CONTEXT 185 : SEPTEMBER 2025 31 ROOFING despite these high-profile examples, this does not mean that panels are the right approach for every building. The inclusion of solar generation into a historic site should be assessed on a case-by-case basis to ensure that they are part of an integrated and whole-building approach. Photovoltaic (PV) systems generate power by converting sunlight directly into electricity. This can be used at the point of generation or exported to the national grid. This form of renewable electricity is part of the range of options to meet net-zero targets and is often a productive way to reduce a building’s overall energy costs. The system’s performance can be reduced by factors such as intermittent shading, the build-up of dirt and dust, and high temperatures. There are a range of different products that have been utilised within the historic environment, from panels that sit above the existing roof covering to solar slates incorporated within the roof and solar film which coats the roof. These three examples of the technology have all be used within the precinct of York Minster to achieve a balance between the visual impact and achieving renewable generation. The solar slates were employed on the rectory building and the solar film on the new Stone Yard building. The array on the minister is currently outperforming the manufacturer’s forecast. The South Quire transept is now regularly producing 80 per cent of the minster’s power at peak daylight hours. This will shift the return on investment from nearly eight years to under four years. Although installing on-site renewable energy generation is a measure to reduce the overall impacts of the built environment, contributing to lower running costs, it is not without wider environmental impacts associated with production, installation, and end-of-life removal and recycling. The value of a high-quality feasibility study is central to ensuring that this is the best option for a site. Reducing demand and increasing efficiency will both deliver cost and comfort benefits and, if PV is installed, increase the overall contribution it can make. The significance of assets should be properly assessed to determine the impact of the installation and evaluate potential harm before seeking permission. The visual impact of PV installations is only one way that they can potentially harm the significance of a listed building. The physical impact on the building is of particular importance, including the type of roof covering and the need for access for maintenance and removal at the end of the installation’s operational lifespan. Where installations would require fixing directly into historic fabric, such as medieval roof timbers, alternative solutions may need to be considered. Many historic buildings are unique, and their structural tolerance should be carefully assessed by a structural engineer with experience of listed and historic structures. In the case of roof-mounted installations it is necessary to consider additional wind, snow and static loading, and the potential impacts on existing fabric. The increasing impacts of climate change and potential increased numbers of high winds and storm events in particular locations should be considered. There were seven named storms in 2023–24, and the wettest 18 months on record in 2024–25. Inspecting for damage after storm events is essential. Historic buildings and sites are often rich habitats for flora and fauna. Both bats and birds are protected by law, and it is important to consider potentially negative impact of works, the disturbance they may cause and the longterm implications for maintenance requirements, particularly around nesting birds. Seagulls and pigeons can pose a particular problem when they use panels to shelter and nest and limit access to roofs during the nesting season. Bird A Somerset roof array in need of cleaning (Photo: Morwenna Slade) PV panels on a roof in Penrith with slipped slates and needing maintenance (Photo: Morwenna Slade) A seagull nesting above solar panels on Romney Marshes (Photo: Morwenna Slade)
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