A large-scale fire test was conducted on a compartment constructed from cross laminated timber (CLT). The internal faces of the compartment were lined with non-combustible board, with the exception of one wall and the ceiling where the CLT was exposed directly to the fire inside the compartment. Extinction of the fire occurred without intervention. During the fire test, measurements were made of incident radiant heat flux, gas phase temperature, and in-depth temperature in the CLT. In addition, gas flow velocities and gas phase temperatures at the opening were measured, as well as incident heat fluxes at the facade due to flames and the plume leaving the opening. The fuel load was chosen to be sufficient to attain flashover, to achieve steadystate burning conditions of the exposed CLT, but to minimize the probability of uncertain behaviors induced by the specific characteristics of the CLT. Ventilation conditions were chosen to approximate maximum temperatures within a compartment. Wood cribs were used as fuel and, following decay of the cribs, selfextinction of the exposed CLT rapidly occurred. In parallel with the large-scale test, a small scale study focusing on CLT self-extinction was conducted. This study was used: to establish the range of incident heat fluxes for which self-extinction of the CLT can occur; the duration of exposure after which steady-state burning occurred; and the duration of exposure at which debonding of the CLT could occur. The large-scale test is described, and the results from both the small and large-scale tests are compared. It is found that selfextinction occurred in the large-scale compartment within the range of critical heat fluxes obtained from the small scale tests.
A series of compartment fire experiments has been undertaken to evaluate the impact of combustible cross laminated timber linings on the compartment fire behaviour. Compartment heat release rates and temperatures are reported for three configuration of exposed timber surfaces. Auto-extinction of the compartment was observed in one case but this was not observed when the experiment was repeated under identical condition. This highlights the strong interaction between the exposed combustible material and the resulting fire dynamics. For large areas of exposed timber linings heat transfer within the compartment dominates and prevents auto-extinction. A framework is presented based on the relative durations of the thermal penetration time of a timber layer and compartment fire duration to account for the observed differences in fire dynamics. This analysis shows that fall-off of the charred timber layers is a key contributor to whether auto-extinction can be achieved.
This monitoring study aims to generate field performance data from a highly energy efficient building in the west coast climate as part of FPInnovations’ efforts to assist the building sector in developing durable and energy efficient wood-based buildings. A six-storey mixed-use building, with five storeys of wood-frame residential construction on top of concrete commercial space was completed in early 2018 in the City of Vancouver. It was designed to meet the Passive House standard. The instrumentation aimed to gather field data related to the indoor environment, building envelope moisture performance, and vertical movement to address the most critical concerns among practitioners for such buildings.
Developed in the mid-1990s in Austria and Germany, Cross Laminated Timber (CLT) is an innovative wood product known for its strength in both orthogonal directions, and its dimensional stability, making it a sustainable alternative to concrete slabs. CLT is created through the cross-lamination process, which glues together odd number of layers of wood planks placed in orthogonally alternating directions. With the growing interest in the application of CLT in North America, numerous studies has been conducted to characterize the acoustical properties of CLT panels. However, most of them focused on the sound-transmission aspect of CLT, very few on the sound absorption. This thesis will explore the sound-absorption characteristics of CLT, the effect on overall room-acoustical conditions, the utilization of resonant sound-absorbing layers on CLT to make it more sound-absorptive, and proposed solutions to improve this performance aspect. To demonstrate the low sound absorption and poor acoustical conditions in rooms with exposed and untreated CLT panels, several in-situ reverberation-time (RT) measurements were conducted in multiple buildings in British Columbia. Average sound-absorption coefficients and estimated Speech Intelligibility Indices (SII) were calculated as baseline performance measures for this study. Based on the results from five different buildings, involving 8 rooms configurations, average sound-absorption coefficients for exposed CLT panels are approximately between 0.02 to 0.13, resulting in barely acceptable conditions for verbal communication. To optimize the sound-absorption characteristics of prototype CLT panels, a transfer-matrix model has been developed to predict the performance of multi-layered CLT panels. This theoretical model was then validated by using three different sound-absorption measurement methods (impedance tube, spherical decoupling, and reverberation chamber) for multiple HR array configurations. After identifying the important parameters of an HR system and their effects on performance, a final prototype configuration with Helmholtz Resonator Array was then created with the goal of improving the room- acoustical performance of CLT, as well as responding to input from the CLT manufacturers and experts. Both the theoretical and experimental results confirmed that the proposed solution has the required sound-absorption performance and achieves all research objectives.
