In order to incorporate real construction material reflectance properties in a Monte-Carlo ray tracing algorithm, a representative cladding material is characterised with a spectrophotometer to obtain reflectance angular distribution. These measurements are used to design a BRDF model with a reduced number of parameters that are further identified, along with their confidence intervals. Obtained results are compared to reflectance coefficients measured with an integrating sphere. The prospects of such a model is to allow for a more accurate modelling of the optical properties of materials in reflection. This knowledge can then allow a better integration of photovoltaic technologies, both in terms of energy and visual acceptance. For the particular HPL cladding material tested and despite a highly specular behavior at grazing incidence angles, we found that the specular term only amounts to 4% of reflection.