The invention relates to a transparent glass substrate including at least one glass sheet provided with a thin-film multilayer coating acting on solar radiation, having a light transmission of greater than 10% and an emissivity of less than 50% after a heat treatment, such as a bending or toughening treatment, characterized in that said multilayer coating includes: a niobium Nb functional layer with a thickness of between about 5 nm and about 35 nm; and at least one layer of another material, chosen from the group formed by Ti, Mo, B, Al or an alloy comprising at least one of these elements, which is placed relative to the glass substrate above the functional layer, said layer having a thickness of between about 1 nm and about 5 nm. The invention also relates to monolithic glazing or double glazing incorporating such a substrate.