Solar Roofs Need a New Fire Safety Standard

We are still testing solar roofs like passive roofing products, even though they behave like active electrical systems.

Solar roofing should be one of the most logical next steps in construction.

It makes little sense to build a roof first and then mount a second energy-producing layer on top of it. A well-designed solar roof should do both jobs at once: protect the building and generate electricity. Done properly, it can reduce material use, shorten installation time, improve aesthetics, and turn the roof into an active building asset.

The problem is not the idea of solar roofing.

The problem is that today's fire safety logic has not fully caught up with what solar roofs actually are.

A solar roof is not simply a roof covering with PV added on top. It is a high-voltage electrical system integrated into the roof assembly. That means fire safety can no longer be judged only by how the outer surface reacts to external flames. It must also be judged by what happens inside the system: beneath the modules, around the connectors, along the cable routes, within the ventilation cavity, and at the interface with the underlying roof structure.

This is where today's fire safety approach starts to show its limits.

Across the industry, BRoof(t1) and BRoof(t2) classifications are often treated as the primary proof of fire safety. These tests are important. They are designed to assess external fire exposure: burning brands, wind-driven flames, radiation, and flame spread across a roof surface.

That logic made sense for traditional roofing.

But many real PV fire risks begin elsewhere - in DC connectors, isolators, damaged cables, junction boxes, and semi-enclosed cavities beneath the modules.

Once ignition starts below the panel, the decisive question is no longer only whether the roof surface resists an external flame. The question becomes: what materials, cable routes, and structural layers surround the ignition point?

That question should be central to the next generation of solar roof design.

In traditional roofing, combustible materials such as timber have been used safely for generations. But solar roofs introduce a different risk environment. They combine building materials with live DC electrical systems, often operating at hundreds of volts. In that context, placing combustible materials directly within the electrical zone becomes a very different engineering decision.

This is especially relevant for in-roof and BIPV systems. In these systems, the PV modules are not simply mounted above the roof. They become part of the roof itself. The electrical system and the building envelope are no longer clearly separated. If a connector overheats, a cable is damaged, or a DC arc fault occurs, the fire may develop inside the roof assembly rather than on top of it.

The role of the substructure

That changes the role of the substructure.

In a solar roof, the substructure is no longer just a mounting component. It becomes part of the fire safety strategy. Properly designed metal battens or metal substructures can serve multiple functions at once: structural support, ventilation space, grounding path, and protected cable route. Most importantly, they remove fuel from the zone where electrical failures are most likely to occur.

Metal does not make a solar roof fireproof. Nothing does. But it changes the failure dynamics. If something goes wrong, the system should not offer the fire an easy path into combustible structural layers.

Cable management is critical

Cable management is just as critical.

In too many systems, cables are still treated as an installation detail rather than a core safety feature. They may be routed loosely beneath modules, exposed to moisture, heat, mechanical stress, debris, and long-term abrasion. Connectors may sit hidden behind panels, difficult to inspect and difficult to replace.

That is not a minor detail in a building-integrated electrical system.

Dedicated cable management should be mandatory in solar roofs. DC cables and connectors should be mechanically protected, separated from combustible materials, drained, ventilated, strain-relieved, and accessible for inspection. If the cable route is uncontrolled, the fire risk is uncontrolled.

Access during a fire

There is another major weakness that the sector rarely discusses: access during a fire.

Many solar roof systems are designed so that a single panel in the middle of the roof cannot be removed quickly without dismantling a large section of the array. From an aesthetic or waterproofing perspective, this may have seemed reasonable. From a fire safety perspective, it is a serious limitation.

If ignition starts beneath a panel, firefighters need access to the source. If the roof cannot be opened locally, the fire remains hidden and protected inside the roof cavity. Suppression is delayed, damage increases, and the risk to emergency responders rises.

This is not necessarily the result of poor engineering. Many systems were developed years ago, before large-scale field experience revealed these failure modes. At the time, the main priorities were waterproofing, visual integration, cost, and installation speed. Firefighter access was often not part of the original design brief.

