Revit MEP

Revit MEP

Tuesday, September 15, 2009

BIM: The Future of Plumbing Design?

By Marvin Titlow

Building information modeling (BIM) is the process of generating and managing building data that can be used from the planning stage, through construction, and well into all stages of a building’s life-cycle. Typically, it uses three-dimensional, real-time, dynamic building modeling software to increase productivity in building design and construction.

The power of BIM is held within the virtual model and its associated database. One can think of it as being able to create “live design.” For instance, a section marker is placed in plan view, and instantly a section view is created. When a selected pump is put into the plan view, a schedule containing flow and electrical information can be created instantly. Flow and pressure drop data for piping and fittings can be included as well. Such information can be extracted and used for material cost comparisons and also can help calculate points for LEED design projects.

Federal and state government agencies are beginning to require BIM to be used in the design of their facilities to help determine long-term building sustainability and to aid in facility management. These agencies normally request that the contractor perform as-built changes to the building model within a set number of days to maintain the accuracy of the model.

Figure 1 Parameters are used to input information that controls intelligent objects.

Drafting’s Evolution to Building Information Modeling

Since the beginning of building construction, there has been some form of building information management. From papyrus scrolls used during the building of the pyramids to drafting boards used at the dawn of skyscrapers, designs have been managed in a format that can be referred to for concept, construction, and then ownership.

When computer-aided design (CAD) was introduced, it brought a new dimension to creating line drawings. Rather than needing a compass or triangle, one could type a command, and a circle could be drawn in any size and any scale. A line could be given any length or angle. Even with the slow speed of early computers, copying and deleting could happen at a pace only previously imagined. Building layouts could be changed much more quickly than on the drafting board.

However, this speed came at a price. When plans were designed on the drafting board, architects and engineers met before the building design started to coordinate mechanical room sizes, water heater locations, electrical panel locations, etc. All members of the design team focused on completing the project with as few changes as possible.

With CAD, oftentimes all disciplines are finishing their design the day the project is due, which leads to more change orders and sometimes higher building costs due to the extra coordination and assumptions made by the plumbing contractor because of insufficient information. Autodesk, Bentley Systems, and other CAD software companies have been trying to eliminate this problem for years.

While the concept of constructing drawings in 3D has been around for a long time, the process has been very time consuming and labor intensive with just CAD because these systems are normally vector based. This means that when a line or circle is drawn, it uses X, Y, and Z points as bases of measurement. To perform higher functions of calculations, the vector points are exported to a database.

Building information modeling software has developed as the next step in CAD’s progression. BIM software has taken the approach of creating the model within a database. This allows higher functions to be applied through the use of parameters. Parameters can input more information than units of measurement. They can be used to apply text, graphic overlay for rendering, and referencing information from other databases. The entire model has the ability to be parametric. Rather than lines representing a pump, the pump now has become a virtual object with the ability to contain real-world information such as plan location, elevation, weight, volume, horsepower, pressure loss, and much more (see Figure 1).

The ability to contain a wide variety of data types gives the BIM program the ability to perform calculations and display the information in multiple views in real time (see Figure 2). Several different products on the market today are used to create BIM models (see sidebar).

Workflow and Building Information Modeling

With BIM, one of the biggest concepts that must be embraced is that collaboration must begin early in the schematic design to ensure that major trouble areas such as mechanical rooms or ceiling heights have been coordinated. When entering the design development stage, most of the issues should be resolved so a more accurate price and layout can be achieved. When ready to start the contract documents phase, most of the layout should be complete, leaving only documentation and final coordination.

The most efficient way for this concept to work is for all the disciplines to work in BIM. For instance, at Michael Brady Inc., BIM software packages for the architectural, structural, MEP, and civil engineering disciplines have been utilized since 2006. Some architectural firms that have made the move to BIM have started requesting that out-of-house MEP firms reduce their fees if they produce their plans in CAD due to the increased time spent on coordination. (See Figure 3.)

