ABSTRACT
The daylight factor is a quantity which describes best the ability of a building to let natural light in. It can be used to assess the fraction of the operating time during which given illuminance thresholds are exceeded. A luminous flux is expressed in lumen (lm). The luminance is a quantity which can be measured to describe the 'brightness' of a surface, such as a wall, a desk surface or a transluscent window. Indoor finishes and glazing materials contribute to final illuminance levels in a building. In areas far away from the apertures, indoor finishes may be the major contributors to the amount of light available. The transmittance of glazing or shading has a direct effect on the amount of light penetrating a building. On-site characterization of material's optical properties has been conducted for each case study. The detail of the procedure is described in the section 'Monitoring procedure'.
