How to Fill Gap at Top of Draft Curtains for ESFR?

2/13/2024

For draft curtains in a warehouse protected by ESFR sprinklers, is there an NFPA standard directing us on the need to fill the gap that occurs between the top of the draft curtain and the underside of the roof deck?

Traditionally I have seen this gap stuffed with mineral wool. If there is an NFPA code reference, though, please share so I can make sure we're going about this correctly.

Thanks in advance.

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10 Comments

Josh

2/13/2024 08:10:17 am

Interesting you should ask. I was just looking at an application like this. For aerosols NFPA 30B 2019 7.3.3.2 says "Noncombustible draft curtains shall extend down a minimum of 0.61 m (2 ft) from the ceiling and shall be installed at the interface between ordinary and high-temperature sprinklers."

I would presume that they would include wording about the gap at the top if it was something that was important, but I never saw any of that language. This specific application is for aerosols separating OH1 and ESFR sprinklers though. In some places, the steel structure was 2' from deck and were used as draft curtains. YMMV.

Jesse

2/13/2024 08:25:02 am

I'm not familiar with anything in 13 specifically directing how (or even if) that gap is to be filled. Historically, I've seen this gap filled with NC insulation or other listed material. I've also seen some small gaps (~1") at the top of these during my tenure in loss control but never made a recommendation to fill them as I didn't have a code reference.

Glenn Berger

2/13/2024 08:52:45 am

I agree with Jesse response. Tiny gaps are typically not "filled." Be careful on the material used and ensure that it is flame resistant / fire treated or whatever the AHJ deems the requirement to be.

J Golden

2/13/2024 10:42:22 am

See NFPA 204 Chapter 7 and Annex A

Mike link

2/13/2024 06:58:09 pm

I don’t believe it’s specifically covered because common sense would dictate this space shall be filled for the proper functionality collecting heat and smoke.
As Glenn stated use none combustible material approved in writing from the AHJ.

Jay

2/14/2024 06:17:12 am

In a recent installation, we had a sheet metal subcontractor that we work with on the mechanical side of our business make inserts to fill the 10" gap between the top of structure and the roof decking. It was a bit of work but the end result was a nice, clean installation.

Dan Wilder

2/14/2024 07:30:55 am

Little late but from a previous project...

Pan decking greater than 3" deep definitely needs to be addressed to fill gaps at the roof deck. The material should be rigid enough and secured to stay in place during a fire event and carry the same characteristics of the draft curtain. Smaller penetrations that are being utilized without excessive annular space (thinking if this were to be fire stopped, would I comply with the standard annular opening to be sealed) are not so much an issue, but anything abandoned should be addressed.

The intent is to trap heat/smoke so the assembly really shouldn't look like a colander. There is no specific wording or reference for this application....draft curtain vs the more commonly and more regulated draftstop.

NFPA 92 Chapter 5 also has some wording and references back to NFPA 204.

Todd E Wyatt

2/14/2024 07:32:51 am

The application you describe is referenced in NFPA 13 - 2023 :

9.3.5.3.2
Where sprinklers are closer than 6 ft (1.8 m), cross baffles shall be provided in accordance with 10.2.5.4.2.
Enhanced Content
Where the features of the opening warrant sprinklers that are spaced at intervals of less than 6 ft (1.8 m), as described in 9.3.5.3.2, the installation of baffles between adjacent sprinklers prevents the occurrence of the cold solder effect. The use of such devices is discussed in the commentary following 10.2.5.4.2 for standard spray sprinklers.

14.2.5 Draft Curtains.
14.2.5.1
Where ESFR sprinkler systems are installed adjacent to sprinkler systems with standard-response sprinklers, a draft curtain of noncombustible construction and at least 2 ft (600 mm) in depth shall be required to separate the two areas.
14.2.5.2
A clear aisle of at least 4 ft (1.2 m) centered below the draft curtain shall be maintained for separation.

The “draft curtains” you described were either installed to serve as “cross baffles” for sprinklers installer closer than 6 ft) OR the ESFR sprinklers were installed adjacent to sprinkler systems with standard-response sprinklers.

The intent for both these conditions is to “prevent the occurrence of the cold solder effect” and not to provide a smoke-resistant barrier that would require the tops of the “draft curtains” to be filled with smoke-resistant materials.

The scoping Code (IBC-2021) only requires “draft curtains” at Escalator Openings not protected with automatic shutters … this condition is to control the passage of smoke through a Vertical Opening.

Todd E Wyatt

2/14/2024 07:33:26 am

REFERENCES
NFPA 13 - 2023
Chapter 9 Sprinkler Location Requirements
9.3 Special Situations.
9.3.5* Vertical Openings.
A.9.3.5
Where sprinklers in the normal ceiling pattern are closer than 6 ft (1.8 m) from the water curtain, it might be preferable to locate the water curtain sprinklers in recessed baffle pockets.

9.3.5.1* General.
Unless the requirements of 9.3.5.4 are met, where moving stairways, staircases, or similar floor openings are unenclosed and where sprinkler protection is serving as the alternative to enclosure of the vertical opening, the floor openings involved shall be protected by closely spaced sprinklers in combination with draft curtains in accordance with 9.3.5.2 and 9.3.5.3.
A.9.3.5.1
It is the intent of this section to require closely spaced sprinklers and draft curtains to openings where protection or enclosure is required by building and life safety codes.

