Performance-Based Design (PBD) has become more common as buildings have increased in complexity. Examples of projects where performance-based design is common include stadiums, casinos with shops, restaurants, performance spaces, etc. This article defines PBD, provides a few examples, discusses the challenges associated with PBD, and solicits feedback on projects where PBD helped reach the design team’s goals.
In a simplified definition, PBD steps away from the prescriptive rules (e.g., the International Building Code, IBC) as key stakeholders (e.g., owners, architects, Authorities Having Jurisdiction, etc.) involved in a project establish design goals (e.g., life safety), and uses those goals to arrive at a performance-driven solution. The Life Safety Code, NFPA 101, devotes a full chapter to performance-based design as an option for design teams, and the Society of Fire Protection Engineers, SFPE, has also published the “SFPE Engineering Guide to Performance-Based Fire Protection.” Both outline the process by which a design team would go through to develop a performance driven solution, whether for an entire building or a specific code requirement (e.g., minimum number of required exits). The process includes concepts like defining goals, establishing measurable performance criteria to compare to the outcomes, developing design fire scenarios, evaluating the design with iterations as needed, and documenting the design.
The following provides examples to contrast the differences between prescriptive and performance driven requirements. An example of a prescriptive requirement is stair riser height and stair tread depth. The 2012 IBC requires a minimum tread depth of 11 inches, a tread height of 7 inches maximum, and 4 inches minimum for new construction. Whereas, an example of PBD is designing a smoke control system for an atrium as outlined in the IBC. While there are some general principles prescribed in the IBC, the design team is required to employ PBD due to the unique nature of these spaces. Unlike stairs, there is no one-size-fits-all solution for atrium designs.
From the examples, it’s clear that PBD offers a creative, alternative approach to following prescriptive code requirements. Why don’t more design teams employ PBD? The answer is simple: designing complex buildings requires complex processes and solutions. While PBD may be the right choice for buildings that are not clearly identified in the prescriptive building codes, it requires the stakeholders’ active involvement throughout the design phase to creatively develop new ways to approach challenging problems. It requires more interaction and feedback as the process is iterative testing and retesting of hypotheses to confirm the goals will be met. It may also require utilizing the latest computer modeling and programs to calculate and predict things like temperatures in a building, visibility, time to steel failure, etc. As a result, it requires input from various published engineering handbooks, journal articles, or other recognized engineering principles not typically utilized in prescriptive codes or standards.
As buildings grow in complexity, PBD is changing the way owners can design their buildings. PBD offers design flexibility and the opportunity to rethink how buildings are and can be constructed. The next time the prescriptive requirements do not seemingly allow or permit a certain design, PBD is an option to consider, especially for unique, complex buildings.
How have you used PBD to solve a problem? Leave a comment below. We would enjoy hearing feedback on how PBD has helped to solve challenging design problems.