Technical meaning
- Maintained illuminance is the planned or estimated illuminance on the assessed plane after delivery and maintenance assumptions are applied.
- It is normally expressed in lux and tied to a named plane, area, UF, MF and luminaire output basis.
Calculation use
- A maintained target can be converted to required lumens with area, utilisation factor and maintenance factor.
- An installed group can be checked by applying UF and MF to luminaire output, then dividing by the assessed area.
Not the same as
- Maintained illuminance is not initial lux from a new, clean installation unless the maintenance allowance is one.
- Maintained illuminance is not a compliance promise. Uniformity, glare, task definition, measurement method and source documents remain separate.
Australian context
- Australian room and workplace estimates should state maintained illuminance as an assessed-plane estimate, not as confirmation that AS/NZS requirements have been met.
Examples
| Example | Value | Planning note |
|---|---|---|
| Room target | 300 lx maintained | Requires area, UF, MF and luminaire output assumptions. |
| Detailed task target | 500 lx maintained | Needs the task and reference document before being treated as suitable. |
| Installed estimate | installed lumens x UF x MF / area | Average estimate only; distribution and uniformity are not shown by the formula. |
Calculation limits and records
- Maintained illuminance can be calculated from public formula inputs. Formal Australian lighting design still needs the applicable source documents, task record and project-specific calculation method.