CIBSE Standards

CIBSE LG7: Office Lighting Guide

The definitive framework for creating visually comfortable, productive, and energy-efficient office environments.

Quick Answer: CIBSE Lighting Guide 7 (LG7) is the primary UK design guide for office lighting. It goes beyond simple lux levels to focus heavily on the visual environment, emphasizing the need to illuminate walls and ceilings (not just the working plane) to prevent the "cave effect". It also provides strict guidance on minimizing glare on computer screens (VDUs) and maximizing energy efficiency.

Why is CIBSE LG7 Important for Offices?

Historically, office lighting was designed solely around achieving a specific lux level (e.g., 500 lux) on the desk surface. This often resulted in dark walls and ceilings, creating a gloomy and fatiguing environment known as the "cave effect".

LG7 changed the paradigm by recognizing that a visually comfortable environment requires balanced brightness across the entire room. A well-designed LG7 compliant office improves employee well-being, reduces eye strain, and boosts productivity.

What are the Core Requirements of LG7?

To claim an office lighting design is "LG7 compliant," it must address several key factors:

  • Cylindrical Illuminance (The 30/50 Rule): LG7 states that the illuminance on the walls should be at least 50% of the illuminance on the task area (the desk). The illuminance on the ceiling should be at least 30% of the task area. This ensures a bright, airy feel.
  • VDU Glare Control (UGR): With the prevalence of Display Screen Equipment (DSE), luminaires must be designed and positioned to prevent reflections and discomfort glare. A Unified Glare Rating (UGR) of < 19 is standard for offices.
  • Task vs. Ambient Lighting: LG7 encourages a mix of ambient (background) lighting and localized task lighting. This is often more energy-efficient and allows users to customize their immediate workspace.
  • Daylight and Controls: The guide strongly advocates for maximizing natural daylight and using intelligent controls (like daylight dimming and absence detection) to minimize energy waste.

How Does LG7 Relate to BS EN 12464-1?

LG7 and BS EN 12464-1 are intrinsically linked. BS EN 12464-1 is the formal European standard that dictates the minimum maintained lux levels and glare limits. LG7 is the practical *design guide* that explains how to physically achieve those standards within a modern office environment while prioritizing human comfort.