But it must be now.

The next generation of solar roofs should be designed not only to prevent fire, but also to allow controlled intervention when something fails. Individual module access, clear cable paths, and maintainable system architecture should become part of the safety standard.

The underlayment gap

Even if many major technical risks can be reduced through better engineering - metal substructures, protected cable management, proper grounding, arc-fault protection, and serviceable panel design - one significant gap remains: the underlayment layer.

Today, the market still lacks cost-effective underlay solutions that can act as a true fire separation layer between the solar roof system and the combustible structure beneath it. Most roofing membranes were developed for traditional roofing, where the dominant fire scenario was external ignition. They were not designed to isolate a high-voltage electrical system from the structural layers below.

High-performance fire-resistant materials exist, but they are often too expensive, too difficult to integrate into standard roofing workflows, or not optimised for drainage, fastening, and long-term durability.

This is one of the missing pieces in solar roof safety.

A truly fire-resilient solar roof needs more than a surface classification. It needs a system-level approach: non-combustible internal layers, protected DC routing, correct grounding, accessible modules, fire-resistant separation from the structure, and testing that reflects real failure modes.

Insurance as a market lever

The industry should not treat this as an attack on solar roofing. Quite the opposite.

Solar roofing has a strong future precisely because the concept makes so much sense. But if the sector wants solar roofs to become a mass-market solution, the safety framework must mature before failures damage public trust.

There is also a market mechanism that could accelerate this change faster than regulation alone: insurance.

These risks are not new to the solar sector. Electrical faults, connector failures, poor cable routing, combustible internal layers, and difficult system access have been discussed for years. Yet the market has continued to absorb the risk because the cost of failure is often carried elsewhere - by homeowners, insurers, and emergency services.

In practice, insurers are already financing part of this market failure.

If insurance companies decide that they will no longer cover solar roof systems with avoidable fire-risk conditions - such as combustible internal layers, unmanaged DC cabling, inaccessible modules, missing arc-fault protection, or insufficient separation from the underlying structure - the industry will change quickly.

Manufacturers will redesign. Installers will adapt. Test bodies will update their methods. Regulators will follow.

Insurance has the power to turn fire safety from a nice-to-have design feature into a market requirement. In the absence of faster regulatory reform, it may be one of the most effective levers available.

The cost of inaction

The PV sector has become cheaper, faster, and more mainstream. But the safety framework around roof-integrated PV has not evolved at the same speed. In a market where price often determines who wins a project, every additional safety feature is seen as a cost. Better cable management costs money. Metal substructures cost money. Fire-resistant underlay costs money. Serviceable module design costs money. Arc-fault protection costs money.

But the alternative costs more.

It costs homeowners. It costs insurers. It costs firefighters. And eventually, it costs the credibility of the entire sector.

The automotive industry did not standardise seatbelts, airbags, crumple zones, and mandatory safety systems because they were cheap. It did so because real-world failures proved that minimum safety assumptions were not enough.

Solar roofing should not wait for the same kind of reckoning.

Before solar roofs move into mass adoption, the sector needs a new safety standard - one that treats solar roofs not as passive roofing products, but as active electrical systems integrated into buildings.

What a New Solar Roof Fire Safety Standard Should Require

A new standard should be built around real failure modes, not only external fire exposure. At minimum, it should address the following principles:

Conclusion

Solar roofing has a strong future.

But if the industry wants it to become universal, it must first make it genuinely safe.

Safety will not come from one good solution or one better component. It will come from the combination of several protective layers working together: non-combustible structures, fire-resistant separation, protected cable routes, correct grounding, arc-fault protection, serviceable modules, and system-level testing. A solar roof should be designed as a safety stack, not as a single certification checkbox.

The authors of this article do not advocate for unnecessary bureaucracy or restrictive barriers to solar adoption. But when human safety is involved, the industry should act before failures become statistics. Prevention must come before damage control - not only for the safety of homeowners and firefighters, but for the long-term credibility of the entire solar sector.