Page 33 - Historic Churches 2013

BCD Special Report on Historic Churches 20th annual edition 33 CATHEDRALC O M M U N I C A T I O N S
than incandescent filaments, and with far
smaller components than a fluorescent tube.
Furthermore, the diode was not degraded
by the process, so LEDs offered a much
longer potential lifespan than any previous
light source. However, LEDs had previously
only been able to produce infra-red light.
Holonyak’s refinement was to achieve light
that was visible to the human eye, and this
breakthrough was hailed by his colleagues as
‘the magic one’. Nevertheless, it has taken over
50 years to develop and refine this technology
to deliver what we have today, credible LED
light sources that are replacing many types of
fluorescent, metal halide and low voltage light
sources. In doing so they are bringing much
reduced energy and maintenance costs.
So this race through the recent history
of lighting technology brings us to a point
where we can start to look at the benefits of
LED lighting and how they can be applied
to lighting in our historic buildings.
shades but an acrylic lens to make them look
similar to a frosted (or ‘pearl’) GLS lamp.
For Flemish pendants or other fittings that
use conventional candle lamps, exposed to view,
there are also options for LED lamps. The LED
chips (normally little orange squares) have to
be carefully positioned to simulate the shape
of the candle lamp filament. While many LED
candle lamps are now available, care must be
taken to note their appearance when turned
off as well as when illuminated. A variety of
LED lamps are illustrated opposite (figure
4) where the yellow/orange chips are clearly
visible when the lamps are off. Illuminated they
present a warm crisp light – almost identical in
appearance to the filament lamps they replace.
LEDs IN SPOTLIGHTS
In traditional pendant schemes there is
frequently an additional requirement for
spotlighting. This may be for accent lighting
for the high altar or in side chapels, or
for general task lighting for the choir or
musicians. Here LEDs provide excellent
colour rendering and quality of light. At
the Church of St Mary the Virgin, Merton,
London (figure 5) LED spotlights are used
throughout the chancel and sanctuary to
provide highlighting for the altar, reading light
for the choir and decorative lighting for the
walls, ceiling and mullions of the east window.
Although pendants are common in
traditional lighting schemes, they are not
always required or appropriate, and spotlights
are often employed on their own to provide
LEDs IN ELECTROLIERS
The most traditional method of lighting
large spaces in older buildings is of course
the chandelier or ‘electrolier’, as its electrical
equivalent is known. Large spaces can be
illuminated evenly and effectively providing
that the fittings are sufficiently powerful and
positioned carefully in the space. However,
when considering LED technology for
electroliers we must immediately differentiate
between bare or exposed lamps and those
with shades. The larger LED lamps, capable of
replacing the conventional GLS lamp (150W,
100W, 60W etc) are not necessarily things
of beauty and work best if they are enclosed
in frosted or non-translucent shades.
St Mary the Virgin at Painswick was
recently re-lit with a set of new electroliers
(see figure 2). The design is based loosely on
the design of the earlier gasoliers. LED lamps
are used within the frosted glass storm shades.
Compared with halogen lamps the 14.5W LEDs
offer an energy saving of up to 85 per cent
and a ten-fold increase in lamp life. The LED
lamps are a comfortable warm white at 2700K,
they are dimmable and last for up to 40,000
hours. The shades make the LEDs almost
indistinguishable from conventional lamps.
The recently completed scheme for the
nave of Wakefield Cathedral, West Yorkshire
(see figure 3) features pendants designed in the
style of Sir Ninian Comper that are fitted with
7W 3000K LED lamps. Again these are warm
white, fully dimmable and last for up to 25,000
hours. Here the LED lamps are fitted not with
Figure 3 Wakefield Cathedral, West Yorkshire
Figure 4 Examples of clear LED lamps including candles
Figure 5 St Mary the Virgin, Merton, London