Back in their 1981 editions, two (BOCA and UBC) of the three legacy building codes (BOCA, UBC and SBC), began requiring sprinklers in new high-rise office and residential buildings. By comparison, the NFPA 101 (Life Safety Code) began requiring sprinklers in new high-rise office buildings in its 1976 edition, and in residential high-rises in its 1991 editions. With the combination of the three legacy building codes into the 2000 edition of the International Building Code (IBC), most new buildings classified as a “high-rise building” were required to be sprinklered. The exceptions were very few and included areas like open parking garages and airport traffic control towers.
These national model codes have almost uniformly classified a high-rise building as a building having occupied floors located more than 75 feet above the lowest level of fire department vehicle access. The codes required sprinklering of these new high-rise buildings because of the numerous benefits sprinklering provides such buildings.
This article will explore a few of the major advantages to the mandatory sprinkler requirement for a high-rise building when it is built under the IBC, which is the predominant building code used throughout the United States. When the plumbing engineer understands some of the advantages under the IBC for sprinklering a high-rise building, he/she will be able to be a real asset to the design team to not only provide valuable life safety/fire protection to the project, but also some major design alternatives and cost savings to the occupants and owners of the building.
Please note as you read this article that:
Code Benefits Provided by Sprinkler Protection in a High-rise BuildingReduction in Type of Construction (Section 403.3.1)
Most assembly, office and residential high-rise buildings that are more than 12 stories in height are required to be of Type IA Construction. Type IA Construction requires non-combustible building elements such as the structural frame to be three-hour fire rated, the floor construction to be two-hour fire rated and the roof construction to be one-and-a-half hour fire rated (IBC Table 601).
For high-rise buildings less than 420 feet in height, the Code will permit the construction type to be reduced to Type IB Construction. Type IB Construction still requires non-combustible building elements, but the structural frame can be reduced to two-hour fire rated, and the roof construction can be reduced to one-and-a-half hour fire rated. However, the columns supporting floors still need to remain three-hour fire rated and the floor construction would still be two-hour fire rated (Section 403.3.1(1) & its Exception).
Under Section 403.3.1(2) in high-rise buildings without factory, retail or storage occupancies, such buildings that would be required to be of Type IB Construction (IBC Table 601) would be permitted to be reduced to Type IIA Construction. This is a one-hour reduction (from a two-hour to a one-hour fire rating) for the structural frame, bearing walls and floor construction.
Finally, under Section 403.3.1(2), the maximum height and area permitted for these high-rise buildings under Table 503 (and in the Footnotes under Table 503) for the higher construction type shall be permitted for the reduced construction type.
Therefore, any reductions in the fire rating of building elements, along with any increase in height and larger floor areas, that are permitted for the reduced construction type can be a huge cost savings.
Reduction in Shaft Enclosures (Section 403.3.2)
For buildings not greater than 420 feet in height, the fire rating of vertical shafts (i.e., HVAC, electrical, plumbing, trash/linen chutes), other than exit enclosures and elevator hoistway enclosures, is permitted to be reduced to one hour where automatic sprinklers are installed within the shafts at the top and at alternate floor levels. This can also be a big cost savings in high-rise building construction.
Elimination of the Access Vestibule for Smokeproof Exit Stairway Enclosures (Sections 403.13, 909.20.5 and 1020.1.7.2 Exception)
For high-rise buildings, the exit stairways off the floors located more than 75 feet above the lowest level of fire department vehicle access are required to be smokeproof exit enclosures (IBC Section 1020.1.7). The access to the stairway in a smokeproof exit enclosure is required to be from an open exterior balcony (IBC Section 909.20.3) or a ventilated vestibule (IBC Section 909.20.4), with a width of not less than 44 inches and a length of not less than 72 inches (IBC Section 909.20.1).
Since the high-rise building is sprinklered, IBC Section 909.20.5 (“Stair pressurization alternative”) can be used to eliminate the open exterior balcony and/or the ventilated vestibule requirements. This alternative saves valuable space on each floor of the building that can be converted into rental or sellable space for the building owner through the life of the building.
