Linear Versus Iterative Design

Richard Garber and others have noted that even though there are many variations on design process, it is not a truly linear thinking exercise. While there is an order to the process, it does not necessarily follow that it begins with site design, moves to foundation and structure, then to the building envelope, and on to the interiors, although the information outputs may be presented that way. Rather, it is more likely that any of these aspects of the design are being worked on at any time, testing different concepts or ideas, receiving feedback on what works well and what doesn't, refining the concepts, or moving on to entirely different ones. That process of repeating by trial and error, hypothesize and test, design and assess, is referred to as an iterative process. The best design results often come about when a design team employs that back and forth workflow or learning from different iterations of a design. Each bit of feedback informs the overall design so that intelligent decisions can be made about how to improve, refine, alter, or abandon a particular design, at the overall level or the detail level. This is true whether geometric form is being pursued or the functional performance of the structure, building envelope, or mechanical system is being tested and assessed for the best outcomes.

Many architects are familiar with the seemingly linear process described in the various forms of owner-architect agreements for services as prepared by the American Institute of Architects (AIA) and others. These documents walk through a traditional set of milestone tasks that may begin with programming and data collection and then move to conceptual designs captured in the Schematic Design (SD) Phase. At this point, the deliverables to the client have historically included sketches and preliminary 3D drawings or perhaps some prepared models. Once a selected concept is agreed upon, it is advanced, usually on different 2D drawings during the Design Development (DD) Phase, which is sometimes also referred to as partial (50-60 percent) construction drawings. Since the ultimate deliverable is viewed as a stamped set of Construction Documents (CD), this phase is where the full details of all building components and coordination with other trades come into play. A full set of construction documents includes both drawings and specifications that provide the details of all materials and systems used in the final building design. It may also include a cost estimate and information on construction time schedules, often prepared by hand using the drawings as the basis. Meeting the deliverables and milestones of each phase is often focused on hours spent on the project and targeted dates for completion. Within those boundaries, the design and drafting work needs to take place and the results need to keep the project moving forward in order to keep the project on budget and on schedule while allowing the firm to remain profitable.

While this all sounds very logical and appropriate, it is worth noting that this phased sequence is useful for contractual arrangements between owners and clients but may not truly reflect the day-to-day process of design. The reality is that the process of analyzing and assessing different design iterations can often defy such clean, sequential design workflows. True design exploration involves creativity and freethinking, which is not always compatible with imposed constraints and time restrictions. Further, each milestone or deliverable is an opportunity for feedback from the client, consultants, or other stakeholders on the project, which means that design revisions may emerge as necessary tasks to meet the overall objectives of the project.

How can this iterative design process be reconciled with linear or sequential workflows? In traditional means of practice, it is difficult at best. Either the design effort becomes the dominant motivation and the budgeted hours are exceeded, or project management dictates, which can compromise the full potential of a building's design or its performance. Fortunately, 21st century practice now has new tools, new emerging contractual agreements, and new methods to transcend the old way of practice to move up to a more holistic, integrated process of design and, ultimately, deliverables. Much of this is possible by embracing computerized systems in ways not used before in architecture.

The Influence of Computers on Design

Those who experienced Computer Aided Design (CAD) in the architectural profession over the last three decades may have developed a limited view of a computer's capability in the design process. In part, that is because many design firms simply transferred the traditional, paper-based workflow process to CAD. The same basic hierarchy of architects, designers, and CAD drafters remained in place in many settings. Further, even though software allowed many greater possibilities, many used the computer to simply draw lines electronically and print out the results on plotters or large-scale printers. Many 3D, computer-generated drawings were similarly based on lines and colored surfaces, which were then rendered and printed electronically but still mostly in the style of creating them by hand. As such, CAD offered much more potential than was often captured although it did help many firms improve the quality and consistency of their graphics and sometimes saved time and money during the execution of design services.

BIM is not the same as CAD just as constructing a cardboard model is not the same as doing a hand drawing. BIM offers a process that is different than CAD in that it uses designer-defined information to create buildings electronically, in effect, building them first within the virtual environment of BIM, not using just lines or simple objects. Beyond that, BIM has emerged as a genuine way to centralize and integrate all aspects of not only the design process but also the delivery of services, the creation of deliverables, and even the process of construction. By allowing the computer to do what it does best, namely organize information, and freeing up the architects and designers to do what they do best, namely create, assess, analyze, and synthesize all aspects of the design, the best of human and computer capabilities come together. This is not a theoretical view of computers and design; instead, it is being successfully done around the world today by a growing number of professionals who are indeed transforming themselves and the design professions.