Category: Riegens Lighting Guide 7 - LG7
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Riegens & Lighting Guide 7 - LG7
When designing to achieve these illuminance levels, care should be
taken with the following:
- The room, where practicable should be uniformly lit, avoiding high
luminance peaks or troughs, against the average
- Shadowing, and sharp cut-offs of light on surfaces, should be avoided
where possible
The recommendations for indirect lighting, was broadly left un-affected
within LG7 Office Lighting, but the section has been re-referenced for
ease of use.
When the Cat1 / Cat2 / Cat3 classification system was withdrawn, a
simple system was introduced to classify computer display screens.
The classification, is based on the anti-reflectivity properties of the
individual screen, ranging from I, (good), through to III, (poor).
Lighting Guide 7 - LG7
One area that is often misunderstood, is the applicable lighting
standards and recommendations, for office interiors.
Combining the right luminaires, in the right application, with the
correct amount of light, is a skill. Our experienced designers, work
with these challenges everyday, and are well placed to offer advice and
guidance.
In 1989, the Chartered Institute of Building Services Engineers, (CIBSE),
introduced a code of practice, or lighting interior office environments.
The guide, LG3, concentrated on areas, where computer terminals were in
operation. The lighting section, soon became wrongly administered, and
broken down into its basic component parts.
It became normal for areas within projects, to be specified as a maximum
luminance, or brightness. LG3 contained parameters, that limited
luminance above certain viewing angles, and the terms Cat 1, Cat 2 and
Cat 3, came into everyday lighting language.
Unfortunately, when these rules were applied, office interiors often
ended up, as dark and gloomy workspaces, especially the upper areas of
the walls, above the cut off angle and the ceiling.
In 2001, an addendum was drafted, the guide re-vitalised and re-issued.
This removed the categorisation system for luminaires and reminded
designers of the necessity to consider the lighting levels of the walls
and ceiling in relation to the working plane.
In 2005, a new and completely rewritten edition of Lighting Guide 7 was
released. The new LG7 covers all aspects of lighting for offices, from
board rooms through general offices to the post room. This new
publication effectively replaces LG3 as the relevant guidance for office
buildings. However, there are many other buildings where display screen
equipment is used. Lighting Guide 3 (now out of print) still provides
useful guidance for such applications.
The guide takes in to consideration the release of the 2002 European
Regulations, regarding lighting in the workspace. BS EN 12464-1 2002, is
considered by many to be on a par with the LG7 : Office Lighting.
The LG7 guide, emphasises the need for a greater understanding and
thought, on all aspects of office interiors. Lighting design, and the
output and control of light from luminaires, must be viewed in
partnership with daylight, and the computer screen position and
geometry. Although the guide is extensive, key parts will play a
fundamental role when approaching an interior office lighting design.
With specific emphasis put on reflectance properties of the area, task
illuminance limitations, daylight, and types and methods of lighting the
area, the guide aims to encompass all aspects.
If the type of screen class, software style and position is not known,
then a set value of a maximum of 200cd/m2 when using direct lighting, or
500cd/m2 if using indirect lighting at a 65º angle of elevation or 55º
in special circumstances. If other parameters are used, it is important
to state any assumptions that apply, this will allow the user to take
informed responsibility.
To follow the guidelines and correct practice of LG7, both the specifier
and the installer, are required to complete certificates of conformity,
stating that the code has been met.
The certificates collate all the relevant information with regard to the
area being lit into one document and covers surface reflectance used for
the design, surface treatment of the display screens including the type
of software being used (positive or negative). Details of the luminaires,
direct, indirect or a combination.
There is also an opportunity to include a statement as to why the scheme
does not comply with the guide. This could be that the installation
positions of the luminaires are determined by the structure of the
building, or that the windows are continuous above the sill, and
therefore it is not possible to mount uplighters around the exterior
walls.
At Riegens, our experienced and dedicated design team are conversant
with all aspects of interior lighting design, and we pride ourselves on
our ability to help and steer are customers through all aspects of LG7.
For more information, or for help and advice, simply contact your local
Riegens sales office or visit www.riegens.com
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RIEGENS Lighting Ltd
2 Elliot Drive
Springwood Industrial Estate
Rayne Road
Braintree
Essex
CM7 2GD
Tel: 01376 333400
Fax: 01376 344108
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