Abstract
The fire protective envelope of any building consists of multiple elements with widely differing properties relating to a fire, such as glass, roof tiles and sheathings, wood cladding, gaps and openings. Where resistance to an exterior fire is required, all elements should be verified to provide a comparable risk of burn-through. Elements are rated by either the material response to fire or fire resistance. In Europe, cladding sheets and wall membranes can be rated by K classes, which effectively include a measure of the time to burn through. A determination of burn-through time of each element of a specific building envelope should be obtained. A design tool to verify the performance of a building's fire protective envelope has been developed. In this paper, a general description of passive elements of the envelope, which should be included in a risk assessment tool such as an index method, is presented. An illustrative approach to visualise the profiles for areas densely spaced structures where an exterior fire may trigger building-to-building fire spread is also included. The research is based on the hypothesis that a relatively subtle and pointed upgrading of an exterior building envelope will severely reduce the speed of building-to-building fire spread, thus allowing firefighting efforts to get on top of the situation. For a burning structure to expose other buildings to fire, the fire has to settle, which leads to a burn-through to the inside. Once inside, an enclosure fire needs to develop and burn through the roof or break one or more large window panes. It is estimated that a 5–10 min delay for a structure to expose other structures to fire can be sufficient to avoid loss of multiple structures. A 10–50 min burn-through time allows for an extended intervention by the fire brigade, which is significant in rural areas. A fire protective envelope may prevent an exterior fire from penetrating the protective envelope at all and the structure can be saved.
Highlights
Exterior fires and wildland urban interface (WUI) fires are global challenges and subject to increasing interest due to the emerging risk from climate change
The US and Australia are familiar with such fires and have established regulations to prevent structural losses due to exterior fire events, referred to as WUI fires
Decisive crucial elements that govern the development of a conflagration and WUI fires have been identified and ranked according to information based on fire-resistive performance, a literature study and interviews
Summary
Exterior fires and wildland urban interface (WUI) fires are global challenges and subject to increasing interest due to the emerging risk from climate change. The US and Australia are familiar with such fires and have established regulations to prevent structural losses due to exterior fire events, referred to as WUI fires In these countries, the standards NFPA 1144 “Reducing structure ignition hazards from wildland fire” [2] and AS 3959 “Construction of buildings in. A full-coverage fixed extinguishing system inside could not have prevented the damage caused by such an exterior fire entering through wall cavities and floor voids Such fires can be prevented by identifying risks and systematically devising adequate, simple and strategic passive protection measures. Based on an index method, the developed risk and design tool FireScore is aimed at assessing the performance of single or multiple structures to resist exterior exposure to fire. New handheld technology allows for maps to be created in the field, prior to the implementation of risk-reducing measures based on statistical analyses
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