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All things considered: the relighting of a World Heritage Site acknowledges the buildings' historical figures--from Pipistrelle bats to a complete set of human remains.

The LED was a foreign concept during Durham Castle's days of yore. In fact, electric lighting in general was still centuries away when the castle was constructed in 1072, six years after the Norman Conquest of England. At first, the structure consisted of no more than a motte (or mound) and an inner and outer bailey (or fenced/walled area). Today, how-ever, Durham Castle and Durham Cathedral, which flank several buildings including Durham University, are illuminated by a modern LED system. The new lighting design, completed for the castle in 2012 and the cathedral in 2013, is the result of a 2009 competition won by U.K.-based Stainton Lighting Design.

The goal of the competition was to upgrade the site's existing floodlighting scheme, which used high-power projector lights and provided a flat wash across the buildings with no differentiation between each building's architectural features. The challenge then became to create a design for the exterior facade that would be cohesive, but also subtly showcase each building's unique features. The design also needed to be modern and high-quality, comply with principles in Durham's Light and Darkness Strategy (developed by Speirs + Major to provide a framework for the city's nighttime lighting), and also consider installation cost, maintenance, energy consumption, practicality and ease of implementation. The design changed significantly between the winning competition concept and the project's completion, but with road bumps well-navigated, the final product delivers on the competition's requirements and provides the two-fold visual impact that the community was hoping for from the beginning.

A METHOD TO THE MADNESS

The castle and cathedral together form Durham UNESCO World Heritage Site, a very early example of Norman architecture in Eng-land, as well as a site whose innovative vaulting foreshadowed later Gothic architecture in the area. "The archaeological, ecological and planning constraints associated with construction work on such historic structures proved to be a significant challenge," says Anthony Smith, director at Stainton Lighting Design.

Indeed, many precautions were taken by the designers, who worked in tandem with a planning coordinator, as well as contractor AK Lighting and Signs. To maintain the architectural and historical integrity of the buildings, existing cable networks were reused when possible, holes from clipped cables were reused and no new holes were drilled into the existing structure. "We removed 46 luminaires and installed in excess of 250 luminaires without drilling any new holes in the fabric of either building," Smith adds.

In addition to using existing cable routes, the designers focused on using previously disturbed ground and limiting the depth of buried equipment--including in-ground luminaires, concrete ground mount plinths and a 1.5-m column--to 300mm below the ground. An archaeologist oversaw the process in order to evaluate any potentially significant historical articles found along the way, such as the complete set of human remains that were discovered when the designers trenched through a medieval graveyard.

The designers also faced a more lively challenge while planning. "The site had a prevalence of bat roosts and foraging routes," Smith says. "Working closely with ecologists we mitigated the effects of the lighting on the bats by a number of means." A survey helped the team to determine three roost areas that they specifically did not illuminate. They also considered the bat survey when deciding to use lighting without UV or blue light emissions, and with minimum levels, low spill, and louvers and glare guards when necessary. Furthermore, the designers implemented timers and movement sensors, avoided the lighting of trees or ground cover, and even removed existing lights in the trees and on the ground.

Not surprisingly, Stainton's careful consideration of both history and ecology resulted in painstaking installation. The roof-mounted luminaires, for example, required a strong platform heavy enough to withstand elements such as wind, but light enough to physically bring onto the roof for installation, and also non-fixed for later re-pairs. "There was no access for cranes and many of the roof access points offered limited space," Smith explains. The team ended up de-signing a platform that was transported in pieces and assembled on the roof, despite the "units weighing from 44 kg (97 lbs) to in excess of 70 kg (154 lbs)," Smith says. In addition, due to the entire system's complexity, the designers developed an external labeling system for luminaires to minimize the chance for error. And lastly, since the contractor was unable to source the required p-clips for the project, the company manufactured the item itself.

THE HIGHLIGHT EFFECT

With a plethora of obstacles to overcome, the team began work on the project, which took about four years to complete. "The lighting highlights the natural beauty of the building, offering modeling to the general fabric of the building and giving depth and interest," Smith

says. "We achieved this by placing lights closer to the building, while other [competition] proposals used projection fl oodlighting, giving the building a flat and uninteresting wash." This effect, whereby the buildings' features were highlighted and therefore became slightly contrastive, was also achieved by reducing each luminaire's watt-age, and using a narrow band of color temperatures--the castle at 3,000K and 3,500K and the cathedral at 3,500-4,000K.

The luminaires by Urbis Schreder and Philips Lighting use high-power Cree LEDs. "Despite the low number of luminiare families, we had 38 different variants of distribution on the scheme," Smith explains. The design also prevents light spill into the windows, particularly helpful in the areas that house university students. "We had to provide a stunning lighting scheme without negatively affecting the users and stakeholders of the building," Smith adds. Another advantage is that building features are now viewable at night, helping to keep the city's night-time economy thriving. Lastly, the design enhances certain stonework features that were neglected in the past, and had even gone undetected.

Because the designers needed to be delicate with the historical building, a hard-wired control system was ruled out early, and a wireless DMX protocol with a Pharos LPC1 controller was specified instead. Overall, the project achieved 77 percent energy savings vs. the previous floodlighting. Maintenance is also Simplified--all luminaire installations are accessible, many are demountable and, to top it off, all of the products used are recyclable--ensuring the royal view will remain for centuries to come.

When Durham Castle and Cathedral's exterior facade needed new lighting, the designers' created a scheme that differentiates between the two historic buildings while remaining aesthetically cohesive.

METRICS THAT MATTER

Watts per sq ft:.25 maximum

Fixture Types: 4

Number of Fixtures: 250

THE DESIGNER

Anthony Smith, director of Stainton Lighting Design Services, was design lead on the Durham Castle and Cathedral project. He has provided technical advice to local authorities with regard to a number of lighting and planning issues, is active with the ILP nationally and regionally, was a member of Mesopic Lighting Panel and sits on the ILP Diploma marking panel.
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Author:Schwirck, Samantha
Publication:LD+A Magazine
Date:Mar 1, 2014
Words:1142
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