Residential-style sprinklers are specifically designed & tested for their response and ability to "enhance survivability" in the room of fire origin. [NFPA 13 2002-07 18.104.22.168, 2010-13 22.214.171.124, 2016 126.96.36.199]
What makes them so attractive to use in residential occupancies?
Specifically Designed Spray Pattern
First, their spray pattern is specifically suited to residential hazards. Unlike light hazard office spaces, dining areas of restaurants, meeting rooms or lobbies, residential rooms regularly contain much of the fire hazard along the perimeter of the room. This hazard often presents itself as bookshelves, cabinetry, curtains, furniture, and an assortment of other potential fuel sources.
Unlike standard-spray fire sprinklers, residential-style sprinklers throw more water to where it's needed-along and up the edges of a room.
Residential-style sprinklers are specifically designed to throw along the outer boundaries of rooms, which better aligns with locations of typical residential hazards. Sprinkler throw data above is of the Victaulic V2738 residential sprinkler.
Residential-style sprinklers are also fast to respond, with the intent to fight the fire earlier in its incipient stages.
While light hazard areas are already required to use one of several specific sprinkler responses, including the option for quick-response sprinklers (NFPA 13 2002-16 188.8.131.52), residential-style sprinklers are still considered 'fast-response'.
The term Fast-Response is defined as a sprinkler with an RTI (Response Time Index) of 50 √m-s or less. It incorporates three specific styles of sprinklers - "Residential Sprinklers", "Quick Response Sprinklers" (including standard and extended coverage), and "Early Suppression Fast Response (ESFR)." Each of these sprinklers qualify as Fast Response, but they are not interchangeable. [Viking Technical Article by Scott Martorano, July 2006]
Based on the ability to better fight a residential fire, the use of residential style sprinklers has a hydraulic kickback that dramatically helps the hydraulic calculations for a residential area.
As residential sprinklers are not quick response sprinklers, the remote area reduction for the use of quick-response sprinklers does not apply.
However, NFPA 13 and NFPA 13R only require that the most hydraulically demanding four adjacent sprinklers be calculated, while NFPA 13D only requires the most hydraulically demanding two adjacent sprinklers be calculated. [NFPA 13 2002 184.108.40.206.1, 2007-16 220.127.116.11, NFPA 13R 2002 18.104.22.168, 2007 22.214.171.124, 2010-19 126.96.36.199, NFPA 13D 2002-10 8.1.2, 2013-19 10.2]
Additionally, NFPA 13R and NFPA 13D permit the design density to be as low as 0.05 gpm/sqft or the listed density of the sprinkler. [NFPA 13R 2002 188.8.131.52.2.2, 2007 184.108.40.206.1.2, 2010-19 7.1.1, NFPA 13D 2002-10 8.1.1, 2013-19 10.1.1]
These reductions can significantly reduce the flow for a remote area, resulting in less friction loss and ultimately a smaller system demand, even with smaller pipe sizes.
It's important to note that due to the different spray pattern, residential sprinklers have their own obstruction rules which differ from standard spray. Try out the Obstruction Calculator with residential-style sprinklers to see the difference.
Where Can Residential Sprinklers Be Used?
Residential style sprinklers are permitted in "dwelling units and their adjoining corridors, provided they are installed in conformance with their listing." [NFPA 13 2002-16 220.127.116.11]. Their limited to wet pipe systems unless listed for use in dry or pre-action, but this is often not a major inhibitor.
Residential sprinklers are allowed to be used in wet systems within dwelling units and their adjoining corridors.
Also of note is new verbiage in the 2013 edition of NFPA 13 annex which includes that "Residential sprinklers can only be used in corridors that lead to dwelling units. However, the corridors that lead to dwelling units can also lead to other hazards that are not dwelling units and can still be protected with residential sprinklers" [NFPA 13 2013-16 A.18.104.22.168].
This verbiage was included to clarify that just because other hazards might be adjacent to these same corridors does not mean residential style sprinklers cannot be used.
Residential sprinklers differ from standard spray in their response categorization and their water distribution. Both of these elements align with residential hazards, and their use offers some positive kickbacks to designers looking to use them in and around residential areas in buildings.
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Joseph Meyer, PE, is a Fire Protection Engineer in St. Louis, Missouri. See bio on About page.