FSRI Research Engineer Presents Heat Transfer and Fire Spread from Post-Flashover Compartment Fires at the UC Davis Wildfire Resilient Structures Conference

Joe Willi, research engineer at UL’s Fire Safety Research Institute (FSRI), presented on full-scale experiments from the Heat Transfer from Structure Fires research project during the UC Davis Wildfire Resilient Structures (WiReS) Conference in February 2023. In his presentation, Willi summarized the project’s first series of full-scale experiments that were divided into three phases.

The research team conducted these experiments at UL’s indoor fire laboratory in Northbrook, IL to minimize the effects of wind and other weather conditions. Phase 1 experiments exposed different building materials to a heptane spray burner fire source. Phase 2 experiments characterized a post-flashover compartment fire that spread to an exterior facade. Willi shared a detailed overview of the third phase of experiments which exposed a target facade using materials tested in Phase 1 to the post-flashover compartment fire tested in Phase 2 to examine the potential risks for building-to-building fire spread. Specifically, Phase 3 experiments studied:

• The ignition potential of siding materials including vinyl, T1-11, and fiber cement board
• How intermediate fuels, like vehicles and attached decks, impacted fire spread from the source compartment fire to the target facade
• Failure potential of windows due to heat transfer from exposure to the source compartment fire

Willi shared that there were no notable differences in heat flux to the target structure when the different siding materials were used. He also noted that during the experiments using intermediate fuel sources, only the attached deck caused the target facade to ignite. The geometry of the intermediate fuel source also affected the heat transfer to the target facade. For the window experiments, the research team discovered a reduction in heat flux of 76 - 79 percent through double pane plain glass windows and 99 - 100 percent through double pane low-E windows. Willi also noted that screens reduced heat flux through windows by 28 - 36 percent compared to no screens. A recording of the full presentation is available to all attendees of the WiReS conference.

Building off the first series of experiments, another series of façade experiments were conducted in October and November of 2022 at the Delaware County Emergency Services Training Center (ESTC) facility in Sharon Hill, PA. These experiments involved longer post-flashover exposures and smaller separation distances between the structures.