Comprehensive Building Modeling
Two-dimensional design representations are largely symbolic, presenting design intent as a set of symbols and annotations that the design and construction community has come to understand as a common language. Because 2D symbols are often not literally representative of a building component's actual size and shape, there is a possibility for misunderstanding during construction. For example, a water closet symbol does not precisely represent the actual product. During installation, such imprecision can lead to interference with other objects.
An integrated building model may be built by the design team by assembling the building object by object, system by system, in a digital environment. This not only allows the designers to visualize 3D representations at any point during design, it can also enable the design and construction teams to extract, almost instantly, much richer information than they could get from 2D drawings.
Several well known firms in Europe, Japan, and the United States have worked with consultants and manufacturers using digital building models to solve complex design and construction problems on unique portions of a building. For example, Norman Foster has worked with Bentley Systems, and Frank Gehry has worked with Dassault Systemes to build extraordinary forms.
But the technology is also useful for less experimental constructions. Using an integrated building model as a design tool can push the design team to solve systems-integration problems during design, long before the project goes into construction. The potential for cost savings by reducing "errors and omissions" is huge.
This is not to say that all integrated building model design activity is necessarily conducted in 3D. Most design activity may still occur in traditional 2D views.
The level of "intelligence" contained within a completed building model depends on the quantity and quality of data embedded in its objects. At the beginning of design, the design team is more likely to construct basic representations of the building, to study form and function with simple, generic representations of building objects such as walls, doors, and windows.
As the design progresses, such simple objects need to be replaced with more data-rich ones. Sometimes these objects are provided by the product manufacturer and include information such as model number, cost, weight, and scheduled delivery.
Reliance on manufacturers to provide intelligent objects for unique situations may help everyone, from owner to builder, understand the implications of specific design choices. This is a different challenge from drawing a graphic symbol with minimal data attached and simply postponing any problems or conflicts that might arise during construction.
By sharing the integrated model with consultants, builders, and owners, some design teams have taken advantage of this approach to realize significant gains in efficiency and error reduction in the field. Some have claimed estimates of up to 14 percent design and construction cost savings.
Realizing the Potential
Integrated building model tools are not necessarily more expensive or more complicated to use than more widely deployed CAD systems. In fact, these tools can be easier to learn in some ways than conventional CAD because they make coordinating 2D and 3D representations more intuitive. When using integrated 2D/3D design tools, architects can focus on design and the integration of building systems instead of on drafting. So why haven't they been more widely adopted?
In their early days, the leap from traditional manual drafting into a 2D/3D computer world was especially daunting. Also, the software and the computers to support them were expensive, sometimes costing $100,000 per seat in the days before the personal computer. Until the mid-1980s, when cheaper computers became available along with technical drafting software, hardware and software both represented serious investments.
Now, of course, most design professionals accept electronic tools as a means of delivering design projects. CAD systems are ubiquitous, and the industry is poised to accept the next generation of software. These will be design tools, not drafting tools.
There is still a simple directness available with single-purpose, design-oriented 2D drawing tools and 3D modeling tools that some designers may prefer for certain design phases. These tools stand in contrast to the potentially Swiss-Army-knife approach of an integrated building modeling system. But such distinctions may not last forever.
Intelligent integrated building models can give design teams instant access to relatively complex design information. Area calculations are one example of a mundane and tedious but necessary exercise that designers perform dozens of times during the course of sorting out a building program. Good building modeling tools allow the designer to derive and update area calculation results effortlessly whenever they modify the building design.
Similarly, cost information can be quickly calculated by attaching to any object the cost per length, per area, per volume, or per item. The software can count or measure the objects and insert them in a schedule, providing fast access to cost information whenever a change is made.
Decreasing the amount of time required to evaluate the effects of a design change can help designers focus more on design study, leaving the computer to perform repetitive calculations. Also under development for many years are "design agents" that perform structural, mechanical, and code analysis calculations and give the designer real-time feedback on the implications of design changes. Integrated into the comprehensive building model, such agents can be powerful design accessories.
Changing the Process
The largest obstacle to realizing the benefits of the integrated building model may lie in the complexity of changing design, documentation, and construction processes. We have learned, taught, and built industries around symbolic 2D communications. Millions of person-years of effort have been invested in developing our current systems of project documentation and delivery. All of our legal precedents are built on those methodologies.
Delivering an integrated building model instead of 2D drawings to a contractor, local building official, or client will require a major change in process and a shift in responsibility and liability. This has been a major obstacle to adoption of the integrated building model in the U.S. construction industry.
Now, however, the design and financial advantages have motivated many firms to begin the transition between old methodologies and new ones. A number of organizations (BAA, The Movement for Innovation, and the Lean Construction Institute) are forming alliances based on their use of integrated building models and other technologies.
They are challenging the very culture of the industry by having owners indemnify team members with the expectation that any remaining reservations about the feasibility of the technology will be mitigated by this shift of responsibility and liability.
These are today's pioneers; the rest will follow eventually. It has taken the industry most of a generation to make the transition from manual drafting to CAD. Some insisted that it would never happen. But it happened, just as the transition to the integrated building model will happen. Based on its potential cost and time savings, clients will demand it, and the industry will require it. Those who understand how to manage the implementation of this type of technology will have an advantage.
The comprehensive or integrated building model can help deliver on the longstanding promise that the computer can help us be more productive. More importantly, the automation of drawing coordination and building information management can give us more time to do what we like to do and what we hopefully do best — design.
Discuss this article in the Architecture Forum...
Larry Rocha is director of information technology at Wimberly Allison Tong & Goo.