Pictured here is an example of a BIM model.

BIM. If you are not acclimated with the term or technology, now is the time - especially if your firm is up to creating lean and green buildings. (In truth, BIM is used for all construction.)

BIM stands for Building Information Model and Building Information Modeling. It is a set of information generated and maintained throughout the life cycle of a building. It is the process of generating and managing a building information model. To be specific, the National BIM Standard is described in this fashion:

“A Building Information Model is a digital representation of physical and functional characteristics of a facility. As such it serves as a shared knowledge resource for information about a facility, forming a reliable basis for decisions during its life-cycle from inception onward.

“A basic premise of BIM is collaboration by different stakeholders at different phases of the life cycle of a facility to insert, extract, update, or modify information in the BIM to support and reflect the roles of that stakeholder. The BIM is a shared digital representation founded on open standards for interoperability.”

Steve Shirley of University Mechanical and Engineering Contractors, El Cajon, Calif., provided a simpler definition. “This is more than just 3-D detailing and coordination,” he said. “BIM is truly ‘information modeling.’”

Universal Mechanical and Engineering Contractors has been involved in BIM for several years now, and Shirley can see the difference in the final product.

“The technology was fully adopted five years ago, with early use over seven years ago,” he said. “It has helped increase productivity, reduce rework, and maintain market share.”

Jack Wilhelmi of Waldinger Corporation-Omaha, Omaha, Neb., is definitely entrenched in the technology, too.

“The values to a mechanical contractor are: (1) ability to develop a bill of material for estimating without quantity surveys; (2) coordination with other building systems to avoid space conflicts; (3) data for building commissioning and recommissioning is readily available; and (4) analysis of system alternates will be considerably quicker and more accurate,” he said.

Steve Shirley, Univ. Mechanical and Engineering Contractors


For all of history, design and construction of buildings have relied on drawings for representing the work to be done. They were defined as contracts - legal documents. They were assessed by building codes and used to manage the facility afterward.

But there are two strategic limitations of drawings, both parties explained:

1.They require multiple views to depict a 3-D object in adequate detail for construction, making them highly redundant and thus open to errors; and

2.They are stored as lines, arcs, and text that are only interpretable by some people. They cannot be interpreted by computers.BIM involves representing a design as objects - generic or product-specific, solid shapes or void-space oriented (like the shape of a room), that carry their geometry and attributes. The geometry may be 2-D or 3-D. The objects may be abstract and conceptual or construction-detailed. Composed together, these objects define a building model.

Jack Wilhelmi, Waldinger Corporation-Omaha

If an object is changed or moved, it need only be acted on once. BIM design tools then allow for extracting different views from a building model for drawing production and other uses. These different views are automatically consistent - in the sense that the objects are all of a consistent size, location, and/or specification, since each object instance is defined only once. Drawing consistency eliminates many errors.

BIM covers geometry, spatial relationships, geographic information, quantities, and properties of building components. BIM can be used to demonstrate the entire building life cycle, including the processes of construction and facility operation.

Quantities and shared properties of materials can easily be extracted. Scopes of work can be isolated and defined. Systems, assemblies, and sequences are able to be shown in a relative scale with the entire facility or group of facilities.

BIM is able to achieve such improvements by modeling representations of the actual parts and pieces including their function, such as 250 gallons-per-minute of chilled water at 42°F being used to build a building. This is a substantial shift from the traditional computer-aided design (CAD) method of drawing with vector file-based lines that combine to represent objects.

BIM, as shown in the illustrations above and below, covers geometry, spatial relationships, geographic information, quantities, and properties of building components. BIM can be used to demonstrate the entire building life cycle, including the processes of construction and facility operation. Modern BIM design tools are designed to go further. The objects are defined as parameters and relations to other objects, so that if a related object changes, this one will also.


The interoperability requirements of construction documents include the drawings, procurement details, environmental conditions, submittal processes, and other specifications for building quality. It is anticipated by proponents that BIM can be utilized to bridge the information loss associated with handing a project from design team, to construction team, and to building owner/operator, by allowing each group to add to and reference back to all information they acquire during their period of contribution to the BIM model.

For example, a building owner may find evidence of a leak in his building. Rather than exploring the physical building, the owner may turn to his BIM and see that a water valve is located in the suspect location. The owner could also have, in the model, the specific valve size, manufacturer, part number, and any other information ever researched in the past, pending adequate computing power.

