The 12464-1:2002 standard did not contain any provisions concerning these surfaces whilst the 12464-1:2011 standard establishes that mean illuminance should be:

for walls: > 50 lx with U0 ≥ 0.10

for ceilings: > 30 lx with U0 ≥ 0.10

The reasons for the introduction of this provision are based upon the fact that both walls and ceiling are included in the observer’s field of view (also called background) and are therefore of the utmost importance for the environment visual comfort.

The standard moreover specifies that a lower illuminance level may be accepted should the above-mentioned level not be complied with due to the dimensions and the complexity of the rooms or to operational factors.

For example, poor mean illuminance values are accepted in case of high ceilings with suspended lighting fixtures located far from the ceiling.

For rooms where visual activities or tasks require luminous surfaces, such as offices, schools and hospitals, the mean illuminance values should be 75lux for walls and > 50 lux for ceilings. For both uniformity must be equal to U0 ≥ 0.10.