IHBC Yearbook 2014

34 Y E A R B O O K 2 0 1 4 the building, how clean it is and the surface articulation. High pressure sodium lamps are efficient but tend to create an overall yellow tinge with a low colour rendering index which can have a distorting effect on the building’s appearance. Ceramic discharge metal-halide (CDM) lamps have excellent colour rendering properties and provide a natural effect which complements most building materials, although they have a shorter projected lifespan. Most importantly, a preinstallation trial should be carried out to ensure that the position and angle of luminaires achieves the best possible outcome. Trials are best carried out before the detailed design stage, but should certainly be carried out before final installation using the luminaires specified for the building or structure. INSTALLATION ISSUES Care in the installation of external lighting is especially important when it is fixed to the building. While the poor selection of light fittings can so easily disfigure a building’s facade, thoughtless installation can result in irreversible damage to historic fabric. Careful consideration in the location of any light fitting should always take into account the material to which it is to be fixed. To avoid unnecessary damage, fixings should be drilled into joints rather than into ashlar stone or facing brick. Bolts, screws or brackets which are directly in contact with the building must be made from non-rusting and non-staining elements such as stainless steel or bronze. The lighting units and the cable routes should be designed and installed so that they do not impede rainwater run-off from the building. They should avoid sills, drip-courses and other architectural features. A key aim for the design team on the Walled City Lighting Project was to make the installation of both the light fittings and the cable runs as discreet as possible. MAINTENANCE There is a balance to be struck between ease of maintenance and the desire to hide or disguise fittings. All external lighting schemes require safe access for maintenance. If access is complex or costly this may discourage routine maintenance inspections and result in a ‘reactive’ approach of responding to problems after they occur rather than seeking to prevent them. Lighting installations should be inspected regularly. All fittings should be cleaned and checked during the inspection and any defective elements replaced. Thoughtful design, specification and installation will help to ensure that a successful scheme is not undermined by a difficult maintenance process. The lighting maintenance schedule should be viewed as part of the overall repair and upkeep of the building rather than an unwelcome expense to be avoided. The Walled City Lighting Project demonstrates that the art of lighting lies in both the control of light and in the sensitive installation of light fixtures and fittings. Bringing Derry~Londonderry’s historic buildings out of the shadows has encouraged visitors and residents to value them in a new way, a fact that should help to secure their future conservation. Paul Millar BSc RIBA RIAI MAPS is a partner at Kriterion Conservation Architects. He has over 30 years’ experience as a conservation architect working with historic buildings throughout Northern Ireland. He is a member of Hillsborough Castle Working Group and the International Network for Traditional Building, Architecture & Urbanism. He is also chairman of the Belfast Buildings Trust. First Derry Presbyterian Church (c1780) Grand Parade on the city’s west wall (c1619)

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