Based Design Concepts for Fire and Life Safety

SUPPLEMENT 7

The Application of Performance- Based Design Concepts for Fire and Life Safety

Milosh Puchovsky, P.E. James Quiter, P.E.

Editor’s Note: This supplement provides a brief overview regarding the application of performance-based design approaches for fire and life safety. Specific examples regarding egress, occupant loading, structural fire protection, smoke management, and sprinkler protection are addressed. Milosh Puchovsky, P.E., is a principal fire protection engineer with NFPA, where he oversees NFPA’s projects on Performance-Based Codes and Fire Risk. He also serves as staff liaison to a number of technical committee projects, including those responsible for NFPA’s Building Construction and Safety Code and Life Safety Code. Milosh also oversees NFPA’s High-Rise Building Safety Advisory Committee. Jim Quiter, P.E., is a principal of Arup and the leader of Arup Consulting in the United States. He is also chair of the Safety to Life Technical Correlating Committee and a member of the NFPA 5000 Technical Correlating Committee, as well as Chair of the NFPA High- Rise Building Safety Advisory Committee. Jim is a registered professional engineer in several states.

The application of performance-based design con- Over the past several years, a more formalized cepts has been permitted by various codes and stan- approach to the equivalency concept has been devel- dards through equivalency or alternative means of oped. This approach is often referred to as perfor- protection provisions. Initially, the overall concept mance-based design. Both the Society of Fire was to allow for the use of alternative approaches or Protection Engineers (SFPE) and NFPA have devel- technologies in meeting the intent of the code. As oped guidance documents in this regard.1,2 As noted such, equivalency concepts were pursued where the in Chapters 4 and 5 of the Life Safety Code, perfor- code did not specifically address a given situation, or mance-based design is now specifically addressed where priority was given to a design concept that and permitted by NFPA 101 as well as NFPA 5000, called for a building arrangement or feature that was Building Construction and Safety Code.3 not in strict compliance with the prescriptive provi- The application of performance-based design for sions of the code. While the equivalency approach fire safety should include a risk analysis to identify has been implemented for decades, no guidance or the types of fires to be considered. This is an im- established approach existed that would aid the de- portant step, as the threat to occupants by fire needs signer or the enforcing authority in making appro- to be identified and quantified if an appropriate fire priate decisions about the equivalent means of safety solution is to be developed. Traditional build- protection. ing regulations do not identify the fire hazard against

1207 1208 Supplement 7 • The Application of Performance-Based Design Concepts for Fire and Life Safety

