INTERIORLIGHTINGDESIGN STANDARDS

Recent changes to standards and industrial guides have affected how lighting schemes are designed, particularly for office interior applications.The two most pertinent documents for interior lighting are:•CIBSE LG3: 2001 - The visual environment for display screen use•BSEN 12464-1: 2002 - Lighting of indoor work placesThe information in this section is provided to assist in the clarification of current requirements and how to design in accordance with them. CIBSE LIGHTING GUIDE 3: 2001 CIBSE LIGHTING GUIDE 3: 2001 (cont’d) Lighting Guide 3 (LG3) was first published in 1989 by CIBSE,covering the lighting of spaces with visual display terminals (VDT).It was updated in 1996, taking into account Health and Safety DSE regulations. The 2001 addendum has been issued by TheSociety of Light and Lighting (SLL), which act as the professionalbody for lighting in the UK. The addendum, which should be readin conjunction with the existing 1996 document, takes into accountchanging international standards, new technology and new screen types, e.g. colour professional screens with high resolution compared withgreen & white screens with low resolution. The changes can be summarised as follows:• In cases where the designer does not have information about the VDT's to be used, luminaires should be selected with a luminance limit of 200 cd/m
2 at 65°elevation (old Cat 2),or 55°(old Cat 1) in special circumstances. The default luminance limit is for negative polarity professional software, and can be increased to 500 cd/m
2 or 1500 cd/m
2 for positive polarity.For indirect lighting, the average luminance for surfaces lit directly should not exceed 500 cd/m
2 , with the peak intensity not exceeding 1500 cd/m

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Withdrawal of the Category rating system There has been a tendency amongst some in the industry to specify 'Category 2' luminaires as a default, without any thought to the actual working environment. 'Categorised' louvresalso create an oppressive 'cave effect' which can result in an uncomfortable working environment. All specification now requires the provision of ergonomic data for the actual application, in order to design or select an appropriate luminaire. •
2 . Luminance should vary gradually across the surface. • Combiform Plus (Pg 66) Reef (Pg 187) New 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 the walls and the ceiling should be lit as follows:i.The average wall illuminance above the working plane should be at least 50% of the average horizontal illuminance on the working plane, avoiding bright scallops or patches.ii.The ceiling average illuminance should be at least 30% of the average horizontal illuminance on the working plane. In the case of large areas with unusually low ceilings,this may be difficult to achieve and so should be as highas practically possible.• Certificate of conformity The addendum 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 specified, in accordance with LG3: 2001 Luminance limits The recommended luminance limits have been brought inline with BS EN 12464, to 1000 cd/m
2 or 200 cd/m
2 (see fig.1). This can be increased up to 1500 cd/m
2 and500 cd/m
2 respectively if positive polarity software only is used. The designer needs to select luminaires with the appropriate luminance limit based on the type(s) of screens likely to be used in the space.
Technical - Interior Lighting Design Standards