IEC TR 63226-2021 pdf Managing fire risk related to photovoltaic (PV) systems on buildings

Roofing materials are tested for certain fire withstand capabilities. However, these product characteristics may not be sufficient to withstand the energy from an arc or fire caused by a fault. If a roofing material is capable of being ignited by an arc or fire caused by a fault, additional measures may be taken into account. Additionally, the presence of PV modules in close proximity to roofing materials may trap or radiate heat from a rooftop fire causing additional roof damage. The higher the fire resistance of the roofing system, the less likely a rooftop fire will cause widespread damage. Depending on the occupancy of the building and the financial risk of loss for the building, it may be necessary to upgrade a roof system’s fire resistance when a PV system is installed on the roof or use additional measures to reduce the fire risk. If the cost of upgrading the fire resistance of the roof or additional equipment is too high, then other installation locations should be considered that require less investment. For buildings covered with exposed flammable roofing materials, additional safety measures should be considered to help prevent fire ignition. Flammable roofing materials include many common roofing materials such as bitumen, asphalt, tar paper, and various polystyrene and polyisocyanurate insulating materials. Higher fire-rated roofing systems that incorporate the most flammable polystyrene insulating materials normally include what is referred to as a cover board between the roof membrane and the insulation to prevent a fire on the membrane from involving the flammable polystyrene materials beneath the membrane. All roofs in Europe – with or without PV – must comply with fire resistance classes according to CEN/TS 1187. There are four different regions with four different tests within Europe.Not only is the roof construction important to the fire risk of a building, the entire building construction is also important. Buildings constructed of concrete, brick, and stone are more fire resistant than steel or wood structures. The concern with building construction types may be accelerated building collapse or propagation of fire to adjacent structures.