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The illuminance for a room/property must satisfy the obligatory entries according to 12464-1 over the entire period of usage; this corresponds to the maintenance value. The electrical planner is responsible for optimally determining the maintenance factor dependent upon the lighting system and the spatial conditions used and ensuring this with a maintenance schedule.

Maintenance Factor

LLMF Lamp lumen maintenance factor
LSF Lamp lifetime factor
LMF Lamp maintenance factor
RMF Room maintenance factor

The necessary illuminance of a new system results when the maintenance value is divided by the maintenance factor. An optimal lighting system is distinguished by a relatively high maintenance factor and results in savings in investment costs, in energy consumption and in CO2 emissions. It also ensures a high level of lighting comfort over the entire service life.


What possibilities do consultants and users have to positively influence the maintenance factor:


RMF – Room maintenance factor bright rooms cleaned at regular intervals, or painted in such a way that they have a high reflection coefficient over a long period are the basis for a high room surface maintenance factor.

LSF – Lamp durability factor when defining the immediate replacement of defective lamps, the maximum value of 1 can be used for this factor.

LLMF – Lamp lumen maintenance factor takes into account the decline of the brightness because of the aging of the lamp or of the LED module.

Through the optimal choice of the lights with the appropriate lamps, the consultant can decisively influence this value. The selection of illuminants with a long service life and a low decline in brightness reduces the costs for the procurement of replacements and the effort involved in changing the lamps.

LMF – Lamp maintenance factor depending upon the design of a light and the environmental influences in the property, contamination can occur in the course of use, which results in reduction of the brightness.


The user is responsible for implementation


Cleaning of the lights in a de-energised and cool state with a soft cloth and pH-neutral cleaning agents. Especially the cleaning of coverings for the radiation of the indirect light proportion, cleaning of all reflectors, where they are accessible, in the same way and cleaning of panes and coverings for the radiation of the direct light proportion.

By selecting lights that can be cleaned with low effort and a shorter cleaning interval than the usual 3 years, a higher luminaire maintenance factor can be achieved, which has a positive influence on investment and energy costs, and which results in a higher degree of environmental compatibility of the lighting system.

The following reference values apply for lighting systems for which the consultant can not adequately determine the potential influence factors concerning a reduction of the illuminance:

Clean room / property

  • Maintenance factor 0,8

Normal room / property

  • Maintenance factor 0,67

Very dirty room / property

  • Maintenance factor 0,5

A maintenance factor of 0.5 means that an illumination twice that of EN 12464-1 must be established as a new value for the usage of the recommended illumination.




When creating lighting systems with LED lamps, the planner should determine the most precise run time of the lamps possible and take the planned useful life of the system into account; in this way a real value for the lamp lumen factor can be defined, which can be significantly higher than the value of 0.7, which, with reference to the useful life of 50,000h, would otherwise be used.