Surface illuminance 
Working plane illuminance requirements are largely governed by the task at hand - the recommendation for office work is generally between 300 and 500 lux. LG7 states that the average illuminance of the ceiling should be 30% of this figure, and the illuminance of the walls should be 50% of the task plane value.
In addition to the surface illuminance ratios, areas where people are working with visual display equipment also need to be considered. Flat screen equipment is much more tolerant of surface glare reflectance, however, where the technologies, which will be employed, are not known, LG7 states that we should limit surface brightness to 1500 cd/m2 above the 65° angle of elevation.
Localised and task lighting 
It has often been the misconception that we should put as much light as possible over the greatest area within a scheme, however lighting an open plan office space to a constant 500 lux is not always best practice, cost effective or energy efficient.
In a typical open plan office only around a third of the lit space is actually made up of working areas. In this environment the most efficient use of lighting could be a maintained level of approx 300 lux with higher task illuminance levels coming from localised or task lighting. This can be achieved by designing the desk layout in conjunction with the lighting scheme to maximise desk illuminance or through the use freestanding luminaires. In these cases, the general luminance levels may be catered for by a fitting such as Officelyte, spaced according to the 300 lux required level.
Energy efficiency 
The latest edition of Part L of the Building Regulations for England and Wales (April 2006) stipulates that office areas, including spaces that involve predominantly desk based tasks (such as classrooms, seminar rooms and conference rooms), should be lit with a luminaire scheme that achieves an average initial efficacy of at least 45 lumens per circuit watt as averaged over the entire area of these types of space in the building.
For new buildings other than dwellings, the average luminaire lumens per circuit watt is calculated by summing lamp lumens x LOR for all luminaires in the relevant areas of the building, divided by the total circuit watts for all of the luminaires.
