Things to Consider Before Using Non-Rated Fixed Glass Assemblies and Special-Purpose Sprinklers in lieu of Fire Resistant Glazing Assemblies
What is AC 385?
The ICC-ES first adopted AC 385 in October 2007 at the behest of a major manufacturer of sprinkler heads. In 2011, the ICC-ES Evaluation Committee issued a memo to withdraw its Criteria for this alternative in lieu of building materials tested to ASTM E-119. AC 385 was revised in February 2013 to try to extend the exception for use the non-rated fixed glass assemblies with special purpose sprinklers, but prohibit their use in lieu of firewalls and fire barriers (Section 5.1.11). In February 2015, a new modified AC 385 was adopted that reauthorizes the use of this alternative as a fire barrier. Read more about the origins of AC 385.
Using special-purpose sprinklers in lieu of fire-resistant glazing assemblies requires prior approval from the Authority Having Jurisdiction (AHJ), who are required to make certain findings found in Section 104.1 2012 IBC.
What AC 385 Fails to Do
- AC 385 doesn’t address sprinkler failure. Fact is, sprinklers can and do fail. Fire resistant glazing assemblies provide built-in fire protection 24/7 without the need for mechanical triggers or regular maintenance that are requried with sprinkler systems, making them susceptible to failure.
- AC 385 doesn’t protect property and people from radiant heat.
- AC 385 fixed glass assemblies with special-purpose sprinklers have hidden costs, such as installation of special-purpose sprinklers and water mains sufficient to sustain water pressure. Read more about the limits of AC 385 exceptions.
Fire Resistant Glazing Assemblies Provide Better Design Options
Even with AHJ approval, there are limitations on the size of the non-rated fixed glass assemblies that you don’t have with fire resistant glazing assemblies that can reach from ceiling to floor because they are tested to ASTM E-119. Use of fire resistant glazing also means you can avoid the unsightly pipes and sprinkler heads. Compare here.
Above: An installation of ASTM E-119 rated Superlite III-XL Butt-glazed in GPX Architectural series perimeter framing. No AHJ approval required.