Lighting Light-Loss Factor (Maintained/Initial)
Light-loss factor from the IES recoverable and non-recoverable factors, and the maintained lumens it yields.
Example
You enter
- Lamp lumen depreciation LLD (0-1) 0.85
- Luminaire dirt depreciation LDD (0-1) 0.9
- Ballast/driver factor BF (up to ~1.2 for high output) 0.95
- Initial lumens (optional, for maintained) 4000
You get
- Light-loss factor (LLF) 0.727
- Maintained lumens 2,907 lm
Checked against published worked examples from: Peerless / Acuity Brands.
Details, formula, and sources
ScopeLight-loss factor = the product of the recoverable factors (lamp lumen depreciation, luminaire/room dirt, burnout) and the non-recoverable ballast/driver factor (which can exceed 1 for a high-output ballast), and maintained lumens = initial x LLF. LLD 0.85 x LDD 0.90 x BF 0.95 = 0.727; a 4,000 lm fixture holds 2,907 maintained. The IES tables and maintenance schedule govern.
Formula or tableLLF = product of the entered factors: recoverable (LLD, LDD, LBO, RSDD) and non-recoverable (BF, up to ~1.2 for a high-output ballast; temp/voltage/tilt); maintained_lm = initial_lm x LLF.
Source and editionThe IES light-loss-factor (recovery-factor) method, by name.
Free accessThe light-loss-factor method and its recovery-factor categories are published in the IES Lighting Handbook. The IES recovery-factor tables and the maintenance schedule govern.
What governsEstimate. AHJ and licensed professional govern.
API field namesLLD, LDD, BF, initial_lm, LLF, maintained_lm
- Multiplicative LLF = product of (LLD, LDD, BF, LBO, RSDD, temp/voltage/tilt) enteredIES Lighting Handbook
- Maintained lumens maintained = initial x LLF, the end-of-cycle outputIES
- Enter the factors uses the entered factors; does not look up the recovery-factor tablesscope of this tile