HOW BIM Will Change Plumbing Design

Many architectural and structural engineering firms that have implemented BIM have stopped hiring CAD operators. Instead, they hire architectural interns and engineering graduates because the lower functions of drafting are being handled by the BIM software. Training for new plumbing personnel should be streamlined to help determine if a plumbing draftsperson can develop the concept of how pipe goes together and what fittings are required to make a system work. When designing in BIM, piping systems are installed in a virtual world, not drawing a line or circle that is printed on a piece of paper. The statement “my drawings are diagrammatic only” no longer applies.

Figure 2 The true power of BIM is its ability to display information in multiple views in real time.

When a company decides to commit to BIM, the plumbing designers will be tasked with learning the new software to produce their designs. The company may need to invest in new computer hardware to run the software effectively. The transition will require training to use the software and might require more time to develop content. This endeavor can take six months to a year before plumbing personnel actually become efficient.

The International Code Council is in the process of developing new standards to incorporate BIM in the code review process. This new project is called SmartCodes. This can have a major effect on plumbing design if plumbing designers and engineers are not involved in the development of this process. There have been numerous discussions about how industry societies need to be more involved in the development of plumbing standards. I believe BIM can be a catalyst. Within BIM’s format, plumbing calculations can be produced to help show building sustainability. Plumbing engineered systems then would have more credibility. (If you would like to learn more about SmartCodes, visit www.

Advantages of Using BIM in Plumbing Design

Coordination with other disciplines always has been at the top of our list when designing a system. Being able to work in a virtual 3D environment really helps detect conflicts. Most BIM solutions have a means of performing conflict detection and will highlight the areas in question. Since BIM solutions are normally databases, the ability to track items such as mechanical equipment, plumbing fixtures, fixture unit counts, and gas loads is much easier. Creation of the final documentation is quicker. BIM models normally contain parametric objects, and information can be added to adjust the physical attributes of these objects. If any piece of information needs to be scheduled, a parameter can be created to allow the object to share information with a schedule.

The 3D view of the BIM model can be rotated to different directional planes to produce plumbing isometrics (see Figure 4). Since most BIM software creates the model using databases, streamlining construction specifications can be done through third-party software such as e-Specs. Cost estimating for plumbing systems becomes more accurate due to the requirement for a more accurate layout within the BIM model. Most BIM software allows CAD files to be imported and models to be exported to CAD so other groups that are not using BIM can coordinate.

Disadvantages of Using BIM in Plumbing Design

I have stated some very compelling advantages for using BIM, but there are some disadvantages as well. Since the technology is new, the plumbing portions of these BIM programs are underdeveloped. Because models are databases, one would believe that being able to conduct performance analysis such as hydraulic calculations live in the model would be a strong point of the software. However, as of now this feature is still in development. While isometrics can be produced in Revit MEP, the tagging features such as pipe sizing and equipment labeling do not work in 3D views, so documentation for these isometrics takes longer.

Training on the MEP portions of these solutions is very hard to find due to the specialized nature of our fields. Some engineers also state that the quality of contract documents is not as good as CAD-produced documents. The linetypes that contain text styles that currently are used in CAD are not available in some BIM programs. Also, when a designer is routing piping inside a vertical
wall cavity from a section view, the floor plan view may not show the single line piping correctly. However, this will improve as these programs mature.

Figure 3 Within a plan view, models can be created to resemble standard 2D contract documents as shown on the first floor of this hotel layout.

The main objective of BIM is to produce a more accurate representation of the building and all of its components, thus providing better engineered systems. More time is required to lay out an accurate BIM model in plumbing due to all of the virtual pipe the designer is modeling. If proper workflow is not followed, results can be untimely delays or increased change orders. Most of the plumbing content for these solutions, such as objects for traps or valves, must be created due to the current development stage of BIM software, which can be very time consuming.