which the standard protects. In most cases, building floor is 795 ft (242 m) above grade. In accordance with regulations prescribe a solution to some unidentified applicable regulations, some floors of the structure or vague fire situation. could include an occupant load in excess of 500 peo- Performance-based design provides a more flexi- ple. Strict adherence to the Life Safety Code requires ble approach, allowing greater design freedom while three remote exit stairs leading from the top of the specifically addressing fire and life safety concerns of tower to the base of the building. The physical area a specific building project. When properly applied, it of the supporting structure is not large enough to provides a more informed approach so that life safety provide remotely located stairs in accordance with risks can be more carefully addressed. Performance- the Code, and the height of the building makes the based design also typically involves the use of com- use of stairs as a means of egress somewhat impracti- puter fire models or other fire engineering calculation cal. An alternative approach based on performance- methodologies, such as timed egress studies, to help based design concepts was necessary to develop a assess if the proposed fire safety solutions meet the workable egress strategy. fire safety goals under the conditions specified. Although performance-based design can be ap- Exit Program plied to any building project, it is most effective for The primary evacuation method for this building is complex and unusual structures, particularly those the use of typical exit stairs for the occupied floors, that do not fit well within the guidelines of prescrip- discharging to areas of refuge on the lowest two floors tive building regulations. Examples include conven- of the pod. In other words, from floors 3 through 10 tion centers, shopping malls, airport terminals, of the pod, three sets of exit stairs are provided, each transportation centers, and buildings with unen- enclosed in 2-hour fire-resistant construction, just as closed vertical openings, all of which pose challenges would be found in most other buildings. However, with regard to egress, spread of fire and smoke, and these stairs discharge to an area of refuge at the low- detection and suppression. Museums and historic est two levels of the pod, which is still 750 ft (230 m) structures also benefit from performance-based de- above grade. These two areas of refuge are used for sign because the designers of these buildings must no other purpose, and consist entirely of non- balance aesthetics and historic preservation with fire combustible construction. Rather than rely on me- safety concerns, and building regulations do not usu- chanical systems to maintain the areas of refuge free ally address property protection or historic preserva- of smoke in the event of a fire, the two floors are tion. For similar reasons, industrial facilities with open to the surrounding exterior environment so that hazardous or sensitive processes and contents also natural ventilation occurs. Since the two areas are benefit from performance-based design. below the occupied levels, it is unlikely that a fire in an occupied level would spread to the areas of refuge. EGRESS FROM AN OBSERVATION TOWER Additionally, all the floors including the areas of refuge are provided with sprinkler, standpipe, and In developing the fire and life safety program for a alarm systems, further reducing the likelihood of building such as an observation tower with a large downward fire spread. (Detectors are located on all population and amusement rides, numerous issues floors other than the open refuge floors.) need to be addressed. The tower rises over 900 ft (274 From the area of refuge, a single stair leads down m) above grade, with eight occupied levels and two through the shaft of the tower to grade. The primary amusement rides in the ‘‘pod’’ or upper portion of evacuation route from the area of refuge involves the the tower. At the base of the tower is a casino building. elevators. These elevators have two levels and travel Occupied floors of the pod include two levels of ob- at a speed of up to 1,800 ft/min. They can discharge servation deck, a restaurant, a meeting room level, either within the main casino or at two specially de- wedding chapels, and a bar level. The top level func- signed discharge levels at the roof of the base build- tions as an amusement level, containing a roller ing. These discharge levels are enclosed in 2-hour coaster and ‘‘space shot’’ ride. Exhibit S7.1 illustrates fire-resistant construction from the roof to grade and level 6 of the pod, which functions primarily as a are separated from all other areas by 2-hour fire- restaurant. Exhibit S7.2 illustrates level 8 of the pod, resistant construction. which functions as the lower observation level. Ex- hibit S7.3 illustrates level 1 of the pod, which serves Special Elevator Shaft Protection as one of two refuge areas. The most obvious concern is providing for emer- To increase the reliability of the elevators and the gency egress, considering that the lowest occupied safety of the elevator car occupants, special protection

2006 Life Safety Code Handbook Egress from an Observation Tower 1209

Exhibit S7.1 Observation tower, pod level 6.

has been provided. The tower design was undertaken 3. Elevator lobbies are on a separate smoke control during the same time period in which the National zone to maintain pressurization with relation to Institute of Standards and Technology (NIST) was adjacent spaces. Therefore, smoke in an adjoining initiating studies on the use of elevators for building area will not spread into an elevator lobby. evacuation. Many of the recommendations developed 4. Openings into the elevators are slightly raised by NIST have been incorporated as design concepts from the remainder of the floor, preventing water for the tower. The concepts include the following: flow on a floor level from spilling into the elevator hoistway. 1. Elevators open into 2-hour fire-resistance-rated el- 5. Because the areas of refuge are at the two lowest evator lobbies on all floors, at both the top and the floor levels of the pod, the elevators will not need bottom of the building. to travel past a fire floor. Elevators will travel only 2. There are four elevators that travel through the between the areas of refuge and the base building. shaft from the base to the top. Two independent Areas of refuge for disabled persons are provided elevator machine rooms serve these elevators. The within the enclosed pressurized stairwells at each elevator machine rooms are separated by 2-hour level. fire-resistant construction and have a 4-in. curb 6. Elevator shafts are vented to the outside at the installed between them so that water flow in one top, and the vents are separate from the machine machine room will not affect the other. rooms. In addition, the machine rooms form sepa-

Life Safety Code Handbook 2006 1210 Supplement 7 • The Application of Performance-Based Design Concepts for Fire and Life Safety

Exhibit S7.2 Observation tower, pod level 8.

