Page 34 - Historic Churches 2013

34 BCD Special Report on Historic Churches 20th annual edition CATHEDRALC O M M U N I C A T I O N S
general downlighting or uplighting to vaulted
ceilings. At Carlisle Cathedral (figure 6), for
example, the choir aisles are lit entirely with
LEDs and almost all of the lighting is focused
upwards to illuminate the vaults, providing only
reflected light for reading. The LED spotlights,
being significantly smaller than equivalent
low voltage fittings, are discreetly located on
the column capitals and are almost unseen.
LEDs IN FLOODLIGHTS
One of the areas where LED technology
has been a little slower to mature is that of
floodlighting. While we can already see a clear
replacement strategy for the majority of GLS,
low voltage and fluorescent light sources, the
modern metal halide floodlight sources, which
are typically higher in output, have held their
own for a little longer. However, in a new
scheme at All Hallows by the Tower in London
(figure 7), 4,000 lumen LED chips drawing
only 50W each have been used to provide both
uplight and downlight from the lighting troughs
in the nave and aisles. This has transformed
the interior of this post-war reconstruction
of one of London’s best known churches.
LEDs FOR EFFECTS
The miniaturisation of light sources has been
able to progress at a great rate with LED
technology. This is mainly due to its energy
efficiency and consequent lower heat output.
In our historic churches it is now very easy
to include decorative lighting elements in
restricted locations such as small cornices
and at the base of window ledges without
substantial building works being required to
hide them. At St Michael at the Northgate
in Oxford (figure 8), LED strips, concealed
behind the timber moulding, uplight the
chancel ceiling. Miniature LED spotlights
uplight the mullions of the east window.
ARE LEDs THE HOLY GRAIL
OF LIGHTING?
The development of LED lighting technology has
kept the lighting design community on its toes
for the last few years. Ten years ago, LEDs were
starting to become interesting alternatives to
some lamp types. Typically, the life expectancy,
performance expectations and colour stability
were over-hyped by enthusiastic manufacturers.
Early LED schemes had high capital costs and
saw many problems which proved equally
costly to resolve. In the last five years we have
seen steady improvements in both reliability
and colour stability. We also have the benefit
of hindsight in understanding the problems of
those early experimental schemes. Nonetheless
there remain some areas for concern:
The capital cost of LED light sources,
and the electronics required to drive them
is considerably more than that of most
other technologies. We are therefore heavily
reliant on the ‘total life cost’ argument to
justify the initial costs of some schemes.
Like all technical systems, the integrity
of LED lighting is only as good as that
of the weakest link in the chain. Great
care has to be taken to ensure that light
sources, luminaires, controllers, dimmers
and accessories are all fully compatible.
It is also important to be wary of the
many products that appear on the market
that are produced to fulfil a specific need
and are then promoted for wider uses. It is
important that products can be replaced if
they fail without having to redesign control
systems or re-engineer luminaires.
So if we note the warnings above
and carefully match light sources to each
application, we can now, with confidence,
specify LED light sources from established
manufacturers in many lighting schemes
in both historic and new build projects.
BRUCE KIRK leads Light Perceptions, a lighting
design practice working almost exclusively with
places of worship and other historic buildings.
Early church work included the relighting of Holy
Trinity, Brompton in 1993. Current work includes
projects in four UK cathedrals, Tewkesbury Abbey
and more than 20 other listed places of worship.
Figure 6 Carlisle Cathedral, Cumbria
Figure 7 All Hallows by the Tower, London
Figure 8 St Michael at the Northgate, Oxford