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JOINING THE DOTS

AJ SPECIFICATION - FOCUS ON: LIGHTING

The British Council for Offices' (BCO) new Offi ce Fit-Out Guide joins existing guidance to create a collection of crucial documents for those involved in office lighting. The guide will sit alongside 'BS EN 12464-1:2002, Light and Lighting - Lighting of Workplaces' and 'LG7: Office Lighting'. In isolation each document is inadequate.

However, each contains nuggets of wisdom that will point the way towards improving the offi ce environment.

NUMBER-TASTIC: BS EN 12464-1:2002 This is a very dry document full of anoraky information.

High standards of offi ce accommodation exist in many EU countries. But in other countries, standards are perhaps not so good and new EU members may not have previously worked with European Standards.

This document sensibly sets a base level. It gives guidance on the minimum standards the designer should attain - it should be viewed as a springboard. Perhaps the most important information to remember is in the introduction, 'this standard neither provides specific solutions, nor restricts the designer's freedom from exploring new techniques, nor restricts the use of equipment'.

The design process is actively encouraged - although the designer must take the information and then design appropriately.

EN 12464 contains lots of figures. You could be forgiven for thinking numbers are the only way forward. Some figures are higher than in other guidance; for example, EN 12464 gives 500 lux, (rather than the usual UK range of between 300 and 500 lux), as a minimum level for an office space. It is therefore vital you have a design conversation to balance such information.

Perhaps it would be useful to revisit why the numbers exist:

visual acuity. The recommended lux level is generated by task and duration. The figures therefore reflect the average experience. However, the recommended lux levels do not reflect the individual human condition - they do not factor in how much you drank last night, whether you love or hate your job or how many phone calls you take. Office products on the market, such as adjustable monitor arms and task chairs, show how important it is to consider individual requirements - and lighting design needs to take a similar approach.

BCO FIT-OUT GUIDE At just one-and-a-half pages long, the BCO Fit-Out Guide is much more accessible. Published largely by non-lighting people, the document gives a more holistic view of the office space.

The document states that:

'The main design objective of office lighting is the creation of a comfortable, stimulating visual environment by careful control of surface brightness and contrast ratios. This also requires management of natural light. Design guidance is no longer prescriptive and allows considerable freedom for a suitably qualified and experienced designer to produce certified compliant schemes of the quality required.'

So, lighting is about user comfort and design is key - not just a bunch of numbers on a page. The approach has largely moved from lighting engineering to lighting design.

We can, of course, still use engineering principles but within a design process - which is good news for architects. The design instinct within the architect should, in any case, react against the lighting-engineering approach.

This instinct should detect that there is something wrong, for example, when this approach is in danger of creating a static environment with light not distributed around the space but concentrated on the desk.

To design an office environment successfully, five people should ideally be involved in the process: the developer funding the project;

the architect or interior designer responsible for the interior realm; the M&E consultant; the employer who is going to pay people to work in the environment; and the employee who is going to work there. All should have discussions with the lighting designer. But, because of the nature of speculative offices, the employer and employee are often unknown. It is therefore usually the architect, client and lighting designer who design the scheme and in these cases it is crucial that the lighting designer steps up. The BCO guidelines encourage this step.

LG7 'LIGHTING OF OFFICES' As its title 'Lighting Guide 3 (LG3): The Visual Environment for Display-Screen Use' suggests, LG3 addressed any area where display screens were used. LG7 is about office lighting and amalgamates previous guidance.

LG7 places an emphasis on visual interest - it states: '? 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.' LG7 also recognises that different office templates - for example, open plan, cellular or deep plan - require different approaches. It also recognises the importance of contrast ratio in deep-plan offices. For example, if you are seated 6m from a window, you can work in a combination of natural and artificial light. Further towards the core you will have less daylight and therefore artificial lighting should be increased to compensate.

However, it is argued that because of the high lux level of daylight (about 2,000 lux), the base lighting level should be increased from 300 lux to 500 lux to address issues associated with contrast ratio.

The energy-saving benefits of daylight linking will be lost if this approach is adopted - what energy savings you make by decreasing artificial light by the window you lose by increasing artificial lighting further into the building.

I would question this approach. The point is to create a good environment and this is not about lux levels - it is about putting light in the right places.

A stumbling block with placing light is that people do not generally engage with multi-product solutions - they are discouraged by either the increased costs or the effort required. It is unlikely that one product will light the ceiling, walls and desk successfully - you need different products to perform different functions.

Also, despite claims from manufacturers, there was no such thing as an LG3 compliant fitting and now there is no such thing as an LG7 compliant fitting. It is spaces, not fittings, that are LG3 or LG7 compliant.

It is not about the fitting but where it is positioned.

A key change (and you may be forgiven for feeling that it's just semantics) between the LG3 addendum and the new LG7 is the specific wording about intensity and angles of output. The limit of intensity is set at 1,500 cd/m 2 but the angle at which this intensity is measured is clarified in the newer LG7 document.

FITTING IN THE ANGLES LG7 states: 'Luminance limits should be applied at and above a 65º angle of elevation where the screens in the area are not tilted back beyond 15º from the vertical.' LG3 Addendum said exactly the same.

The significance of the 65° angle is a relic from the past. In order to guarantee absolutely no glare on glareintolerant screens when VDTs first came into the work place, intensity and angle were restricted to 200cd/m 2 at 65°.

This meant that very little light could come out above this angle and this harsh cut-off resulted in a third of the wall being in darkness and little inter-reflection onto the ceiling.

To get a reasonable level on the desk, fittings had to be close together - approximately 1.8m apart. This created spaces with lots of light on the desk, but not on the walls. As a result the environments were left looking rather gloomy.

Recognising advances in screen technology, the LG3 addendum removed the limit of 200 cd/m 2; instead the limit was raised to 1,500cd/m 2, (providing the correct screen and software are used).

Now, with the advent of LG7, the limits can be applied over a higher angle than 65º.

Increasing the angle means that the space between the fittings can be increased, and therefore the number of fittings reduced. This is good in terms of energy. Fittings can now be placed up to 3m apart and therefore approximately 25-30 per cent fewer fittings are used in total. In short, higher angles equals more output equals less fittings equals energy saving. (Though the downside could be a possible increase in unit cost. ) However, beware of the guidance regarding cellular offices. LG7 suggests that if you put in a cellular office, you then have to increase the number of fittings but decrease the wattage - which isobviously bad news for designers but good news for manufacturers!

PLAY FAIR Knowledge is power and can be used to confuse or frighten the client.

Designers can take two approaches. We either can scare the client with rules and regs or, and I prefer this method, we can tell them the regulations are guides and then give them professional design advice based on these.

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