rate smoke control zones, and air-conditioning for pressurized. Each of these stairs has areas of evacua- the machine rooms is on emergency power. tion assistance, with communication capability to the 7. All four elevators are on emergency power. The central control room. emergency power riser is in a separate dedicated 2-hour shaft. Occupant Load Determination 8. Only three of the elevators are assumed to be available for evacuation purposes. The fourth elevator With a building of this type, it is important to under- is dedicated for use by the fire department. stand and control the occupant load. Three methods were used to determine occupant load. Once the Stairs three calculations were performed, the lowest occupant load calculated was used as the limiting factor In addition to the elevator evacuation, a single stair for the building. leads down through the tower and discharges to grade. The stair enclosure is pressurized and remains Areas of Refuge. Building codes and the Life Safety independent of the base building. Enlarged stair Code typically allow holding areas or areas of refuge landings at predetermined levels allow occupants to for horizontal exits. Where those holding areas are stop and rest as they descend through the building. used, the codes require a minimum of 3 ft2 (0.28 m2) In addition, the three stairs in the pod of the building per person. Therefore, one of the limiting factors for are enclosed in 2-hour fire-resistant construction and this building was the size of the areas of refuge. De-

2006 Life Safety Code Handbook Egress from an Observation Tower 1211

Exhibit S7.3 Observation tower, pod level 1.

termining their maximum holding capacity provides of the entire building is limited by the size of the a factor of safety for several reasons, as follows: area of refuge.

1. The area of stairs leading to the areas of refuge Code Calculations. The second means of determin- was not included in the holding area. These stairs ing the occupant load of the building was based on would significantly increase the number of people code calculations. The expected occupant load, based that could be safely accommodated within an area on the applicable building code, was calculated for separated from the fire by 2-hour construction. each floor of the building. The load was then totaled 2. The calculations assume that no occupants are for the entire building, and this occupant load was leaving the building via elevator or stair. Instead, used as a limiting factor for the number of people in they assume that all occupants are contained the building. within the areas of refuge. 3. The evacuation scenario is to evacuate the floor of Evacuation Capacity. The third determining factor origin, the floor above, and the floor below. There- was the capacity of the elevators to evacuate occu- fore, only a portion of the building would be simul- pants. The speed of evacuation was based on calcula- taneously evacuated. However, the occupant load tion methods for elevator evacuation contained in

Life Safety Code Handbook 2006 1212 Supplement 7 • The Application of Performance-Based Design Concepts for Fire and Life Safety

