CIBSE Lux Level & Design Guide
SLL Code for Lighting Compliance Standards
1. Sector / Application
2. Specific Environment
Targets are based on the SLL Code for Lighting EN 12464-1 standards.
Maintained Illuminance Target (E)
500 Lux
At Working Plane Height (0.8m)
Visual Quality Criteria
Max Glare (UGR) ≤ 19
Uniformity (U0) ≥ 0.60
Lamp Specification
Colour Rendering (Ra) ≥ 80
CCT Recommendation 4000K (Cool White)
Design Notes & Considerations
Lighting should be designed to minimise reflections on display screens. Task lighting may be required for complex drafting.
Understanding CIBSE Lighting Standards
In commercial and industrial electrical engineering, guessing the required light output for a space is not an option. Lighting design in the UK is strictly governed by the CIBSE Society of Light and Lighting (SLL) Code for Lighting and BS EN 12464-1 (Light and lighting – Lighting of work places).
Key Lighting Metrics Explained
- Maintained Illuminance (E_m / Lux): The statutory minimum average illuminance that must be maintained on the task area over the lifetime of the installation. For example, 500 lux on an office desk. As LEDs degrade over time, initial designs must actually aim higher than this target (factoring in the Maintenance Factor).
- Unified Glare Rating (UGR): A psychological measure of the discomfort caused by glare from luminaires. Lower numbers are better. A standard office requires a strict UGR of ≤ 19 to prevent eye strain during screen use, whereas a warehouse may permit a UGR of 25.
- Uniformity (U0): The ratio of minimum illuminance to average illuminance. A U0 of 0.60 ensures there are no severe "dark spots" or "pooling" of light in the task area, ensuring a smooth, visually comfortable environment.
- Colour Rendering Index (Ra / CRI): Measures how accurately the artificial light reveals the true colours of objects compared to natural sunlight. Offices require Ra 80, while clinical healthcare or high-end retail applications often demand Ra 90+.
Task vs. Ambient Lighting
Modern BS EN 12464-1 regulations heavily promote energy efficiency. It is often unnecessary, and wasteful, to illuminate an entire open-plan room to 500 lux. Instead, designers are encouraged to light the specific Task Area (the desk) to 500 lux, while the immediate surrounding ambient area can safely drop to 300 lux, reducing overall energy consumption and carbon footprint.
ENGINEERING DISCLAIMER: The targets provided in this database are baseline references derived from BS EN 12464-1 and CIBSE SLL guidelines. Final lighting designs must be calculated using dedicated photometric software (such as RELUX or DIALux) incorporating specific luminaire LDT/IES files, surface reflectances, and specific Maintenance Factors (MF).