Area reduction using quick response sprinklers NFPA 13 Section 11.2.3.2.3.1

[SprinklerDesigner2]

I have a Light Hazard building with a ceiling exactly 20'-0" AFF so I can apply the ceiling height reduction using quick response sprinklers except we do have skylights.

The top of the skylights are at 24'-0" AFF so the upright QR sprinkler protecting the skylight is around 23'-0".

Can I apply the area reduction based on 20'-0" ceiling height? I think I can but I've never had this come up before.

Let me add just to make sure I am on the safe side I'll go with without the area reduction because I like to play safe.

 

[TravisMack]

You can do two design areas. In the area with the skylights, I would say you need to calculate 1500 sq ft that includes the sky lights. If you have an area that is 20' and no sky lights, then you could reduce the design area in that location.

Travis Mack, SET, CWBSP, RME-G
MFP Design, LLC

http://www.mfpdesign.com

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[skdesigner]

How big are the skylights?

If they comply with NFPA 13-2016 8.5.7 (32 sq. ft. max, 10' from any other unprotected skylight or ceiling pocket), I believe you'd still be able to apply the QR reduction.

 

[SprinklerDesigner2]

Of course nothing is easy.

While the skylights themselves are only 16 sq ft the tapered edges make them much larger.

The way it worked out with lights/HVAC this is one of those situations were extended coverage heads work out really well... I will use the extended coverage heads, calc to 1,500 sq ft and install a QR upright sprinkler in the skylight itself 6" off the side and 12" max down from the skylight "dome".

 

[MatthewJWillis]

Looks like a pretty big volume brother.

When in doubt....

 

[SprinklerDesigner2]

Matthew, when in doubt indeed!

I'm going with the 1,500 sq ft.