NIST studies. For this project, it was concluded that system, with alarm verification to reduce the number a 1-hour time frame was reasonable to fully evacuate of unwanted alarms. Manual fire alarm boxes are also the areas of refuge. This 1-hour time frame was based provided in the facility. To reduce unwanted alarms, on three of the four elevators being used for evacua- the boxes have been placed within the stairways. tion, with the fourth dedicated solely to fire depart- The alarms report to the main central control ment use. The 1-hour calculation also ignores the room for the casino, as well as to two auxiliary control availability of the stair leading down through the rooms. One of the auxiliary control rooms is located shaft. Therefore, by this calculation, all occupants are at the base of the tower; the second is located within expected to leave via the three elevators. It should the area of refuge at elevation 750 ft (230 m). The be noted that operational considerations require the control room within the area of refuge is accessed occupant load to be further limited if one of the eleva- directly from the fire fighters’ elevator. Communica- tors is out of service for repair. tion and information flow from the three control Once these three methods of calculation were rooms is identical. completed, an occupant load of approximately 2600 The fire alarm system is a Class A system, with people was developed as the expected load of the separate risers running up through the shaft. The building. This was the load factor around which the risers are separated by 2-hour fire-resistant construc- remainder of the building was designed. To ensure tion. that this load factor is not exceeded, the building Emergency power is sized to accommodate all owner has instituted an occupant counting system portions of the fire protection system, including the that keeps track of the number of people entering fire pumps, fire alarm system, all elevators, smoke and leaving the tower. Therefore, the load of the control, and necessary lighting. The emergency power building will not exceed the calculated occupant load. riser is routed through a separate 2-hour shaft up A key aspect of the egress program is crowd man- through the tower, in order to prevent a single event agement during an incident. The tower staff have been from impacting the primary and emergency power. trained to direct people to the nearest stair and areas The building is provided with an automatic of refuge. Other staff have been trained to respond im- smoke control system. Upon actuation of an alarm, mediately to the area of refuge and to direct people the floor of origin and any floors open to it go to to either the stair or the elevator queue. Railings are full exhaust while adjoining floors are pressurized. provided to help establish queues at the elevators. In addition, the elevator lobbies for all floors are pres- Signage and floor path markings are also evident to surized, as is the stair leading down through the shaft help guide people arriving in the refuge area. of the tower. Exhaust from the smoke control system is ducted to discharge above the ride level at the top Other Features of the tower, in order to eliminate reintroduction of The evacuation system was not designed as a stand- smoke into the building. alone system. The fire protection features for the proj- The observation tower required a fire protection ect were specifically designed to rapidly detect and approach that departs from the typical building code control a fire, to control smoke generated by likely approach to a building. Use of stairs as the sole evacu- fires, and to ensure that a backup electric power sys- ation method was not feasible or reasonable. Requir- tem was available. ing all of the occupants to utilize stairs would result The building is completely protected with auto- in an unsafe condition for many of the expected occu- matic sprinklers. Sprinkler densities exceed those re- pants of this building. A more reasonable method quired by the codes. The sprinkler system was was to provide an area where people could be staged calculated to provide a very high density for the first until evacuated and a reliable means to perform that four sprinklers operating, plus ordinary hazard den- evacuation. In this example, the performance-based sity for the most remote 1500 ft2. design approach was shown to provide protection in Water supply is from two pumps at street level, accordance with the overall intent of the building which pump up to the pod. There is on-site water codes, while departing significantly from the detailed storage within the pod and two additional pumps prescribed code requirements. sized for sprinkler plus standpipe demand in the pod. With these pumps and on-site water storage, redun- SPRINKLER PLACEMENT IN AN ART dant water supply is available. GALLERY The building is fully protected with automatic smoke detectors, except that kitchens contain heat The design concept for the upper floor of an art gal- detection. The smoke detectors are on an addressable lery called for a unique roof/ceiling structure con-

2006 Life Safety Code Handbook Sprinkler Placement in an Art Gallery 1213

Section 1–1 Section 2–2 Exhibit S7.4 Plan view of ceiling arrangement.

Section A–A

15 ft–6 in. 4 ft–0 in.

38 ft–1¹⁄₂ in.

3 ft–10 in.

sisting of a grid of approximately 800 skylight pockets. Section A-A NFPA 13, Standard for the Installation of Sprinkler Sys- tems,4 does not address the ceiling arrangement, and a fire engineering analysis was necessary to address the relevant fire safety concerns and develop appro- 3 ft –10 in. priate sprinkler positioning and spacing criteria. The ceiling/roof structure consisted of a grid of circular skylight pockets extending approximately 60 17 ft 9¹⁄₂ in. in. (1500 mm) from their base to their peak. The open- ing to the skylight pocket was approximately 42 in. (1070 mm) in diameter. The separation between adjacent skylight pockets was approximately 14 in. (360 ¹⁄₂ mm), with the supporting members approximately 38 ft – 1 in. 48 in. (1200 mm) apart. The ceiling height (to the base Exhibit S7.5 Section view of ceiling/roof arrangement. of the skylight pockets) was approximately 216 in. (5490 mm) from the floor below. A rendering of a section of the ceiling/roof arrangement is shown in Exhibits S7.4 and S7.5. Locating sprinklers in the supporting grid at the Because of the depth, area, and arrangement of base of the pockets appeared to offer the best option. the skylight pockets, the specific rules of NFPA 13 However, because of the depth of the pockets, the concerning sprinkler positioning were not directly sprinklers would be positioned more than the dis- applicable and did not adequately address the rele- tance permitted by NFPA 13 from the top of the sky- vant fire and life safety concerns. light pocket. In this case, proper sprinkler spacing Locating sprinklers in each pocket was undesir- needed to be determined. able in terms of both functionality and aesthetics. Fire engineering employing computer fire mod- Locating sprinklers in the pockets would place them els offered an effective means of analyzing how sprin- farther away from the floor where a potential fire was klers would perform under the skylights. During a expected to occur, prolonging the time to sprinkler fire, the skylight pockets, because of their depth and activation. Once activated, the sprinklers would not number, would serve as heat reservoirs and have an be able to develop their proper spray pattern if posi- impact on sprinkler activation. How much of an im- tioned in the skylight pocket; the result would be a pact would be a function of numerous factors includ- column of water discharged from each skylight ing the design fire, fire dynamics, ceiling and room pocket. Also, locating sprinklers in alternating pock- geometry, and sprinkler type, spacing, and position- ets would result in an unacceptable delay in sprinkler ing. It is important to note that NFPA 13 only provides activation unless the fire was located directly below information on how to install sprinklers; it provides a skylight with a sprinkler. no information or criteria for how soon after the start

