Flammability of Facades Across Scales and International Standards

ABSTRACT Facade fires are a rare but destructive hazard that can lead to the rapid spread of fire between the floors and fire compartments of a building. Today, there are at least 21 different national standards for facade fire tests in use around the world, which seek to categorize facades based on their flammability. Each of these standards measures some aspect of upward flame spread, alongside other aspects of fire behavior, but the size and geometry of the facades tested, and the type of, and peak heat flux from, the ignition source vary significantly between standards. It is unclear whether these different standards categorize similar facades consistently, such that the results are robust, correct, and safe when applied to buildings. This paper presents a series of 25 experiments: testing five facades (two ETICS and three rainscreen facades) using five test standards (PN‐B‐02867, ISO 13785‐1, DIN 4102‐20, NFPA 285 and BS 8414). The average heat release rate was reconstructed and the average vertical flame spread rate was measured to determine whether they varied more with the choice of facade build‐up or the choice of standard. We found that different standards could not rank the flammability of the facades more consistently than random chance in terms of flame spread rate, but that the average reconstructed heat release rate provided a consistent rank. Qualitatively, the facades showed similar burning behavior across the different standards, which suggests that it may not be justifiable to use larger, more expensive tests to study facade flammability. However, in some experiments, complex fire dynamics were observed—such as pool fires forming beneath the facade—that could not be captured by simple metrics, and that were sensitive to the details of each standard. This research presents a unique comparison of different facade test standards that can inform fire engineering judgements made from such standards, allowing for the safer use of facades in tall buildings.