Lighting of religious buildings
تاريخ الاضافة
28/07/2019
نوع المحتوى
Article
Category
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الرابط للمحتوى
الكاتب
David Haddon-Reece
الناشر
electrical.theiet.org
الوصف
David Holmes,
an experienced lighter, spent two years visiting dozens of different types of
places where religious assembly takes place, from the more familiar churches,
synagogues and mosques to the more unusual, such as chapels in airports and
hospices. In these buildings he looked not only at the typical features of the
buildings but also discussed with those in charge how their spaces were used,
the particular ways they performed their rituals and any particular
sensitivities they had about people entering the spaces during the design
process.
In this
article, the Society of
Light and Lighting (the SLL) gives us an overview of the
different requirements for lighting religious buildings.
A place of worship is taken to be a building, or a particular room
within a building, where people congregate to carry out prayer and activities
relevant to their faith. As many gatherings take place at night as well as
during the day, a system of artificial lighting is necessary.
Lighting in places of worship has four objectives:
- to enable participants in the religious
activity or ceremony to see what they are doing;
- to enable the congregation or assembly to
see what’s happening around them;
- to contribute to the safety of everyone
within the room or building; and
- to create a good visual environment.
It’s important to apply the correct source of lighting so that a
specified illuminance can be accurately achieved. The success of an
installation should not be judged by light meters but through the eyes of those
who have to perform the ceremonies as well as those who watch them. Similarly,
efficiency should not be rated simply by the effectiveness of gathering all the
lamp lumens and exclusively directing them onto the task plane, but rather by
the ease with which the task can be seen and by the contribution of the
lighting installation to making the environment more agreeable.
Types of bulbs
With the reducing price and increasing availability of good LED
spot and floodlights, these should normally be considered as a first option.
They provide a good low-energy option with a very long life, thus reducing the
need for maintenance access to often high places. The wide availability of LEDs
with different beam angles means that one family of fittings can provide light
for many different purposes. Wide beams can be used for washes over vaulted
ceilings, medium beams for lighting down over seating areas and narrow beams
for picking out altars or features in the space. Most LED spotlights can come
with integral dimming of many forms, from simple trailing edge mains dimming to
DALI (digital addressable lighting interface) or DSI (digital serial
interface). A dimming system allows simple changes in the feel of the space, from
simple lighting for general access to higher levels for services, with special
scenes reserved for weddings, festivals or concerts.
Lighting considerations
When considering the design, an installer should analyse the visual
task that will be performed in the religious building and any possible lighting
problems. For example, if members of a congregation or assembly tend to sit in
one particular area this should be a focus of the design brief. Similarly, if
certain parts of the service or ceremony appear better with the aid of
daylight, try to understand why – and how this can be supported.
The theatrical performance of the ceremony and the appearance of
the room or building should also be considered. For example, it’s recommended
that uniformity within a prayer or worship area can be lowered if a particular
lighting effect is justified, perhaps by using a narrow beam spotlight over a
font in a Christian church, to light the Koran in a mosque or the Scriptures in
a synagogue.
It is common in places of worship for tasks to occur on different
planes: horizontal, vertical and anywhere in between. It is recommended that
illuminance is produced on the plane in which the task will be performed. A
common failing of lighting in Christian churches is the provision of low
illuminances on the vertical plane. The usual causes are the use of narrow
distribution luminaires, the choice of luminaire by lay people or insufficient
numbers of luminaires. Illuminance on the vertical plane in buildings with high
ceilings is much more sensitive to changes in spacing between luminaires than
is illuminance on the horizontal plane. It is therefore possible to have
conditions in which the illuminance on the horizontal plane meets the
illuminance recommendations but the illuminance on the vertical plane is much
reduced and markedly non-uniform. Typically, the best approach to avoid this
problem is to use luminaires with a wide distribution, at a reduced spacing.
Higher room surface reflectances can also be beneficial, although it is appreciated
that this particular aspect cannot always be controlled by the lighting
designer.
In addition to lighting the task area, the volume of space occupied
by any people should be lit. This particular light is required to light
objects, reveal texture and improve the appearance of people within the space.
The terms ‘mean cylindrical illuminance’, ‘modelling’ and ‘directional
lighting’ describe the lighting conditions. Good visual communication and
recognition of objects within a space are essential within any religious
building. This is achieved by providing adequate mean cylindrical illuminance
(Ez) in the space.
Obstructions
Where architectural features can add much to the atmosphere of a
religious building, unfortunately, from a lighting perspective, they are
commonly the cause of extensive obstruction to the distribution of light from
the lighting installation. Large vertical stone pillars, wooden cross beams,
heaters and banners are all examples. If obstruction and consequent shadowing
are thought likely to be a problem, special care should be made when designing
the installation. A number of approaches can be used to reduce such problems:
- if the obstruction is by overhead cross
beams, etc., the possibility of positioning the lighting below the
obstruction should be considered.
