The 2009 International Building Code includes many significant changes for the design of high-rise buildings, which are defined in the Code as buildings "with an occupied floor located more than 75 feet above the lowest level of fire department vehicle access."
In this month’s featured article, we will highlight some of these changes, the majority of which are intended to improve the life safety of occupants of high-rise buildings. Changes covered include provisions for construction, automatic sprinkler systems, emergency systems, means of egress, and elevators in high-rise buildings.
Clicking on the section hyperlinks within the article will provide you temporary online access to the referenced codes and standards at MADCAD.com eLibrary. Temporary access will expire on 11/20/2009.
Structural Integrity of Exit Enclosures and Elevator Hoistway Enclosures
Photo: Klaas Lingbeek- van Kranen
High-rise buildings and skyscrapers fill the skyline in New York City. New changes in IBC 2009 aim to improve the life safety of high-rise building occupants.
To protect the structural integrity of exit and elevator hoistway enclosures from blasts, impacts or projectiles during fire, IBC 2009 for the first time added impact-resistance requirements for wall assemblies of these enclosures. The new requirement applies to buildings that are more than 420 feet in building height and high-rise buildings of occupancy category III or IV (see Section 1604.5
for occupancy category).
According to new Section 403.2.3
, the wall assembly must have a minimum Soft Body Impact Classification Level 2, as tested according to ASTM C 1629/C 1629M.
Additionally, the face of the wall assembly that is not exposed to the interior of the enclosure -the outer face- is required to incorporate one of the following:
• A minimum of two layers of impact-resistant construction board, each with a minimum Hard Body Impact Classification Level 2
• One layer of impact-resistant construction material with a minimum Hard Body Impact Classification Level 3
• Multiple layers of any material, tested in tandem, with a minimum Hard Body Impact Classification Level 3
While concrete or masonry walls are considered to satisfy the structural integrity requirements of exit and elevator hoistway enclosures, any other wall assembly which provides impact resistance equal to the requirements of the new section for Hard Body Impact Classification Level 3 is also permitted to be used.
Sprayed Fire-resistant Materials
IBC 2009 added new minimum bond strength requirements for sprayed fire-resistant materials (SFRM) in high-rise buildings in order to reduce the risk of dislodgement during high risk fires.
According to new Section 403.2.4
, the minimum bond strength for SFRM is 430 psf in high-rise buildings up to 420 feet in height above the lowest level of fire department vehicle access, and 1,000 psf in buildings with a height greater than 420 feet.
AUTOMATIC SPRINKLER SYSTEM
Number of Sprinkler Risers and System Design
Photo: Jimmi Larsen
Redundancy of the automatic sprinkler system in high-rise buildings is increased with new requirements in IBC 2009.
To increase the redundancy of active fire protection systems, IBC 2009 added new requirements for sprinkler risers in high-rise buildings that are more than 420 feet in building height.
According to new Section 403.3.1
, each sprinkler zone is required to be supplied by a minimum of two risers. Additionally, each riser must supply sprinklers located on alternate floors, and if more than two risers supply a zone, "sprinklers on adjacent floors shall not be supplied from the same riser."
Water Supply to Required Fire Pumps
Another redundancy was added to the water supply of fire pumps in high-rise buildings.
According to new Section 403.3.2
, "required fire pumps shall be supplied by connections to a minimum of two water mains located in different streets." While separate supply piping is required between each connection to the water main and pump, each connection and supply piping must be sized to provide sufficient flow and pressure to operate the pumps.
An exception is provided for having two connections to the same water main if the main is valved and permits the interruption to be isolated so that the supply of water will continue to the required fire pump.
Emergency Responder Radio Coverage
Photo: Brandon Laufenberg
IBC 2009 now requires emergency responder radio coverage to be provided in high-rise buildings in accordance with IFC 2009.
The use of radio communications by emergency responders in high-rise buildings is generally adversely affected by the lack of signal coverage and interferences. Therefore, previously in IBC 2006, a wired two-way communication system for emergency responders use was required in high-rise buildings. The system was used for communication between a fire command center and elevators, elevator lobbies, emergency and standby power rooms, fire pump rooms, areas of refuge and inside enclosed exit stairways.
The use of two-way communication by emergency responders created issues related to safety and operational efficiency during emergencies. To address these issues, IBC 2009, Section 403.4.4
now requires emergency responder radio coverage to be provided in high-rise buildings in accordance with Section 510 of the 2009 International Fire Code (IFC 2009).
While IFC 2009, Section 510
specifies the required radio signal strength for emergency responder radio coverage, Appendix J
-which is non-mandatory unless adopted by the jurisdiction- provides technical requirements for the design of the emergency responder radio coverage system including amplification systems, signal boosters and testing requirements.
IBC 2009 added a new requirement to facilitate smoke removal in post-fire salvage and overhaul operations in high-rise buildings.
