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

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 brand transport calculations in NIST’s Wildland Fire Dynamics Simulator (WFDS).

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 post-fire field 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) for brand transport and structural ignition.  WFDS will be used to guide/assess standard laboratory test methods and building codes by allowing exposure conditions to be simulated over a broad parameter space.

What is the research plan?  Developing the scientific basis necessary to support test methods for firebrand resistant building components^[1] is a key component required to reduce the WUI fire problem, as it is a structure ignition issue.  Yet, in the WUI, buildings are often surrounded by vegetation that, when ignited, can produce intense, localized firebrand showers and provide direct flame contact onto building elements, leading to ignition of buildings.  The creation of defensible space around structures is a common mitigation strategy, yet in many areas the requirement for the creation of defensible space is either not popular due to resistance to modify the natural environment and landscaping around structures, or not practical due to limited lot size. 

The full-scale continuous Firebrand Generator will be used to expose mulch commonly found in WUI settings to continuous firebrand showers to determine: (1) ignition regime maps of mulch, (2) conditions that  may lead to ignition of the structure due to flaming mulch.  Pre-wetting of vegetation and dead fuels by water, foams, and gels is believed to be a potential mitigation strategy for urban fuels such as mulch, but the ignition resistance of pre-wetted fuels have never been tested against continuous wind driven firebrand showers under controlled laboratory conditions. Overall, both non-wetted and wetted mulch beds will be exposed to continuous firebrand showers and these mulch beds will be placed adjacent to a reentrant corner assembly to determine if ignition of the structure is possible.  A worst case scenario will be considered in these experiments, specifically continuous firebrand showers will be applied to wetted mulch beds within 10 minutes of application of the wetting agents.  Three wetting agents will be used: (1) water will be applied in the form of spray using a garden hose sprayer, (2) type A foam suppressant (applicable to ordinary combustibles found in the WUI) will be applied using a portable self-contained nitrogen pressurized system specifically designed for the foam WUI fire application, and (3) commercially available gel suppressants will be applied using a commercially available home use applicator available from the manufacturer of the gel product used. These experiments will be used to provide the scientific basis for new mulch test standards in ASTM E05.14 (External Fires), a critical gap. All of the component experiments described above will be conducted at the Building Research Institute (BRI) in Japan because the facility allows the testing under reproducible conditions for components or smaller section of buildings. Now that the prior BRI/NIST MOU has expired, a new cooperation agreement has been developed jointly with the National Institute for Land and Infrastructure Management (NILIM) and BRI.  BRI/NILIM shares the same office complex and the Fire Research Wind Tunnel Facility (FRWTF) as well, so this new partnership will greatly reduce costs associated with doing these experiments in Japan since they have large funding starting from April, 2012.  The BRI/NILIM/NIST cooperation agreement is in the final stages of review (in Japan) and will be in place by the start date of this project.

In FY13, the project will also explore developing a working relationship with the Institute of Business and Home Safety (IBHS).  IBHS has cloned the non-continuous NIST Firebrand Generator concept in their facility.    After the testing of the component sections at BRI, testing on larger sections of structures or complete structures will be conducted at IBHS.  Although the size of the IBHS facility is very large, it does not allow burning of building elements or significant amount of vegetation (no smoke abatement system), and it is not practical for the component testing experiments described in the previous section.  There is also no continuous firebrand generation capability in the facility at present.  Nevertheless, since the facility can perform high wind speed tests, it is anticipated that a limited number of tests of specific building assemblies suspected of higher wind speed vulnerabilities will be conducted there in FY14.

In FY 13, Manzello will also lead an ASTM task group with the focus on preparing a draft ASTM ballot to allow the NIST Bench Scale Continuous Firebrand Generator to become the ASTM Standard Firebrand Generator.  The main premise is to use this unique experimental device as the ASTM Standard Firebrand Generator and, if accepted as an ASTM standard, it will be available for use in a variety of existing ASTM standards, such as the ASTM E108 roof test, as well as new WUI standards under development at ASTM.  NIST presented this concept, namely using this device as an ASTM Standard Firebrand Generator, to ASTM E05.14 (External Fires) subcommittee in FY 12 and received positive comments and support.

