Reduced Ignition of Building Components in Wildland-Urban Interface (WUI) Fires Project

Summary:

The Wildland-Urban Interface (WUI) fire problem is a structure ignition problem. To reduce the risk of structural ignition, the technical basis for improved test standards and building codes are being developed. Post-fire damage assessment evidence suggests that firebrands (embers) are a major source of structural ignition in WUI fires. A unique experimental apparatus, known as the NIST Firebrand Generator (NIST Dragon), has been constructed to produce a controlled and repeatable firebrand attack. The experimental results generated from the marriage of the NIST Dragon to the Building Research Institute’s (BRI) Fire Research Wind Tunnel Facility (FRWTF) in Japan are being used by standards organizations to guide the development of new standards and provide the scientific basis for new performance-based requirements with the intent to make structures more resistant to firebrand attack. An experimental database is also being created to support and validate NIST’s Wildland Fire Dynamics Simulator (WFDS).

Description:

Objective: To reduce the risk of structural ignition during a WUI fire by developing, by 2014, the technical basis for new and improved standard laboratory test methods and building codes.

What is the new technical idea? The new technical ideas are to use full scale experiments and computer modeling to quantify the vulnerability of structures to ignition in WUI fires. The full scale experiments will use a unique experimental apparatus, the NIST Firebrand Generator (or NIST Dragon). The NIST Dragon can generate a controlled firebrand shower on a realistic scale and direct this firebrand shower onto components of a structure to ascertain their resistance to ignition as a part of a full scale structural system. The full scale experiments will be targeted to specific vulnerabilities observed from NIST’s studies of structures exposed to actual WUI fires. Finally, experimental results obtained from this work will be used to generate a database to validate NIST’s WUI Fire Dynamics Simulator (WFDS). WFDS will be used to guide/access standard laboratory test methods and building codes by allowing exposure conditions to be simulated over a broad parameter space.

What is the research plan? Post-fire evidence exists related to vulnerabilities of decking treatments to firebrand showers yet standard test methods are not available to evaluate the ability of decking treatments to resist firebrand showers. Decking has not been properly dealt with since the inception of the 2005 California Building Code, Title 24, Part 2, Chapter 7A, since there has been no testing capability to generate wind driven firebrand showers. Therefore, full scale tests will be conducted to quantify the vulnerability of decking treatments (e.g. various common decking materials) and to firebrand showers using the experimental apparatus developed in support of the project; the NIST Firebrand Generator (or NIST Dragon). The experiments will be conducted at the FRWTF at BRI in Japan to generate wind driven firebrand showers. NIST will consider input from a decking workshop, to be held in June 2011, to finalize these full scale experimental plans. The LA Basin Chapter of the ICC is serving as the host for the workshop, Mr. Ruben Grijalva, former CALFIRE director, is serving as the moderator and the workshop will be attended by key stakeholders (ICC, NFPA, Office of the State Fire Marshall, California Building Standards Commission, Decking Industry, American Wood Council, and Cedar Industry). When completed, these decking experiments will have the potential to provide the scientific basis for code change that can significantly reduce WUI fire losses. These findings will be disseminated to key organizations: ICC, CALFIRE, ASTM, and NFPA and these experiments will be supported in part by funding from DHS (see below).

In WUI fires, firebrands are produced not only as vegetation burn but also as structures are ignited and burned. In addition to the experiments delineated above, a series of experiments will be conducted as part of an experimental campaign at BRI inside the FRWTF to quantify firebrand production from a full scale burning structure. This work is possible due to a successful series of experiments completed last FY that considered firebrand generation from individual building components under various wind speeds. Wind is very important and influences the size and mass of firebrands that are generated; thus the need to conduct the experiments in a wind tunnel. Firebrand size and mass distribution will be determined as a function of building material type and wind speed. Such data will enable the NIST Firebrand Generator to generate firebrand showers representative from burning structures to test structure vulnerabilities to ignition exposed to various firebrand size/mass distributions. The firebrand size/mass distributions collected from burning structures will also enable WFDS to simulate firebrand transport of firebrands that are characteristic of burning structures in addition to burning vegetation (see details below).

