Sprinkler Criteria for Exterior Opening Protection?

11/18/2024

What is the design criteria for exterior openings protected by a water curtain in IBC 2021?

Section 705.8.2 (protected openings in exterior walls) says that opening protection is not required when the building is sprinklered in accordance with NFPA 13 and when the exterior openings are protected by a water curtain approved for that use.

"Water curtain" is not defined in the IBC or NFPA 13.

NFPA 13 (2019 edition) gives design approach requirements for water curtains in Section 19.4.3, but none apply to protecting openings in exterior walls.

What is the intention of the IBC here? Window sprinklers? Exposure protection sprinklers?

Is there a different NFPA standard that covers the design of this water curtain?

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7 Comments

Pete H

11/18/2024 06:57:58 am

Best guess:

From NFPA 13 2016 Edition:

11.3.3.1 directs the water curtain such as described in 8.15.4 or 8.15.17.2.

Admittedly these are two separate types of water curtains. 8.15.4 is standard sprinklers no more than 6 feet apart (and protected by baffles when less than 6 feet apart) and placed 6 to 12 inches away from the opening. This is the method for vertical openings with draft stops.

8.15.17.2 is for stages requiring proscenium opening protection. A deluge system that shall be provided with open sprinklers not more than 3 ft away from the stage side of the proscenium arch and spaced up to a maximum of 6 ft on center.

---

My take: Bring it up to your AHJ as you are in a grey area. But place some sprinklers (wet if you only have wet systems and the exterior projection is heated, deluge if you already have other deluge systems on the job or if deluge makes sense in application) no more than 6 feet apart (and with baffles between them when less than 6 feet apart), within 6-12" of the opening to the exterior projection, calculate them as per 11.3.3.1, and move forward.

Or just be prepared to provide opening protection so that section of IBC wouldn't apply.

As always, I can be wrong.

Dan Wilder

11/18/2024 07:23:20 am

I think you'll need to jump into 8.7.9 (13-19') for exposure protection in addition to NFPA 80A to figure out classification/severity, separation distances and the appropriate adjustments for design.

Brett

11/18/2024 08:52:16 am

This was my first thought, but that exposure protection section is about more than just protecting openings. It's about protecting the entire wall and the openings. That's where I got hung up.

Todd E Wyatt

11/18/2024 08:39:38 am

See a prior discussion : https://www.meyerfire.com/daily/use-fire-rated-construction-in-lieu-of-sprinklers?utm_source=MeyerFire&utm_campaign=db4de460ee-MeyerFire+PE+Problem+Campaign&utm_medium=email&utm_term=0_7ca6b7b006-db4de460ee-471968684&mc_cid=db4de460ee&mc_eid=eaca5d8309

Per IBC-2021, “water curtains” are permitted to be substituted for fire-resistance rated (FRR) opening protectives in buildings protected throughout by an automated sprinkler system (ASPS) by the scoping Code (e.g. IBC-2021 705.8.2) if approved by the AHJ (e.g. Building Official).

Opening Protectives (OP) are (typically) required based on the Fire Separation Distance (FSD) between the Exterior Walls (EW) and adjacent building(s) and/or the property line(s). Other than the exception for Opening Protectives per 705.8.2, the 1-Hr Fire Barrier (1FB) protection of atrium (window) walls can be downgraded to a 1-Hr Smoke Barrier (1SB) if IBC-2021 404.6 (3) Exceptions are met. ASPS providers have tried to use this atrium ASPS exception as a substitution for other FRR assemblies. Only the AHJ can approve of these “alternative designs.”

“Water curtain” is referenced in IBC-2021 410.2.5 Proscenium Curtain but does not provide prescriptive requirements. IBC-2021 404.6 Enclosure of Atriums Exception 1 includes a description ( See REFERENCES below) but does not include the term “water curtain.”

Todd E Wyatt

11/18/2024 08:41:53 am

REFERENCES
IBC-2021
Chapter 4 Special Detailed Requirements Based on Occupancy and Use

Section 410 Stages, Platforms and Technical Production Areas
410.2 Stages
410.2.5 Proscenium Curtain
Where a proscenium wall is required to have a fire-resistance rating, the stage opening shall be provided with a fire curtain complying with NFPA 80, horizontal sliding doors complying with Section 716 having a fire protection rating of not less than 1 hour, or an approved WATER CURTAIN complying with Section 903.3.1.1 or, in facilities not utilizing the provisions of smoke-protected assembly seating in accordance with Section 1030.6.2, a smoke control system complying with Section 909 or natural ventilation designed to maintain the smoke level not less than 6 feet (1829 mm) above the floor of the means of egress.

Section 404 Atriums
404.6 Enclosure of Atriums
Assembly
Atrium spaces shall be separated from adjacent spaces by a 1-hour fire barrier constructed in accordance with Section 707 or a horizontal assembly constructed in accordance with Section 711, or both.
Exceptions:
A fire barrier is not required where a glass wall forming a smoke partition is provided. The glass wall shall comply with all of the following:
1. Automatic sprinklers are provided along both sides of the separation wall and doors, or on the room side only if there is not a walkway on the atrium side. The sprinklers shall be located between 4 inches and 12 inches (102 mm and 305 mm) away from the glass and at intervals along the glass not greater than 6 feet (1829 mm). The sprinkler system shall be designed so that the entire surface of the glass is wet upon activation of the sprinkler system without obstruction;

Glenn Berger

11/18/2024 08:50:30 am

In addition to the comments stated above, additional guidance can be found in NFPA 15 Section 7.4.

Brett

11/18/2024 10:01:31 am

Are there any building code or fire code references that point to NFPA 15 in this case?

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Sprinkler Criteria for Exterior Opening Protection?

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