Burning Questions: Alternate methods of construction and fire-rated

by Catherine Howlett | June 1, 2013 3:33 pm

[1]HORIZONS
Jeff Griffiths, CSI
The ancient principles of Yin and Yang have given rise to many philosophies, including those underlying modern passive and active fire protection. Yin and Yang have always been complementary forces, unseen (passive) and seen (active), that interact to form a greater whole as part of a dynamic system. Any attempt to eliminate one element in favor of the other has its risks, giving rise to the inevitable need and emergence of the missing element that restores balance. Such has been the case over the past decade in the effort to maintain a balanced approach to fire protection in all types of buildings.

In October 2003, for example, a U.S. manufacturer of sprinkler heads and fire equipment accessories sought to demonstrate how a solely active fire suppression system could replace the need for passive fire-rated glazing. With the help of Underwriters Laboratories (UL), this manufacturer constructed six test assemblies made up of three 6.4 mm (¼-in.) tempered glass panels butt-glazed together to form a 4 x 4.26-m (13 x 14-ft) wall attached to the face of UL’s test furnace.

Each test assembly used either its vertical pendant or sidewall window sprinkler spaced at various distances from the glass face. The furnace temperature settings followed the time/temperature curve established by ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials, and the equivalent UL 263, Fire Tests of Building Construction and Materials. Temperature probes were placed at various locations on the non-fire-side glass surface for monitoring purposes.

At the end of a half-dozen of the two-hour tests, no probe recorded a temperature higher than 70 C (158 F). By relying solely on water dispensed at 76 L/min (20 gpm), the sprinklers seemed to have supplanted the need for passive fire protection. The staff at the UL test laboratory apparently saw no need to conduct the final phase of both the ASTM E119 and UL 263 test requirements—the application of the hose stream.

The next logical step for this manufacturer was to share its invention with code officials and the construction community. It submitted the test documentation to the International Code Council Evaluation Service (ICC-ES) for review. This resulted in the 2007 issuance of Acceptance Criteria (AC) 385, Acceptance Criteria for Special-purpose Sprinkler Heads Used with Fixed Glazed Assemblies to Provide a Fire-resistance-rated Wall Assembly. Not only was this big news among fire-rated glass manufacturers, it was also the first supposed ASTM E119 test conducted and passed while relying solely on an active suppression system. It gave rise to the first assembly deemed a fire-resistive wall without ever passing the hose stream test. The sprinkler head manufacturer had achieved a proverbial ‘twofer.’

Implications for glazing?
The proposed ICC-ES acceptance criteria stated:

Because the sprinkler heads are used to limit the rate of heat transfer through the glazing, the ASTM E119 test method and test assembly are modified to take into account the sprinkler heads and their discharge.

Given the intumescent properties of interlayers contained within the various makeups of fire-resistant glazing, and their demonstrated ability to limit the rate of heat transfer through glazing components, some manufacturers and experts in fire-rated glass circles felt the logical follow-up would be that the ASTM test method should be modified for glazing products as well.

The ‘pass’ for sprinklers was also perplexing given the common knowledge both wet and dry sprinkler systems have a documented rate of failure. In a 2006 study, “An Analysis of Automatic Sprinkler Reliability Using Current Data,” published by the National Fire Protection Association[2] (NFPA), John Hall Jr. states:

The new estimates are that sprinklers failed to operate in 7% of structure fires (reported in NFIRS [National Fire Incident Reporting System] 5.0 in 1999–2002, after adjustment for errors in coding partial systems). The percentage varies from a low of 2% for apartments to a high of 14% for storage properties. The percentage rises to 9% if all types of automatic extinguishing equipment are included. This primarily reflects dry chemical systems used in public assembly properties. Two-thirds (65%) of the sprinkler failures to operate were because the system had been shut off before the fire. Another one-sixth (16%) occurred because manual intervention defeated the system, for example, by shutting off the sprinklers prematurely. Lack of maintenance accounted for 11% of the sprinkler failures to operate and 5% occurred because the wrong type of system was present. Nearly all failures were therefore entirely or primarily problems of human error. Only 3% involved damage to system components.

The same conclusions are supported by numerous other studies prior to those Hall cites. The sprinkler head manufacturer did not demonstrate elimination of human error and equipment failure as part of the modified test procedure, and it was not apparent whether ICC-ES had considered the need for any such evidence.

Hall also points out:

Effectiveness tended to be associated with a small number of sprinklers operating. When only one sprinkler operated, performance was effective 95% of the time. This fell slightly to 94% when two sprinklers operated, to 91% for three sprinklers, 89% for four to 10 sprinklers, and 81% for more than 10 sprinklers.

