Engineers built full scale test decks designed to replicate typical low slope roofing assemblies used on large buildings, then mounted photovoltaic solar panels on these structures. They subjected the leading edge of the deck to flame and a crosswind to study how fires can initiate and propagate under and around the panel arrays, while also assessing how different design features influence the resulting hazards for structures and first responders.
SwRI first performed baseline tests using three common types of photovoltaic panel racking orientations to determine which configuration supported the fastest flame spread beneath the modules. Once the most critical racking orientations were identified, the team evaluated two mitigation approaches on those layouts, incorporating uncovered walkways and vertical barriers to see how these features changed fire growth behavior and pathways across the roof.
To provide a reference condition, the researchers also ran a comparison test on a bare deck with no photovoltaic panels installed. This allowed them to contrast fire performance of typical roofing materials alone with the more complex geometry and ventilation pathways introduced by solar arrays and their mounting hardware on similar roof constructions.
According to project principal engineer Alexandra Schluneker, SwRI's large indoor fire test facilities and custom pollution abatement system made it possible to conduct what she described as the largest scale photovoltaic panel evaluations to date under controlled conditions. "SwRI's large indoor fire testing facilities and custom pollution abatement system allowed us to safely conduct the largest-scale evaluations of PV panels to date with greater exposure control while protecting the environment," Schluneker said. She noted that earlier work in this area relied on smaller scale setups or outdoor testing where exposures are harder to control.
The work was sponsored by the National Fire Protection Association's Fire Protection Research Foundation and its Property Insurance Research Group, reflecting strong interest from both code developers and insurers. The resulting datasets are expected to support updates to building codes and fire mitigation protocols that specifically address the behavior of commercial and industrial rooftop solar panel installations during fire events.
Karen C. Carpenter, director of SwRI's Fire Technology Department, emphasized the broader goals of the program in the context of renewable energy deployment and community safety. "Large-scale fire testing of PV panels to evaluate performance, flame spread and potential prevention and suppression strategies is not just a technical necessity - it is a cornerstone of advancing fire safety to ensure renewable energy solutions remain both sustainable and secure for the communities they power," Carpenter said.
Schluneker has already shared preliminary findings from the test series with the fire protection community. She co-presented early results at the 2025 NFPA conference in Las Vegas, Nevada, on June 18, 2025, giving stakeholders an initial look at how different racking arrangements and mitigation details may affect roof level fire dynamics.
A second round of large scale fire testing is planned for early 2026 to examine additional mitigation concepts and refine the understanding of design features that can slow or redirect flame spread beneath photovoltaic arrays. These follow on experiments are expected to broaden the range of configurations evaluated and provide further guidance for builders, property owners and first responders as rooftop solar penetration continues to increase on commercial and industrial facilities.
For more technical information on SwRI's fire research and engineering activities, including photovoltaic system fire testing, visit the Institute's fire technology pages here.
Related Links
Southwest Research Institute
All About Solar Energy at SolarDaily.com
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