4 BCD SPECIAL REPORT ON HISTORIC CHURCHES 32nd ANNUAL EDITION NEWS REVIEW GOING SOLAR York Minster’s 184-panel solar installation saves nearly £20,000 in electricity costs and offsets eight tonnes of CO2 emissions annually, contributing towards the Church of England’s target to reach net-zero operation by 2030. (Photo: SolarEdge) The use of photovoltaic slates in a continuous plane on the south-facing slopes is particularly unobtrusive (Photo: Mark Candlish, GB-Sol) Exposing electricity-generating devices to the elements on the rooftops of historic buildings comes with obvious risks, particularly now that extreme weather events are becoming more frequent. Fortunately, fires caused by solar installations on roofs remain rare, but as specialist engineer Jim Glockling pointed out in the 2025 edition of The Building Conservation Directory, ‘even small statistical risks become important when the object at risk is irreplaceable’ (see www.buildingconservation.com/books/ bcd2025/46/). His article does not rule out the installation of rooftop solar panels on historic building, but it does provide detailed guidance on mitigating risk. At York Minster a rooftop solar system completed in 2025 was carefully designed in close consultation with insurers EIG to reduce fire risk. Power optimisers were provided for each panel which are designed by the manufacturers, Solar Edge, to continuously monitor for abnormal heat build-up at the connector level – an early indication of potential faults. If excessive heat is detected, the system can automatically prevent an electrical arc from forming. In addition, the installation includes an over-ride for fire-fighters which is wired into the building’s fire alarm system. This allows the entire solar array to be shut down quickly – either manually or automatically – giving fire crews control of the system during an emergency and ensuring the roof can be accessed safely, without risk from high DC voltage. Solar panels work best where hidden from view on low pitched roofs behind parapet walls. However, steeply pitched roofs without parapets can be highly visible from the ground, and here solar panels can present an alien element, disrupting the uniform sweep of materials from one end to the other. One alternative is to replace all the slates with solar slates, so that the roof still reads as a continuous entity, uninterrupted by panels. Fortunately, manufacturers are getting better at replicating the appearance of traditional slates. Where a building is listed, the replacement of historic materials with modern ones is likely to meet some opposition, but the change can be justified in some circumstances. Where re-roofing is required (usually as a result of nail fatigue) it is common to find that a high proportion of the older slates and tiles cannot be reused, and it is normal practice to combine all the original material on one slope with new materials on the other. Given the traditional east-west orientation, many churches have south-facing slopes which would be ideal for PV slates, and if the loss of original fabric is unavoidable due to the age of the fixings, the change may be considered reversible.
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