A coated article or layer system is provided which includes at least one infrared (IR) reflecting layer including niobium (Nb) sandwiched between at least a pair of dielectric layers. In certain embodiments, a Cr inclusive barrier layer is provided to protect the Nb inclusive IR reflecting layer, for chemical durability purposes. In other example embodiments, a protective overcoat including a zirconium oxide inclusive layer may be provided to protect the Nb inclusive IR reflecting layer for durability purposes.