At facility design or renovation project meetings, a relatively new concept is coming up during discussions about fire safety: performance-based design. Performance-based design is becoming more common as facilities incorporate unique features to achieve aesthetic, cost, and functional goals while maintaining safety levels for building occupants and emergency responders. Design teams are finding that performance-based design provides the flexibility to maintain safety while using a progressive design that might otherwise have been restricted by stringent enforcement of building code requirements.
As performance-based designs become more common, however, they present a special challenge to facility executives: maintaining fire protection features during future operations, maintenance, or renovation work.
The easiest way to understand the concept of performance-based design is to start with the traditional prescriptive-based design. Building codes have typically prescribed specific design criteria, such as the number of exits or the number of feet to an exit; these are numeric criteria that can be easily measured.
By contrast, a performance-based code allows the use of any design that demonstrates compliance with the fire safety goals of the code. Those fire safety goals are explicitly spelled out in the code, as are methods that can be used to demonstrate compliance. A performance-based design starts with an analysis of fire scenarios to determine which design alternatives will meet those fire safety goals.
Performance-based provisions can be found in a variety of codes and standards, including:
- International Fire Code (IFC)
- National Fire Protection Association (NFPA) 1, Uniform Fire Code
- NFPA 101, Life Safety Code
- NFPA 5000, Building and Construction Code
Performance-based provisions have been allowed for some time but are now recognized specifically in code text. Previously, performance-based approaches were typically referred to as either “Alternate Means and Methods” or “Equivalencies.”
The building codes and the Life Safety Code have similar egress requirements and provide examples of prescriptive requirements. Some common means of egress limitations include:
- A 300-foot maximum travel distance in a fully sprinklered office building, per NFPA 101.
- Two required exits from an assembly occupancy with an occupant load of greater than 50 people, per the International Building Code (IBC).
- Three required exits for a floor area with an occupant load greater than 500 people, per NFPA 1.
The prescriptive requirements are set numbers that may not account for the variability encountered nowadays in construction methods and features. The prescriptive requirements of NFPA 101, for example, simply state that a travel distance of 299 feet, 11 inches in an office building is acceptable, but 300 feet, 1 inch is not.
Similarly, under the IBC, only one exit is needed in a conference room with an occupant load of 49, whereas when an extra person is added to the occupant load, two exits are required. The same line is drawn between 500 and 501 people in a floor exit scenario in NFPA 1. Prescriptive code requirements are meant to encompass the majority of occupancies and building situations, drawing upon past loss history and standard construction methods.
The intent of the Code
In comparison, performance-based requirements delve into the main purposes of the numerical prescriptive requirements to determine the intent of the code. The same requirements from a performance-based perspective might look something like this:
- Provide a maximum travel distance over which safe conditions for egress — technically known as tenability — can be maintained for building occupants throughout the egress period. (Tenability is most commonly defined as parameters that indicate the ability to build occupants to escape from a building during a fire. Examples of these parameters can include visibility, carbon monoxide levels, and temperature.)
- Provide a sufficient number of exits from an area of generally high-density occupant load to allow for safe egress, where the determination has been made that only a single means of egress presents an unacceptable risk.
- Provide a sufficient number of exits from a floor area where a large number of people need more than two exits from the area in the event of an evacuation.
The performance-based approach affords the design team greater flexibility than the prescriptive code requirements. The maximum travel distance is flexible, depending on the method used to maintain tenability along with the means of egress. Tenability might be maintained for a distance significantly longer than 300 feet in a building where neither radiant heat transfer nor a descending smoke layer is an issue, such as in a building with an extremely large atrium. Other fire protection features may also be used in meeting the performance criteria for multiple exits, both from specific occupancies — such as assembly — or general floor areas. Examples include an increased number of separations, such as a demising wall between tenant spaces, or an increase in the fire