Lighting Design (Lumen Method)

Quick pick (TL;DR)

Look up the required illuminance (lux) for the task — e.g. 300 lux control room, 500 office, 200 process, 750 lab.
Then the lumen method: N = E·A / (F·UF·MF), where F = luminaire lumens, UF = utilisation factor (room geometry/reflectance), MF = maintenance factor (dirt/aging).
Round up, lay out on a uniform grid, check uniformity ≥ 0.6, and add emergency/egress lighting.
Verify in DIALux for the final layout.

Step 1 — Required illuminance

Area	Illuminance	Note
Process area	150–200 lux	General
Control room	300–500 lux	Low glare
Office	500 lux	Desk work
Lab	750 lux	Detail

Step 2 — Worked lumen method

Control room 10×8 m, 300 lux

Lumen method N = E · A / (F · UF · MF) Given E = 300 lux , A = 10 × 8 = 80 m² F = 3200 lm (LED panel) UF = 0.6 , MF = 0.8 Step 1 — Compute N = 300 × 80 / (3200 × 0.6 × 0.8) N = 24,000 / 1,536 = 15.6 Step 2 — Round up → 16 luminaires, 4 × 4 grid Check uniformity ≥ 0.6 ; add emergency lights

UF and MF both raise the count — skip them and the room is dark within a year. DIALux confirms.

Step 3 — Layout & emergency

Grid spacing & uniformity / glare.
Emergency & egress lighting.
Ex luminaires for hazardous areas.

Lumen-method calculator

Number of luminaires

N = E·A / (F·UF·MF).

Illuminance E (lux)

Length (m)

Width (m)

Lumens / luminaire

Average method — verify uniformity (≥0.6) in DIALux; add emergency lighting.

Common mistakes

Ignoring UF/MF.
No uniformity check.
Non-Ex luminaires in hazardous areas.

Requisition & datasheet

Area type, lux, dimensions.
Luminaire, factors, count, emergency.

Frequently asked questions

What should I know about Lighting Design (Lumen Method)?

Look up the required illuminance (lux) for the task — e.g. 300 lux control room, 500 office, 200 process, 750 lab. Then the lumen method: N = E·A / (F·UF·MF), where F = luminaire lumens, UF = utilisation factor (room geometry/reflectance), MF = maintenance factor (dirt/aging). Round up, lay out on a uniform grid, check uniformity ≥ 0.6, and add emergency/egress lighting. Verify in DIALux for the final layout.

Which standards or codes apply?

EN 12464-1 (indoor workplaces), IES Lighting Handbook, ISO 8995, NFPA 101 (emergency lighting), verify with DIALux/Relux.

Standards — EN 12464-1; IES; ISO 8995; NFPA 101.