The Room Cavity Ratio (RCR) is a measurement in lighting design that describes the relationship between the height, width, and length of a room . It is used to calculate light reflection and light distribution in a room , specifically how light is distributed from the ceiling and walls to the work surface.
1. How is the RCR calculated?
The Room Cavity Ratio (RCR) is calculated using the following formula:
whereby:
- = the height of the room cavity (distance from the work surface to the ceiling)
- = the width of the room
- = the length of the room
📌 What does this formula mean?
- Higher RCR values → More light loss and less efficiency in light reflection.
- Lower RCR values → Better light distribution and less shadow formation.
2. Why is the Room Cavity Ratio important?
✅ Determines the lighting efficiency → How effectively is light reflected in the room?
✅ Helps with light calculations → Together with the reflection values of walls, ceiling and floor, RCR determines the required light intensity.
✅ Affects light uniformity → Lower RCR means more even lighting, higher RCR means additional fixtures may be needed.
✅ Used in the Coefficient of Utilization (CU) → An important factor in lighting plans for energy efficiency.
📌 RCR is essential to find a good balance between light output and energy consumption.
3. Applications of the RCR
🏢 Offices and workspaces → For even, shadow-free lighting on desks.
🏪 Shops and showrooms → Ensures that products are well lit.
🏗 Industrial buildings and warehouses → Determines how many luminaires are needed for optimal visibility.
🏠 Residential Lighting → In homes with high ceilings, RCR helps determine indirect and accent lighting.
📌 A well-designed lighting scheme takes RCR into account to avoid unnecessary light loss and shadows.
4. Difference between RCR, FCR and CCR
| Ratio | What does it measure? | Application |
|---|---|---|
| Room Cavity Ratio (RCR) | Light reflection between ceiling and work surface | General lighting efficiency |
| Floor Cavity Ratio (FCR) | Light reflection between floor and work surface | Assessment of light absorption through the floor |
| Ceiling Cavity Ratio (CCR) | Light reflection between ceiling and fixtures | Optimization of ceiling reflection |
📌 Together, these ratios determine how efficiently and evenly light is distributed in a room.
💡 In short:
The Room Cavity Ratio (RCR) is a key metric in lighting design that determines how light is distributed from the ceiling and walls to the work surface. It helps optimize lighting efficiency and uniformity in offices, retail, industrial, and residential spaces .