The BCO Guide to Specification aims to provide information on how to specify  workspaces when the end occupier is not known ( Shell and Core, CAT A). It was last published in 2019 and subsequently updated in June 2022.

Shortly after the 2019 Guide was released, the UK adopted a legally binding Net Zero Carbon target for 2050 and an interim target to reduce emissions by 78% by 2035. Covid also presented new challenges to the workplace.

The latest 2023 Key Criteria Update aims to deliver guidance to balance targets required to meet the Net Zero and a healthy, comfortable and productive workspace for occupiers. 

Occupancy level has a fundamental effect on many key design parameters. The updated recommendation on occupancy is 10m2 per person at 80% utilisation.

Lighting load power allowance has been reduced to reflect the improved efficiency of LED lighting and lighting controls from 8w/m2 to 4.5 W/m2 (CAT A) and 5.5W/m2 (CAT B).

More Detail.


This revision is aimed at CAT A lighting. Office lighting is provided by a combination of daylight and artificial light. Daylight should be maximised. Task lighting might be required to suit the actual occupants ( this could be either the nature of the task or the eyesight). 

The average maintained illuminance has been reduced from 300-500 lux to a target of no less than 300 lux. The maintenance factor of no less than 0.8 is targeted. 

Lighting installation needs to take into consideration the embodied carbon of the actual light fixtures and the energy needed to power them. New criterion for the overall lighting system performance has been added in line with the recent Building Regulations ( Part L, Volume 2, 2022). This is 7-11kWh/m2 per year ( compared to 8-18 kWh/m2 per year).

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