Published by Neo Han Shern · 13 August 2026
DIALux maintenance factor in Malaysia: why day-one lux is not the design result
Learn how maintenance factor changes DIALux lux results for Malaysian warehouses and outdoor sites, and what should support the selected value.
Maintained illuminance is different from day-one output
A new lighting installation normally delivers more light than it will after years of operation. LED output can depreciate, optical surfaces can collect dirt and room surfaces can become less reflective. If a calculation only shows the clean, new condition, the result may not describe the light available later in the maintenance cycle.
A maintenance factor reduces the calculated initial result to a maintained design condition. CIE guidance describes it as part of planning for the expected fall in available light and the maintenance schedule intended to limit that decline. It is therefore not a decorative report setting: it connects the lighting design to how the installation will be operated and maintained.
What should inform the selected maintenance factor
There is no single value that is automatically correct for every Malaysian warehouse, office, car park or industrial yard. The selection should consider the light source and luminaire data, expected operating hours, dirt in the environment, cleaning interval, component replacement strategy and the condition of relevant room surfaces.
CIE 97:2005 addresses maintenance of indoor electric lighting systems, while ISO/CIE TS 22012:2019 outlines a way of determining maintenance factors for both indoor and outdoor installations. These references emphasise the equipment, environment and maintenance programme rather than choosing a number from habit. Manufacturer data should be used where accurate product-specific performance information is required.
Why a familiar default can still be a weak assumption
A value such as 0.80 is often seen in project discussions, but familiarity does not make it suitable for every site. A clean, controlled interior with a defined cleaning programme is different from a dusty production area, a high-bay installation that is difficult to access, or an outdoor fitting exposed to site contamination.
The opposite mistake is to choose an unnecessarily low factor without evidence. That can increase the calculated quantity or output and may lead to avoidable energy and capital cost. The useful approach is to state the basis, apply it consistently and review it when the luminaire, environment or maintenance plan changes.
Questions to resolve before the DIALux calculation
For an industrial project, confirm the operating environment, annual burning hours, access for cleaning, planned cleaning frequency and whether failed fittings will be replaced promptly. Check that the selected IES, LDT or GLDF data matches the actual model and optic. Product ingress protection, lifetime claims and lumen-maintenance information may support the discussion, but no single label replaces a complete maintenance assessment.
For indoor spaces, room-surface condition can also influence maintained performance. For outdoor areas, the assumptions should reflect the real exposure and service plan. If the client has no maintenance programme, record that gap instead of presenting an unexplained factor as a guaranteed future condition.
What a clear DIALux report should record
A useful report identifies the maintenance factor applied, the calculation areas it affects and the source or reasoning behind it. It should also distinguish the maintained result from any initial value shown. DIALux allows maintenance information to be set through standards, utilisation profiles and space-related inputs, so the final documentation should match the model actually calculated.
Record the cleaning and replacement assumptions alongside the luminaire model, mounting arrangement and calculation results. If the project brief or maintenance strategy changes, update the model and issue a revised result. The calculation supports a design decision, but final acceptance and compliance remain with the responsible consultant, client and relevant authority.
Frequently asked questions
What maintenance factor should I use in DIALux for a warehouse?
There is no universal warehouse value. It should be determined from the selected equipment, operating hours, environmental dirt, access, cleaning frequency, replacement strategy and applicable project guidance. Record the evidence and assumptions used.
Does a lower maintenance factor automatically mean I need more lights?
It lowers the maintained result for the same layout, so the design may need changes to meet an agreed target. The correct response could involve quantity, output, optic, spacing or maintenance planning; adding luminaires is not automatically the only answer.