The domestic windows in the exterior building facade play a significant role in sound insulation against outdoor airborne noise. The prediction of their acoustic performances is classically carried out in laboratory according to standard ISO 10140. In this work, a 3D elasto-acoustic finite element model (FEM) is proposed to predict the sound reduction index of three different glazing configurations of domestic window, which are compared to laboratory measurements. Two acoustic cavities with rigid-boundaries on both sides of the window are used to simulate respectively the diffuse field on the source side and the pressure field on the receiver side. By using a simplified FEM for the double glazed windows, the sound reduction index is calculated from the difference between the source and receiving sound pressure levels in the one-third octave band from 100 to 500 Hz.