For 20 years, contractors and architects have been increasing their use of building information modeling to reduce conflicts, provide comprehensive material takeoffs and deliver beautiful 3D renderings for improved design and construction of buildings. But mechanical, electrical and plumbing engineers have been stuck in 2D.
The MEP engineers did not demand 3D+ modeling until quite recently. Most MEP engineers have never been trained in BIM or its relevant software applications.
But now, many MEP firms—such as our company, MDP Engineering Group—are seeing opportunities in BIM and investing in 3D+ design. For example, our company did its first BIM project in 2010. Then, in 2013, we advanced to our first HVAC design, which was created using Revit MEP software and covered approximately 150,000 sq ft. In 2014, we designed another HVAC design, which also was created using Revit and covered 450,000 sq ft. Today, the scope of our BIM projects has skyrocketed to more than a million sq ft of full HVAC, electrical, and plumbing design.
We have learned a lot about designing for MEP BIM in the process, and we have discovered a few recurring issues. More important, we have found—and would like to share—some work-arounds to address, at least partially, those issues and ultimately help to improve MEP 3D design for construction.
The Skills Gap
For MEP design firms attempting to transition to 3D BIM from 2D programs such as AutoCAD, the biggest obstacale is staffing. The older generation of engineers have been using 2D software for twenty years or more, and they are understandably resistant to learning new programs. But, surprisingly, the younger generation of MEP engineers are not yet learning to use BIM software in school.
Generally, the few students who do learn to use BIM software are in architectural programs or enrolled at technical or community colleges. Typically, they have little knowledge of MEP systems and require extensive on-the-job training, even when they do know how to use 3D design tools. I was lucky to be exposed to HVAC design during my undergraduate studies, but I have met or interviewed very few engineers with the same experience.
Despite the staffing challenges, MDP Engineering is striving to use BIM software for all large construction projects. Therefore, we have had to develop a strong in-house BIM program.
Hiring a full-time BIM manager was an important first step. With his guidance, we are actively developing implementation plans, adopting company standards for 3D modeling and generating standard content for BIM modeling.
Staff education is the next big hurdle. We hold companywide educational seminars on a regular basis, but only so much can be learned about a complex software program while sitting at a conference-room table.
To address the need for deeper education, we make it our mission at MDP to support each other and sit down, one on one, with engineers and designers who are new to Revit modeling.
We also encourage our employees to self-educate, using company-provided tutorials or by subscribing to related online forums and YouTube channels.
As an alternative to in-house training, we also can send employees to offsite, multiday training sessions. However, as a company, we have prioritized in-house training, based on our company standards. Because of the in-house training effort and a few recent strategic hires, we now have a core of professionals familiar with the use of Revit software.
One of the biggest benefits of Revit MEP is the automatic scheduling of modeled equipment and elements. On the other hand, this capability is one of the main challenges facing MEP engineers, due to the lack of global standards for shared parameters. The official Revit style guide acknowledges the need for standards and attempts to direct users on proper naming and use. However, so far, there is no agreed-upon convention.
Our work-around for shared parameters is to develop a custom file that is synchronized with equipment schedules. Due to the way parameters are identified in the BIM database, we have to load our custom parameters into each new "family" that we receive from a manufacturer. The process is time-consuming, but it allows for a consistent appearance and format of schedules.
Generic Equipment Models
Another common issue we run into is a lack of manufacturer-generated BIM models available for download. Generic models work fine for equipment such as air diffusers and valves, because they vary only slightly among manufacturers. But larger equipment, such as rooftop units and generators, have unique properties that vary by manufacturer. Using generic models for this type of equipment means that we lack the detailing or operational parameters that reflect the actual equipment being scheduled.
This information lack defeats the main purpose of BIM, which is to create an accurate representation of the systems being designed in order to promote coordination among the trades.
Unfortunately, there is no convenient work-around to this issue. The availability of equipment models is increasing over time as manufacturers begin to respond to the demand for BIM-Revit models of their equipment. In the meantime, we continue to use a generic model as a place-holder for large equipment.
On many occasions, we have seen equipment that we have modeled for installation end up on a different floor in an architect’s model. How did this happen? When an architect moves a hosting element, such as a ceiling or a wall, the MEP elements attached to it can be moved unintentionally, orphaned or deleted.
As a work-around, we host ceiling-mounted elements, such as diffusers and lights, to reference planes that we create in the MEP model. This method of hosting allows architects to move ceilings or walls without having to worry about accidentally moving the MEP systems.
However, a downside to this approach is that the reference plane elevations that we create in our MEP model may not identically match the architect’s elevations. Misaligned elevations can cause issues with the proper visibility of elements, such as ducts, diffusers and lights, in the ceiling plan.
Shortcuts sometimes used by architects also can lead to inconveniences in the MEP model. We have worked on projects with “typical” hotel rooms or apartment units that were modeled in a 2D format and then copied throughout the building as assemblies. When an MEP engineer creates a 3D model, the existence and placement of individual walls as objects is important for hosting lights, receptacles, grilles and many other pieces of equipment. As a work-around, we have created place-holder walls so that we can provide a 3D model; however, these place-holders can create discrepancies between disciplines. Properly modeled hosting elements will lead to fewer inconsistencies and coordination errors.
Things are changing quickly in the AEC industry. The bright future that BIM promises has yet to be fully realized, but each year we’re moving closer to it. There certainly will be additional challenges for the MEP Revit user, but our design approach acknowledges that, despite these short-term challenges, the long-term goal of fully adopted BIM modeling will improve the quality of our work and the industry’s work as a whole.
Michael Grose, P.E., is a mechanical engineer with MDP Engineering Group in Denver, Colo., and has been actively using Revit for five years. He is director of mechanical and plumbing Revit standards for MDP.