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November/December 2009
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Exterior Wall Assemblies

Recommendations from the California Office of the State Fire Marshal and the International Wildland-Urban Interface Code have led to the development and approval of a new ASTM International standard regarding the enhancement of exterior fire protection of structures in a wildland fire.

The new standard, E2707, Test Method for Determining Fire Penetration of Exterior Wall Assemblies Using a Direct Flame Impingement Exposure, was developed by Subcommittee E05.14 on External Fire Exposures, part of ASTM International Committee E05 on Fire Standards.

According to Howard Stacy, vice president and director of testing services, Western Fire Center Inc., recommendations from the California Office of the State Fire Marshal established performance criteria for a variety of materials to be used on exterior buildings, structures and detached accessory structures. E2707 was designed to closely follow the test procedure of California SFM Method 12-7A-1.

E2707 is intended to address one component of an exterior wildfire exposure, that is, exterior walls exposed to direct flame impingement.

“The purpose of this standard is to provide a definitive set of procedures for the evaluation and measurement of the resistance to fire penetration of exterior wall structures,” says Stacy. “The test is a practical attempt to simulate a case in which flammable materials — such as plants, trash, a deck or a shed, that might be adjacent to a building — are ignited. The test method provides data suitable for comparing the performance of vertically oriented materials, products or assemblies in exterior construction applications.”

Users of the new standard will include product manufacturers in response to regulatory requirements and testing agencies.

Stacy notes that the measurement science involved with the quantification of wildland fire exposures of structures and understanding the mechanism ignition leading to structural loss is in the early stages of development.

“This test method as it stands is intended as a starting point and only measures the response to one type of ignition scenario — direct flame impingement,” says Stacy. “Refinements to the standard are being studied, including the addition of methodologies for the measurement of the impact of radiant heating coupled with direct flame impingement, the effect of ember exposure and heat release of the wall structure corresponding to potential spread of flame.”

A new task group within E05.14 has embarked on a quantification of exterior fire exposures, which will lead to the development of potential guides and practices for fire exposure metrics usable for the development of improved standards covering both urban and wildland environments. “Input from knowledgeable parties, including those with scientific, regulatory and fire service experience, would be valuable in the task group,” says Stacy.

In addition to these activities, there are currently two proposed new standards under the jurisdiction of Subcommittee E05.14 on E05 main committee ballot: WK12052, Test Method for Evaluating the Under-Deck Fire Test Response of Deck Structures, and WK14401, Test Method for Evaluating the Fire Test Response of Deck Structures to Burning Brands.

New activities recently started under E05.14 include: WK21343, Test Method for Evaluating the Ability of Vents to Resist Entry of Embers and Flame Impingement; WK23700, Test Method for Evaluating Roof Field Vent Response to Wind Blown Flame and Burning Ember Exposure; and WK25760, Guide for Quantification of Fire Exposures.

CONTACT

Technical Information: Howard Stacy, Western Fire Center Inc., Kelso, Wash.

Phone: 360-423-1400

ASTM Staff: Thomas O’Toole

Phone: 610-832-9739