While full-scale experiments are required to observe the vulnerabilities of structures to firebrand showers, bench test methods afford the capability to evaluate firebrand resistant building materials and may serve as the basis for new standard testing methodologies. Last FY, this project developed the Dragon’s LAIR facility (Lofting and Ignition Research) and it is the only bench scale apparatus in the world capable of generating wind driven firebrand showers. The NIST Dragon’s LAIR consists of a bench scale continuous feed Firebrand Generator (Baby Dragon) coupled to a reduced scale wind tunnel. This unique facility has set the stage to be able to evaluate and compare various building materials resistance to ignition from firebrand showers for the first time. As part of this FY plans, the ability of NIST Dragon’s LAIR facility, with input from ASTM E05.14, to rate relative ignition resistance of building materials to firebrand showers will be demonstrated.

Finally, this FY, efforts to extend NIST’s Fire Dynamics Simulator (FDS) to handle fire spread in the WUI will continue. The resulting computer simulation code has been named WFDS for WUI Fire Dynamics Simulator. To date, a firebrand transport model has yet to be incorporated into the model. This FY, a first generation firebrand transport model will be added to WFDS. The transport model will be validated using results of full scale firebrand transport experiments conducted at the FRWTF using the NIST Dragon. It is desired that WFDS can simulate locations of potential firebrand accumulation for various structure façades. Firebrand accumulation in front of structures, first observed by this project, possesses a serious ignition threat to structures.

Major Accomplishments:

Recent Results:

Outputs

7 archival journal articles in FY2010 and FY2011^[1]; 14 since project inception
7 conference proceedings in FY2010 and FY2011; 13 since project inception
1 NIST Technical Note
1 NIST Special Publication
2 workshops were organized in California for testing input in FY2010 and FY2011; The type of input provided included most common construction assemblies to test as well as configurations believed vulnerable to firebrand showers, such as reentrant corners
18 invited lectures

Outcomes

First generation rapid response instrumentation co-developed and tested.
Developed world’s first full-scale test method, in collaboration with BRI, to determine building component vulnerability to firebrand showers.
New knowledge regarding building component vulnerability (siding, eaves, glazing, vents) to firebrand showers.
New knowledge regarding the ignition hazard due to accumulated firebrands in front of structures.
New full scale test methods to determine firebrand generation from vegetation and building components.
New capability, in collaboration with CALIFRE, to determine firebrand size distribution from actual WUI fires using digital burn pattern analysis.
Drafted revised performance based requirements for firebrand penetration through building vents (California Code of Regulations, Chapter 7A, known as the 2007 California Code of Regulations).
Results of NIST comparison testing protocol included in new test standard for firebrand resistant building vents (ASTM E05.14.06 Vents Subcommittee).
Developed bench scale test method to expose building materials (vents) to wind-driven firebrand showers.
Development of unique experimental apparatus:
- NIST Firebrand Generator,
- Continuous Feed Firebrand Generator,
- NIST Dragon’s LAIR (Lofting and Ignition Research) Facility.

Standards and Codes: In 2005, CALFIRE created WUI building standards (California Code of Regulations, Chapter 7A, known as the 2007 California Code of Regulations) focused on reducing the risk of building fires. Manzello was appointed as a task force member (invitation only) to revise the California WUI Building Code. Based on the measurement science developed as part of this project, Manzello was instrumental in drafting revised performance-based requirements for building vents. These have been adopted and are now binding in California in 2011. Manzello is a voting member on ASTM E05.14 (External Fire Exposures) to develop and assess new standards to construct firebrand resistant structures. Specific activities include the completion of a comparison testing protocol with ASTM E05.14.06 (Vents Subcommittee) aimed at developing firebrand resistant building vents. The results of this comparison testing protocol have been included in the vent test standard recently balloted by the ASTM E05.14.06 Vents Subcommittee. Manzello is a charter member of a newly formed ASTM subcommittee, E05.14.08 (Quantification of Exterior Fire Exposures Subcommittee) and served as an organizing member, in cooperation with CALFIRE, National Research Council Canada (NRC-C), and the Australian Building Code Board (ABCB), of an international ASTM workshop in February, 2011. The purpose of the workshop was to identify where sufficient or insufficient data based on research, field data, and post-fire analysis exists to allow the formulation of appropriate fire exposure metrics that may be usable in new WUI fire test standards and regulatory development organizations. ASTM has requested that he deliver a presentation at the upcoming ASTM E05 Research Review this coming June. This event is attended by members of the entire E05 Fire Standards Community.