Life Safety Code Handbook 2006 1214 Supplement 7 • The Application of Performance-Based Design Concepts for Fire and Life Safety

of a fire the sprinklers are to activate. It is understood, evaluated to determine those that would result in a however, that sprinklers need to activate during the time to sprinkler activation that was less than that early stages of fire development to be effective in established as the acceptance criteria. controlling the fire. The analysis established sprinkler activation time Computational fluid dynamics (CFD) was ap- criteria for ceiling arrangements addressed by NFPA plied to help understand the performance expected 13. Three cases (smooth, flat ceiling; ceiling channels; from an NFPA 13–specified system, to quantify the and ceiling grid) were evaluated for the types of fires associated delay caused by the skylight pockets, and expected in the gallery. The maximum sprinkler spac- to help determine appropriate sprinkler spacing and ing and maximum distance between the sprinkler positioning to achieve the intent of NFPA 13. In this deflector and ceiling were evaluated to determine regard, design fires representative of the fuel load in acceptance criteria. the gallery were quantified, and acceptable sprinkler The engineering analysis included several factors activation performance criteria were determined. that allowed a degree of conservatism to account for Sprinkler positioning and spacing appropriate to uncertainties in both the analysis and the forthcom- meet the activation criteria for the design fires were ing installation process and allowed some flexibility identified. Exhibit S7.6 illustrates one scenario mod- in potential future modification of the design concept. eled and analyzed using Fire Dynamics Simulator, a These factors included the following: CFD computer fire model developed and maintained by NIST. 1. Using ceiling heights less than that proposed for The overall approach was to establish design fires the upper gallery in the determination of accept- representative of the types of fires expected in the able criteria as allowed by NFPA 13. This created gallery space. Various ceiling/roof arrangements per- shorter sprinkler activation times. mitted by NFPA 13 were then evaluated, using CFD 2. Spacing ceiling members closer than the maxi- computer models for the specified design fires, to mum permitted by NFPA 13 in the determination determine sprinkler activation times. These activa- of acceptable criteria. This created shorter sprin- tion times were established as acceptance criteria. kler activation time. Various sprinkler spacing configurations under the 3. Establishing a design fire with higher rates of heat roof structure proposed for the upper gallery were release than those for the types of combustibles

Exhibit S7.6 CFD analysis of sprinkler activation.