This should lead to a concern that the longer the run of glass, the greater the risk of the sprinklers failing to properly wet the glass in order to maintain a sufficient barrier to temperature rise and avoid subsequent glass breakage resulting from thermal shock as the fire spreads. This author sees a correlation between the fire spreading and causing more sprinklers to be activated and the amount of water discharged being reduced, increasing the risk of the glass being overheated.

[3]

Code changes
On May 4, 2011, the ICC-ES Evaluation Committee invited interested parties to submit comments on three proposed revisions to AC 385 due to the passage of Proposed Code Change FS4-09/10. The following was added to the 2012 International Building Code (IBC) as a result of the adopted code change:

703.4 Automatic sprinklers. Under the prescriptive fire resistance requirements of the International Building Code, the fire resistance rating of a building element, component or assembly shall be established without the use of automatic sprinklers or any other fire suppression system being incorporated as part of the assembly tested in accordance with the fire exposure, procedures, and acceptance criteria specified in ASTM E119 or UL 263. However, this section shall not prohibit or limit the duties and powers of the building official allowed by Section 104.10 and 104.11.

On June 3, 2011, due to a lack of public comments being submitted prior to the established deadline, the ICC-ES Evaluation Committee issued a memo announcing it had disapproved of the proposed revisions to AC 385, withdrawn AC 385 from use, and revoked the evaluation report (ESR-2397) based on the acceptance criteria. Undeterred by the setback, the sprinkler head manufacturer’s renewed effort emerged.

In August 2012, the ICC-ES Evaluation Committee invited public comments on the reinstatement of AC 385. The central theme among those respondents supportive of reinstatement focused on IBC sections addressing alternative materials, design, and construction methods. For example, in his written supportive submission to the committee, David Collins, FAIA, NCARB, contended the American Institute of Architects (AIA):

believes that the very existence of AC385 is directly derived from the authority granted to the code official authority through Sections 703.3 and 104.11 of the 2012 IBC. Alternative methods and materials has been a strong element of virtually every model building code and survive today to assist the entire industry to be able to respond to the evolution of systems.

Section 104.11 of IBC states:

An alternative material, design, or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method, or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code in quality, strength, effectiveness, fire resistance, durability, and safety.

Section 104.10 of IBC addresses that a waiver of code requirements is to be considered:

Wherever there are practical difficulties involved in carrying out the provisions of this code, the building official shall have the authority to grant modifications for individual cases, upon application of the owner or owner’s representative, provided the building official shall first find that special individual reason makes the strict letter of this code impractical and the modification is in compliance with the intent and purpose of this code and that such modification does not lessen health, accessibility, life and fire safety, or structural requirements.

So in the case of AC 385, the code does not seem to inhibit an evolution of systems since no practical difficulty seems to exist given fully code-compliant fire-rated glazing is readily available, and no equivalency has been established as the hose stream test requirement has been ignored. However, the onslaught of innovative ‘green’ products streaming into the construction marketplace while fully complying with existing testing standards are but one example of how system evolution can freely develop without any hindrance posed by the IBC code cycle and the need for ICC-ES reports.

AIA’s sentiments were echoed by two prominent engineers at Arup USA Inc.—Matthew Johann and Ray Grill. In a written supportive submission to the committee, they claimed:

The assembly supported by ESR-2397 provides design freedom to architects and code consultants and has been utilized to help maintain the design vision for several of our projects. Our typical applications involve the separation of adjacent occupancies when there is a need or desire to include glazing to promote an open feel or to support a given operation.

Again, there was no mention of any practical difficulty being overcome by virtue of AC 385. Their endorsement did mention:

There is no history of failure associated with this type of assembly, and no evidence that it provides a reduced level of fire and life safety as compared to a solid, fully-passive fire-rated barrier when designed and installed in accordance with ESR-2397 and applicable standards.

This faith in ESR-2397 and the stipulated alternative method of construction seems to hinge on the absence of any disaster to date, but overlooks the empirical research data confirming sprinklers systems can fail.

Robert Davidson, an independent fire and life safety consultant, points out in his public comments the code:

specifically allows for the use of wetted glass in two locations – for enclosures of atriums, a low fuel load use area, in Section 404.6, in addition to other fire protection system installation; and in pedestrian walkways connecting buildings, in Section 3104.5, also a low to no fuel load area, with additional conditions including automatic sprinkler systems throughout both buildings and the walkway.