- if there are a few large obstructions in
the space, such as stone pillars, a suitable approach is to check that all
parts of the space are lit by at least two luminaires, either roof mounted
or via floodlights mounted on the walls or the pillars themselves. This
approach, together with high surface reflectance’s in the interior, should
eliminate any patches of low illuminance.
- often, the spacing between luminaires can
be reduced, the amount of reduction being greater the larger the size and
number of obstructions and the lower the reflectance’s of the
obstructions. Typically, a one-third reduction in the maximum spacing to
mounting height ratio may be required.
Maintenance
Several factors need to be considered when it comes to maintenance:
- lighting installations start to
deteriorate from the moment they are first switched on.
- the light output from lamps reduces with
increasing hours of use.
- the light emitted from luminaires will
diminish as the luminaires become increasingly dirty.
- the inter-reflected light in an interior
will reduce as the interior becomes dirty.
To maintain the light output of a lighting installation, it’s
necessary to carry out maintenance of the installation. The first requirement
of such maintenance is ease of access. This is something that should always be
considered when designing an installation. In a church or mosque with a high
ceiling it may be best to mount the luminaires on vertical surfaces such as
pillars, instead of suspended from the high ceiling. In so doing, luminaires
can usually be positioned to allow for easier maintenance, while still taking
the lighting requirements into consideration. Selecting suitable intervals for
cleaning the luminaire and for the lamp replacement, together with the best
method of carrying out this work, should all be considered when designing the
installation.
Energy consumption
A designer must consider energy consumption and running costs. Two
aspects of the installation determine the energy cost: the installed power of
the installation and the number of hours the installation is used.
Installed power is determined by the choice of light source and
luminaire, the proportions of the interior and the reflectance of the interior
surfaces. Legislation pertaining to energy conservation in England and Wales is
governed by the Building Regulations, with particular reference to Part L: Conservation
of fuel and power. Similar legislation applies in Scotland and Northern
Ireland.
When lighting places of worship, the basic requirement is that all
general areas should be illuminated by light sources that have a minimum
efficacy of 60 lumens per circuit watt. Many places of worship are only used
for a few hours each week and therefore full-life economics must be considered
when choosing a lighting system. An elaborate and expensive array of luminaires
may be impressive to the public at large, but if a payback period is being
considered and calculations show this to be in excess of 20 years, the validity
of the decision must be studied carefully.
Over recent decades, due to low weekly usage in churches, there was
a trend towards the use of tungsten halogen lamps for general lighting in cheap
exterior floodlights. With current legislation and the need to carefully
consider a building’s energy consumption, the use of high-wattage tungsten
halogen lamps is no longer a viable option. However, it is increasingly easy to
provide luminaires that match the environment aesthetically (even in listed
buildings) while using efficient light sources such as modern LED types.
Emergency lighting
Emergency lighting may be required in places of worship wherever
there is deemed to be a risk to the safety, health or welfare of staff and the
public, should the normal lighting fail. For all buildings, a hazard exists if
people have to evacuate the building in darkness, so emergency lighting must be
provided to allow people to safely and quickly leave the building.
Listed buildings
Many religious buildings will be of architectural or historical
interest and may be listed. If they are, planning consent or listed building
consent may be needed before works can be carried out. In any case the
integrity of the building must be maintained and the fabric of the building
respected when choosing locations of lights, how they are fixed to the
structure and the routing and fixing of cables to them. There will often be
restrictions on drilling through or fixing into listed buildings and clear
guidance should be sought before commencing work.
Example: St John’s Church,
Cirencester. (Lighting design by Lighting Design & Technology)
The Catharine chapel has slim LED lighting strips concealed on ledges high up on each side to provide soft up-lighting of the magnificent fan vaulting. The spotlights are mounted on brackets that are fixed over the ledge so that no fixing damages the historic main wall. The spotlights provide emphasis on to the altar and provides lighting for both the seating area and for the areas of revealed wall paintings. The wiring is run along the high-level ledges to conceal them from view and each spotlight or LED strip can be separately dimmed via a DALI control system, so that the balance of up-light to down-light or from altar to seating area can be changed to suit the use of the space.
The spotlights in the Lady Chapel are concealed behind the wooden down-stands from the ceiling so that they cannot be seen from most positions in the pews. As well as lighting the pews and altar area, additional spotlights with specific beam angles give emphasis to the monuments at the side of the space and to certain carved features on the wooden ceiling. These can be individually dimmed down via the control system.