Additional Perks Available for Any Sprinklered Building Under the 2006 IBCThe following benefits that were listed in my Jan. 2007 article in pme for any sprinklered building under the 2003 IBC are also still valid to use for high-rise buildings under the 2006 IBC.
Provides Increased Egress Capacity (Table 1005.1)
For all occupancies in sprinklered buildings, except High-Hazard and Hospital, the means of egress capacity for the means of egress components can be increased 50% for the stairway width and 33% for all other egress components (i.e., corridors, doors, ramps).
For example, in a non-sprinklered building, a 44-inch exit stair can serve 146 persons; in a sprinklered building, such a stair can serve 220 persons. In a non-sprinklered building, a 44-inch corridor can serve 220 persons; in a sprinklered building, such a corridor can serve 293 persons.
(Caution: Check which edition of the IBC Code is being enforced in the jurisdiction your project is being built in. Please note that, under the new 2009 edition of the IBC, this perk has been eliminated.)
Provides Increased Exit Access Travel Distance Capacity (Table 1015.1)
An increase in exit access travel distances is a major distinct advantage for sprinklered buildings over non-sprinklered buildings. The exit access travel distance is the distance from any occupied portion of a building to an exit (i.e., an enclosed stairway). Depending on the occupancy, anywhere from an additional 50 to 100 feet of exit access travel distance can be gained when the building is sprinklered.
Reduces or Eliminates Corridor Fire Rating (Table 1017.1)
For most non-sprinklered building occupancies, when an exit access corridor serves greater than 30 occupants, the corridor is required to be one-hour fire rated. If the corridor is one-hour fire rated, then all door openings into the corridor are required to be listed as 20-minute fire door assemblies (the listed door assembly includes the frame, door, hardware and door self-closer: Section 715.4.3).
Any glazed openings are required to be labeled fire-resistance rated (Section 715.2). Fire dampers (Section 716.5.4) and smoke dampers (Section 722.214.171.124) will be required in these one-hour corridor walls, unless such duct penetrations can comply with the stringent exceptions of these sections for limited size and steel duct thicknesses.
Under the International Mechanical Code (IMC), the exit access corridor cannot serve as supply, return, relief or ventilation air ducts (see Section 601.2 for requirements and limited exceptions). However, in a sprinklered building, almost all occupancies are allowed non-fire rated corridors, so no fire rated door assemblies, no listed glazed openings, and no fire and smoke dampers are needed.
Under the IMC, the use of the space between the corridor ceiling and the floor or roof structure above as a return air plenum is permitted (see Section 601.2 Exception #1 or IBC Section 1017.4 Exception #1). The cost and design flexibility benefit for sprinklers in the corridor design alone has been a major reason architects and building owners have supported the installation of sprinklers in many projects that were not required by the code to be sprinklered.
Reduces Exit Separation Distance (Section 1015.2.1, Exception #2)
In a non-sprinklered building, when two exits are required from a floor of a building, the exits are required to be placed a distance apart equal to not less than one-half of the length of the maximum overall diagonal dimension of the floor served. However, when the building is sprinklered, the distance is reduced from 1/2 of the diagonal dimension to not less than 1/3 of the diagonal dimension. This sprinkler reduction benefit is used many times over to obtain vast design flexibility on numerous projects.
Class I Standpipe in lieu of Class III Standpipe (Section 905.3.1, Exception #1)
When a floor of a building is more than 30 feet above the lowest level of fire department vehicle access, the entire building is required to have a Class III Standpipe system. A Class III system has one-and-a-half-inch hose stations to supply water for use by building occupants and two-and-a-half-inch hose connections to supply a larger volume of water for use by fire departments and those trained in handling heavy fire streams. However, when the building is sprinklered, only a Class I Standpipe system is required throughout the sprinklered building.
The Class I system only has two-and-a-half-inch hose connections to supply water for use by fire departments and those trained in handling heavy fire streams. In addition, since IBC references under Section 905.2 say that the standpipe system shall be installed in accordance with NFPA 14, in a sprinklered building a combined standpipe/sprinkler system can use the standpipe water demand to satisfy the sprinkler system water demand.
