A window assembly includes a window frame having a front wall and a lateral wall, the window frame being set within a building opening. A thermal break liner having a laterally extending portion is provided wherein the laterally extending portion is positioned on the lateral wall of the window frame. The window assembly also includes a glazing with at least one pane of glass mounted in the window frame, a glazing bead for holding the glazing in place against the window frame, and a glazing bead retainer fixed to the thermal break liner for retaining the glazing bead in place on the thermal break liner. The thermal break liner is formed of a material having a low thermal transmittance factor and is positioned to prevent direct contact and thermal transfer between the glazing bead and the window frame. The window assembly may be a fixed or operable window assembly.