Does 2-hr Window Sprinkler Require 2-hr Supply?

12/12/2019

High-rise office building, predominantly light hazard occupancy. Water supply is designed for a 30 minute duration (roof mounted gravity water storage tanks).

We need a 1-hour separation between two tenant spaces. The architect has specified a glass partition. As such closely spaced heads are being proposed to achieve an equivalent rating.

Does the water supply now need to be upgraded to provide a 1 hour supply of water?

Similarly, if sprinklers are being used to provide an equivalency rating on a required 2-hour rated partition, does the water supply need to be able to supply 2-hours of demand?

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4 Comments

Salvatore Izzo

12/12/2019 10:18:49 am

Sprinklers used for protection of glazing must be specifically listed to provide an actual fire resistance rating. This website already has some excellent clarifying information on glazing protection:

https://www.meyerfire.com/blog/windows-sprinklers-fire-ratings-part-i

The water supply duration in NFPA 13 is meant for the hazard classification of the occupancy, and not regarding fire resistance.

Mike

12/12/2019 01:10:21 pm

Must check what the glazing design actually is. Window sprinklers have very specific designs to which they may be applied and therefore have VERY limited applications. The most stringent is mullions.

Also, refer to NFPA 13, 2019, 9.3.15 (7) for water duration requirements.

Cliff

12/12/2019 01:28:14 pm

The answer is yes, if the sprinkler system, utilizing closely spaced heads, is used in lieu of a 1 hour or 2 hour fire rated partition, the sprinklers need to be able to operate for that period of time.

Randy

12/12/2019 04:05:48 pm

There's not really enough specific code information here to say definitively. My general take:

Providing a "1-hour" wall or window does not mean it will stand for 1 hour in a fire. It means it withstood a standard test for 1 hour. An intense fire could destroy a 1-hour rated wall in 45 minutes, for example.

Since this seems to be an alternate means approach, you will need to satisfy your AHJ regarding water supply.

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