Very important part of room lighting is the vertical illumination, reflecting the habit of an eye to react to sunshine and daylight coming from above. With correct vertical lighting a person feels safer and fares better at recognition of shapes and faces. The diffused light reflected from the walls adds to this feeling. The usual standards do not take soft diffused and reflected light into account. Horizontal illumination is not perceived as strongly by a human eye and therefore is much less important to human well-being.
From the LQS point of view it is not important how the full effect of illumination is achieved as long as it is fully present. The types of light sources used do not matter. If the illumination is not sufficient, the lighting solution cannot receive full marks in the LQS rating. The vertical spaces have to be lighted sufficiently enough to make the occupant feel comfortable.
For the correct light to be used when working it is important for walls to be of white colour, otherwise the reflected light would take on different properties than normal light. For LQS purposes only full illumination effect awards the highest marks.