The American Institute of Architects has further defined BIM as “a model-based technology linked with a database of project information,” and this reflects the general reliance on database technology as the foundation. In the future, structured text documents such as specifications may be able to be searched and linked to regional, national, and international standards. “BIM enables the contractors to fully coordinate and prefabricate more extensively than ever before,” said Shirley.

“CAD is one of the tools used to create a building information model, and as such is an incomplete solution by itself.”

Modern BIM design tools are designed to go further. They define objects parametrically. That is, the objects are defined as parameters and relations to other objects, so that if a related object changes, this one will also. Parametric objects automatically rebuild themselves according to the rules embedded in them. The rules may be simple, requiring a window to be wholly within a wall, or complex, defining size ranges and detailing.

“BIM has afforded the opportunity to resolve design and spatial conflicts earlier in the process to avoid field rework,” said Shirley.


Because 3-D objects are machine-readable, spatial conflicts in a building model can be checked automatically. Because of this capability, at both the design and shop drawing levels, errors and change orders due to internal errors are greatly reduced, said Shirley. Thus, as a building representation, BIM technology is far superior to drawings.

But, in the eyes of the Mechanical Contractors Association of America (MCAA), the larger implications are not just consistent drawings and clash detection. Because building models are machine readable, it becomes practical to use that data in many other ways: to generate bills of material that can be used for cost estimation or automatic ordering and tracking, for energy, lighting, acoustic, HVAC systems, and/or other analyses.

It is not as ex post facto checking if an almost finished design is OK, said MCAA, but rather to provide feedback while designing, informing the designer of the effects of changes. Thus, building models allow for better integration of many processes, allowing the kind of tracking and control that computers allow in manufacturing and at local grocery or department stores, tracking every item from creation to delivery.

Bottom line:Contractors can harness the abilities of this technology to estimate, design, and build more leaner and greener buildings.

“Having more information in a single model allows better integration throughout the building life cycle,” said Shirley.

Added Wilhelmi, “BIM will provide the ability to maintain and restore the building’s design conditions that were created as part of the original design for sustainable construction.”

In a nutshell, proponents claim that BIM offers:

• improved visualization;

• improved productivity due to easy retrieval of information;

• increased coordination of construction documents;

• embedding and linking of vital information, such as vendors for specific materials, location of details, and quantities required for estimation and tendering;

• embedding and linking of vital statistical information, such as flow rates, capacities, temperatures, etc.;

• increased speed of delivery; and

• reduced costs.

In August 2004 the U.S. National Institute of Standards and Technology (NIST) issued a report titled “Cost Analysis of Inadequate Interoperability in the U.S. Capital Facilities Industry,” which came to the conclusion that, as a conservative estimate, $15.8 billion is lost annually by the U.S. capital facilities industry, resulting from inadequate interoperability due to “the highly fragmented nature of the industry, the industry’s continued paper-based business practices, a lack of standardization, and inconsistent technology adoption among stakeholders.”

BIM is designed to eliminate such waste. “The best way to get involved is to do a project that requires it,” said Shirley.

As Shirley explained, BIM, in a sense, is similar to the automation of manufacturing in the 1980s, when most manufacturing industries first adopted 3-D modeling and digital representations. The changing of ways of operating in manufacturing is still evolving.

As noted, these capabilities also facilitate much improved coordination and collaboration. Designing a building once for contract drawings, then developing a set of detailed drawings for shop fabrication later, is recognized as involving much waste and inefficiency. Design-build and other forms of architect-contractor teaming have been recognized as more efficient, in terms of cost, time, and for reducing the potential for litigation. Building models tremendously facilitate this process.

According to Wilhelmi, a 3-D model is easier for all parties to interpret and visualize. Design or fabrication work can be coordinated in person or at a distance using Web conferencing tools, such as Webex and GoToMeeting and virtually walking through the 3-D model.

Because 3-D objects are machine readable, spatial conflicts in a building model can be checked automatically.


This is not to say that there is no room for improvement with new technology. “Entry into BIM is costly in terms of capital investment and learning curves,” said Shirley. “At a minimum, you should have personnel skilled in installation of systems with good computer skills.”

Added Wilhelmi, “The biggest expense in getting into BIM will be the time required from the contractor’s staff.”

There is also the concern regarding lack of interoperability among CAD programs. In the green building movement, such fears are being addressed through gbXML (see related sidebar).

“Current project delivery and contracting methods are outdated and do not allow full benefits to be realized,” said Shirley.

To get involved in BIM, a contractor first must be proficient in CAD and related software, have a proficient IT person or department, and the desire to move to the next level, said Wilhelmi.

