King's College, Cambridge has its own 2030 net zero target. This, together with the need to replace the lead on the Chapel roof provided the catalyst for this application to install solar panels on both the north and south sides of the roof of the Chapel, a building of exceptional significance. The court recognised the contribution of amenity societies and consultees to the work of the faculty jurisdiction, and set out their responses in some detail.
The court made the following observations. A large carbon-neutral generation scheme would strongly support the fifth mark of mission: ‘to strive to safeguard the integrity of creation and sustain and renew the life of the earth’. Because the project had been carefully planned and managed, it ought to act as an encouragement to churches and other public buildings to consider whether they can contribute to the net zero target in this way. As the scaffolding was already in place for re-leading the roof, the lost opportunity cost of not installing solar panels now and up to 2050 (the expected lifespan of the panels) equated to 410 tonnes of CO2; the cost of that scaffolding alone was £700,000.
Following amendments to the proposed siting of the panels, moving them away from the ridgeline and lower to the roof itself, there would still be some degree of visual harm, but that from most locations, the panels would be concealed by the parapet and generally only visible, if at all, through piercings and crenellations. The concerns expressed in some quarters about the reflectivity of solar panels was unconvincing. In terms of the Duffield questions, the harm to the significance of the Chapel as a building of special architectural or historic interest would be more than minimal, given the singular importance of the building, but less than substantial. The work would be reversible.
It was estimated that panels on the north roof would be around 60–70% as efficient as those on the south roof. This, combined with the significant embodied carbon cost of manufacturing, transporting, installing and maintaining the panels, and the decreasing carbon savings arising from the increasing decarbonisation of the national electricity supply as a whole, called for separate consideration of the two roofs. However, the court also acknowledged the possible effect on the structure of the roof if the weight of panels on the south roof were not matched by a similar weight on the north roof.
A faculty would be granted, subject to an updated assessment and consultation on the potential payback from panels on the north roof and the structural effect of panels only being installed on the south roof. Further conditions included a test on an adhesive overlay to reduce reflection; monitoring of the effect of the panels on the roof covering; and the requirement that the panels be removed at the end of their useful life or when superseded by technological advances.
In a subsequent judgment concerning panels on the north roof, the court noted the differing approaches of the petitioners and the CBC in calculating the benefits of solar panels. According to the long-run marginal costs approach, panels on the north roof would have a carbon payback time of 7.4 years (therefore having a 69% efficiency of those on the south roof, which had a payback time of 4.5 years). According to the grid average costs approach, favoured by the CBC, there would be no carbon payback over the lifetime of the panels. The court agreed with the DAC that the former approach was the correct one. The court would, therefore, grant a faculty for solar panels on the north roof as well. The concerns voiced by the court and confirmed by a structural engineer concerning uneven loading would, therefore, fall away. In relation to other matters, the suggested non-reflective overlay would reduce the efficiency of the panels by 10%, and would not have sufficient visual benefit. It could, in any event, be retrofitted later if necessary. The end-of-life removal condition was modified, omitting reference to technological advances, to ensure that the panels were not removed and replaced prematurely. [DW]
