You might have heard this phrase, or more appropriately ‘design approach,’ tossed around at some point during a conference call or possibly your last meeting with the authority having jurisdiction (AHJ). Maybe you nodded your head blindly in agreement and told yourself you’d research it later. Well here we are, months later and 3 different definitions deep with no greater understanding of what exactly performance-based design is, how it applies to fire protection, or what the process even looks like. We have a couple of ways to demonstrate a compliant design in the construction industry, 1) based on prescriptive codes and requirements, and 2) through a performance-based approach. Let’s take a look at each.
The prescriptive approach requires strict compliance with established criteria for each individual system, material or component within the building. This often creates a “check the box”-type approach to compliance. A good example of a prescriptive requirement are the fire-resistance rating requirements for building elements. Fire-resistance rating is the period of time a building element, component, or assembly maintains the ability to confine a fire, continues to perform a given structural function, or both, as determined by the tests or the methods based on tests, prescribed in the building code. Table 601 of the 2018 edition of the International Building Code (IBC) defines the required fire-resistance rating of each building element based on the construction type of the building. The type of construction in conjunction with occupancy classification and whether the building is sprinkler protected, primarily dictates the maximum allowable building height and area.
You can see the straightforward “if this, then that” logic. It is a “no-thought, commonly accepted, low risk” approach. As a result, implementation and enforcement is significantly simplified! However, flexibility is limited, and creativity stifled. Typically, prescriptive requirements are initially developed based on the results of some sort of testing or study, well-established practice or expert opinion. However, we find they are all too often reactively molded by tragedy or agenda.
Perhaps Gibson from the International Council for Research and Innovation in Building Construction (CIB) stated it best back in 1982: “first and foremost, the performance approach is the practice of thinking and working in terms of ends rather than means. It is concerned with what a building or building product is required to do, and not with prescribing how it is to be constructed.”
Performance-based design approaches consider the ultimate goal and establish objectives and performance criteria that would result in achieving that ultimate goal. A goal could be as simple as ensuring reasonably safe occupant egress during a fire scenario or limiting the damage and minimizing operational impact in the case of a fire. These goals must be agreed upon by all project stakeholders including the AHJ, owner, design team, end user, insurance company, etc. Once goals and objectives have been established, they are achieved by means and methods which are specific and unique to the building as determined through an engineering analysis. Commonly, a combination of a hazard/risk analysis and computational fire and egress modeling techniques are used as tools in demonstrating compliance. Some of the challenges associated with this approach might seem obvious: AHJ support and acceptance, commissioning of integrated systems, and maintaining design integrity over the life of the building.
Prescriptive codes, given the typical revision and adoption cycles, cannot keep up with today’s rapidly developing, emerging technologies and society’s demand for complex, dynamic and interconnected buildings and systems. Nor can we afford to wait for another tragedy to highlight its shortcomings. The one-size-fits-all approach that has become the status quo often results in generalized blanket requirements which opt for simplicity and redundancy over unique specialized solutions that reduce construction costs and provide a better product.
And the good news? We have performance-based options within our currently adopted codes! The International Code Council (ICC) Performance Code is adopted in some states and the National Fire Protection Association (NFPA) 1 Fire Code contains a chapter dedicated to performance-based design. In addition, the International Building Code provides a gateway to the utilization of performance-based design in Section 104, where it outlines alternative materials, design and methods of construction and equipment. The verbiage provided therein is that “the provisions of [the IBC] are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved.”
Keep an eye out for some of our upcoming blog posts including: History of Performance-Based Design, Why More Countries are Moving Towards Performance-Based Building Regulatory Systems, and Five (5) Misconceptions About Fire Modeling.