2006 Life Safety Code Handbook Life Safety for a Botanical Garden Project 1215

typically expected in the gallery. This flexibility and the methods of fastening. The analysis indicated allowed for contents that might be present in the that the structural elements could withstand the re- gallery for special exhibits and functions. spective fire loads represented by the design fires for The analysis of the gallery roof structure indicated the time period associated with the code-prescribed that a sprinkler spacing arrangement could be devel- fire resistance rating. oped that would result in a sprinkler activation time To account for a degree of uncertainty and to shorter than that derived from NFPA 13. A perfor- provide for a factor of safety, it was proposed that mance-based approach was used to develop a means the spacing of the structural members supporting the of protection equivalent to that prescribed by NFPA walkways and roof structure be decreased from what 13. was initially specified, resulting in some redundancy of the structural support system. The effect of this STRUCTURAL FIRE PROTECTION FOR A arrangement was that, should a given structural STUDENT CENTER member prematurely fail, there was a reduced likelihood that the entire structure would fail. Thus, it was One of the design objectives for a university student demonstrated that the conventional fire resistance center project was to create an open and uncluttered rating of the structural elements could be achieved feel for the atrium. The intent was to use exposed through other means, and that an equivalent means slender structural steel elements to support the of protection could be provided for the anticipated glazed fac¸ade, the circulation ramps, and the roof. design fires. A timed egress study was also under- According to the applicable building regulations, taken to verify that occupants could evacuate from the structural elements in the atrium needed to have this space before the building structure suffered any a certain fire resistance rating. Conventional methods negative effects from the fire. of achieving such a rating — such as cladding or An approach based entirely on prescribed code coating the structural members with a cementitious requirements does not specifically consider building material or intumescent paint — would have been performance or occupant response under expected effective but would have diminished the desired ar- fire conditions. Building codes consider classes of chitectural effect and negatively affected overall proj- buildings generically and do not address specific fire ect functionality. hazards, unique building features, and occupant A performance-based design approach was characteristics. As a result, code-prescribed solutions developed as an equivalent means of meeting the can provide for excessive fire protection in some in- building code requirements. A code analysis was con- stances and inadequate protection in others. With a ducted, and a fire strategy outlining the approach to performance-based approach, the architects in the resolve the relevant issues was prepared. The con- university student center project were able to imple- cerns of the associated stakeholders, including the ment their design vision while adequately addressing local enforcing authorities, were identified and artic- applicable fire safety concerns. ulated, as were the design fires and criteria for determining acceptance of the alternative design. LIFE SAFETY FOR A BOTANICAL GARDEN Risk analysis principles were used to determine PROJECT the likely fire hazards expected in the atrium space. Design fires were developed to quantify the relative The design of a botanical garden project consisting size, duration, and characteristics of the fires antici- of multiple floor levels carved into the surrounding pated. At the same time, the failure criteria — in terms hillside presented unusual challenges for fire and life of fire resistance — of the structural steel members safety. The project entailed a freestanding structure proposed were also determined. It was agreed that reaching 180 ft (55 m) at its highest points and covered the alternative design would need to withstand the an overall area of 5.4 acres (21,853 m2). From the out- impact of the design fires for a minimum time period set, it was clear that a prescriptive code approach of hourly fire resistance rating specified by the build- would be of limited value for the project. ing code. The applicable building regulations classified the The performance of the structural steel members structure as an assembly occupancy, but if the project when exposed to the specified design fires was evalu- had been designed to fit the requirements of the pre- ated through the use of modeling and with the collab- scriptive code, the design team would have been oration of structural engineers. The analysis included faced with trying to make the building conform to the effect of the structural member composition, as requirements derived from safety measures intended well as the means and spacing of structural supports for theaters, arenas, and other more conventional

Life Safety Code Handbook 2006 1216 Supplement 7 • The Application of Performance-Based Design Concepts for Fire and Life Safety

