The average illuminance values set out in the tables in UEFA illuminance requirements should be achieved during matches. A maintenance factor is used to take account the depreciation of luminous flux caused by the ageing and soiling of the light sources, reflectors and front glasses. In the absence of any other information, the maintenance factor indicated in the relevant table in UEFA illuminance requirements should be used.
However, if relevant information is available and systems are in place that facilitate a calculated alteration to that value for a given project, it is possible to modify that maintenance factor.
Reasons to alter the maintenance factor are as follows:
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A proactive, frequent maintenance programme. This requires a comprehensive and documented schedule of lamp replacement, luminaire cleaning, voltage regulation and illuminance testing. Most stadium pitch illuminance systems would not be suitable for this kind of very proactive maintenance.
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Luminaires that use LED technology. The rate of lumen depreciation is very low with this technology. To alter the maintenance factor, there should be a documented schedule of work including luminaire cleaning, voltage regulation and illuminance testing. It is not recommended to increase the maintenance factor beyond 0.90 when using LED luminaires in normal circumstances.
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Lumen depreciation may be compensated for by using ‘constant illumination lamp technology’, which would need to be available and supported by the luminaire manufacturer, with documented analysis of the pitch illuminance system’s performance with voltage regulation. It would also require a schedule of lamp replacement, luminaire cleaning, voltage regulation and illuminance testing.
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If the stadium environment is subject to harsh weather conditions or airborne dirt that could affect the long-term performance of the luminaires, the maintenance factor needs to be lowered to an appropriate level. In such circumstances, a study should be carried out to evaluate the conditions. A typical maintenance factor in the above circumstances might be 0.70 or 0.75 for HID luminaires and 0.8 for LED luminaires.