Do Window Sprinklers Need Separate Zone?

9/15/2021

I was hoping to get some feedback on whether interior Special Application Window Sprinklers would require a separate zone from the remainder of the floor fire sprinkler system?

I do not see any provisions that would require separate zoning per NFPA 13 nor the IBC. However, I can see why it would be important to zone these areas separately seeing as the intent of the window sprinklers is to maintain the integrity of the fire rated separation (as opposed to actively suppressing the fire).

Thanks in advance!

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10 Comments

Alex

9/15/2021 07:19:14 am

HI Anonymous,

To answer your question, I haven’t heard of a requirement for window sprinklers to be installed on a separate zone.

I do want to note, that when you are installing window sprinklers, you are still only designing for a single zone to operate at one time. Installing sprinklers on a separate zone does not allow for two zones to operate simultaneously (of course any heads will open when heated, but the system is not designed to produce the flow or pressure required).

An additional zone may be requested by the fire department to indicate the location of the fire via the flow switch and FACP, but that’s all I can think of.

Thanks,
Alex

(PS, take a note of NFPA 13 (2019) 9.3.15 which states that your “water supply duration for the design area that includes the window sprinklers shall not be less than the required rating of the assembly”. This is important where window sprinklers may be installed in an office where the duration is typically 30-60 minutes and the assembly may be 2-hour)

Paul G

9/15/2021 08:21:38 am

To only add personal experience to the above, when applying with a smoke control system, typically for atrium which provide an exception for sprinklers on glass in lieu of 1-hour barrier, they may need to be zoned with the atrium sprinklers or separately depending on the requirements of the Rational Analysis. The requirement stems from appropriately zoned sprinklers for activation of the smoke control systems. The engineer of record for the rational analysis or smoke control system would be able to answer this question and would not be on the sprinkler designer to determine alone.

Glenn Berger

9/15/2021 08:18:23 am

The standard answer is that a separate zone is not required. Separate zones may be required if the sprinklers are being furnished to cover fire rated openings.

James

9/15/2021 08:19:28 am

The only scenario I've ran into is when the window sprinklers were used for a stairwell/atrium separation. This separation needed window sprinklers as it was a 2-hour separation and not just 'closely-spaced-sprinklers' to meet an atrium separation.

The sprinklers on the atrium side needed to be zoned together because the waterflow switch was used to activate the smoke control system (among other things).

Jesse

9/15/2021 08:52:46 am

For window sprinklers, no. There is no specific requirement these be zoned separately.

Casey Milhorn

9/15/2021 09:17:11 am

The only thing I could/would add to the previous comments would be that separate zoning may be desirable for hydraulic purposes. I assume these sprinklers are being provided as a means to maintain rating per NFPA 13 "Sprinkler-Protected Glazing", if so the demand of the "window sprinklers" should be added to the fire sprinkler demand ONLY if adjacent to the remote design area. I would argue that you would MAKE this area possibly the remote area by adding it to the ceiling level sprinkler demand, but that's a debate for someone on the 13 committee to make I guess. So long story short, IF your "window sprinklers" are adjacent to your remote design area by chance, don't forget you will need to add the two demands together and balance. That becomes a lot easier to do if you have them zoned, or at least fed separately so you can adjust pipe sizing and help them balance easier. You don't want to beef up your entire system just because your overall design area doesn't balance correctly or is inefficient. Also, don't forget that IBC, NFPA 13, and the cut sheets should be consulted for all the appropriate requirements. More often than not (in my experience), architects/engineers attempt to use these in non-compliant situations to avoid the expensive fire rated glass. From memory, they cannot protect operable doors/windows, they cannot protect glass in a load bearing wall/assembly, no protruding horizontal mullions are allowed, unless sprinklers are located below every mullion, deflector must be located at top level of glass (not inches or feet above glass at ceiling), and plenty of other requirements to boot. The cut sheets of both availably listed heads for this use even tell you to check other applicable building codes and standards, or something along those lines. Lots of ways to misuse these heads other than the way they were listed and intended for. Be careful and remember, if you are the contractor, don't be afraid to let the design team know when these heads are being used outside of their listed/intended purpose. Sorry for the long winded message! Good luck!

Brian Cockburn

9/15/2021 09:52:46 am

Thanks for asking this. I've been wondering about it too.

Does anyone know if window sprinklers are ever allowed to be on a dry zone? I always see them on wet zones even in underground parking garages that then require the piping to be heat traced.

ken Thackery

9/15/2021 10:14:43 am

Are they listed for dry systems? Always best to consult an FPE.

Brian Cockburn

9/15/2021 10:31:36 am

The Tyco WS sprinklers are listed for wet only, or deluge in exterior applications. I was curious if there are window sprinklers listed for dry systems.

Franck

9/15/2021 03:00:16 pm

As quite often, a possible answer is : it depends

All the following is my personal opinion.

The standard (Nfpa 13) does not require a separate system, but does not prevent it as well.
There are some good comments for separate systems listed above, such as balancing the system or having a “fire barrier” that is somehow independent from the sprinkler system (as a fire door / fire wall is a passive protection, independent from the active sprinkler protection).

Then you can use common sense. If the window protection is provided to protect from an outside exposure, it may be on the same system as the sprinklers inside the building. The aim is to avoid that an external fire could activate sprinklers inside the building. I would anyway suggest to provide a valve to possibly isolate the piping to the windows sprinklers in that case : if you activate the system and open heads, you don’t need to impair your entire building protection until you change the open sprinklers.
If the aim is to provide a rated fire separation inside a building, it would be advisable to have a separate system : in case of sprinkler impairment in the building, you still have a 2h fire rating for your separation.

But this is not required by the standard. Just common sense.

Do Window Sprinklers Need Separate Zone?

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