 

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• FY 12 a full-scale continuous-feed Firebrand Generators was developed.   Firebrand size/mass distributions were obtained from ignited building components as well as full scale burning buildings under well controlled laboratory conditions.
• In FY 13 continuous-feed generator used to expose building elements and vegetation.   Test will target those building elements where prior experiments of fixed firebrand exposure did not produce vulnerabilities.
  
• Results from building component exposures will be compiled, with prior full scale experiments, to provide the first comprehensive database of building components exposed to firebrand showers of: (1) fixed/variable duration and (2) exposed to different firebrand size/mass distributions commensurate of burning vegetation and structures.
• This database will provide the scientific basis for code change that can significantly reduce WUI fire losses and feed into the ASTM ballot of the bench scale continuous feed Firebrand Generator (described below).  As always, these findings will be disseminated to key organizations such as ICC, CALFIRE, ASTM, and NFPA.
  

 

Recent Results:

Outputs:

• 8 archival journal articles in FY2011 and FY2012^[2]; 18 since project inception
• 7 conference proceedings in FY2011 and FY2012; 13 since project inception
• 1 invited magazine article
• 1 NIST Technical Note 
• 2 Invitations to be Guest Editor: Fire Safety Journal and Fire Technology
• 4 NIST Special Publications^[3]
• 1 workshop was organized in California for testing input in FY2011 and FY2012; The type of input provided included most common decking assemblies to test
• 1 international workshop was organized at NIST in FY2012 (1st Japan-USA workshop); 
• Statement of Intent between NIST and the Japan Association for Fire Science and Engineering to collaborate in the development of scientifically based building codes and standards to address WUI fires. 
• Invited plenary lecture at the October 2012 9th Asia-Oceania Symposium on Fire Science and Technology (AOSFST); organized by the International Association of Fire Safety Science (IAFSS).
• 18 invited lectures since project inception.

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 knowledge regarding the ignition hazards of decking exposed to firebrand showers.
• New full scale test methods to determine firebrand generation from vegetation and building components.
• New methodology developed 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 2010 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.
• Developed unique experimental apparatus:
• • NIST Firebrand Generator,
  • Continuous Feed Firebrand Generator (both bench and full scale),
  • NIST Dragon’s LAIR (Lofting and Ignition Research) Facility.
• Standards and Codes:  Based on the measurement science developed as part of this project,  revised performance-based requirements for building vents were drafted.  These have been adopted and are now binding in California (California Building Code, Title 24, Part 2, Chapter 7A, effective January, 2011).  Manzello is very active and serves as 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.    Manzello was also invited to present his research to the entire ASTM E05 Fire Standards Committee as part of their annual research review in FY11.  Most recently, in FY12, Manzello presented the recently developed bench-scale continuous feed firebrand generator and suggested that the device would make an ideal ASTM Standard Firebrand Generator and could be used for any ASTM test.  ASTM E05.14 members agreed, and as a result, ASTM E05.14 subcommittee Chairman Craig McIntyre formally created a new task force (with Manzello as Chairman of this task force).  Manzello’s second presentation to the entire ASTM E04.14 Subcommittee in FY12 provided an overview of the kick-off Japan-USA workshop held at NIST in June 2011.  An overview of the upcoming 2nd Japan-USA workshop scheduled for next Julyne (2012) in Tokyo was presented as well.  The 2nd Japan-USA workshop is focused on urban/WUI fires and fire-structure interaction/NIST’s NFRL. The objectives of these workshops are to discuss potential research collaborations to develop scientifically-based building codes and standards that will reduce the devastation caused by unwanted fires.

