CA452001EN - March 2015
Interior Lighting Design
There is a wide range of lighting application standards and guides
available to aid the designer in creating a comfortable and efficient
The recent updated edition of BS EN 12464-1:2011, which not only
sets a standard for illumination levels for specific tasks but, also
provides advice on how to achieve a lighting solution to meet the
human need. Also the SLL Lighting Design Guides provides a very
good source of guidance for the design of working spaces, and can
be considered as best practice. Lighting Guide (LG) 7 is possibly
the one most commonly referred to, but it is often misunderstood
being used to specify luminaires rather than the total environment
of the space.
LG7 was written to supersede the original LG3 which had very
restrictive cut off criteria for the luminance of luminaires. With the
development of improved and flatter VDT screens this could be
relaxed, allowing for higher luminance values from the luminaire.
The increase being 3000 cd/m
or 200 cd/m
if the screen type
is unknown. This can be increased up to 1500 cd/m
and 500 cd/
respectively if positive polarity software only is used. LG7 also
recommends values for the wall and ceiling illuminance, which are
based on a direct percentage of the working plane level.
The intention being to alleviate the “cave like” appearance that the
single use of the original Category 2 cut off luminaires produced.
The LG7 lighting guide for office lighting was amended in 2012
to align with EN12464-1. This changed the recommendation for
the wall and ceiling illuminances to be a percentage of that of
the working plane to specific levels of illumination (lux) with a
In addition the recommended range for the Cd/m
at the relevant cut off angle was changed and now has a range of
for screens having luminances (brightness) of
less than 2000 Cd/m
which increases to 3000 Cd/m
with higher luminances.
It must be stated that LG7 is often referred to as being guidance
for luminaires but it was written as a complete guide for lighting of
the office environment, taking into account the total need of the
occupants to create pleasant working space.
Recommendation for Wall and Ceiling Illuminance
The guide provides recommendations to address the dark and
gloomy effect that can be created by ‘categorised’ louvres,
including the sharp wall cut off and bright scalloping. To avoid
this, walls and the ceiling should be lit as follows:
- The average wall illuminance above the working plane
should be at least 75 lux with a uniformity of >0.1
- The ceiling average illuminance should be at least 50 lux
with a uniformity of >0.1
The other misconception is that office lighting is all about creating
a uniform lighting level across the whole space. What is needed is
uniform lighting across each task area, which normally consists of
relatively small areas on each desk. The lighting in the wider office
space can, and indeed should, vary somewhat to create visual
interest. Even the most dedicated office worker looks up from his
or her work from time to time, and when they do they need to see
an interestingly lit office space and, ideally, a more distant view out
of a window.
If the building and the visual requirements of the users of an
office space are understood and all possible lighting options are
considered, a lit environment can be created for each office space
that not only provides the required levels of lighting for each task
but also provides an interesting and stimulating lit environment for
people to work in.
This is a direct quote from the introduction of LG7 which goes
on to discuss the whole design process. The overall intention of
the guide has not been fully utilised by the majority of users and
the reliance on a “single luminaire solution” has still been widely
requested. The single luminaire approach when used in regular
arrays to produce a high level of uniformity across the whole
working space can be in contradiction to the original intent.
If designing to LG7 the certificate of conformity should be used to
show the criteria of the design.
Certificate of Conformity
The guide requires that the designer and installer of the
installation complete and sign a Certificate of Conformity to
demonstrate that all known visual and ergonomic criteria were
fully considered during the design process and installed as
Due to the regular development of these guides, Eaton
recommends you visit CIBSE onwww.cibse.org
to ensure the
latest guides are being referred to.
The lighting design standards detailed in EN12464-1:2011
break the design process into a number of key elements to aid
the design process. It however is not intended to provide
specific solutions, nor restrict the designer from exploring new
techniques or restrict the use of innovative equipment. Daylight,
as well as artificial light, should also be fully utilised for both
quality and to reduce energy.