Also, if other disciplines are using 2D CAD, coordination becomes much more involved because the plumbing designer no longer can take advantage of designing in the 3D environment and cannot run any automated interference checks, increasing the chances for error and liability due to the accuracy of the model.

Tips for Using BIM Successfully in a Project

First, research what product would best suit your needs. Have vendors send a trainer to demonstrate how their software works. A good test is plumbing two water closets with cold water, sanitary, and vent. Ask others about their experience, cost impact, training requirements, and vendor software support. Ask the vendors about the computer system requirements to run their software. Since most modeling software programs are databases, the system requirements are much greater than that of standard business class machines. BIM software requirements can affect the network infrastructure of your office. Upgrading to a BIM software package is like buying an old house—do your homework and research and be prepared to do a lot of repairs and customizations.

When you finally decide what software you will be using and have updated your computers to handle the software, make sure to purchase proper training. As stated earlier, training seems to be hard to find when looking for plumbing solutions for BIM. BIM software can be self-taught, but the learning curve can be very steep. Vendors normally recommend searching online for forums dealing with the software package that you have chosen. The personnel chosen for training should have a positive attitude and specific experience in your type of design work.

Once training is complete, start developing a template containingyour company’s standards. This template will continue to evolve as you develop more content for other projects. Converts much information from CAD as possible to your BIM software and, if time allows, create this information from scratch. When trying to import information from one software to another, databases can become unstable or corrupt.

When you are ready to start using BIM on a project, it is preferable to select a pilot project, such as a small job that can take a loss. Don’t use BIM for the first time on a project with a short deadline. This can be counterproductive and can ruin morale. When your pilot project is complete, make a list of things that did not work properly and a list of things that did work properly and use this as a benchmark for your next project. As your team develops their skills, the list of issues will grow smaller, and your team will have the confidence to complete any project.

Figure 4 Since the model is in a 3D environment, waste and water isometrics become easier to produce.

Marvin Titlow has been working in the HVAC, plumbing, and fire protection design field since 1987. In 2004 Michael Brady Inc., located in Knoxville, Tennessee, hired Marvin as a senior plumbing/fire protection designer. In 2008 Marvin was promoted to technologies administrator and BIM manager. For more information or to comment on this article, e-mail

BIM Users Speak Out

Plumbing engineers who have used building information modeling software on past projects were asked to comment on their experiences. Their responses follow.

“We use Autodesk Revit MEP because of our long-term relationship with Autodesk products. The use of one building/structure model provides an efficient way of coordinating MEP building systems components. However, file sizes sometimes mean slow or lagging performance.

“Comparing BIM and 2D CAD is like comparing night and day. On BIM, when you draw systems such as plumbing stacks that extend vertically from one floor to another, you do so by specifying the height of the stack. In a 2D environment, you have to open every level’s floor plan and paste the stack from one level to another.
“My advice for other plumbing engineers considering making the switch to BIM is that the longer you wait, the more behind your firm will be regarding technology. Owners are starting to demand BIM projects, not the other way around.”

Samuel Le
J.A. Croson LLC
Sorrento, Florida

“At Nashville Machine, we use CADMEP as developed by TSI as an Auto-CAD third-party add-on in conjunction with AutoCAD 2009. This software was chosen because it afforded us the opportunity to develop accurate coordination drawings in a timely fashion as well as keep abreast of the growing three-dimensional design movement taking root in the architectural community. Eventually we will expand the software to include electronic sheet metal fabrication. I like the aspect of seeing what I have been drawing in 2D for years! As a young designer/drafter, it really has put practical knowledge in perspective.

“However, I dislike the memory usage it takes to run such a large graphic program. Even with a top-of-the-line computer, I still experience problems.