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1. S.L. Manzello and E.I.D. Foote, Characterizing Firebrand Exposure from Wildland-Urban Interface (WUI) Fires: Results from the 2007 Angora Fire, Fire Technology, in review, part of special issue that Manzello is serving as Guest Editor of Fire Technology), 2012.
2. S. Suzuki, S.L. Manzello, and Y. Hayashi, The Size and Mass Distribution of Firebrands Collected from Ignited Building Components Exposed to Wind, Proc. Combust. Inst., accepted in press, 2012.
3. S.L. Manzello, S. Suzuki, and Y. Hayashi, Enabling the Study of Structure Vulnerabilities to  Ignition from Wind Driven Firebrand Showers: A Summary of Experimental Results, Fire Safety Journal, accepted in press (part of special issue that Manzello is serving as Guest Editor of Fire Safety Journal), 2012.
4. S. Suzuki, S.L. Manzello, M. Lage, and G. Laing, Firebrand Generation Data Obtained from a Full Scale Structure Burn, Int’l J. Wildland Fire, accepted in press, 2012.
5. 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, published online; awaiting issue assignment, 2012.
6. S.L. Manzello, S. Suzuki, and Y. Hayashi, Exposing Siding Treatments, Walls Fitted with Eaves, and Glazing Assemblies to Firebrand Showers, Fire Safety Journal, 50: 25-34, 2012., 2012.
7. 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, Fire Safety Journal, 46: 568-578, 2011.
8. 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 10th International Symposium, 10:1437-1448, 2011.
9. S.L. Manzello, Firebrand Attacks and Dragons: Pioneering Research on WUI Structures Protection, Wildfire Magazine, March/April 2012.
10. S.L. Manzello and S. Suzuki, Determining Ignition Regime Maps of Building Materials Exposed to Continuous Wind-Driven Firebrand Showers, 49^th Japanese Combustion Symposium, Kanagawa, Japan, 2011 (published in proceedings but not orally presented due to travel restrictions at NIST).
11. S. Suzuki and S.L. Manzello, Firebrand Generation Data Obtained From a Full Scale Structure Burn, 49^th Japanese Combustion Symposium, Kanagawa Japan, 2011 (published in proceedings but not orally presented due to travel restrictions at NIST).
12. 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.
13. S.L. Manzello, S. Suzuki, and Y. Hayashi, Exposing Glazing Assemblies to Firebrand Showers, Japan Association for Fire Science and Engineering, Tokyo, Japan, 2011.
14. E.I.D. Foote, J. Liu, and S.L. Manzello, Characterizing Firebrand Exposure During Wildland-Urban Interface (WUI) Fires, Fire and Materials Conference, 2011.
15. 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.
16. S.L. Manzello, S. Suzuki, and Y. Hayashi, Summary of Full-scale Experiments to Determine Vulnerabilities of Building Components to Ignition by Firebrand Showers, NIST Special Publication 1126, 2011.  
17. S.L. Manzello and S. Suzuki, Summary of the 2011 Workshop on Research Needs for Full Scale Testing to Determine Vulnerabilities of Decking Assemblies to Ignition by Firebrand Showers, NIST Special Publication 1129, 2011.
18. S.L. Manzello, S. Suzuki, and K. Himoto, Summary of Workshop for Urban and Wildland-Urban Interface (WUI) Fires: A Workshop to Explore Future Japan/USA Research Collaborations, NIST Special Publication 1128, 2011.
    

 

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S.L. Manzello, S. Suzuki, and Y. Hayashi, Summary of Full-scale Experiments to Determine Vulnerabilities of Building Components to Ignition by Firebrand Showers, NIST Special Publication 1126, 2011.

S.L. Manzello and S. Suzuki, Summary of the 2011 Workshop on Research Needs for Full Scale Testing to Determine Vulnerabilities of Decking Assemblies to Ignition by Firebrand Showers, NIST Special Publication 1129, 2011.

S.L. Manzello, S. Suzuki, and K. Himoto, Summary of Workshop for Urban and Wildland-Urban Interface (WUI) Fires: A Workshop to Explore Future Japan/USA Research Collaborations, NIST Special Publication 1128, 2011.