Designing Roofs for Life Safety and Sound Isolation

Explore expert insights on how to specify sound-rated automatic smoke vents
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Code-Mandated Use of Automatic Smoke Vents

Although much of the discussion in this course up to this point has focused on the ability to provide smoke vent openings without compromising the acoustic integrity of the roof, it is important to address the bigger safety-driven reason that smoke venting is incorporated into a roof in the first place. Automatic smoke vents, sound rated or not, are life-safety products that are typically incorporated into large, one-story buildings to satisfy the several standards and building codes that require their use. Following is a brief exploration into the ways that the National Fire Protection Association (NFPA), the International Building Code (IBC), and the International Fire Code (IFC) define design objectives for and mandate the installation of smoke and heat venting systems.

NFPA 204: Standard for Smoke and Heat Venting, 2018 Edition

The standard identifies design objectives for smoke and heat venting systems and explores vent design constraints, methods of operation, and vent dimensions and spacing, as well as information on air inlets, draft curtains, mechanical smoke exhaust systems, and required inspection and maintenance. Ultimately, NFPA 204 helps designers meet selected performance objectives related to a specific building and a specific set of circumstances. These performance objectives include designing a vent system that will “slow, stop, or reverse the descent of a smoke layer produced by fire in a building by exhausting smoke to the exterior.” By controlling the smoke layer, a well-designed vent system will provide occupants with a safe path of travel to a safe area, facilitate manual firefighting, and reduce the damage to buildings and contents that results from exposure to smoke and hot gases.

The 2018 IBC requires smoke vents in factories, industrial buildings, and storage facilities that have more than 50,000 square feet of undivided area, where the upper surface of the story is a roof, but architects often install these safety devices into other types of buildings, including theaters, convention centers, and performing arts facilities.

Although NFPA 204 is technically referred to as a standard, it does not specify under which conditions venting is to be provided or required. The decision whether to provide venting in a building depends on the design objectives set by a building owner or occupant and on local building and fire code requirements.

The 2002 edition of NFPA 204 was converted from a guide to standard, and the 2018 Edition is its latest iteration. As it describes in Chapter 1, “This standard shall apply to the design of venting systems for the emergency venting of products of combustion from fires in buildings.” Provisions are included to address appropriate designs for both non-sprinklered, single-story buildings and sprinklered buildings.

2018 IBC: Section 910: Smoke and Heat Removal

While NFPA 204 guides the design of automatic venting systems where they are required, the 2018 IBC: Section 910: Smoke and Heat Removal addresses the specific types of buildings that require these automatic smoke and heat vents. Here is the specific language from the code.

910.1 General

Where required by this code, smoke and heat vents or mechanical smoke removal systems shall conform to the requirements of this section.

910.2 Where Required

Smoke and heat vents or a mechanical smoke removal system shall be installed as required by Sections 910.2.1 and 910.2.2. Exceptions include:

  1. Frozen food warehouses used solely for storage of class I or II commodities where protected by an approved automatic sprinkler system.
  2. Areas of buildings equipped with early-suppression fast-response (ESFR) sprinklers.
  3. Areas of buildings equipped with control-mode special-application sprinklers with a response time index of 50 (m-s)1/2 or less that are listed to control a fire in stored commodities with 12 or fewer sprinklers.
910.2.1 Group F-1 or S-1

Smoke and heat vents installed in accordance with Section 910.3 or a mechanical smoke-removal system installed in accordance with Section 910.4 shall be installed in buildings and portions thereof used as a Group F-1 or S-1 occupancy having more than 50,000 square feet (4645 m2) of undivided area. In occupied portions of a building equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 where the upper surface of the story is not a roof assembly, a mechanical smoke removal system in accordance with Section 910.4 shall be installed. Exception: Group S-1 aircraft repair hangars.

910.2.2 High Piled Combustible Storage

Smoke and heat removal required by Table 3206.2 of the International Fire Code (IFC) for buildings and portions thereof containing high-piled combustible storage equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, a smoke-and heat-removal system shall be installed in accordance with Section 910.3 or 910.4. In occupied portions of a building equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, where the upper surface of the story is not a roof assembly, a mechanical smoke-removal system in accordance with Section 910.4 shall be installed.

In summary, the 2018 IBC requires the installation of smoke and heat vents in factories, industrial buildings, and storage facilities that have more than 50,000 square feet of undivided area and where the upper surface of the story is a roof assembly. Table 3206.2 of the IFC (referenced in the code language above) requires smoke and heat removal in high-piled storage areas holding commodity classes I–IV that are greater than 12,000 square feet or considered nonpublic accessible and between 2,501 and 12,000 square feet in size. High-piled storage areas containing commodities deemed 'high hazard' must have a system for smoke and heat removal if the area is larger than 2,501 square feet or identified as nonpublic accessible and between 501 and 2,500 square feet. The IBC and IFC also contain provisions that state the minimum ratio of area of vents provided to the floor area and the maximum spacing of vents. The NFPA also provides guidelines on the ways that smoke vents should be incorporated into a project and the local fire authorities are generally involved in this decision.

 

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Originally published in Architectural Record
Originally published in August 2020

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