Specialized glazing materials are being used more frequently in architecture for energy conservation. In the past, there was no standard way to compare the properties of materials, particularly regarding the luminous properties of glazings. A validated database of glazing properties was required. New optical measurement procedures have been developed and many are applicable for use on-site. Transmitted light patterns are modified by glazing used for thermal insulation and other energy saving applications such as daylighting and variable transmission windows. Translucent insulation has high potential for energy conservation but the light reaching the rooms may be reduced through scattering. This may be used to the designer's advantage in rooms where privacy may be required. Changing the direction of the light by using special blinds in the glazing, can help make the most of daylight. The blinds redivert light upwards and into the room rather than down to the floor. Angular selection must be considered as insulating materials absorb or reflect different amounts of light, depending how they are positioned with respect to the incoming light. Glazing can also cause a colour shift if the glass is tinted, leading to beneficial or negative effects. All these properties should be described in the same way across industry, so that they are transferable. To standardise the characterization of glazing materials for daylight applications, much research and testing was necessary. The project considered the optical measurements of glazing materials used in windows, and a numerical analysis of the optical data obtained was carried out. A simplified assessment method was elaborated to be used in the field by designers. The optical properties of glazing in 9 selected buildings was then monitored to test the techniques. Two modelling programmes, Genelux and Radiance, were also compared in their ability to simulate different glazings and properties such as light dispersion and shift in colour. In summary, the three main results were a database of glazing properties, obtained by measurements in two independent laboratories; a file format to allow portability of measured or simulated glazing properties to light simulation software; and standard procedures for assessing the properties in laboratories or on-site. A database is available holding the information collected, as are two simulation programmes.