Light reflectance is expressed as a percentage and states how much of the light falling on a surface is reflected back.
In order to get the best efficiency, both for incident daylight and lighting, the ceiling's light reflectance should be high. High light reflectance also reduces the risk of glare from light fittings, because this in turn reduces the luminance ratio (i.e. the difference in brightness between the light fittings' luminous surfaces and the ceiling). In the case of direct lighting the suspended ceiling's light reflectance should be at least 70%.
With indirect lighting, light reflectance needs to be higher, because the level of illumination in the room then depends largely on how much light the ceiling surface reflects. For satisfactory indirect lighting, the ceiling surface requires a light reflectance of at least 80%.
Ceilings with high light reflectance also lead to cost-effective lighting, particularly when combined with indirect lighting.
Light reflectance is measured in accordance with the CIE Publication No. 15.2 (1986). Measurement values are evaluated with CIE 10 degree Standard Observer (1964) and CIE Standard Illuminant D65.