^[1].

S.L. Manzello and S. Suzuki, The New and Improved Dragon’s LAIR (Lofting and Ignition Research) Facility: Coupling the Reduced Scale Continuous Feed Firebrand Generator to Bench Scale Wind Tunnel, Fire and Materials Journal, in review, 2011.

S.L. Manzello, S. Suzuki, and Y. Hayashi, Exposing Siding Treatments, Walls Fitted with Eaves, and Glazing Assemblies to Firebrand Showers, Fire Safety Journal, in review, 2011.

S.L. Manzello, S.H. Park, S. Suzuki, J.R. Shields, and Y. Hayashi, Determining Structure Vulnerabilities to Firebrand Showers in Wildland-Urban Interface (WUI) Fires, Proceedings of the Royal Society of London A, in review, 2011.

S. Suzuki and S.L. Manzello, On the Development and Characterization of a Reduced Scale Continuous Feed Firebrand Generator, Fire Safety Science - Proceedings of the 10^th International Symposium, accepted, 2011.

S. Suzuki and S.L. Manzello, Characteristics of Heat Flux and Firebrand Generation Data Obtained from a Full Scale Structure Burn, Japan Association for Fire Science and Engineering, Tokyo, Japan, 2011.

S.L. Manzello, S. Suzuki, and Y. Hayashi, Exposing Glazing Assemblies to Firebrand Showers, Japan Association for Fire Science and Engineering, Tokyo, Japan, 2011.

E.I.D. Foote, J. Liu, and S.L. Manzello, Characterizing Firebrand Exposure During Wildland-Urban Interface (WUI)Fires, Fire and Materials Conference, 2011.

S.L. Manzello, S. Suzuki, and Y. Hayashi, Exposing Siding Treatments and Walls Fitted with Eaves to Wind-Driven Firebrand Showers, Fire and Materials Conference, 2011.

S.L. Manzello, S. Park, and T.G. Cleary, Development of Rapidly Deployable Instrumentation Packages for Data Acquisition in Wildland-Urban Interface (WUI) Fires, Fire Safety Journal, 45:327-336, 2010.

S.L. Manzello, Y. Hayashi, T. Yoneki, and Y. Yamamoto, Quantifying the Vulnerabilities of Ceramic Tile Roofing Assemblies to Ignition during a Firebrand Attack, Fire Safety Journal 45:35-43, 2010.

W.E. Mell, S.L. Manzello, A. Maranghides, D. Butry, and R.G. Rehm, The Wildland Urban Interface Fire Problem – Current Approaches and Research Needs, International Journal of Wildland Fire 19:238-251, 2010.

S.L. Manzello, S.H. Park, J.R. Shields, Y. Hayashi, S. Suzuki, Comparison Testing Protocol for Firebrand Penetration through Building Vents: Summary of BRI/NIST Full Scale and NIST Reduced Scale Results. NIST Technical Note 1659, 2010.

S.L. Manzello and S. Suzuki, Summary of Workshop on Research Needs For Full Scale Testing to Determine Vulnerabilities of Siding Treatments and Glazing Assemblies to Ignition by Firebrand Showers, NIST SP 1111, 2010.

S.L. Manzello, S.H. Park, J.R. Shields, Y. Hayashi, and S. Suzuki, Quantifying Wind Driven Firebrand Penetration into Building Vents Using Full and Reduced Scale Experimental Methods, 12^th Int’l Conference on Fire Science & Engineering (INTERFLAM), London, UK, 2010.

S.L. Manzello and Y. Hayashi, Quantifying Structure Ignition from Firebrand Showers, 10th International Conference on Combustion and Energy Utilization (10th ICCEU), Mugla, Turkey, 2010.

S.L. Manzello, S. Suzuki, and Y. Hayashi, Investigating Wind Driven Firebrand Penetration in Building Vents, Japan Association for Fire Science and Engineering (JAFSE), Sapporo, Japan, 2010.

NIST's Firebrand Generator generates burning embers (or firebrands) that are major sources of ignition of house fires during blazes at the wildland-urban interface (WUI). Photo credit: NIST