As solar energy continues to expand across commercial and industrial rooftops, understanding their fire behaviour has become a growing safety priority
Southwest Research Institute (SwRI) recently completed a series of large-scale fire tests designed to evaluate how flames spread beneath photovoltaic (PV) panel installations and how those risks can be reduced through design and mitigation strategies.
The research focused on flat rooftops commonly used for large solar panels. The findings from the SwRI study are expected to support updates to fire safety standards, building codes, and emergency response practices related to rooftop solar installations.
Rooftop conditions
For the study to be accurate, SwRI had to closely replicate real rooftop environments; they did this by constructing a full-scale test desk representing commercial roofing assemblies fitted with PV panels.
These desks were exposed to controlled flames and crosswind conditions, allowing the team to observe how fires might behave during realistic ignition scenarios.
These decks were exposed to controlled flames and crosswind conditions, allowing the team to observe how fires might behave during realistic ignition scenarios.
The testing was conducted indoors using SwRI’s large fire testing facilities, which include a custom pollution abatement system. This setup enabled precise control over exposure conditions while minimising environmental impact, enabling researchers to safely conduct some of the largest PV fire tests to date.
Comparing racking orientations and fire spread
A key objective of the study was to understand how different solar panel mounting configurations influence flame spread. Researchers conducted baseline tests using three common PV panel racking orientations to determine which designs allowed fire to move most rapidly beneath the panels.
In addition to these baseline evaluations, the team tested specific fire-prevention features. These included uncovered rooftop walkways and vertical barriers intended to interrupt flame spread. Each mitigation strategy was evaluated using the most fire-prone racking configurations identified during initial testing.
For comparison, researchers also performed a test using a bare rooftop deck with no solar panels installed. This allowed them to measure how the presence of PV systems affects fire behaviour compared with traditional rooftop conditions.
Benefits for builders, insurers and fire responders
The data collected from the tests provides valuable insights for multiple people. Builders and designers can use the findings to improve rooftop solar layouts. Insurance groups can better assess fire risks associated with solar installations. Firefighters and emergency responders can gain a clearer understanding of how rooftop fires may behave when PV systems are present.
By identifying design features that slow or redirect flame spread, the research supports safer integration of renewable energy systems into commercial and industrial buildings.
Supporting updated safety standards
The project was sponsored by the National Fire Protection Association’s Fire Protection Research Foundation and its Property Insurance Research Group. The results will help inform updates to fire mitigation protocols and building codes that specifically address rooftop solar installations, an area where standards continue to evolve as the industry grows rapidly.
Findings from the study were shared at the 2025 NFPA conference in Las Vegas, providing early insights to fire safety professionals and industry leaders.
SwRI plans to conduct a second round of large-scale fire testing in early 2026. This next phase will explore additional mitigation strategies and further refine best practices for reducing fire risks associated with rooftop solar systems.