“BIM to me is the future of design. 2D drafting is a thing of the past and does not compare. When I think of BIM, I think of fewer changes and more things being caught before the field. Switching to BIM is definitely a wise decision. It is new standard for designing and installing and, with smaller crews in the field, can help cut costs.”
“For example, a project we currently are working on is Middle Tennessee Medical Center. The pros of using BIM are labor and schedule savings through coordination to allow much of the work to be prefabricated, reduction of change orders, reduced time lost in field decisions, and overall streamlining of the installation and fabrication process with a very tight control on scrap losses. The cons is needing CAD staff who are knowledgeable and proficient in the 3D software and the cost of training. However, the pros defiantly outweigh the cons, and the startup fee will be recouped in the project easily.”

April Newlan
Nashville Machine Co.
Nashville, Tennessee

“We use Autodesk Revit MEP 2009. I like the ability to find and notify the designer of conflicts with objects. However, this is the only thing worth while about the software in its present state. “First, the hardware is too slow, even with the fastest machines and network connections. Second, the sizing routines are basically useless. For instance, water sizing does not allow for pressure drop through the system. (The information is there, but they didn’t take the algorithm to its logical conclusion.) Waste sizing will reduce the size of pipe if a steeper slope table allows a smaller size for that particular fixture unit value. There are no natural gas or storm drain sizing routines. There is no ability to create a sizing routine for systems not provided. Third, content creation (making ‘smart’
elements) takes too long and is cumbersome to say the least. Fourth, opening a project in Revit takes a considerable amount of time. Fifth, setting up sheets is cumbersome. Sixth, there’s not enough flexibility in the final presentation. Next, changing symbology to match a company’s standard is time consuming and in some cases impossible. Program bug fixes are slow to nonexistent. The software company has time to add content but not enough time to go back and fix
what doesn’t work. It seems their interest lies in creating content just good enough so they can advertise that it does more to get companies to buy a ‘new’ and ‘improved’ version. Lastly, creating the information in elements so you can use the dynamic schedules is too cumbersome.

“I think 2D is more stable and faster (therefore cheaper for the client) to use. Unless you have a client that insists on BIM, wait about 10 years to buy it until it becomes useful. As a bare minimum, quadruple your time estimates for project completion in BIM versus 2D CAD.”

David Faubion, CPD
Houston, Texas
“Revit was being used in my company long before I came to the office. Since I work in an architectural office, they were already using the Revit for Architecture. They ordered Revit MEP 2008 and recently installed Revit MEP 2009, which is much improved over the previous version. I like the fact that you can see your design in many different views without duplication. Since you are using a single model with multiple disciplines linked into it, you can easily coordinate any conflicts with structural beams, mechanical ducts, etc. Also, when selecting fixtures, the software keeps track of them, making it easy to schedule and locate. Additionally, if you’ve got a large job and you need more than one person working on it at the same time, both can be in the same drawing and not have to worry about getting a read-only message and waiting their turn.

“On the other hand, it can be quite tedious at times and very time consuming. The more work you have on your model, the longer it takes to regenerate. I haven’t had a lot of formal training, so there can be a steep learning curve. The out-of-the-box fixtures are not good. You have to look around forums and websites to get the fixtures and fittings you need or create them yourself.

“BIM and 2D CAD are pretty much night and day. You can get your BIM model to look like an ordinary 2D CAD drawing if you want, but since you’ve put in the time and hard work it’s best to display that work and coordination in various views. With Revit, it’s easy to cut a couple of sections and have a rendered 3D point of view to show how your work interacts with the building and its varied components. For certain, 2D CAD is faster and the way to go for a quick turnaround deadline, as well as simple jobs. In my opinion, Revit is the way to go for the more complex projects
where the line work can get busy, space is tight, and coordination is paramount.

“For example, there was a corporate office building that we just completed. Revit certainly helped when it came to the coordination with the structural beams. There was a restroom/locker room in the basement garage, and there were beams overhead that pretty much boxed us in. By looking at various angles of the 3D model and sections, we could coordinate with the architect to get the furring and chases needed to get though the structure and avoid a possible RFI and/or change order.
“For business owners, is can be quite a hefty investment. The software is not cheap, and while there is training out there, it’s not always specific to the MEP side of the software. Not all the architectural firms are using BIM software yet, so you still can keep using 2D CAD. You should keep it in mind if you start to see a trend toward BIM in your area.”

