Effects of Storage Height on the Density of Ceiling Sprinklers

There are two Figures in chapters 14 and 16 of NFPA 13 (2016 edition) for adjusting the density of ceiling sprinklers in according to the storage height where CMDA sprinklers are applied.
Consider the following example:
Double Row Rack Storage, Open Rack type, Non-encapsulated Class I commodity, 15 ft. Storage height, 4 ft. Aisle width, Using CMDA Ordinary temperature with in-Rack sprinkles

As it shows in the figure below (Design criteria window of “Fire Protection Design software”), NFPA 13 requires that the selected density adjustment according to Figure 16.2.1.3.4.1

For the assumed 15 ft. storage height, the selected density shall be multiplied by 60%, this means if the selected density from Figure 16.2.1.3.2(a) is 0.255 gpm/ft.², the final design density will be:
0.255 x 0.6 = 0.153 gpm/ft.²

And this is great! Because now we can use K 5.6 Sprinklers (12.6.1- NFPA13, 2016). A smaller K factor means a cheaper sprinkler system.

As it shows in Figure 16.2.1.3.4.1, for storage height lower than 20 ft., this curve helps to decrease density, for storage height more than 20 ft., it increases and for storage height equal 20 ft., no effects on the required density!

Written by: Hesam Tavoosi, CFPS, CWBSP, CSITMS