Technical meaning
- Reflectance describes how much light a surface returns rather than absorbs.
- Ceilings, walls, floors, shelving and large furniture can all affect how much emitted light contributes to the assessed plane.
Calculation use
- Reflectance is one reason a utilisation factor may be higher or lower in a room-lighting estimate.
- Changing reflectance assumptions can reveal when a dark room needs more output or a different distribution.
Not the same as
- Reflectance is not luminaire output. It changes delivery, not the light produced by the fitting.
- Reflectance is not a measured lux result. It should be checked with the actual surfaces, geometry and fitting data where accuracy matters.
Australian context
- Australian lighting notes for dark finishes, high racking, exposed ceilings or bright fitouts should keep reflectance assumptions visible beside UF and MF.
Examples
| Example | Value | Planning note |
|---|---|---|
| White ceiling | higher reflected contribution | Can support a better UF assumption when the luminaire distribution suits the room. |
| Dark walls or shelving | lower reflected contribution | Can reduce delivered light and raise required lumens. |
| Warehouse racking | directional and obstructed | Vertical surfaces and shadows may matter more than a simple room average. |
Calculation limits and records
- Reflectance notes support early estimates. Detailed designs should use suitable photometric data and the applicable project method.