Section 104.11 of the International Building Code anticipates the changing dynamics of materials, design, and construction methods.

In many respects, alternate means and methods is a smart, judicious provision. It recognizes the built environment as a living, continuously evolving ecosystem. For AHJs (authorities having jurisdiction), section 104.11 offers a degree of decision flexibility within the strict demands of public health and safety.

Consider assemblies for one- and two-hour wall applications, for example. Recently an alternative to one- and two-hour wall assemblies emerged: ICC-ES ESR-2397 3.3 represents an alternative fire, smoke, and radiant heat containment solution. This mixed-method approach offers a transparent, code-compliant wall system without a fire-resistive glazing material that needs prior AHJ approval

Weakened ASTM E-119 Test

The heart of ESR-2397 is a special purpose deluge sprinkler system. In the event of a fire, special wall-directed sprinklers bathe the adjacent non-rated tempered-glass partition in water, to form an insulating barrier against fire, smoke, and radiant heat. This water-on-glass method meets the requirements of a specially modified, less stringent ASTM E-119 test. Other than following the time and temperature curve, there is nothing that resembles the original ASTM E-119 test. There is no cotton-waste test; there is no hose-stream test; and there is no documented report showing how it limits the temperature rise on the non-fire side to less than 250 degrees F over ambient.

By contrast, fire-resistive glazing passes all ASTM E-119 test requirements without modifications. More than three decades of life-safety experience demonstrates its effectiveness in shielding occupants and first responders from fire, smoke, and radiant heat in a safe, “never fails” manner.

AHJ Review

Which approach is best? That depends on the application, budget and, in the case of the ESR-2397, the discretion of the AHJ. “It’s a question of trade-offs,” explains Tim Nass, vice president of sales for Safti-First, a leading U.S.-based manufacturer of fire-rated glass and framing products.

Nass says the application of sprinklers as a fire-resistive wall substitute may not be as well understood as a rated window assembly. In the IBC, one to two-hour fire-resistive ASTM E-119 wall assemblies are required to compartmentalize smoke, flames, and limit radiant heat transmission to less than 250 degrees F above ambient temperature without the need for mechanical triggers. “ESR-2397 is an exception to the rule,” Nass says, requiring prior AHJ review and approval.

For their corporate office, a Tech Giant wanted a transparent, 2 hour wall for daylight and visual connectivity between spaces. Initial designs showed an alternate assembly requiring prior AHJ approval that uses a combination of special purpose sprinklers with non-rated glass. This was later abandoned because the designers wanted unobstructed, floor-to-ceiling views that can only be achieved with 2-hour, ASTM E-119/UL 263 fire resistive glazing – no AHJ approval required.
For their corporate office, a Tech Giant wanted a transparent, 2 hour wall for daylight and visual connectivity between spaces. Initial designs showed an alternate assembly requiring prior AHJ approval that uses a combination of special purpose sprinklers with non-rated glass. This was later abandoned because the designers wanted unobstructed, floor-to-ceiling views that can only be achieved with 2-hour, ASTM E-119/UL 263 fire resistive glazing – no AHJ approval required.

For their corporate office, a Tech Giant wanted a transparent, 2 hour wall for daylight and visual connectivity between spaces. Initial designs showed an alternate assembly requiring prior AHJ approval that uses a combination of special purpose sprinklers with non-rated glass. This was later abandoned because the designers wanted unobstructed, floor-to-ceiling views that can only be achieved with 2-hour, ASTM E-119/UL 263 fire resistive glazing – no AHJ approval required.

Six Factors to Consider

What should an architect anticipate in seeking AHJ approval of the ESR-2397 exception? Nass says the architect, who assumes all the work and related costs for submitting the required documentation necessary for the AHJ to consider the exception, should anticipate at least six factors:

1. Sprinkler design and installation requirements are met. This alternative assembly uses a special wet-pipe sprinkler system that is different from the sprinklers used throughout the building. Also, design limitations such as a 3-feet pony wall, height restrictions, and no horizontal mullions must be considered.

2. Hydraulic calculations for each installation are provided.

3. Design of the dedicated water source with the capability of supplying one or two hours of water, depending on the rating of the wall.

4. Documentation of water pumps and pipes sufficient to maintain prescribed water pressure across all installations.

5. Budget allocations for ongoing sprinkler system maintenance.

6. Any additional costs, such as ceramics.

Nass also advises architects prepare for at least three questions the AHJ panel may ask:

1. Does the sprinkler manufacturer guarantee sprinkler performance? (Sprinklers fail 12% of the time, according to an October 2021 NFPA report.)

2. What is the danger of a failed sprinkler system to building occupants and first responders?

3. Due to the weakened ASTM E-119 test, what evidence does ESR 2397 have to show that the wetted glass approach limits the passage of radiant heat to less than 250 degrees F over ambient?

More Clarity and Simplicity

“It’s the architect’s right and privilege to consider any code-compliant alternative,” Nass says. “The more you know about ESR-2397, the more the simplicity, safety, and flexibility of fire-resistive glass stands out for the clarity, transparency, and natural daylight most architects seek.”

Learn more about how to enhance the fire-rated safety, transparency, and beauty of your next project.