Fire dynamics inside an open-plan compartment with an exposed CLT ceiling and glulam columns: CodeRed #01, Fire and Materials.

The desire by developers and architects to build mass timber buildings using cross laminated timber (CLT) and glulam has significantly increased globally in the last decade due to its benefits with regards to sustainability as well as other architectural and commercial drivers. This paper presents novel experimental evidence from CodeRed #02, the second in a series of large scale fire experiments carried out inside a purpose‐built, open‐plan compartment to capture fire dynamics in large compartments with exposed timber. The experiment used a continuous wood crib (6 × 29 m) as a controlled movable fuel load.  The aim of the CodeRed #02 experiment was to study the impact of reduced ventilation on fire dynamics by keeping all other parameters the same as CodeRed #01 (Kotsovinos et al., 2022), with the exception of ventilation area which was reduced by almost half. The reduction in ventilation was found to significantly impact the fire dynamics by slowing the fire spread and burning rate. The reduced ventilation led to an increased fire duration by 4 min 30 s, which corresponds to 20% longer duration compared to CodeRed #01. The reduced ventilation had a greater overall impact on the rate of flame spread across the CLT (−23%) than the crib (−8%) compared to CodeRed #01. While the maximum temperature and incident heat fluxes inside the compartment were approximately the same as in CodeRed #01, their evolution in time and space were significantly different. The external flames were higher than in CodeRed #01 (3–3.5 m compared to 2.5–3 m) and protruded further laterally (up to ~4–5 m compared to ~1 m) outside of the compartment from the large end openings. Unlike CodeRed #01, the external flaming from CodeRed #02 pulsated between visible flames and dark soot with significantly greater frequency. This was caused by the limited ventilation resulting in incomplete combustion in CodeRed #02. The peak heat release rate of CodeRed #02 was estimated to be 16.5% lower than CodeRed #01, despite having the same fuel load. The average char depth in the ceiling, as measured at the end of the experiment, was 28 mm. This was 11% greater than in CodeRed #01 and was likely due to the increased duration of the fire. After the extinction of the flaming, smouldering occurred for CodeRed #02 as it did for CodeRed #01. One of the glulam columns lost its restraint and fell to the ground because smouldering spread through the thickness of the member. The findings from this work can help engineers quantify the hazard and therefore identify appropriate solutions for the fire safety design of exposed mass timber buildings.

proportionately large number of vertical and horizontal cavity barriers of a higher specification than required by statutory guidance. These aids to meeting the criteria are not proscribed by BS 8414-1 but are not commonly found in actual rainscreen system designs.

The use of mass timber in construction is becoming a compelling option when faced with the high carbon footprint of traditional concrete and steel production. However, fire safety standards are yet to evolve to support these designs. Encapsulation is commonly used to protect all, or some, of the timber surfaces and reduce the risks introduced. This paper presents the results from CodeRed #04, the final experiment of the CodeRed experimental campaign. This experiment was carried out inside a purpose‐built facility to capture fire dynamics in large compartments with exposed timber. CodeRed #04 had identical characteristics to CodeRed #01 with the exception that ~50% of the cross‐laminated timber (CLT) ceiling was encapsulated. The experiments were intentionally similar to the traveling fire experiments, x‐ONE and x‐TWO, which had a non‐combustible ceiling to enable a direct comparison. The overall fire dynamics experienced in CodeRed #04, intersect the characteristics observed in CodeRed #01 and x‐ONE and x‐TWO.1. In CodeRed #04, there was a delay in the ignition of the CLT ceiling as the CLT directly above the crib was encapsulated. Once the CLT ceiling ignited, the fire spread rapidly throughout the compartment. The peak heat release rate (HRR) was estimated to be approximately 100 MW, a 17% decrease from CodeRed #01. Following CLT ignition the resulting fire duration, maximum temperatures, and heat fluxes were broadly similar to CodeRed #01. Flame heights of approximately 1.5 m were observed from the windows while flame heights of 2.5–3 m were observed in CodeRed #01. Therefore, flame heights were found to be comparable to x‐TWO.1, though over a greater number of windows, reflecting the greater extent of simultaneous burning within the compartment. The average charring depth of the exposed CLT panels was ~25 mm, which is similar to that measured in CodeRed #01‐suggesting that the fire severity near the ceiling was not strongly impacted by the 50% encapsulation of timber. No charring was observed where the ceiling was encapsulated and loaded service fixings installed through the encapsulation were found to be less likely to fail than when attached directly to the exposed timber. Smoldering was observed after the cessation of flaming and, in a few locations, was observed to progress through the thickness of the CLT panel and continue behind the encapsulation. This illustrates that, while encapsulation can succcessfully prevent flaming, it cannot be completely relied on to avoid smouldering. The findings from CodeRed #04 contribute to the development of evidence‐based fire safety design methodologies for exposed mass timber buildings.

A qualitative assessment of fire hazard posed by laminated glass balcony balustrades was carried out through an in-depth analysis of empirical evidence from six (6) past balcony fires with glass balustrades to deduce the type of glass used and understand the mechanism for fire spread in these fire scenarios. Post-fire conditions of these balconies were studied based on their post-breakage integrity and presence of decolourisation/delamination in order to determine the type of glass used in these balconies. A visual observation of the overall fire spread during the fire and extent of damage post-fire was then carried out to determine whether there was a correlation between the type of glass used and the extent of fire spread. It was found that fire spread was mainly driven by combustible materials around the balcony construction as the fire damage on the balustrades was limited to the area in the vicinity of the combustible materials and the balustrade glass did not contribute to the fire. Given the current regulatory framework in England that limits the use of laminated glass in balcony balustrades from a fire safety perspective despite its architectural benefits and structural safety, this study shows that there is no evidence that the use of laminated glass would constitute a fire hazard when used as glazed balcony balustrading.