Experimental study of the post-flashover fire performance of multi-pane low-energy windows

Windows play an important role in the fire safety of buildings since, if the glass breaks and falls out due to fire, this can allow: (i) oxygen to enter the fire compartment; (ii) flames and hot gases to exit the fire compartment and expose the façade; and (iii) external fires to spread into the building. In this study, we investigate the fire performance of modern energy efficient windows to increase the understanding of how the use of such windows affect the fire safety of buildings. Three window configurations, one smaller window with three glass layers, and two larger windows with two and three glass layers, respectively, were tested in a total of eight furnace tests. Two different fire curves were used, a standard and a parametric fire, and the results showed that there were similarities between the cracking times of each pane for equally sized windows and fire exposures. Additionally, the time interval between cracking of panes 1 and 2, and panes 2 and 3 were seen to be somewhat consistent. For the small window specimens, no cracking of pane three was observed after 30 min of parametric fire exposure. The resulting fallout area of the three-layered specimens were practically negligible (≤ 2%), whereas the two-layered specimens had fallouts of 15–53%. The fallout area did not seem to be influenced by the fire exposure. Based on the results, we conclude that the most energy-efficient three-layered windows also results in the smallest ventilation openings.