According to new Section 403.4.6
, the building must have either natural or mechanical ventilation for smoke removal. The natural ventilation must be provided by "easily identifiable, manually operable windows or panels” distributed at maximum 50-foot intervals around the perimeter of each floor with a minimum area of 40 square feet per 50 linear feet of perimeter. Exceptions include Group R-1 occupancies which have a lower venting area requirement and the use of fixed windows “provided that the glazing can be cleared by fire fighters."
The option to use mechanical ventilation for smoke removal in high-rise buildings requires air handling equipment to provide "one exhaust air change every 15 minutes for the area involved." Additionally, “return and exhaust air shall be moved directly to the outside without recirculation to other portions of the building."
As a third option, Section 403.4.6
also permits "any other approved design that will produce equivalent results" for smoke removal in high-rise buildings.
Emergency Power Loads
While IBC 2006 classified electrically powered fire pumps as standby power loads, IBC 2009, Section 403.4.8.1
moved electrically powered fire pumps under emergency power loads.
The change was made to provide correlation with referenced standards NFPA 20 Standard for the Installation of Stationary Fire Pumps for Fire Protection, 2007 and NFPA 110, Standard for Emergency and Standby Power Systems, 2005.
According to NFPA 20, Section 18.104.22.168
, on-site generator systems that are used to supply power to fire pump motors are required to meet the requirements of Level 1, Type 10, Class X of NFPA 110. And according to NFPA 110, Table 4.1(b)
, a Type 10 Emergency Power Supply System (EPSS) is required to provide a source of electrical power within 10 seconds, thereby classifying electrically powered fire pumps as emergency power loads.
MEANS OF EGRESS AND EVACUATION
Remoteness of Exit Stairway Enclosures
Photo: Tony Colter
A new remoteness requirement for exit stairway enclosures in high-rise buildings is added in IBC 2009.
IBC has long included separation requirements for exits and exit access doorways to ensure that they are not clustered together. These requirements have not changed in IBC 2009 (see Section 1015.2.1
However, while these requirements establish a minimum distance between the doors of exits and exit access doorways, they do not always guarantee sufficient remoteness between exit stairway enclosures. For example, two stairway enclosures with doors facing opposite sides that are interconnected by a rated corridor may satisfy the separation requirement in terms of travel distance but may actually be located in close proximity to each other.
To address this issue, IBC 2009 added a new remoteness requirement for exit stairway enclosures in high-rise buildings. According to Section 403.5.1
, required exit stairway enclosures must be separated "by a distance not less than 30 feet or not less than one-fourth of the length of the maximum overall diagonal dimension of the building or area to be served, whichever is less." However, unlike the separation requirements of Section 1015.2.1
, the distance must be measured in a straight line between the nearest points of the enclosures.
Additional Exit Stairway
During a fire where full evacuation of a building is required, the egress capacity may be reduced by firefighters using one of the egress stairways for ongoing firefighting operations.
To ensure sufficient egress capacity is maintained in significantly tall buildings where full evacuation takes a longer time, IBC 2009 added a new requirement to provide an additional stairway. According to Section 403.5.2
, one additional exit stairway, in addition to the minimum number of exits required by Section 1021.1
, must be provided in buildings that are more than 420 feet in building height.
Group R-2 occupancy, which is considered to have a low occupant load, is exempt from this requirement. The additional exit stairway is also not required if the building is equipped with occupant self-evacuation elevators. Additionally, any combination of the stairways -with one removed for firefighters use- must provide the minimum total width required by Section 1005.1
Luminous Egress Path Markings
IBC 2009, Section 403.5.5
added a new requirement to provide luminous egress path markings "in accordance with Section 1024
", which requires high-rise buildings in Group A, B, E, I, M and R-1 to install luminous egress path markings showing the exit path. The luminous markings must be provided in exit enclosures, including vertical exit enclosures and exit passageways
Detailed requirements and exceptions for the luminous markings are also included in Section 1024
Fire Service Access Elevator
Photo: Paul Pgiam
IBC 2009 requires at least one fire service access elevator in buildings with an occupied floor more than 120 feet above the lowest level of fire department vehicle access.
IBC 2009, Section 403.6.1
added a new requirement to provide at least one fire service access elevator in buildings with an occupied floor more than 120 feet above the lowest level of fire department vehicle access. The intention of the requirement is to provide a reasonably safe means to access a staging area near the fire for firefighting operations.
Specific requirements for the elevator, including the requirement for the elevator to open into a rated elevator lobby and have direct access to an exit enclosure through the lobby, are provided in Section 3007
Occupant Evacuation Elevators
IBC 2009, Section 403.6.2
now permits passenger elevators, installed in accordance to Section 3008
, to be used for occupant self-evacuation in high-rise buildings. Section 3008
provides specific requirements for occupant evacuation elevators including special provisions for the elevator lobby and signage.
While the use of occupant evacuation elevators is not mandated, they may be voluntarily installed to provide an additional means of egress for occupants in high-rise buildings, and to be exempt from the requirement to provide an additional exit stairway as required by Section 403.5.2