VISION ISSUE SEVEN | WINTER 2018
Key Considerations of Stair Pressurization Design Life safety systems in high-rise buildings are extremely critical not only for building occupants, but also for the firemen and women using these systems to save lives. There are many different kinds of life safety mechanical systems that can be designed such as smoke control, post-fire smoke purge, and pressurization. Each system serves its own purpose and each is required for different scenarios in the International Building Code. This article will discuss relevant considerations when designing a stair pressurization system. Keeping It Simple The key to designing a successful stair pressurization system is to keep the design simple across all disciplines. Simple design approaches that have been proven successful are the following: (1) the provision of the required two-hour rated wall assembly around the stairwell and mechanical stair pressurization system, which eliminates the need for fire smoke dampers (FSD) for each mechanical penetration, and (2) the provision of an additional two-hour rated assembly around the mechanical shaft. This second provision
State Official measuring the amount of force required to open the door and to activate the push bar
allows for easier construction when the contractors seal the stairwell. Simplicity can also work for controlling the pressurization system and reducing the square footage of the stairwell. Having less FSDs to control, as well as a straight forward programming logic to ramp up the fan to maintain the static pressure set point, will reduce the potential for error and component failure. Additionally, by maintaining a pressurized stairwell to a minimum of .10 inches of water and a maximum of .35 inches of water, and by providing an automatic sprinkler system, we eliminate the need for a stairwell vestibule. Power The introduction of a stair pressurization system can affect several electrical systems which in turn affect architectural space programming. A stair pressurization system requires power from a standby generator through a continuous raceway. The standby equipment (switchboards, transformers, panelboards, automatic transfer switch, etc.) must be located in a dedicated onehour rated room, separate from a normal power room, and ventilated directly to and from the exterior. The exit stairwell doors must be equipped with magnetic hold opens as well as smoke detectors to initiate the fire alarm system thereby initiating the stair pressurization system. The quantity of smoke detectors can be reduced if elevator lobbies and exit stairwell doors share a common space, allowing the smoke detector to serve a dual purpose of initiating both stair pressurization and elevator recall. Through extensive coordination between the architect and engineer, the added cost of providing a stair pressurization system may be controlled and prove to be cost effective. Air Pattern The purpose of the stair pressurization ALL TEXT Š2018 KOHLER RONAN, LLC
Pressure manometer used to measure the difference in pressure inside and outside the stairwell
system is to prevent smoke from the building from infiltrating the emergency egress for the general public and life safety personnel. That being said, when the system is operational, the air throw and pressure will definitely be felt. Further, this pressure can hamper the functioning of self-close doors, require greater force to open, and cause the system to fail upon testing and inspection. Engineers and architects should ensure that the air outlet is not directly facing stairwell doors. This is especially important for the exit door at the discharge level as this door swings outward, making it more difficult to close if an air outlet is directly blowing on it. Air outlets should be spaced at every other floor for even pressure distribution, and the architect and engineer should make full use of intermediate landings for equal continued on page 4
IN THIS ISSUE Early Observations
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RevitÂŽ Corner 3 On the Boards
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