If you use QR sprinklers, have light or ordinary hazard and ceilings less than 20', you can reduce the design area per a formula in NFPA 13.
In storage situations, the ceiling height as well as storage height are variables that affect design density.
If you are under FM guidelines, they have criteria based on hazard classification and ceiling height.
Some jurisdictions (I believe Las Vegas, or maybe it is Clark County) require a design area of 10x the ceiling height once you exceed 20'. That is all going from memory so may not be fully accurate.