This is not an article to help you resolve the conflict with your coworker about who should get the cube with a window. I work as a consultant for Autodesk and I have witnessed a growing trend of “zero conflict models” or “all objects shall be modeled that are larger than one inch” in many contracts for BIM projects. This sounds like a great idea as it will lead to more efficient construction and lower costs in the process. This article is about trying to separate “what is commonly desired” against what is really practical. Architects and structural engineers usually do not object too much and then the MEP engineer comes onboard and messes everything up. So what can the MEP engineer do to address this issue and still be competitive in the marketplace?
In the past year, I have worked with numerous MEP firms that are struggling with satisfying these requirements and still keeping their fees competitive and meeting project deadlines. I work mostly with our Revit MEP platform for design and Autodesk Navisworks® Manage for collision reporting. However, the methods I will discuss could easily be applied to other software packages.
The majority of engineering firms have based their fees on creating design intent documents, not design build. With the increasing demand for “zero conflict models,” these firms are being tasked with producing something equivalent to “shop drawings.” Even design build firms are being asked to produce more detailed models. This is especially true for the plumbing, piping, fire protection, and electrical disciplines. Engineers are more accustomed to producing diagrammatic documents even though they are creating a 3D model as part of the deliverable.
One of the best examples of this dilemma was a recent conversation with a fire protection engineer on a project. He was supposed to model the entire fire protection system, including the primary routing design. In the past, the secondary routing was typically done by the contractor who actually installed the system. Another example was an MEP firm that was facing increasing criticism over the number of conflicts that were being found in their models. Were these conflicts real or just part of the construction coordination process?
There are several approaches to resolving these problems and still meeting the intent of the contract. The first idea revolves around clearly identifying, with the other disciplines, what is classified as a conflict. The second idea revolves around creating zones in the model for each discipline. The third idea is probably the most difficult: Having a different standard for conflict resolution in MEP.
Now let’s look at the obstacles that the MEP engineer or designer faces. Pipes and conduit are not typically placed in their actual location in order to produce a clear set of construction documents, which is what is typically used for construction. Ducts and pipes go through walls; pipes and conduit are inside walls; and very few firms place dimensions to the center line of ducts, pipes, and conduit on floor plans.
More and more firms are, in fact, placing dimensions to these objects in their floor plans as part of their documentation process. The next dilemma: The bottom of pipe or duct tag does not report the correct elevation if insulation is added to these objects in Revit MEP. As a result, there is a duct or pipe that is not correctly identified or placed and now when we go to the coordination meeting, this is identified as a conflict. It is just not one, but sometimes thousands. There are several ways to approach this issue.
The first approach involves creating parameters that identify pipes or ducts by their placement. Using Selection Sets within Autodesk Navisworks Manage you can correctly identify these objects. These items would not be included in collision tests. You can create an instance Shared Parameter or Project Parameter that can be added into runs or systems by using the Tab select method in Revit MEP. At first this may appear like a lot of extra work, but it is not near the amount of work that is involved in going through several thousand conflicts and identifying which ones are true conflicts. By identifying each run by this parameter, countless conflicts are eliminated. These parameters should be clearly identified to the coordinating authority so they know what Selection Sets to create. The instance parameter could be named something like “disposition” or “coordination” and then assigned a value either as a letter or a number.
This method does involve some negotiation and coordination with the other project members, but is a more common sense approach to the underlying problem. The architect and structural team members do not typically have these issues and do not always understand the workflow of the MEP engineer. There have been many other approaches to resolve this issue, but most involve much more work. Some firms have resorted to maintaining two models—one for plan production and one for collision detection. This method requires much more coordination and work. Another approach has been to place pipes in the actual location, which often results in a poor presentation in the plan view, but this is supplemented with a 3D section to clarify their actual placement. This does help with the coordination, but the plan drawings are not acceptable to other participants.
I prefer the second method, which is the creation of zones for the placement of pipes and conduit. These zones can be created using a generic line-based family template. It needs to have both width and height parameters and it is necessary to create reference planes or levels in the model. These zones are placed in the areas the pipes or conduit will occupy, but this method does not require the exact placement of these items. When your model is submitted for the coordination effort, collision tests are conducted using these zones rather than the actual pipe or conduits.
This method is good for most projects unless there are a great number of elevation changes in the architectural model. One of the advantages to this method is that these zones can be placed by technicians or designers that do not have the experience to design actual systems. The designer or Engineer can now design pipe and conduit systems within these boundaries established by the zones and also create a correct presentation in the plan view.
The last method is more about negotiation and coordination, allowing the MEP disciplines to model to a different standard concerning the size of modeled objects. Often the other disciplines do not understand the extra effort that is required for the MEP engineer to meet the one inch or larger modeling requirement. I have worked on several projects where we had these discussions to educate other disciplines on the effort involved to meet this requirement and the lack of real value to the overall coordination of the model.
Engineers spend a large portion of their time correcting small pipes and conduit that in reality would have been adjusted in the field as a normal part of the construction process. A one-inch piece of pipe or conduit that hits a 12-inch beam is typically a pretty easy conflict to resolve in the field. This method revolves around education and honest discussions about the amount of effort involved and the return on this investment. This method typically requires a close working relationship with the other disciplines and is one that requires the greatest amount of work up front by the MEP engineer.
I have worked on projects where the tolerance was to 1/16th of an inch due to the large number of small pipes and conduit and the number of each involved. This is not a typical project for most firms and this level of coordination is not a typical situation. Revit MEP is being used on so many different types of projects that Autodesk never envisioned for the software that it requires users to develop processes to fit their own unique needs.
The next issue revolves around the final disposition of the model and what its use will be. Design Build projects by their nature require a greater effort by all disciplines, but this is generally understood when bidding the project. Design Bid projects should not involve the same amount of effort as these projects. The present course is blurring these lines. This again revolves around education, both internally and externally, about the actual needs for the project. Many of the senior MEP engineers that negotiate contracts are not aware of what is being asked of them.
I am not advocating a relaxing of standards for coordination, but rather a more common sense approach to this issue. MEP firms are being asked to deliver more and more for the same fees, often because they have not addressed the issues above. I have been asked repeatedly by MEP firms how to address these concerns, and typically the solution has been to ask the right questions and educate all parties on what they are really trying to accomplish. Walls, doors, windows, beams, and trusses are placed with precision with little doubt to their size and placement in the model. The vast majority of MEP objects are placed with less precision and this is often governed by local codes for their final disposition. Every project is unique and it is difficult to find one solution that works for every situation.
There are many other smaller items that can help with this process in the creation of templates and content that can also help in streamlining the MEP design process. I just don’t have the space here to address all of the issues. The real solutions revolve around developing a process for a sound understanding internally and then delivering that message to the other disciplines. In the vast majority of MEP firms I have worked with over the past eight years, the senior engineers have not been aware of the amount of effort that is required to meet these increasing standards on their work.
The real purpose of this article is to start the discussion within MEP firms on how they can best address the issues. The many disciplines involved and the variety of projects makes it difficult to find one solution to fit all situations. That does not mean a solution can’t be found, but rather that solution does not revolve totally around the software being used, but instead on developing a process to use the software more effectively.
As a business analyst for Autodesk, Ed Hannabas spends his time assisting clients in the utilization of a variety of Autodesk software. He focuses on assisting firms in the adoption and use of Revit and AutoCAD-based software on projects ranging from office buildings and hotels to waste water treatment plants and hospitals. Crossing Architectural, Structural, and MEP disciplines, Ed’s duties include training, project set up, and hands on work, along with the development of standards and workflows for utilizing Autodesk software. Contact Ed by email at email@example.com .