Impact of Mass Timber Compartment Fires on Façade Fire Exposure

Engel, Thomas; Werther, Norman

doi:10.1007/s10694-022-01346-8

Cited by 7 publications

(3 citation statements)

References 16 publications

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“…The majority of small-and medium-scale compartment fire experiments conducted to date have shown that this can result in larger external flames [7], [8] and increased heat flux to both the building of fire origin and opposite [9] than from an otherwise identical compartment constructed from non-combustible materials. One experimental series, with a very high movable fuel load (of 1085 MJ/m 2 ), did not observe a significant increase in flame height when mass timber was introduced, but did report higher temperatures [10]. Significant external flaming was also observed during the large-scale CodeRed experimental series [11]- [13].…”

Section: Exposed Mass Timber and External Flamingmentioning

confidence: 96%

A Design Approach to External Fire Spread From Buildings With Exposed Mass Timber

Glew,

Turnbull,

Møller Poulsen

et al. 2023

World Conference on Timber Engineering (WCTE 2023)

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Engineered wood products (EWPs) are relatively new, innovative construction materials which, if used correctly, can serve as sustainable alternatives to more common construction types. They provide an opportunity for designers to reduce the embodied carbon of proposals. Given the climate crisis, it is vital that the sector decarbonises. However, lessons must be learnt from previous sustainability-driven design decisions that did not sufficiently consider safety implications. Often there is a desire from building owners, occupiers and/or designers to expose mass timber. Doing so can provide aesthetic, wellbeing, cost and carbon benefits over encapsulation. However, exposing large areas of mass timber introduces an additional fuel load to the compartment -the structural fuel load, and compartment fire experiments to date have shown that this can lead to larger external flaming. This paper aims to investigate potential implications of this phenomenon on: (i) large-scale 'standard' façade tests, and (ii) radiation assessments to neighbouring buildings. First, temperature data recorded outside the opening(s) of seven mass timber compartment fire experiments is compared to temperatures in front of the façade recorded during three 'standard' industry façade fire tests. It is found that BS 8414 and the proposed harmonised European test generally expose the façade to more/as severe temperatures than observed during mass timber compartment fire experiments. Therefore, these tests are considered applicable to exposed mass timber buildings. The NFPA 285 test, which was designed for traditional buildings, is less severe than the mass timber experiments reviewed. Heat fluxes recorded opposite openings in three mass timber compartment fire experimental series are then compared to heat flux predictions made following first principles-based radiation calculations following the enclosing rectangles and configuration factor method (as in BR 187). Using the "low" and "high" fire load assumptions in BR 187 leads to underpredictions of heat flux received. Modelling the external flame as an emitter (of the same temperature as the opening) has little impact on results. Therefore, a higher emitter temperature is recommended when carrying out radiation calculations from exposed mass timber compartments.

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Section: Exposed Mass Timber and External Flamingmentioning

confidence: 96%

A Design Approach to External Fire Spread From Buildings With Exposed Mass Timber

Glew,

Turnbull,

Møller Poulsen

et al. 2023

World Conference on Timber Engineering (WCTE 2023)

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“…BS EN 13501-2:2016 defines the performance of an encapsulation system to protect a substrate, with the designation of a K2 classification [2]. The standard requires the encapsulation system to limit the temperature increase at the surface of the substrate to below 250 ℃ on average or 270 ℃ in any location while preventing the 1 Arup London, eirik.christensen@arup.com 2 Arup London, benjamin.khoo@arup.com 3 Arup Manchester, panos.kotsovinos@arup.com 4 Arup Melbourne, david.barber@arup.com 5 Arup London, judith.schulz@arup.com pyrolysis of the protected material when exposed to a "standard fire". In addition, there can be no collapse of the covering during the test.…”

Section: Introductionmentioning

confidence: 99%

“…The temperature distribution within real fires is such that the thermal severity of a floor may be expected to be less than that of a ceiling in a timber compartment. Studies found that, in a ventilation controlled fire, gas temperature near the floor are on average 100 -200 °C lower than near the ceiling [3][4][5][6][7], as shown in Figure 1. As such applying the same fire protection for encapsulation on both the ceiling and floor may result in excessive conservative encapsulation, inflating the mass, embodied carbon, and cost of a building.…”

