FIREBRAND PROTECTION AS THE KEY DESIGN ELEMENT FOR STRUCTURE SURVIVAL DURING CATASTROPHIC WILDLAND FIRES

摘要

In Southern California in particular, fires that descry large numbers of structures are inevitably carafe, wiud-driven events. Characteristics of this class of fire include sttong gale-foree winds, inw probability o f professional fire intervention, and the tresence of wind-driven firebrans before, during and dihir the passage of the fire front Ignition by radiant heat or direct flame exposure can be prevented by separating the structure from fuels, and this practice is being increasingly disseminated and enforced. Protection from firebrands, however, requires that the structure have no potential ignition points where small wthd-driven brands can lodge and pilot structure ignition, or that this ignition be somehow prevented. We present two new results that point to brands as an ignition source. One of these highlights a new potential threat by showing that there is a possible correlation between "Sparnish tile", or curved tile roofs, and home ignition, as observed in the Scripps Ranch neighbourhood of San Diego during the Cedar Fire. The other result conisis of a case-study of an interface stucture that survived the Cedar Fire through the application of light water spray. This system was designed by one of the authors (Mitchbell) to be wind- resilient, and previously disclosed3 as a "Wind-Enabled Ember Dousing System", or WEEDS. This system used much less water than necessary to protect against peek radiant heat, empleyud techniques that made it resistant to over-dispersal of spray in strong winds, and was designed and implemented in such a way as to make it independent of external utility and water supplies.