||Optical utilization factor (OUF) is applied to architectural lighting, searching to obtain low light pollution. It is demonstrated that OUF could not be used for the assessment of light pollution, because the inter-reflections could not be neglected. DIALUX simulations and MATLAB original functions are used. Onsite measurements for illuminance and luminance are performed. It is demonstrated that OUF could be greater than one for the facade. For the small scale inter-reflections, a luminance gain is demonstrated. Due to this, the floodlighting could be reduced. The understanding about the light pollution assessment is changed, which is a major achievement. It means that a greater OUF don't represent a lower light pollution, and also a facade could be more “visible” on lower level of floodlighting.