Davidson goes on to make the point:

Both of these provisions are for very specific use areas and require specific levels of fire protection above and beyond the fire barriers where the wetted glass is permitted. Just as important, both of these provisions were added to the body of the code with specific language vetted by the appropriate code committee and the membership. What is being proposed to the Evaluation Services committee does not meet those parameters.

The conditions of use stated in ESR-2397 only limit the wetted wall assembly from being used in:
• areas containing potentially explosive materials;
• areas having penetrations or protected openings; and
• exterior wall applications where the distance between buildings is greater than 1.5 m (5 ft). No other prescriptive guidelines for use are identified.

Radiant heat concerns
Another aspect of the ASTM E119 and UL 263 test requirement apparently waived for the test was the confirmation the glazing has sustained the fire endurance test without passage of flame or gases hot enough to ignite cotton waste during the testing period. This portion of the test would be impractical under lab conditions using a water cur tain since the cotton waste is positioned approximately 25 mm (1 in.) from the glass surface. However, the significance of a potential ignition of the cotton waste is its indication of radiant heat transmission.

Fire-resistive glazing relies on the use of one or more interlayers of a reactive intumescent material to literally shield the non-fire-side glass surface. It is not uncommon for unexposed fire-resistive glass surfaces to remain cool enough to be safely touched during the test procedure. This shield serves to block temperature rise as well as the transmission of radiant energy waves that can potentially cause the spontaneous combustion of surrounding building materials and pose an extreme danger to building occupants.

Davidson calls on the experience of firefighters in addressing the potential danger of relying on water curtains by noting, “the fire service eventually realized that a water curtain does not stop fire spread. Heat is transmitted to other objects by conduction, convection, direct flame impingement and radiation. The water curtains may be able to effect convection to some degree depending on the size of the fire, but they do not stop radiated heat because the water is not opaque.”

It is understandable architects, engineers, and building officials lacking real world firefighting experience may overlook the invisible danger of radiant heat transmission. However, the threat of radiant heat to occupants eager to flee from fire through glazed corridors, stairway enclosures, or occupancy separations remains real. The sole reliance on a water curtain seems to be courting disaster.

In December 2012, the ICC-ES Evaluation Committee once again invited public comment of the reinstatement of AC 385 in light of the pros and cons voiced in the preceding public comment period. However, this time the committee was seeking comment on several proposed modifications to AC 385. The most important of which was the prohibition of horizontal muntins because they can block the contiguous flow of water over the glass surface, and the clear assertion the system is an alternative to a fire-resistance-rated wall assembly and not a fire-resistance-rated fire barrier assembly itself. The committee also proposed the insertion of the following new section:

Special-purpose sprinklers with fixed glazed assemblies are an alternative to a fire-resistance-rated wall assembly requiring approval by the code official. The registered design professional shall provide the code official with documentation outlining the basis of compliance with the criteria specified by the IBC for a code modification in accordance with Section 104.10 or for an alternative method of construction in accordance with Section 104.11.

However, neither this proposed addition to AC 385, nor IBC Sections 104.10 and 104.11 for that matter, require the design professional or the building official to confirm the practical difficulty serving as the basis for alternative construction. Further, the additional AC 385 section does not address allowable occupancy types or limit changes to occupancy types in the future.

Conclusion
The need to backtrack through AC 385 as the result of a reinstatement request calls into question the wisdom applied during the initial ICC-ES review process. The overriding lesson to be learned through this controversy—no matter how it is resolved—is the incentive and desire to circumvent building codes and test requirements for the sake of expediency, cost savings, aesthetic vision, and any number of other factors is ever-present.

The need for a balanced approached to most circumstances is often seen as good advice to be applied in daily life. This knowledge stems from insights handed down from one generation to the next. When public safety is at stake, it becomes even more important to consider not only the systems, but also the impact human error can have on the materials and construction methods we employ to create safe environments. When it comes to fire protection, having a fully tested Plan A and Plan B just makes sense.

Jeff Griffiths, CSI, is the director of business development for SaftiFirst. With over 25 years of experience within the glass and glazing industry, he has worked with both sloped and vertical glazing systems incorporating wood, aluminum, and steel structural components along with various glass products. From 1985 to 1992, Griffiths oversaw the manufacturing of SaftiFirst’s earliest generation of fire-resistive glazing systems. He currently serves on Glass Association of North America’s (GANA’s) Fire-rated Glazing Council Educational Committee, Window and Door Manufacturers’ (WDMA’s) Interior Products Code Committee, and ASTM Committee E60 on Sustainability. Griffiths can be reached via e-mail at jeffg@safti.com[4].

Source URL: https://www.constructionspecifier.com/burning-questions-alternate-methods-of-construction-and-fire-rated/

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