| Résumé | Water mist systems are considered in protection of encapsulated mass timber construction (EMTC), due to their typically low water spray rates. This technical best practice provides an overview of regulatory requirement for the fire protection of residential mass timber buildings including fire suppression systems, and it discusses applicable characteristics and design considerations of water mist systems, which are not addressed in the existing standards and guidelines.
In designing a water mist system, any special hazard of mass timber buildings should be considered, whilst construction materials are not specifically addressed in the hazard categories of the existing standards. The water mist system should be designed to provide enhanced property protection in addition to the typical residential system performance when the hazard assessment indicates relatively large areas of exposed mass timber elements, post-fire retrofit difficulties of damaged mass timber elements or other special hazardous circumstances.
While the evaluated design objectives are the same for water mist and conventional sprinkler systems, the design approach of water mist system is fundamentally different from the prescriptive manner of sprinkler systems. Water mist systems are designed based on acceptable performance demonstrated in full-scale fire tests meeting the specified pass criteria. For the case where the existing standard test protocols are not applicable, test protocols should be developed to represent the actual hazard condition (e.g., fuel loads, ventilation conditions, room dimensions) in the protected area, and to test the performance objectives, design, and component functionality. This technical document provides aspects to take into account in selecting test scenarios, protocols and pass-fail criteria. Technical notes are also provided to design parameters, such as delay times of a dry-pipe/pre-action system, water-spray shape, design area and durations, which are particularly relevant to the fire protection of residential mass timber buildings. |
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