The Real Trade-Offs When Using Special-Purpose Deluge Sprinklers to Meet Fire Ratings

The Real Trade-Offs When Using Special-Purpose Deluge Sprinklers to Meet Fire Ratings

Only recently has the use of sprinklers been considered as a trade-off for fire rated materials.  However, using special-purpose deluge sprinklers instead of fire rated glazing in 1-2 hour walls requires prior AHJ approval.

So before considering alternate assemblies that use special-purpose deluge sprinklers, below are the real trade-offs:


Architects assume all responsibilities and costs of applying for AHJ Approval. 

This includes the cost of:

Cost 1 of 6

Preparing documented proof that the design and installation requirements are met.

Cost 2 of 6

Hydraulic calculations for each installation.

Cost 3 of 6

Dedicated water source for sprinklers.

Cost 4 of 6

Upgrading the pumps and pipes to maintain the prescribed water pressure needed for each installation.

Cost 5 of 6

Ongoing maintenance for special-purpose deluge sprinklers.

Cost 6 of 6

Deluge sprinklers using ceramics are more expensive than readily available, clear, fire resistive glazing assemblies.

Safety and Liabilities

While special-purpose deluge sprinklers are effective in controlling and suppressing fires, studies have shown that sprinklers can and have failed.  Sprinkler system breakage can put you and the building occupants at risk when you need it the most.

Below are some safety and liability issues when using special-purpose deluge sprinklers:

Safety 1 of 3

No sprinkler manufacturer or installer will guarantee that it will work 100% of the time.

Safety 2 of 3

When sprinklers fail to operate, non-rated glass will be useless in preventing fire, smoke and dangerous radiant heat.

Safety 3 of 3

Sprinkler failure puts building occupants and firefighters in real danger.

Design Limitations

There are several design restrictions for special-purpose deluge sprinklers used with fixed glazed assemblies.

This includes, but not limited to, the following:

Limitation 1 of 3

Cannot exceed 13 ft. in height.

Limitation 2 of 3

No horizontal mullions allowed.

Limitation 3 of 3

A 3 ft. opaque pony wall is required for tempered or heat-strengthened glazing.


After comparing the hidden costs, safety risks and design restrictions on special-purpose deluge sprinklers that requires prior AHJ approval vs. already approved 1-2 hour fire resistive assemblies, it is clear to see that merely looking at this in terms of ‘a few sprinkler heads and tempered glass’ exposes the designer and building owner to various costs and liabilities.