HVAC Duct Enclosure Assemblies - ICC-ES Acceptance Criteria Outlines New Alternatives for Duct Fire Protection

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New technologies are rapidly being developed for passive fire protection of ductwork to meet increasingly stringent testing and code requirements. In response, a newly revised Acceptance Criteria from ICC Evaluation Service, LLC (ICC-ES) was developed specifically for fire protection of HVAC ductwork. These criteria provide a means for qualifying new code compliant protection options that will benefit life and building safety.

For many years, duct enclosure assemblies have provided a proven, effective, and economical means of passive fire protection for commercial kitchen exhaust ducts. In fact, it was an Evaluation Service Report (ESR) issued by ICC-ES in 1995 based on Acceptance Criteria (AC 101) that permitted duct enclosures to first enjoy widespread use in the building construction industry. Typical duct enclosure assemblies include, but are not limited to applied flexible and rigid enclosure systems or prefabricated systems, all of which are intended to serve as alternates to fire-resistance-rated shafts. Following the issuance of AC 101, the effectiveness and advantages of enclosure assemblies for passive grease duct fire protection led to their addition in the International Mechanical Code (IMC). Based on a history of successful performance in kitchen exhaust applications, the industry has subsequently worked to develop a viable passive fire protection solution for heating and ventilation ductwork.

ICC-ES issues evaluation reports (ESRs) based on acceptance criteria to describe qualified systems that have not been defined in the building codes, but will otherwise meet or exceed all the current requirements in the code for quality, strength, effectiveness, fire resistance, durability and safety (IBC 104.11). These reports are an indispensable tool for code officials to evaluate a commercially viable system, as an alternate method or material prior to official adoption into the building code. ICC-ES ESRs more than ever before are becoming a necessity with the rapid development of new technologies and lagging code cycles. Today, ESRs are available to manufacturers for metallic HVAC duct enclosure assembly systems.

Recently, the ICC-ES Acceptance Criteria for Metallic HVAC Duct Enclosure Assemblies (AC179) was updated to reference a new test standard, ASTM E2816, for evaluating fire-rated HVAC duct work configurations. Acceptance Criteria

(AC) are a set of defined provisions developed by ICC-ES for building products and systems that are alternatives to what is specified in the code, but otherwise meet or exceed the intent of the code. The ASTM E2816 standard was developed to evaluate full size duct configurations under standardized fire conditions (ASTM E119 fire exposures). The development of an ASTM standard and subsequent update to the Acceptance Criteria is a significant first step in the advancement toward recognition of the ability of HVAC duct enclosure assemblies to satisfy the performance requirements of the model Codes.

* This article is intended to provide information about ICC-ES AC179 – Acceptance Criteria for Metallic HVAC Duct Enclosure Assemblies. It should not be construed as an endorsement or procedural recommendation by ICC-ES.

AC 179 is an important document to code and building officials since it contains both system and material testing requirements and provides formal guidance on the sections of the code where systems covered under these criteria are applicable. Analogous to pre-code kitchen exhaust applications, an ESR can now be obtained by HVAC duct enclosure manufacturers as verification of code compliance as an alternate to a required fire damper or a fire-rated shaft under specific conditions.

Fire testing per ASTM E2816 evaluates duct systems and is based on the ASTM E119 standardized time temperature curve for fire resistive assemblies. Full size duct configurations are tested in four separate conditions: horizontal-open, horizontal-closed, vertical-open, and vertical-closed. These configurations evaluate ductwork systems with fire exposures inside (open) and outside (closed) the ductwork. Each one of these configurations represents a conceivable HVAC application outlined in AC 179. Further evaluation includes transition connections from a vertical to a horizontal duct, along with the HVAC support mechanisms. ASTM E2816 even includes provisions to evaluate the effects of rapid cooling and erosion upon the duct work through the use of a hose stream test. Other notable testing requirements include material combustibility, flame spread and smoke developed limitations. The breadth of this testing exceeds existing passive fire protection options currently referenced in the IBC or IMC for fire protection of HVAC systems.

