The optical characteristics of an advanced glazing system are presented in this paper. The investigated glazing system is based on the incorporation of a paraffin-based Phase Change Material (PCM) into a transparent component, made of two extra-clear glass panes and a cavity where the PCM layer is placed. Due to the highly scattering property of the system (when the PCM is in solid state), the use of a large integrating sphere equipment (75 cm diameter) is necessary to obtain reliable results. The spectral transmission, reflection and absorption coefficients of the PCM glazing system are measured between 400 and 2000 nanometers, and the integrated values are calculated according to the relevant standards. The optical properties are determined with a maximum relative error of 4% (on the sum of the transmission, reflection and absorption coefficients), when the PCM layer is either in complete solid state or liquid state. The average error for all the optical properties is 2%. Different thicknesses of the PCM layer are used in order to assess the dependency of the optical properties on the PCM layer thickness. The angular dependency is also investigated for beam angle up to 45 deg