Section: Introductionmentioning

confidence: 99%

Protection and Thermal Exposure of CLT Ceiling and Floor Surfaces

Christensen¹,

Khoo²,

Kotsovinos³

et al. 2023

World Conference on Timber Engineering (WCTE 2023)

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Timber is increasingly used in buildings because of its favourable embodied carbon credentials compared to traditional materials such as steel and concrete. However, due to it combustible nature, encapsulation products are frequently used to prevent or limit the timbers contribution to a fire. These encapsulation products introduce additional weight, cost and carbon to project, which limit the benefit of timber construction. The performance of these products in natural fires and the relative fire severity experienced by products placed near the ceiling and the floor has received little attention. Here we present data on the performance of encapsulation applied to the timber ceiling and floor elements within the CodeRed experiments -a series of large-scale timber compartment experiments with varying ventilation and extent of exposed timber. Compartment temperatures were measured at the ceiling and near the floor, indicating a lower temperatures at floor level; the time temperature curve 'seen' by the floor encapsulation is dependent on whether or not there is residual glowing embers on the floor. Both the 25 mm calcium silicate encapsulation to the floor, when located below the wood crib and when adjacent to it, and the three layers of 12.5 mm gypsum fibreboard board applied to the ceiling were shown to be adequate in preventing the ignition of the underlying timber. However, smouldering was observed to sustain remote to encapsulation, but eventually spread beneath the encapsulation which facilitated continued smouldering. This highlights that smoulder can progress behind encapsulation. A 1D Finite Difference Model (FDM) was used to explore the temperature development of timber surfaces beneath simulated encapsulation details using the gas temperatures measured near the ceiling and floor. Converting the modelled peak temperatures to time equivalent times revealed an 23% average reduction in time equivalent fire severity near the floor level for natural fires with a severity equivalent to a 30 min standard fire. When considering greater fire severities, this reduction remained similar, indicating that applying the same fire protecting rating to the floor as to the ceiling is likely overly conservative. The study represents the first step in quantifying a more refined protection required at the floor and to the ceiling; with further research it may be possible to justify a reduction in the required fire protection performance of floor level encapsulation for long duration fires compared to that on the ceiling, taking into account the observed distribution of compartment gas temperatures in large compartments. Ultimately this offers an opportunity to reduce the embodied carbon, costs, and weight of the structural design.

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Fire Safety for Green Façades: Part 1: Basics, State-of-the-Art Research and Experimental Investigation of Plant Flammability

Engel,

Werther

2024

Fire Technol

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This study is the first part of a larger investigation into the fire behaviour of green façades. In this study, the currently known international research status on this topic is presented and discussed. In addition, the flammability of green façades is investigated through 43 fire tests on a medium scale according to the SBI (Single Burning Item) test method EN 13823. The focus of the investigation was placed on climbing plants. A total of 25 different plant species were investigated. A comparison of the heat release rate of all the investigated vital plants shows similar behaviour. In the course of exposure, there are short peaks in the heat release rate. These peaks are “flare-ups” that occur when parts of the plants dry out due to exposure to the flame and then ignite. The plant species itself had no substantial influence on fire behaviour. Horizontal fire spread occurred to a very limited extent within the investigations of vital plants. They were self-extinguishing. The significant factor in the assessment of flammability is the moisture content of the plants. With dried plants, an abrupt heat release occurs at the beginning. Dried-out plants, as well as unmaintained plants with a high content of deadwood, represent the most critical case. Graphical Abstract

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Impact of Mass Timber Compartment Fires on Façade Fire Exposure

Cited by 7 publications

References 16 publications

A Design Approach to External Fire Spread From Buildings With Exposed Mass Timber

A Design Approach to External Fire Spread From Buildings With Exposed Mass Timber

Protection and Thermal Exposure of CLT Ceiling and Floor Surfaces

Fire Safety for Green Façades: Part 1: Basics, State-of-the-Art Research and Experimental Investigation of Plant Flammability

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