public buildings. The relevance of the prescriptive the upper levels, where smoke would accumulate. requirements was clearly limited for the project — While this route would result in evacuation distances there was no ‘‘rule book’’ to follow. of up to 450 ft (137 m), these distances were demon- Early on in the design project, it was proposed strated to be acceptable due to the overall low level that fire and life safety provisions be developed of hazard and large size of the space. through performance-based design. This was dis- To verify the proposed strategy, combined smoke cussed and agreed upon with the client and the local and evacuation calculations using computer models building and fire authorities. were undertaken. Based on the design fires, this al- The fire hazards in a building like this are very lowed for a dynamic fire and smoke spread analysis different from those typically encountered in conven- of the actual geometry of the space. The timed egress tional buildings. The vegetation clearly constituted a study also considered various scenarios, such as the fire load, potentially an extremely large one, so the effect of blocked exits. potential for a forest fire-type scenario was discussed. Due to the structure’s unique geometry, conven- The team carried out a qualitative hazard analysis of tional smoke modeling software packages — which the risk — in terms of frequency and consequences assume rectangular ‘‘box-type’’ enclosures — were — of a vegetation fire in the structure, but this showed unsuitable for calculating the rate of smoke fill. Proj- such a fire to be of sufficiently low probability that ect-specific calculations were therefore developed it was an impractical design parameter. that allowed for the geometry of botanical garden The examination of fire loading, therefore, turned spaces, using a three-dimensional model of the struc- to items other than the vegetation. Throughout the ture. From the model, it was possible to accurately structure, huts are provided as information points for determine the cross-sectional plan area of the project visitors. The huts are built of timber, with thatched at various heights, and hence assess smoke filling roofs, and also have electrical power. Scenarios in- rates using design fire scenarios agreed upon with volving a fire in a hut were therefore developed as the local authorities. the basis for the fire safety design. The egress modeling showed that the project Because large visitor populations were antici- could be evacuated in 5 to 6 minutes, while the smoke pated, safe and efficient evacuation was a key concern modeling indicated that a smoke layer would not de- in developing the fire strategy. The circulation (and, scend to levels where it would impede evacuation for hence, evacuation) routes are far from conventional, 15 to 25 minutes (depending on the fire scenario). as visitors walk around the botanical gardens on The team concluded that the escape distances could winding pathways linked to exits around the perime- be safely extended and evacuation conditions would ter. Also, because the structure cuts into the hillside, be acceptable under the conservative scenarios stud- pathway elevations vary considerably. A major chal- ied. lenge was to address the scale of the building, re- Many fire safety systems conventionally associ- flected in the length of the travel routes. If travel ated with public assembly spaces were unsuitable. distance requirements of the building regulations Detection methods including optical and aspirated were to be met, escape from the upper parts of the smoke detection were found to be ineffective, due to structure would require tunnels cut through the side the potential for smoke stratification to delay detec- of the hill. Such tunnels would probably need to have tion at high levels and plants obscuring optical detec- been pressurized, as they would have been at the tion sight lines. upper levels of the project near potential smoke lay- Although the associated structures are essentially ers. Other options were needed. low fire hazard spaces, the fire safety strategy had to The fire engineers proposed that evacuation be be developed from a common-sense, first principles based on the time period necessary to egress the point of view. The recognition that there was little building rather than strictly on the distance to be relevant guidance for the project, and that adherence traveled. The approach was to demonstrate that occu- to conventional codes would result in unnecessary, pants could egress the facility prior to the onset of costly, and ineffective measures, unlocked the design untenable conditions. The majority of the exits were process. Close collaboration with the architect, en- located on the lower grades of the project, so, in the forcement officials, and other engineering disciplines event of a fire, the occupants would travel to lower- allowed each team member to fully participate in level exits rather than use exits at the top of the botan- developing the design and clearly understand the ical garden. Lower-level exits were also preferred as thought process and reasoning behind the proposed they encouraged the population to move away from strategy. The result is a simple, robust, and cost-