ENHANCED CONTENT
Closely spaced sprinklers and draft stops are required around a vertical opening only if the local building code or NFPA 101, Life Safety Code, would otherwise require that it be protected by a barrier. As a general rule, vertical openings in buildings are required to be separated from the rest of the building by rated barriers in order to protect against the vertical spread of the products of combustion. However, not all vertical openings require such protection. Large open spaces, such as atria, as described in 9.3.5.1, are intended to be uncompartmented and, for aesthetic purposes, not separated from the rest of the building. The sheer volume of these types of spaces creates a level of safety from the accumulation of the products of combustion. Because of this characteristic, there is no additional benefit to installing draft stops and closely spaced sprinklers in such spaces.

Smaller vertical openings might be referred to in the local building code or NFPA 101 as “communicating spaces” or “convenience openings.” Such spaces are not required to have a barrier around the opening perimeter. (See NFPA 101, Section 8.6, Vertical Openings, for more details.) An example of a communicating space is shown in Exhibit 9.11. Because a communicating space is permitted to be unenclosed by NFPA 5000, Building Construction and Safety Code, or by NFPA 101, 9.3.5.1 does not require draft stops and closely spaced sprinklers.

Escalator openings in department stores (see Exhibit 9.12) are examples of vertical openings that would not be considered a convenience opening or a communicating space. As a result, they would be required by NFPA 5000 or by NFPA 101 to be enclosed to protect against vertical fire spread, or to be protected in accordance with one of the alternatives listed. One alternative permitted is the use of draft stops and closely spaced sprinklers as established in 9.3.5.2 and 9.3.5.3.

9.3.5.2 Draft Curtains.
Draft curtains shall meet all of the following criteria:
1. The draft curtains shall be located immediately adjacent to the opening.
2. The draft curtains shall be at least 18 in. (450 mm) deep.
3. The draft curtains shall be of noncombustible or limited-combustible material that will stay in place before and during sprinkler operation.

9.3.5.3 Sprinklers.
9.3.5.3.1
Sprinklers shall be spaced not more than 6 ft (1.8 m) apart and placed 6 in. to 12 in. (150 mm to 300 mm) from the draft curtain on the side away from the opening.

9.3.5.3.2
Where sprinklers are closer than 6 ft (1.8 m), cross baffles shall be provided in accordance with 10.2.5.4.2.

Where the features of the opening warrant sprinklers that are spaced at intervals of less than 6 ft (1.8 m), as described in 9.3.5.3.2, the installation of baffles between adjacent sprinklers prevents the occurrence of the cold solder effect. The use of such devices is discussed in the commentary following 10.2.5.4.2 for standard spray sprinklers.

Sprinklers used to achieve the protection outlined in 9.3.5 can be of the open type or the automatic type. Privately conducted tests using closed sprinklers have indicated their effectiveness. The use of deluge-type water curtains has become quite rare since the early 1960s. Accidental discharge of deluge-type water curtains results in considerable water damage, as well as potential injury to persons on escalators.

ENHANCED CONTENT
Where the features of the opening warrant sprinklers that are spaced at intervals of less than 6 ft (1.8 m), as described in 9.3.5.3.2, the installation of baffles between adjacent sprinklers prevents the occurrence of the cold solder effect. The use of such devices is discussed in the commentary following 10.2.5.4.2 for standard spray sprinklers.

Sprinklers used to achieve the protection outlined in 9.3.5 can be of the open type or the automatic type. Privately conducted tests using closed sprinklers have indicated their effectiveness. The use of deluge-type water curtains has become quite rare since the early 1960s. Accidental discharge of deluge-type water c

Todd E Wyatt

2/14/2024 07:34:48 am

Sprinklers used to achieve the protection outlined in 9.3.5 can be of the open type or the automatic type. Privately conducted tests using closed sprinklers have indicated their effectiveness. The use of deluge-type water curtains has become quite rare since the early 1960s. Accidental discharge of deluge-type water curtains results in considerable water damage, as well as potential injury to persons on escalators.

9.3.5.4 Large Openings.
Closely spaced sprinklers and draft curtains are not required around large openings such as those found in shopping malls, atrium buildings, and similar structures where all adjoining levels and spaces are protected by automatic sprinklers in accordance with this standard and where the openings have all horizontal dimensions between opposite edges of 20 ft (6.1 m) or greater and an area of 1000 ft2 (93 m2) or greater.

14.2 Early Suppression Fast-Response Sprinklers.
14.2.5 Draft Curtains.
14.2.5.1
Where ESFR sprinkler systems are installed adjacent to sprinkler systems with standard-response sprinklers, a draft curtain of noncombustible construction and at least 2 ft (600 mm) in depth shall be required to separate the two areas.
14.2.5.2
A clear aisle of at least 4 ft (1.2 m) centered below the draft curtain shall be maintained for separation.

IBC-2021
Section 712 Vertical Openings
712.1 General
712.1.3 Escalator Openings
Where a building is equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, vertical openings for escalators shall be permitted where protected in accordance with Section 712.1.3.1 or 712.1.3.2.
712.1.3.1 Opening Size
Protection by a draft curtain and closely spaced sprinklers in accordance with NFPA 13 shall be permitted where the area of the vertical opening between stories does not exceed twice the horizontal projected area of the escalator. In other than Groups B and M, this application is limited to openings that do not connect more than four stories.
712.1.3.2 Automatic Shutters
Protection of the vertical opening by approved shutters at every penetrated floor shall be permitted in accordance with this section. The shutters shall be of noncombustible construction and have a fire-resistance rating of not less than 1.5 hours. The shutter shall be so constructed as to close immediately upon the actuation of a smoke detector installed in accordance with Section 907.3.1 and shall completely shut off the well opening. Escalators shall cease operation when the shutter begins to close. The shutter shall operate at a speed of not more than 30 feet per minute (152.4 mm/s) and shall be equipped with a sensitive leading edge to arrest its progress where in contact with any obstacle, and to continue its progress on release therefrom.

How to Fill Gap at Top of Draft Curtains for ESFR?

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