The same downlight casts very different light onto a matte grey wall vs a satin white one. LRV (Light Reflectance Value) is the spec line designers miss, and the one that makes the most difference at handover.
Four ideas to carry into the next specification conversation you have.
LRV 80 = bright white reflects 80% of light. LRV 5 = near-black reflects 5%. A change of 30 LRV is a doubling of inter-reflection.
Matte finishes give even ambient. Gloss gives sharp hot spots and visible fixture reflections. Choose for the visual goal, not just aesthetics.
Light walls (LRV > 60) keep interiors bright and lower lux requirements by ≈ 15–20%. Dark accent walls cost lumens.
Write 'wall: LRV ≥ 70' alongside the paint code. Without it, the contractor is free to substitute and your DIALux model breaks.
Approximate Light Reflectance Values for common Saudi interior finishes.
| Finish | LRV | Effect on room lux |
|---|---|---|
| White matt paint | 80–85 | Baseline (DIALux default) |
| Off-white matt | 70–75 | −5% |
| Cream / beige matt | 55–65 | −10 to −15% |
| Light grey matt | 40–50 | −20 to −25% |
| Medium grey matt | 25–35 | −30 to −35% |
| Dark grey / charcoal | 10–15 | −40 to −50% |
| Walnut wood veneer | 10–20 | −40 to −45% |
| Polished marble (light) | 60–70 (gloss) | Hot spots; +15% with reflections |
Five points the finishes consultant and the lighting consultant should agree on early.
In a typical office, ~50% of the lux hitting a desk has bounced off a wall or ceiling at least once. Drop ceiling LRV from 80 to 50 and total lux drops 12–18% with no fixture change. Drop wall LRV from 70 to 30 and another 10–15% disappears.
A gloss-white wall has nearly the same LRV as a matt-white wall but sends specular reflections back at the eye. UGR can jump from 19 to 24 in the same room. Premium offices specify eggshell or matt for vertical surfaces; satin or gloss for trim only.
Office carpet runs LRV 12–25 regardless of how light it looks. Hospital and aged-care floors use LRV 30+ vinyl to bounce more light back up onto faces. Choose carpet LRV consciously.
Painted gypsum baseboard ceilings range LRV 65–85 depending on paint sheen and number of coats. A ceiling installed without final coat reads 10–15 LRV lower than spec. Inspect at commissioning.
A repaint two years later from white to dark accent silently undoes the lighting design. Document the LRV assumption on the O&M manual so future tenants understand the trade-off they are making.
Our paint shop applies fixture finishes to a controlled LRV with a spectrophotometer-verified sample on every batch, your DIALux model stays accurate.
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