DIALux evo: An Interior Study

Key Takeaways

What you'll walk away with

Surfaces decide the reflection budget.

Ceiling 70%, walls 50%, floor 20%, the EN 12464-1 default. Get these wrong and your Em is fiction. Survey real reflectances on retrofit jobs before you trust the model.

IES files are the photometric truth.

Don't sketch luminaires with rectangles. Import the manufacturer IES, DIALux uses the real distribution. A wrong IES is the most common cause of a failed design review.

Calc grid spacing is 0.5 × mounting height.

At MH 3 m, grid = 1.5 m. Tighter than EN 12464-1 inflates compute time without improving accuracy. Spec the standard grid, not a custom one.

UGR is the metric you'll be argued on.

Em and Uo are easy. UGR 19 for offices is where designs fail. Add wall surfaces, set viewing direction, run UGR per task area. Don't trust the global UGR number.

Reference

DIALux evo × design standards × Saudi

Target lux × uniformity × surface, the numbers DIALux verifies.

Space type	Target lux × Uo	Source standard
Office (general)	500 lx · Uo ≥ 0.60	EN 12464-1 T5.26
Office (open plan)	500 lx · Uo ≥ 0.40	EN 12464-1 T5.26
Classroom	300-500 lx · Uo ≥ 0.60	EN 12464-1 T5.36
Hospital ward	100 lx · Uo ≥ 0.40	EN 12464-1 T5.46
Hospital exam	1,000 lx · Uo ≥ 0.70	EN 12464-1 T5.46
Warehouse aisle	200 lx · Uo ≥ 0.40	EN 12464-1 T5.50
SBC compliance default	CIBSE LG / EN 12464	SBC 601

Deep Dive

Five decisions that ride on the DIALux file

DIALux is a calculator. The inputs decide whether the room is designed or guessed.

Photometric file (.ies / .ldt) is the only input that matters.

Generic 100 lm/W LED tells DIALux nothing about beam shape. The .ies file from the manufacturer's lab is the calculation source. Demand it; refuse projects without it.

Surface reflectance changes everything.

Default DIALux walls are 70% / floor 20% / ceiling 70%. A real Saudi gypsum-board wall is closer to 60%, dark stone floor 10%. Wrong reflectances inflate the result by 15-25%, design fails on site.

Maintenance factor (MF) is not optional.

Specify dust/dirt/lamp lumen depreciation: typical office 0.80, industrial 0.65, dusty environments 0.55. The MF reduces design lux to maintained lux, what the room delivers at scheduled cleaning.

UGR is co-equal with lux.

EN 12464-1 caps UGR: 19 for offices, 16 for VDU work, 25 for circulation. DIALux calculates UGR per workstation. High lux + high UGR = visual fatigue and rework requests.

Calculation grid resolution affects result.

0.5 m grid is enough for general space. Use 0.25 m for circulation, 0.1 m for task-area accuracy. Coarser grids hide hot/cold spots; the field reading from a lux meter then fails the design.

From the Academy to the Field

NLC DIALux service, per project.

Every NLC lighting tender includes a DIALux evo calculation with our actual photometric files, Saudi-typical reflectances, and EN 12464-1 compliance report. Free on quote.

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