The performance required by AC 179 for compliant HVAC ductwork is equivalent or better than performance levels that currently exist for these applications. When comparing shaft wall or damper protection methods, it is important to recognize that ASTM E2816 tests and evaluates the entire duct system, rather than a single component. Whereas, approved fire dampers are only required to have a rating equivalent to 75% of the barrier, duct enclosure systems provide protection equivalent to 100% of the fire barrier rating. For example, a HVAC duct penetrating a 2-hour rated wall assembly only requires a 90 minute rated fire damper by current code standards. In this case, the duct enclosure system provides a 2 hour fire rating. It is crucial to remember fire test assemblies evaluated by ASTM E2816 are also required to demonstrate the structural stability of their support system under large scale fire exposure conditions, and are required to remain in place throughout the entire duration of testing. Testing also evaluates the effects the ducts and enclosure systems have on the wall or floor assembly they are penetrating.

Systems that meet AC 179 offer tested solutions equivalent to shaft enclosures permitted by code. Shaft enclosures tested to ASTM E119 are evaluated as vertical or horizontal assemblies only. They are not evaluated in the actual configuration required for HVAC duct protection systems as constructed (i.e.as a 4-sided boxed enclosure of a duct). Similarly, they are not specifically evaluated for horizontal runs or for circumstances where the duct and enclosure have openings. ASTM E2816 systems include provisions for penetrations at both the floor & wall assemblies. Overall, ASTM E2816 represents the most rigorous and realistic criteria for evaluating passive fire protection HVAC duct enclosure assemblies.

A system complying with AC179 and ASTM E2816 will provide increased safety along with a variety of installed benefits and value to the construction industry, some of which include: clearance reduction, space and labor savings, design flexibility, ease of installation and reduced maintenance.

In conclusion, the criteria defined by AC 179 and test method ASTM E2816 represent a significant step forward in the passive fire protection of HVAC ductwork that positively benefits the building industry. ICC-ES evaluation reports represent testing and evaluation of these systems to give designers, building owners, installers, and code officials confidence to utilize this alternate means of passive fire protection and to realize the benefits they offer. Most importantly, HVAC duct enclosure assemblies evaluated against AC 179 give the code official a means to satisfy the performance requirements of the model Codes because they are tested to rigorous standards developed to evaluate full size duct configurations to severe fire exposures, as they are constructed in the field, and offer an alternative to existing code prescribed solutions such as fire dampers or fire rated shafts.

More information on ICC-ES and the acceptance criteria for Metallic HVAC duct enclosure assemblies can be found online at the ICC-ES website: http://www.icc-es.org.

The International Firestop Council (IFC) is a not-for-profit association of manufacturers, distributors and installers of passive fire protection materials and systems in North America. The IFC’s mission is to promote the technology of fire and smoke containment in modern building construction through research, education and development of safety standards and code provisions. Additional information can be found on the IFC website: http://www.firestop.org.

Figure 1. Full Size Horizontal Duct Test Assembly

ASTM E 2816 and AC179 – The Rundown

The International Firestop Council (IFC) worked with ASTM to develop a North American based test method to evaluate air duct configurations.

Testing- ASTM E119 Time Temp Curve- ASTM E119 Exposed Thermocouples- ASTM E814 Unexposed Surface TC’s

Material PropertiesASTM E2816 measures additional pertinent material properties:- Combustibility- Flame Spread- Durability- Smoke Generation

Support & Integrity- Evaluates HVAC support system as

installed in the field- Hose stream test included to

evaluate rapid cooling and erosion upon system

Duct ConfigurationsEvaluates 4 separate full size duct configurations (horizontal/vertical & fire outside/inside of duct) providing zero clearance to combustibles- Conditions A&B – fire outside- Conditions C&D – fire inside

AC 179 System Advantages Over:

Fire Damper Alternative• Fire-rating matches penetrated

assembly• Tested with a full size duct

assembly• Evaluates penetrations at specific

wall/floor assemblies

Fire Rated Shaft Alternative• Full size construction tested as

applied in the field

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