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Fenestration with Combustible Components in Buildings of Noncombustible Construction

Fenestration Canada

Peter L. Senez, M.Eng., P.Eng.

Presented to:

Presented by:

Global Leaders in Fire Engineering Vancouver Toronto Calgary Singapore

Sereca Fire Consulting

Forensic

Engineering

Building & Fire Code

Consulting

Fire Protection

Engineering

Fire and CFD

Modelling

Industry Specialties

Detection and

Suppression


Presentation Overview

› Regulatory Requirements - Fire

› Challenges

› Approach

› Process


Regulatory Requirements

› Construction in Canada governed by Provincial building codes

› Provincial building codes substantially based on the model National Building Code of Canada (NBCC)

› The NBCC is developed by the Canadian Commission on Building and Fire Codes (CCBFC) and its related committees

› Canadian Codes Centre provides technical and administrative support to the CCBFC

› NBCC developed on a 5 year cycle, next anticipated edition is the 2015 NBCC


Regulatory Requirements

› The NBCC regulates type of construction as a function of building size

› Larger and taller buildings are required to be constructed of noncombustible construction

› Noncombustible means:

a material meets the acceptance criteria of CAN/ULC-S114, “Test for Determination of Non-Combustibility in Building Materials.” [Div. A, 1.4.1.2.(1)] This test [sic] is severe, and it may be assumed that any building material containing even a small proportion of combustibles will itself be classified as combustible [D-4.1.1.(2)].


Regulatory Requirements – Acceptable Solution

› The NBCC permits certain combustible components in buildings required to be constructed of noncombustible construction on the premise that those items will insignificantly contribute to fire growth and spread

› Combustible window sashes and frames are permitted [Sentence 3.1.5.4.(5)]


Limitation (a): Individual Unit


Limitation (b): Storey Separation

1 m


Limitation (c): Aggregate Area

≤ 40% Area


Resulting Challenges

› Energy requirements – 2011 National Energy Code of Canada

– Increasing demand for low conductivity materials, typically combustible

– Increased demand for daylighting

› Design Limitations

– Typical curtain wall design

› Market penetration

› Cost


Solution

› Submission of a Code Change Request

› Requirements:

you must provide sufficient information to allow the Canadian Commission on Building and Fire Codes (CCBFC) and its standing committees (Code committees) to determine that your suggested change is needed and that it is technically correct [NRC website for submitting a code change]

› Risk Assessment: A code change permitting greater use of combustible components in buildings required to be constructed of noncombustible construction will require a risk analysis to address perception of increased risk [Impact Analysis]


Approach

› Demonstrate that permitting combustible sashes/frames in buildings required to be of noncombustible construction will not increase the risk of fire spread to adjacent fire compartments or contiguous storeys beyond that currently permitted by the NBCC acceptable solutions:

– Historical assessment and quantification of risk associated with sash/frame combustibility

– Development of code change rationale

– Testing to supplement the code change rationale

– Supplementary modelling to support window assembly design variations beyond those physically tested.

– Documentation and presentation of the code change rationale


Considerations

› Combustible window sash/frame acceptable solutions are expressed in specification terms

› Specification-based acceptable solutions are time-specific “snapshot” solutions to address risk

› If we want to change these acceptable solutions, how do we address risk?

– Need an understanding of the intended performance of the specifications

– Intended performance requires an understanding of the basis of the specifications


Considerations

R.S. Ferguson, National Research Council of Canada, 1959


Historical Assessment

› Identify the risk that initiated the development of the specification(s)? [Implicit Risk]

› Identify the capability, materials and methods considered in mitigating the risk? [Mitigation Measures]

› Quantify to what level is/was the risk mitigated? [Acceptable Risk]

› Are the specifications still relevant? Re-examination of implicit risk, mitigating measures and acceptable risk [Current Context]


Implicit Risk

› Risk that initiated the development of the specification

› Conflagrations:

Baltimore, MD - 1904


Implicit Risk

› Flying brands igniting combustible window sashes and frames considered to be a contributing factor in storey-to-storey and building-to-building fire spread in city-wide conflagrations

› Contribution of sash/frame material to spread of fire to adjacent fire compartments or contiguous storeys


Mitigation Measures

› The capability, materials and methods considered in mitigating the risk:

– Noncombustible materials to limit ignition and significant contribution of sashes and frames to fire growth and spread

– Or

– Separation of openings by noncombustible material (a), 1 m from storey-to-storey (b) and limit area of window openings (c) to reduce the probability of fire spread to adjacent fire compartments or contiguous storeys as a result of ignition of the sash or frame

– Acceptable Solution requirements in the NBCC

› Developed approximately 100 years ago


Acceptable Risk

› The Acceptable Risk is the risk remaining once the Mitigation Measures have been implemented to reduce the Implicit Risk:

– Acceptable Risk: ignition and burning involving sashes/frames of a single fire compartment

– Unacceptable Risk: ignition and fire growth of combustible window sashes or frames in a single fire compartment sufficient to spread fire to adjacent fire compartments or contiguous storeys leading to full building involvement and conflagration


Current Context

› Are the requirements still relevant?

› Since the mitigation measures associated with window sashes and frames were developed there have been significant advancements in:

– Understanding of fire dynamics

– Construction materials and practices

– Exposure protection methodology

– Fire protection systems (ie: sprinklers)


Development of Code Change Rationale

› Utilize historical assessment to define risk benchmark

› Anecdotal evidence of material performance –forensic observations

› Risk rationalization based on material performance and other overriding fire spread mechanisms


Testing to Support Code Change Rationale

› Demonstrates performance under actual fire conditions

› Provides baseline data for noncombustible case

› Permits examination of dimensional and material impacts on fire behaviour

› Development of data to support/validate supplementary modelling


Supplementary Modelling

› Provides a cost effective alternative to testing of additional variations to configuration and material properties

› Future proofing


Documentation and Presentation of Code Change Rationale

› Preparation of the proposed code change in appropriate format, including a supplementary report

› Development of a technical presentation outlining the technical rationale, testing and other analyses to support the proposed change

› Preparation of follow-up documentation to address questions from the appropriate Standing Committee, CCBFC and any public comments, should the proposed change be approved for public review

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