“BIM will provide the ability to maintain and restore the building’s design conditions that were created as part of the original design for sustainable construction,” he said.

Contractors must make a conscience decision to do all projects with BIM, said Shirley. “The decision must come from the CEOs,” he said.

Concluded Wilhelmi, “It requires a strong commitment from all involved, from the top down.”

Sidebar: MCAA and BIM

How important is Building Information Modeling (BIM) to the Mechanical Contractors Association of America (MCAA)? A lot. Which is why it is putting on conferences in June to address this new technology, as well as provide other estimating and designing tools.

The association has put together two conferences, both to take place at the Indianapolis Marriott. The first conference, Estimating Essentials, is set for June 9-10. Following it is the Strategic Estimating conference, June 11-13.

The first conference is billed as a hands-on skills building workshop, designed to help individuals who are new to estimating. Participants are to find out how to use MCAA’s WebLEM™ to determine the labor hours required for installation.

Attendees are also to be taught how to make bid/no-bid decisions, how to establish an estimating schedule, how to understand killer contract clauses, how to compute performance and productivity adjustment factors, how to understand the impact of overtime inefficiencies, how to compute the true costs of change order impacts; and how to compute unit pricing.

In this working seminar, participants are to learn about issues involved in the bidding decision, the various contract documents, what to look for in technical specifications and plans, and how to organize estimate preparation. Each attendee will be assigned to a company team that will go through the complete process of bidding a mock project.

Instructors for the seminar will be Emmett Reilly, president of John W. Danforth Co. in Tonawanda, N.Y., and Ron King, a veteran of the mechanical construction industry. This seminar is limited to 40 people. Registration fee is $750 per person.

BIM will be one of the discussions at the Strategic Estimating conference. In today’s highly competitive construction environment, MCAA thought it should focus in on high-performance, rapid estimating, especially since traditional estimating is undergoing profound changes. The association said participants are to learn how to find a competitive advantage “that turns a good customer into a great customer.” In addition, attendees are to gain an understanding of how to develop the scope of and cost out a high-performance building.

During this seminar, BIM will be explained and demonstrated in full. Instructors for the conference will be Matt Gregg, lead professional engineer for McKinstry Co. in Seattle; Tim Wentz, teacher of construction management at the University of Nebraska-Lincoln; Jack Wilhelmi, president of the Omaha Division of Waldinger Corp. in Omaha, Neb.; Raghi Iyengar, construction product manager in the AEC Solutions division of Autodesk; Tom Williams, former president of the Construction Division of McKenney’s Inc.; and Steve Shirley, president and CEO of University Mechanical & Engineering Contractors Inc., in El Cajon, Calif.

For more information, contact the MCAA Meeting Department at 301-869-5800 or eventregistration@mcaa.org.

Sidebar: What Is gbXML?

gbXML is an emerging schema, a subset of building information model (BIM) efforts, focused on green building design and operation. It was developed to facilitate the transfer of building information stored in CAD (computer-aided design) BIM, enabling integrated interoperability between building design models and a wide variety of engineering analysis tools and models available today.

Using gbXML, the building design process is streamlined, allowing the project team to complete the design and analysis of building scenarios faster and more accurately than traditional processes, eliminating the need for plan takeoffs.

For example, gbXML seamlessly links architects using Autodesk® Revit® 6.1 with HVAC engineering teams at Trane using Trace™ 700 for design specifications, allowing them to develop geometrically accurate building models in minutes, rather than days or weeks. It allows the building energy analysis team to assess design alternatives using whole-building energy analysis like GeoPraxis’ Green Building Studio, and supports the immediate development of detailed input files for DOE-2, EnergyPlus, and eQuest, leading building energy modeling tools. It also allows immediate information sharing with Elite Software’s HVAC duct design tools, and Ecotect’s environmental analysis tools.

Market leader HVAC manufacturers standardizing on gbXML include Trane, Carrier, and York, a Johnson Controls Company. Leading architectural design software and engineering companies supporting gbXML include Autodesk, Graphisoft, Bentley Systems, Elite Software, Ecotect, and GeoPraxis.

While Trane has supported gbXML for several years, the adoption of gbXML by other leading HVAC manufacturers indicates that the industry is now standardizing on gbXML.

“Trane can eliminate the need to perform time-intensive plan takeoffs of key building design information by using gbXML to input building design information from an architect’s CAD model into Trace 700,” Joe Riemer, marketing manager, Trane, told azobuild.com.

Publication date:03/03/2008