Fire-Induced Cracking of Modern Window Glazing: An Experimental Study

The knowledge of the behaviour of windows and, thus, of the actual ventilation in a fire room is paramount for predicting the fire development and the thermal response of structural elements. In this study, 75 tests were conducted on different glazing units made of annealed, toughened, and laminated glass, to investigate how modern insulating glazing units (IGUs) break and contribute to the ventilation factor in fires. The glass was tested as single, double, and triple pane glazing. The tests considered variations in glass pane thickness (3-8 mm) and sizes (side lengths 200-500 mm). A constant radiant heat flux of ca. 20 kW/m² was applied to simulate post-flashover conditions. No cracking and no fallout were observed in toughened and laminated glass panes, respectively. In annealed glass pane units, the onset of cracking of subsequent panes was delayed depending on the amount of fallout of the first pane, indicating that such unit could provide no ventilation at flashover.