This work was carried in support of NRC’s Mid-rise Wood Buildings (MRWB) program, whose objective is to improve the performance of mid-rise and tall wood buildings. The main objective of the work was to determine the scope for future research to develop new technologies to prevent, fight and mitigate the impacts of fire during construction. The work involved an extensive literature review and some discussions with potential stakeholders to understand their views, concerns and research needs. The literature review covered approximately 115 publications (including magazine and newspaper articles). The current literature clearly identifies the significant fire risks faced by wood buildings during the construction phase and there are numerous examples of fires that have occurred at wood building construction sites. The literature review revealed that the current state-of-the-art essentially encompasses the development and promotion of safe working practices and fire safety guidelines for mid-rise wood buildings under construction, which is being adequately addressed by many industry stakeholders. There is a lack of research and methods to address the critical areas of active and passive fire protection during construction. This is likely due to the fact that the acceptance of mid-rise and tall wood buildings has only happened recently and was largely based on the fact that the fire safety of finished buildings is assured by proven adequacy of their fire resistance design features, such as the encapsulation approach, and mandatory requirements for fire protection systems, such as sprinklers. Therefore, NRC can make a more valuable contribution in areas where its existing fire research expertise and unique test facilities can lead to the development of new knowledge to improve safety in mid-rise wood buildings under construction by undertaking research in the following areas identified by this study: 1. Characterization of construction site fires and evaluation of detection systems; 2. Evaluation and development of active fire protection systems/technologies applicable to construction sites; 3. Evaluation and development of passive fire protection systems/technologies applicable to construction sites; 4. Improvement of firefighting tactics using scientific knowledge of construction site fires and effective suppression technologies. The research can be undertaken in phases, with Phase 1 focusing on the characterization of mid-rise wood construction site fires, evaluation and development of fire detection and suppression systems. Subsequent phases of the project could address the evaluation and development of cost-effective passive protection systems and the improvement of firefighting tactics using the fire scenarios developed in Phase 1. Further details of the potential scope for research in the above areas are presented and discussed in this report.
"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.
"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.