Given the major role played by windows with regard to energy losses and gains from buildings in respectively cold and hot climates, accurate prediction of the heat transfer through its glazing materials is of great importance in building energy simulation. In most of the building energy simulation programs, solar radiation absorption inside glazing layers is usually treated considering that all the radiation is uniformly absorbed in the glazing. The present assumption is obviously valid in the case of thin homogeneous glazing but, when dealing with thick glazing (commonly used in buildings), it poorly represents the complex non-uniform distribution of absorbed solar radiation. The present study aims to numerically investigate the error induced by such approximation in the case of thick and multilayered glazing. Results show that if the error remains negligible for glazings under steady-state solicitations, it becomes more important in particular for double glazings under transient conditions.