Historic Churches 2018

24 BCD SPECIAL REPORT ON HISTORIC CHURCHES 25 TH ANNUAL EDITION CONSERVATION PRINCIPLES FOR WIRING LIGHTING SYSTEMS Bruce Kirk T WO OF the key goals of lighting and other electrical projects in historic buildings are to ensure that as much of the infrastructure as possible is unseen and that the level of intervention into the building fabric is managed and minimised. Many important factors contribute to the project team’s ability to achieve these goals; some are visual and aesthetic while others, which are of equal or sometimes greater importance, relate to less visible aspects of the project such as the type and positioning of cables and fixings. THE VISIBLE SIGNS First and foremost, the lighting design must meet the overall needs of the project brief. There should be the correct levels of general illumination, which may differ for areas of circulation, reading and formal meetings. There should be highlighting for points of focus and the provision of general architectural enhancement to help visitors enjoy and interpret the building. The choice of luminaire is critical to minimising the aesthetic impact of a new lighting installation. Irrespective of the optical power and performance of the fittings, their physical shape and size is likely to be the most obvious manifestation of the scheme. For example, a cylindrical shaped light fitting might be more appropriate near to the rounded shafts of a column than to a rectilinear pilaster. Similarly, square-edged fittings do not sit comfortably alongside curved architectural details. Users also tend to be more accepting of the aesthetic impact of technology when they can see that it is serving a useful purpose, so light fittings appear less intrusive when they are lit than when they are off. For example, visitors will pay little attention to art gallery lighting which is obviously illuminating the artwork and improving the quality of their experience. The careful selection of louvres and other accessories is important in minimising glare and unwanted ‘stray’ light, further reducing the visual impact. Nonetheless, some luminaires are often seen when they are turned off and care should be taken to ensure that they look, as far as possible, appropriate to the space. Another essential part of the design is that the controls must provide the level of functionality and flexibility required to meet the needs of the building’s various uses. This might just mean the correct switching arrangement but could involve a manual or pre-set dimming system. WHAT LIES BENEATH Beyond these visible attributes are the aspects that lie below the surface, or are otherwise out of view of building users and visitors. This is where it is necessary to consider how the Guildford Cathedral: the main lighting is provided by LED spotlights at 22m in bespoke housings suspended from existing hanging points. These provide general downlighting as well as accent lighting for liturgical points of focus and spotlighting for concerts and events. (Photo: Nikhilesh Haval, all other photos: Light Perceptions Limited)