In a case where the sprinkler water demand plus the hose allowance under NFPA 13 is greater than the standpipe flow demand under NFPA 14, the larger water flow demand value is only required to be met. In a sprinklered building, the water flow demands of both the standpipe and the sprinkler systems are not required to be cumulative. This sprinkler perk can provide a potential cost savings in the size of standpipe mains and fire pumps in a high-rise building.
Elimination of Manual Fire Alarm Boxes
In a building that is required to have a manual fire alarm system, the manual fire alarm boxes are not required in a sprinklered building in the assembly, factory, and retail occupancies where the building is equipped throughout with an automatic sprinkler system and the fire alarm notification appliances (horns/strobes) will activate upon sprinkler water flow.
For hotels and multi-family occupancies, only one manual fire alarm box is required to be installed at an approved location. These exceptions are cost benefits that help eliminate false alarms and the vandalizing of fire alarm boxes. (See the following sections: in Assembly, Factory, Mercantile [retail], Hotel and Multi-Family Occupancies Section 907.2.1, Exception; Section 907.2.4, Exception; Section 907.2.7, Exception; Section 907.2.8.1, Exception #2 and Exception; and Section 907.2.9, Exception #2.)
Reduction of the Clear Width of Accessible Means of Egress for Enclosed Exit Stairways (Section 1007.3, Exception #3)
In buildings required to have accessible means of egress for persons with physical disabilities (which would be essentially any building with an elevator), enclosed exit stairways that are part of an accessible means of egress must have a clear width of 48 inches minimum between handrails, and must either incorporate an area of refuge within an enlarged floor-level landing or must be accessed from either an area of refuge or a horizontal exit. However, when the building is sprinklered, the stairway’s clear width can be reduced to 44 inches (Section 1009.1), but the area of refuge (or horizontal exit) is still required.
Please note that in the 2006 IBC, Exception #2 to the 2003 IBC Section 1007.6.2 was deleted, but in the 2006/2007 IBC Code Cycle the IBC Means of Egress Code Development Committee recommended for approval Code Proposal E25-06/07 (submitted by the U.S. General Services Administration) that again permitted the elimination of areas of refuge at exit stairways in sprinklered buildings. As for the elimination of the areas of refuge, the architect would need to check with the Code Official on his/her position on accepting a code modification to use the change in the 2007 IBC Supplement to Section 1007.3 Exception #3.
SummaryHopefully, this article has whet your appetite to learn more. For there are other numerous code benefits to sprinklering a high-rise building project, such as reduced flame spread requirements (Table 803.5), atrium design (Section 404), and greater dead-end corridor distances in business/factory occupancies (Section 1017.3 Exception #2).
Spend some quality reading time with your 2006 IBC Code and you will be able to help your clients save some money in their sprinklered high-rise projects while ensuring that the project will be a fire-safe haven for its future occupants.
Statistics on Automatic Fire SprinklersJust over two years ago, in the Jan. 2007 issue of pme, I wrote an article entitled “The Perks for Automatic Sprinklers in the 2003 IBC.” I begin that article with quotes from the abstract and executive summary of the latest study by NFPA, U.S. Experience with Sprinklers and other Fire Extinguishing Equipment (Aug. 2005). Those quotes noted the excellent performance record for sprinklered buildings as it related to fire protection and life safety. In Jan. 2009, the NFPA updated this study, and again confirmed the excellent record for automatic sprinkler protection in its noted abstract, which states:
“Automatic sprinklers are highly effective elements of total system designs for fire protection in buildings. When sprinklers cover the area of fire origin, they operate in 95% of all reported structure fires large enough to activate sprinklers. When they operate, they are effective 96% of the time, resulting in a combined performance of operating effectively in 91% of reported fires where sprinklers were present in the fire area and fire was large enough to activate sprinklers.” The entire report is available free for downloading at www.nfpa.org/assets/files//PDF/Ossprinklers.pdf.