FP models should focus on overall dimensional accuracy of equipment,ducts, pipes, and other items that will require coordination with other disciplines. This virtual coordination for physical location must satisfy everyone's needs, including those of the facility engineers who will eventually maintain the equipment and facility. These expectations should be clarified in meetings with the various teams when collaborating to create a joint BIM execution plan (JBEP).

Creating the JBEP

Collaboration to create the JBEP is another key factor for a successful project. Quite often the request for proposal (RFP) for a potential project is accompanied by the client's BIM requirements. The JBEP is simply a response to the requirements, defining the plan and processes that will be used throughout the length of the project to meet the goals. If the RFP or the client does not have any BIM requirements, it is still in the best interest of the project team to create a JBEP so that all members understand what is created and delivered to each other-and finally to the client at turnover. Without an agreed-upon JBEP,teams often move forward with their own definition of BIM goals, which results in misaligned expectations,at times allowing the architect and/or contractor to continually ask the MEP/FP engineers and designers for small changes in the model's detail or accuracy that may add up to a significant amount of work beyond the contractual scope.

When creating the JBEP the MEP/FP team needs to pay special attention to topics like roles and responsibilities, BIM uses, model organization/setup, models exchange, level of development (LOD),modeling matrix, software used, and data export. Quite often Construction-Operations Building Information Exchange (COBie) is required as a data deliverable, though it is not always clear how it will be used by the owner. While all the elements of the JBEP are important, the topics noted above are the core working parts of a well-defined BIM execution plan. Once these topics are defined in the plan, effort must be maintained to stay within the bounds of the JBEP. For projects within the U.S. the following documents provide good references for creating the JBEP:

It is important to keep the JBEP simple; the goal is to create a virtual building before the contractors start working on the real building. Contractor input for constructability is necessary to create the virtual building, which defines the necessity to model major items in 3-D. The LOD matrix identifies the development of objects in the model, which should be used to populate the modeling matrix, identifying MEP/FP systems and element authors.

Figure 4: Modeling matrix lists objects using the Construction Specifications Institute UniFormat code and requires the project team to fill in the appropriate level of development values based on project phase.The modeling matrix is an excellent place to start identifying which items will be modeled at the agreed-upon LOD. Accept the fact that certain elements will always be at LOD 300 and continue to add such elements to your content library. Elements like pumps, fans, chillers, panelboards, transformers, ducts,pipes, and cable trays should always be shown in 3-D, in the correct X, Y, and Z location with respect to the architectural model.

The goal is to build a virtual building, and one similar to a real building. If the structure is not in place,none of the MEP objects can be installed. Every effort should be made to have the right models in place so the most appropriate elevation is given to elements as they are modeled. An important item that needs to be added to the JBEP is the variance in size of objects given that MEP/FP engineers specify equipment with final dimensions by the manufacturers. This entry gives the flexibly needed to design the right system. If you are part of a design-build project, there must be an agreement regarding level of detail necessary from the design team given that the trade contractor's model will show the elements in greater detail with all the necessary fittings, flanges, hangers, and other details.

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