2006 Life Safety Code Handbook Cultural Preservation of a Historic Building 1217

effective strategy that provides a high level of fire required level of safety. In historic landmark build- safety for the botanical garden’s occupants. ings, this integrated approach typically results in im- proved building functionality and more cost-effective CULTURAL PRESERVATION OF A HISTORIC fire protection systems. BUILDING One of the major fire and life safety challenges in this courthouse building pertained to the compart- For historic structures, performance-based design mentation of building spaces. Building regulations concepts often offer the most viable and effective require compartmentation to help prevent the hori- solution for meeting both fire safety needs and cul- zontal and vertical spread of fire through the build- tural preservation goals. One such project was a des- ing. The existing building construction did not ignated landmark building consisting of cast iron and provide for the rated fire separations required by decorative masonry construction with ornate public building regulations. Many doors were of original and ceremonial spaces centered around an open heavy wood construction with decorative wood and atrium. The building was originally constructed in glass features and did not meet current fire protection the mid-1800s to operate as a courthouse. It consisted ratings. It was proposed that the atrium remain open of approximately 150,000 ft2 (14,000 m2) over several to multiple floors, existing non-rated shafts be reused floors. as mechanical shafts, and certain building areas be The proposed design concept for the courthouse open to each other through open stairways. building called for a comprehensive, government- In developing an appropriate strategy, the aim funded restoration and rehabilitation program to pre- was to assess the inherent fire protection qualities pare the building for adaptive reuse as a multifunc- of existing building features (such as substantially tional public and cultural facility with exhibition constructed walls and high ceilings), to take advan- space, offices, and a restaurant. The design concept tage of the inherent degree of fire protection, and to for the project called for the preservation of a number supplement it with certain new active systems where of areas and building features, including the open necessary. The overall approach was to identify the atrium, the ornate original wood doors, and numer- fire loads (design fires) to be considered and then ous cast iron columns. demonstrate through fire engineering that sufficient Although building code requirements are relaxed fire safety could be provided for the time period in- somewhat for specific features of historic structures, tended by the building regulations. In some cases, it imposing the applicable prescriptive requirements was determined that the prescribed fire resistance on the project would have affected the overall historic rating would be needed; for other situations, a perfor- authenticity and compromised the functionality and mance-based solution was developed. significance of the public spaces and unique architec- In general, a fire that starts in the non-public tural features. Therefore, the overall fire strategy was areas is to be controlled so that it does not develop to identify and meet the intent of the applicable and grow to a point where it could threaten occupants building regulations regarding life safety, while min- in public spaces. Therefore, it was proposed that non- imizing the aesthetic and visual impact of new con- public areas — the attic and basement, mechanical struction and maintaining the open environment and spaces, and kitchens — be separated from public original design features to the greatest degree possi- spaces by fire-rated construction. Additionally, areas ble. During the early stages of the development of the traditionally constituting a higher fire hazard, such fire strategy, it became obvious that a conventional, as electrical switch gear rooms, mechanical rooms, prescriptive code-based approach would have forced and storage areas, were also constructed to form sep- a dramatic change to the proposed design concept arate compartments. As most of these spaces were and that an alternative approach could provide for a non-public spaces, the new construction had a lim- more effective and robust level of fire and life safety. ited impact on the aesthetic features of the building. In most code-mandated prescriptive designs, the In addition to compartmentation, other fire and various fire safety features and systems are addressed life safety issues were identified and addressed independently of one another. The performance- through a performance-based approach. Issues re- based concept calls for an integrated approach of fire garding smoke management, egress, structural fire and life safety systems. Such an approach is espe- resistance, active systems, and fire-fighting facilities cially pertinent to existing and historic building proj- were addressed in a comprehensive manner. The ects because it can result in less intrusive fire and overall fire safety solution integrated existing fea- life safety systems and features while meeting the tures with new systems and construction so that the

Life Safety Code Handbook 2006 1218 Supplement 7 • The Application of Performance-Based Design Concepts for Fire and Life Safety

level of safety provided by the building code was level with the prescriptive rules that are, in essence, satisfied, while preserving the historic value of the the law. As such, code reviews and interpretations building to the extent possible. are often the first step in developing the fire safety design process. For certain projects or for specific aspects of proj- CLOSING REMARKS ects, the prescriptive code does not adequately address a given situation or would be incompatible with While considered by some a relatively new approach, the developer’s or architect’s design vision. In other performance-based design has been practiced for cases, a more cost-effective alternative would result many years through the equivalency option in many in the same level of protection as that required by codes and standards. The past several years have seen the prescriptive building code. In such cases, perfor- the development of a more formalized approach for mance-based design concepts can be used to develop practicing performance-based design, as well as the solutions that address specific issues while comple- revision of codes and standards that specifically ad- menting the requirements prescribed by traditional dress performance-based design approaches. Even building and fire codes. so, where a performance-based design is pursued, it usually involves a variance by the local building offi- REFERENCES cial or regulating body. However, the development of guidelines and definitions of applicable terms 1. The SFPE Engineering Guide to Performance-Based Fire serves to better facilitate the discussion between de- Protection Analysis and Design, Society of Fire Pro- signers and enforcers and allow for better-informed tection Engineers, Bethesda, MD, 2000. decisions. 2. Performance Based Primer for Codes and Standards This supplement has provided a brief overview Preparation, National Fire Protection Association, of the types of projects in which performance-based Quincy, MA, 2000. design has been successfully applied and accepted 3. NFPA 5000, Building Construction and Safety Code, by the authorities having jurisdiction. Even though 2006 edition, National Fire Protection Association, performance-based design is gaining more accep- Quincy, MA. tance, the prescriptive code is likely to remain the 4. NFPA 13, Standard for the Installation of Sprinkler first means of developing a fire safety strategy for a Systems, 2002 edition, National Fire Protection As- building. Enforcing authorities have a greater comfort sociation, Quincy, MA.

2006 Life Safety Code Handbook