Andrew Cole
Irvine, California

“We use AutoCAD Revit because we felt it was the best for the overall firm. It offered the best local support.

“With BIM, I like that you can see the 3D piping as you’re designing (what pipes are running through other pipes). However, I dislike the learning curve and lack of fixtures. Yet there is no comparison between BIM and 2D CAD. Revit shows it like it should be installed. Projects we have used BIM on are churches and schools. It helped seeing the 3D picture, using the sizing in the program, and connecting the piping to a fixture or piece of equipment. If you use the software correctly, you’re forced to treat the plumbing system as a system, not just hooking up fixtures.

“The hindrance is that you need to approach the project totally differently. You need the correct project setup, and there is a shift in time allocation from the old SD, DD, CD time allocation. You need more time in the beginning of the project and less time in the CD phase.”

Bob Dana, PE, CPD
Omaha, Nebraska

“We use Revit MEP 2009 due to compatibility with clients. I like the potential for reduction in conflicts and ability to work through complex designs. However, performance, stability, and the requirement to provide more information than normally required are downfalls of the software. At this point, I think BIM requires significantly more man hours to complete the same task. For other plumbing engineers considering making the switch to BIM, I say wait. The technology is not there yet.

“For example, in designing a 12-story hotel, the architect located some floormounted, tank-type water closets over a corridor below. By looking at the section, we realized that the architect had only allowed 9 inches of ceiling space for the corridor below. If we weren’t already looking at that section to check the pipe and fittings, we may not have caught this ceiling space issue as early as we did. Also, on the same project, because of the amount of work and pipe in a hotel, the model became so large that it would take a minimum of 15 minutes just to open the drawing. At one point it took almost an entire day to draw one storm line from a roof drain down to below the slab and out the building. As more information is put in the model, the slower it gets. Eventually the file crashed, and all work from the previous day’s backup had to be exported to AutoCAD to be able to complete the project on time. As I previously stated, BIM is great for coordination but awfully slow in the real world.”

Emigdio Hinojosa Jr., CPD
CHP and Associates
Houston, Texas

“We use Autodesk Building Systems. We already use AutoCAD extensively, so this was the easiest transition. We are currently testing Revit MEP but are not convinced of its capability for piping design.
“BIM allows us to coordinate our designs much better. With NavisWorks, even people who don’t know how to draw in 3D can walk around the project and see where issues are. However, drawing in BIM takes significantly longer than 2D. Making what seems like slight changes can take a lot of time. The increased file size makes the drawings open slowly and makes plotting take forever with our current computers.

“BIM adds a lot of extra information and complexity. In theory, this gives the client a better, more thought-out design. However, in reality this gives the client one of two options: a well-designed 3D building with very poor-looking 2D documents or our normal standard for 2D documents with a less complete 3D model. The problem lies in elevation. Piping can be installed at many different elevations, which usually is required in a tight space. This works great in 3D, but the 2D documents look like a mess. Typically we would coordinate this space and then draw the 2D documents to show the design intent clearly but not necessarily in the exact location on the plans. If we draw the piping clearly in 2D, it collides with many things in 3D.

“We currently are struggling to define the line between engineering design responsibilities and construction coordination. How much time should the engineer spend above and beyond what they normally would do to coordinate their piping in 3D? Does this time spent save the client money? Or will the contractor simply look at the 2D drawings and make their coordination set anyway? We have yet to see a BIM project into the construction phase, so these questions should be answered soon. Drawing in 3D takes so much additional time that we have to be careful not to omit general good design practices in an effort to get the drawings done on time. It’s very easy to get wrapped up in the 3D coordination and forget about codes and standards.”

Eric Busch
Affiliated Engineers
Madison, Wisconsin

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