Grid spacing
p = 0.2 × 5^log10(d) (10 m at most)
- d = the area’s longer side (m)
STANDARDS & FORMULAS
Lighting Design
Luminaires from their IES / LDT files, and the room calculation point by point like DIALux.
Standards and regulations
- EN 12464-1Light and lighting - lighting of work places, indoor
The calculation grid, the maintained illuminance Em and the uniformity U0.
- CIBSECIBSE / SLL lighting guidance
The first-reflected-flux estimate of the light reflected by the room.
Formulas
Direct light at a point
E = I(C, γ) × cos³γ / h²
- I(C, γ) = the luminaire’s candela from its file
- h = its height above the work plane
Reflected light (first reflected flux)
E(reflected) = (ρf × Φ(plane) + ρw × Φ(walls) + ρc × Φ(up)) / (A(surfaces) × (1 − ρ(mean)))
- ρ = the floor, wall and ceiling reflectances
- Φ = the light that first lands on each surface
Results
Em = mean(E) × MF · U0 = Emin / Em
- MF = the maintenance factor
Design rules it applies
- Photometric files: IES or LDT (the files DIALux takes)
For reference. MO.tool works these out to help your design; the engineer remains responsible for it. Always check the edition of each standard your project uses and the requirements of the local authority (DEWA, ADDC, Civil Defence…).