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Standard deviation

The standard for workplace lighting is set to change this autumn with the publication of EN 12464-1: 2011. Andy Pearson takes a look at the draft document and outlines ten of the proposed amendments

The design of workspace lighting is set for a shakeup this autumn with the publication of the revised European standard for lighting indoor workplaces.

The focus of EN 12464-1: 2011 Lighting of Indoor Work Places is on quality lighting and controls and on developing a lighting scheme around a task or activity, according to Lou Bedocs, lighting applications adviser at Thorn Lighting, honorary president of LIF, and a member of the committee that drafted the revisions.

“It encourages designers to introduce suitable lighting controls for regular lighting layouts so the electric lighting can be subdivided and used only when a specific space is occupied,” he says. The document has been drafted and delivered to CEN, where it is expected to be rubber-stamped before publication.

Although the revised standard has the same structure as its predecessor, and many of its recommendations remain the same, there are some significant changes contained within it that could affect the work of lighting designers and specifiers.

1 Daylight

The current standard is focused on electric lighting, but the revised version encourages designers to consider all light sources, including daylight. “We wanted to eliminate the idea that the standard only covers the electric lighting requirement,” says Bedocs.

The standard highlights the importance of daylight for energy saving and recognises that it introduces other benefits such as variability of light, distribution and colour to a space.

2 Illuminance on surfaces

An addition to the standard is a requirement for specific wall and ceiling illuminance to increase the brightness of a room. This can be achieved by using light-coloured walls “and squirting some light onto them”, according to Bedocs. He says this will mean “a space cannot be exclusively lit by concentrating downlights”.

3 Background illumination

The revised standard defines the background area to be illuminated. The minimum size is a band 3m wide next to the task area that has an illuminance at one third of that of the immediate surrounding area.

Previously the background was defined as the entire space, so the whole office had to be lit even if it was occupied by a single person – far from energy efficient. The new definition lets designers use intelligent luminaires and controls to detect and illuminate areas occupied by workers and switch off the remaining lights.

Bedocs says that if you don’t know where the task area will be, install a scheme to light the entire space as a task area but install controls so lights will only switch on where needed. “Install as many luminaires as you need, but only bring on what is required.”

4 Illuminance uniformity

The required uniformity of task illumination is now activity-related and varies between 0.4 and 0.7 (the ratio of minimum to average illumination).

Previously the ratio was 0.7 for all activities. Now, for critical tasks uniformity should be high at 0.7, while 0.4 will be adequate for circulation areas, for example. The 0.5m-wide area immediately surrounding the task now has a minimum ratio of 0.4. Then around that is the 3m-wide background band.

Background illuminance has a new uniformity requirement of 0.1 to allow substantial variation of illumination over a larger area – but at a tenth that of the task illuminance. “The standard recognises that high uniformity is only important for a very small area where the task is,” says Bedocs.

5 Illuminance grid

A grid system similar to that in the sports lighting standard EN 12193 is required for areas in which the illuminance values are calculated and verified to avoid conflicts on specification. The size of the grid will depend on the area illuminated and is defined in the document. Once the grid is defined, the intersections will be the measuring points for the space.

6 Mean cylindrical illuminance

Another new recommendation, this time for 50 lux on the vertical plane at heights between 1.2 and 1.6m above floor level for the activity area. This will, for example, aid facial recognition. It is based on measurements of the illumination at the surface of an upright cylinder.

According to Bedocs, the requirement will encourage the use of daylight – because side windows produce lots of vertical illuminance – but will discourage the use of downlights that produce narrow shafts of light – particularly LEDs – and may demand extra lighting to throw light horizontally. “It is a very big step forward in the standard to promote quality of lighting,” he says.

7 Modelling

Modelling is the balance between diffuse and directional light and is important when looking at people. The idea of an “indicator of modelling” ratio between cylindrical and horizontal illuminance has been introduced to enhance the appearance of three-dimensional objects. It has values between 0.3 and 0.6.

8 Display screen equipment

For lighting workstations with display screens, luminaire luminance limits now range from 1,000 to 3,000cd/m2. This change acknowledges the improved performance of modern displays when it comes to reducing reflections. However, a lower luminance limit of 200cd/m2 will still apply where cathode ray tube monitors are used.

9 Energy-efficiency requirements

The use of lighting controls is strongly recommended. The standard now directs readers to EN 15193, which describes how to manage energy for lighting. This standard was not available when the original standard was published.

10 Variability of light

Another new section. It acknowledges the role of light in maintaining people’s health and wellbeing, and the role of light in maintaining circadian rhythms. There are no recommendations in this section because the science is still in its infancy. However, it is there to make designers aware of this developing area and to read other documents to keep abreast of the latest thinking.

 

A designer responds

We gave the proposed changes to the workplace standard to lighting designer Kevan Shaw of KSLD to find out how he interprets the new document. Here he outlines his thoughts on the impact of some of the potential amendments.

● He thinks requirement for specific wall and ceiling reflectances will limit the choice of colours available to designers. “If the standard is properly implemented, it will affect architects and interior designers because it will limit their colour choice.”

● In addition, he thinks the standard places the onus of determining task requirements on the lighting designer. It also includes a requirement for lighting redesign if the task area changes. “Depending on how it is interpreted, this is potentially a nasty clause because it could be an unlimited extension to the scope of works for lighting designers.”

● Similarly, he sees the requirements for illuminance uniformity as potentially onerous. “Now every lighting level for every task has a uniformity level associated with it – and they are pretty high – which places a huge extra burden on the designer and also limits what you can do because it influences the number and spacing of fittings.”

● He thinks modelling requirements will limit creative design because they “will restrict what you can do and how you do it.”

● However, the reference to the standard on lighting controls EN 15193 is welcome. “This standard introduces a lot of sensible flexibility into lighting design.”

 

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