In early 2019, with funding support from Natural Resources Canada, the National Research Council Canada conducted a series of room scale fire tests of Encapsulated Mass Timber Construction (EMTC) with nail laminated timber (NLT) and Glulam structural elements. The goal of this test series is to quantify the contribution of NLT mass timber elements to compartment fires and to provide additional data as the technical basis for the amount of exposed mass timber elements to be allowed in EMTC buildings without significantly increasing the fire severity and duration.
"This report presents the findings from a simulation parametric study to investigate the use of water mist systems for a residential compartment fire involving exposed mass timber structures. The fire and suppression models were first validated against experimental data obtained from the NRC fire tests that were conducted under the same project. Seventeen simulations were conducted using Fire Dynamic Simulator (FDS) software. The following parameters were investigated: effect of fuel arrangement and location on fire severity in exposed wood compartment, effect of different finishing on fire severity in compartment, fire and suppression in open space vs compartment, effectiveness of water mist systems in fire suppression in compartments with different finishing. The results show the effectiveness of the water mist system in suppressing the fire in exposed wood compartments where a high heat release is expected due to the high fuel load"--Executive summary, page iv.
This paper documents the findings of a series of full-scale room fire tests, which includes tests on fully protected, partially protected CLT rooms as well as light-frame timber/steel rooms under real natural fires, aiming to investigate the fire behaviour and performance of CLT panels as an increasingly popular engineered wood product and to compare it to the performance of more traditional construction methods. Results show that the CLT panels when left unprotected get involved in the room fire as part of the combustible contents, responsible for over 60% of total heat release in the fully unprotected CLT room and double the heat release rate of a fully protected room fire where the CLT does not contribute. Partially-protected CLT rooms also demonstrates various levels of fire contribution. The amount of CLT exposure is also related to the occurrence of re-ignition and a second flashover after all the movable fuels are consumed. The behaviour of CLT delamination and charring as well as the performance of gypsum boards in fire are also discussed.
In compartment fires with boundaries consisting of exposed mass timber surfaces – for example in compartments with exposed cross-laminated timber (CLT) walls or floors – the thermal penetration depth, i.e. the depth of timber heated to temperatures significantly above ambient behind the char-timber interface, during fire exposure may have a significant influence on the load bearing capacity of structural mass timber buildings, particularly in the decay phase of a real fire. This paper presents in-depth timber temperature measurements obtained during a series of full-scale fire experiments in compartments with partially exposed CLT boundaries, including decay phases. During experiments in which the timber surfaces achieved auto-extinction after consumption of the compartment fuel load, the thermal penetration depth continued to increase for more than one hour, whilst the progression of the in-depth charring front effectively halted at extinction. A simple calculation model is presented to demonstrate that this ongoing progression of thermal penetration continues to reduce the structural load bearing capacity of the CLT elements, thereby increasing the potential for structural collapse during the decay phase of the fire. This issue is considered to be most important for timber compression elements. Currently utilised structural fire design methods for mass timber generally assume a fixed ‘zero strength layer’ depth to account for thermally affected timber behind the char line; however they make no explicit attempt to account for these decay-phase effects.
"As an alternative option to conventional sprinkler system, water mist systems are considered for the protection of timber buildings because they use much less amounts of water compared to sprinkler systems. The effectiveness of high pressure water mist (HPWM) and low pressure water mist (LPWM) systems was investigated in comparison to sprinkler systems for a residential fire scenario involving mass timber structures. The most distinct characteristic of the HPWM and LPWM systems was fine water droplets generated from the nozzles, which demonstrated effective smoke cooling in the room. Although the water spray rate of the HPWM was four times lower than that of the sprinkler system, the water mist systems effectively control the fire and maintained the room tenable. Most systems (HPWM, LPWM and sprinklers) tested in this study did not prevent fire damage on the CLT walls, but the HPWM system with a wide spray angle demonstrated rapid fire suppression and protection of the CLT walls. In all tests, a large water pool formed on the floor, which appeared proportional to the total water spray discharge in each test, and the moisture contents measured on the surface and bottom edges of the CLT panels indicated that water can penetrate into the interface between the floor and the wall in a typical CLT assembly"--Executive summary, page 1.
