Understanding Light Loss Factor (LLF)

All lighting systems decline in lumen output over time due to reductions in lamp emissions and changing surface properties. Utilize a proper light loss factor measure to better design lighting systems for long-lasting value.

Maintained illuminance = initial illuminance × LLF

What Makes Up the LLF

LLF (light loss factor) is the percentage of light output reduction over time: LLF = LLD × LDD × LBO × RSD × RLF.

LLD: Lamp Lumen Depreciation (lumen maintenance factor at the end of luminaire rated life)

LDD: Luminaire Dirt Depreciation (dust accumulation on the luminaire)

LBO: Lamp Burnout (malfunctioning lamps over the installation lifetime)

RSD: Room Surface Depreciation (cleanliness of room surfaces)

RLF: Room Luminaire Factor (luminaire efficiency)

Recommended LLF Values

Typical interior space: 0.75, 0.85

Warehouse / industrial environment: 0.55, 0.75

Typical outdoor application: 0.60, 0.75